KR20010072569A - Automated chemical process control system - Google Patents

Abstract

Chemical delivery systems for liquid chemicals having a predetermined chemical composition use an analyzer to measure the proportion of one of the predetermined chemical components in the liquid chemical to be delivered. Precise analyzer sample delivery batches in the form of automated sample syringes deliver the correct amount of liquid chemical sample to the analyzer. Information about the measurement by the analyzer of the proportion of at least one or a predetermined chemical component in the liquid chemical to be delivered is stored in a controller that can be installed in the microcomputer. The controller then controls a replenisher that emits a precisely controlled amount of a predetermined chemical component relative to the liquid chemical source. Repeat the analysis and check values and trends to ensure that the results are accurate, reasonable and repeatable. During titration analysis, the titration is controlled, especially near the end point, so that the operation of multiple phases is performed to ensure accuracy. After each analysis, a cleaning procedure is performed using a purge gas, such as air, and a cleaning solvent to force sweep of the preceding sample. Sample syringes are cycled repeatedly until the preceding sample is cleared.

Description

Automated Chemical Process Control System {AUTOMATED CHEMICAL PROCESS CONTROL SYSTEM}

Chemical mechanical planarization or polishing (CMP) processes are widely used in the manufacture of microcircuits. Typical CMP processes use abrasive slurries in diluents, in some cases oxidants. Dynamic measurements of slurry properties such as pH, specific gravity, solids (wt%), or slurry particle size distribution should be made to stabilize the slurry. That is, the slurry must be resistant to sedimentation and aggregation and free of contaminants such as slurry particle aggregates, foreign particles, adsorbed carbon dioxide, and ionic contaminants.

Monitoring and measurement of slurry properties and chemical composition analysis can be done on-line or off-line. While on-line measurements provide real-time data, many analytical instruments cannot easily adapt to on-line stamping, forcing users to choose off-line analysis techniques. In addition, on-line analysis tools require quick maintenance and calibration for proper operation. Thus, there is a need in the industry for improved automatic on-line CMP process control.

One of the most difficult aspects of controlling an existing CMP process is the mechanical action. As circuits become smaller, the mechanical action is too coarse and difficult to control to the required fine resolution. Thus, new CMP processes are being developed that are more sensitive to chemical polishing than mechanical polishing. However, chemical polishing requires greater control of the chemical bath because many of the chemicals added are inherently dynamic and difficult to use, particularly in the case of hydrogen peroxides (decomposing over time and varying feedstock concentrations supplied). These variables and degradation affect both the manufacturing (blend) and distribution (or maintenance) steps of CMP slurry preparation and use. The only way to properly control a chemical bath is through fast and accurate chemical analysis and resupply.

In addition to the above, the chemical composition of the CMP chemical bath should be monitored and resupply as required. For example, Semi-Sperse ^R W2000, a tungsten CMP slurry manufactured by Cabot Corporation of Aurora, Illinois, USA, is a non-metallic slurry useful for polishing tungsten and titanium when mixed with an oxidant. However, oxidant (hydrogen peroxide) concentrations must be monitored and resupplied. Ideally, monitoring and resupply should be on-line and automated. The weight percent hydrogen peroxide in Semi-Sperse ^R W2000 can be tested using reduction titration with an oxidizing agent such as cerium sulfate (Ce (SO ₄ ) ₂ ) or potassium permanganate (KMnO ₄ ). However, to be useful, automated titration / control systems must be as reliable, accurate, and repeatable as or better than manual titration. To this end, differential endpoints (ie, inflection points) can be detected using platinum ORP, gold ORP, temperature or calorimetric sensors. Accordingly, the industry requires accurate, reliable and repeatable in-line analysis of chemical CMP baths and automatic resupply of depleted bath components.

Summary of the Invention

Purpose of the Invention

Accordingly, the present invention provides a chemical analysis and control system that protects a process by blocking false results.

It is another object of the present invention to provide a chemical control system that achieves accurate and variable water and reagent delivery.

It is an object of the present invention to provide a chemical analysis system for performing continuous titration vessel level sensing.

It is a further object of the present invention to provide a chemical analysis system that achieves automated inspection of problems related to proper vessel level changes, such as insufficient reagents, low water pressure, or inoperable valves.

In addition, it is an object of the present invention to provide a chemical analysis and control system that fixes potential problems in a system where the user requires, for example, cleaning or preventive maintenance.

It is a further object of the present invention to provide a chemical analysis system that provides a user with a change index in the daily performance of the system.

It is another object of the present invention to provide a chemical analysis system that automatically and safely resupply a predetermined amount of chemical.

It is an additional object of the present invention to provide a chemical analysis system which achieves a minimum water consumption during cleaning and filling of the titration vessel.

It is another object of the present invention to provide a chemical analysis system that achieves a wide range of continuous level measurements of corrosive and caustic alkaline solutions in a predetermined space.

It is a further object of the present invention to provide a chemical sampling system capable of extracting sample chemical samples from stationary tanks hundreds of feet apart to achieve an accurate, repeatable measurement of the chemical properties of the extracted samples.

It is a further object of the present invention to provide a chemical sampling system capable of extracting sample chemical samples from stationary tanks hundreds of feet apart without requiring installation and operation of a pump in the tank making the additional recycle loop.

In addition, it is a further object of the present invention to facilitate the accurate preparation (blending) of peroxide slurries and other mixtures by analyzing and compensating feedstock feed changes and degradation.

A further object of the present invention is to prevent waste of unused chemicals in testing by providing the ability to return the drawn sample back to the tank.

It is a further object of the present invention to provide a chemical analysis system that adjusts a wide range of sample volumes and concentrations to increase system flexibility.

Another object of the present invention is an extended period of time in solution without causing ion transfer problems associated with the use of gel-filled reference cell electrolytes, or flow-limiting, electrolyte protection, porous wood, ceramics, or plastics mounted on the tip. A chemical analysis system is provided that provides a reference cell with a zero potential electrical connection of.

Another object of the present invention is to maintain the blended amount by measuring the level of the mixture and measuring the individual portions, and then adjusting the amount of refeed determined by analysis or by reaction over time, in response to the solution tank volume. It is to provide a chemical treatment system that accurately maintains the concentration of the mixture.

It is another object of the present invention to provide a chemical control system provided with monitoring, chemical analysis, and peroxide control levels in the blend and distribution (or maintenance) tanks in CMP slurry preparation.

It is an object of the present invention to provide a chemical processing system with electronic host exchange of data containing information relating to analysis results, locations, errors, refeed amounts, etc., with a remote host operator interface.

Introduction to the System of the Invention

These and other objects are achieved by the present invention providing a microprocessor-based system for performing various wet chemical analysis procedures such as pH measurement or pH, ORP or colorimetric titration directly in a titration analyzer embodiment of the present invention. The analyst of the present invention performs sample retrieval, sample preparation, purge, data manipulation, auto-calibration, and diagnostics.

Once the analysis is initiated by an automated processing unit of the system that can be performed on a personal computer, the analyzer performs a series of tests without the need for further teaching by a human operator. Each analysis is replicated automatically and the results of the analysis are statistically evaluated to ensure that the final reported results are repeated within the tolerances specified by the user. The final result is confirmed by the computational processor by performing a series of range and trend checks.

The computational processor may allow the user to view and modify analysis structural parameters such as sample volume, dilution volume, and tolerance. In addition, the computational processor allows the user flexibility in operating various valves, syringes, and mixer (s), and in obtaining electrodes and detection values. These devices will be described in detail below.

According to one aspect of the present invention, an on-line automated analyzer eliminates the need for manual analysis and provides better analysis accuracy and repeatability than manual methods and conventional tools. The system of the present invention, in some aspects of the present invention, works with a resupply system that controls the process bath and its monitoring is automated.

The analyzer of the present invention automatically extracts samples from multiple process baths to perform chemical analysis of process chemicals. The results of the analysis are passed to the processing system. The analyzer programs self-calibration and diagnostic paths to ensure consistent and reliable system performance.

As pointed out, the analyzer of the present invention includes a precision resupply system that receives a chemical addition apparatus from the treatment system. According to the present invention, the chemical addition apparatus is based on analytical results, amp-minutes, process time (time in bath), or manual operator instructions. The processing system identifies the specific pump to be operated by the refeed control system and the specific valve to be opened and closed. A precision flow sensor is used to monitor the amount added. The system is designed to maintain a list of chemical raw materials and reports on chemical usage by the process tank. The digital keypad can be used to remotely control system operation.

In one aspect of the invention, the PC interface is a MICROSOFT Windows ^R system that uses graphical icons to simplify the operation of the system. The computer processor communicates with all other modules to be described herein by the RS-422 interface and processes the data according to the intended operator settings. The commands exported by the computer processor begin to control function functions and operator alarms. In a further aspect of the invention, the computational processor comprises a database providing a history of all parameters monitored by the system. This history information can be used to generate valid reports from computer processors. Thus, at any time, for time frames and parameters, baths, chemicals, or modules, the operator can print various tables, graphs, charts, and location reports.

Summary of How It Works

The analyzer of the present invention performs three basic functions, in particular sampling, analysis and cleaning. These functions also include diagnostics, auto-calibration and calculations.

sampling

Sampling recovers liquid from a tank, sample loop, or grab sample reservoir and delivers it to an assay cell. For titration and / or analysis where the correct amount of sample is required, the sample syringe is circulated to pump the sample and purge other liquids. Several sample cycles are transferred to the reaction cell beaker so that the sample is a sample of the liquid in the tank. During this state, both a timer and a sample arrival detector are used to ensure that the sample arrives within the appropriate analysis time. The beaker is thoroughly cleaned before the final sample is consumed. For assays in which samples are tested directly without dilution, the liquid is pushed into the assay beaker by pressure in the sample loop or drawn by the eductor.

analysis

The analysis is performed after the sample is delivered to the cell. Titration analysis can be performed using any controlled reagent delivered by gravity through a solenoid valve in one aspect of the invention. The titrant is delivered to a syringe that is run under the control of a stepper motor. The titrant is added continuously while taking similar values at predetermined intervals to find the endpoint. If the end point is found, clean the beaker and repeat the test until the results are within user specified tolerances. In a viable aspect of the present invention, at least three iterations are required and a maximum of nine are allowed. If the results are satisfactory for non-continuous analysis, the analyzer is cleaned to avoid cross contamination.

washing

The cleaning procedure cleans all analyzer components in contact with the sample solution. This starts with air purge through the rotary valve (s) and filter. If the sample is not cleaned through the line, an error condition occurs for subsequent analysis warnings with low air pressure. When cleaned by air, bursting wash water is activated to maximize the cleaning effect, and when used, the sample syringe is circulated until it is cleaned. Depending on the process in which the analyzer is used, there may be no water cleaning of the sampling line. Thereafter, the direct filling line into the beaker is cleaned.

Grab samples

The bottled sample may be provided to the analyzer for analysis at the Grab Sample Shipper Port. For optimal results the sample concentration should be within a certain range (alarm limit) of the parameters tested.

pH electrode calibration

After a user-determined time since the last pH calibration, pH calibration is performed prior to analysis using the pH electrode. The calibration uses two pH buffers to measure the slope and offset of the pH electrode. Once a stable value is obtained in one buffer, the beaker is washed and the value in the remaining buffer phase is taken. The slope value is sent to the computer processor to allow the operator to know the electrode conditions. The slope and upper limit value are retained by the analyzer to convert the voltage value into a pH value. The calibration frequency is shown in the analytical structure table record titled "Hours calibration valid".

ORP electrode calibration

Since the ORP electrode is used differentially rather than absolute titration, no correction is necessary. However, its measurement is preferred because the sensitivity of the electrode may vary in use. The electrode sensitivity, calculated as the ratio of the actual response: ideal response, is reported after each analysis and can be seen in a computerized processor using other analyzer parameters.

ISE method and calibration

Ion selective electrodes (ISE) are used to measure various analytes using standard addition methods. In the standard addition method, a known amount of standard solution with a known concentration of analyte is subsequently added to a solution of unknown concentration. Electrode potential is measured after each addition. The increased signal generated by the ion selective electrode is extrapolated back to zero analyte concentration points to determine the amount of analyte in the original sample.

3 to 5 additions are made and approximately double the concentration for each addition. In this way the potential varies from one addition to another and E is sufficient to provide precise results. A change above about 20 mV is preferred and should not be below 5 mV. The larger the value of DE, the more repeatable the analysis. Higher concentration standards are best for minimizing dilution of the test solution. (Ion selective electrodes are also sensitive to solution ionic strength).

Standard addition methods are accurate and repeatable. This eliminates the need to prepare calibration standards with background solutions (matrix) that match the unknown. The basic assumption of using standard (known) additions is that the matrix has the same effect on the original analyte and the added analyte in the unknown sample.

Turbidity probe method and turning

A turbidity sensor is used to measure titration values with 1) concentration proportional to turbidity and 2) turbidity (cloudy) endpoints. The proportional method requires correction to establish the correlation between turbidity and concentration. Sulfate measurement (barium sulphate form) is an example of this type of measurement.

There is an example of the turbidity end titration used in the case of cyanide in the plating solution. This method is to titrate the unknown cyanide solution concentration using silver nitrate. When all cyanide is consumed by silver ions, additional silver ions combine with the iodide indicator to form a cloudy precipitate in the beaker. This blur is detected with a haze sensor that signals the end point of the titration. Graphically, this increase in turbidity is in the form of curved or abrupt bands above the turbidity.

For the endpoint method, the turbidity probe does not require calibration except when the probe is replaced. This is due to the fact that the titration is a relative change and not an absolute value. The resistor combined with the probe is set to provide rich sensitivity to detect even slight turbidity. By adjusting the detection value in the analysis structure table, the titration value can be changed to match what the operator first observes in the form of an endpoint. Endpoint detection can be set from almost invisible haze to very turbid.

Summary of claimed invention

According to a first system aspect of the present invention, there is provided a chemical control system for a chemical solution having a predetermined chemical component. According to this aspect of the invention, the analyzer determines the proportion of one of the predetermined chemical components in the solution. The precision analyzer sample delivery device delivers liquid chemical samples to the analyzer. The controller accepts information about the determination by the analyzer of the proportion of at least one of the predetermined chemical components in the delivered liquid chemical. The controller can be implemented with a microcomputer. The refeeder responding to the controller provides a controlled amount of the predetermined chemical component. A controlled amount of predetermined chemical component is delivered to a tank or vessel holding a chemical solution.

In one aspect of the invention, the analyzer is a titrator system. The properties of the sample are monitored by one or more sensors or electrodes that respond to the addition of certain reagents.

The analyzer includes, in certain embodiments, a reaction cell for receiving a liquid chemical sample from the precision analyzer sample delivery device. The electrode measures the predetermined electrical properties of the liquid chemical in an embodiment of the invention and the reaction cell is a glass beaker. The sensor may be one or more pH electrodes, ORP electrodes or ion selective electrodes, or turbidity sensors.

The present invention can monitor the slurry. In this embodiment, one of the predetermined chemical components in the slurry is H ₂ O ₂ . Chemical delivery is performed by a large loop that dispenses chemical solutions in the plant. Large loops can be pressurized.

In certain embodiments a display is provided to the aforementioned controller that presents information responsive to measurements by the analyzer. In addition, the display may include information related to the scheduled parameters of the chemical delivery system, diagnostic conditions of the chemical delivery system, history of resupply operation, history of system faults, information relating to the calibration of chemical sensors, Amount, and a plurality of additional system parameters and their history.

In a further aspect, the liquid level in each feed tank is delivered from a pressure regulator through an orifice and monitored by monitoring the head pressure of a gas such as N ₂ coming out of the tube being immersed in the feed tank. The pressure of the monitoring gas passing through the orifice is usually maintained at approximately 1 to 15 psi, preferably 2 to 10 psi.

In a highly advantageous aspect of the present invention, the precision analyzer sample delivery device includes an eductor for drawing a sample into the analyzer. The eductor produces negative pressure in the sample line.

After recording each value, the analyzer is cleaned with a purge system. In one aspect, the purge system includes a gas purge valve that controls the pressurized purge gas to clean the analyzer. In addition, certain aspects include a cleaning solvent purge valve that controls the flow of cleaning solvent to clean the analyzer. The cleaning solvent may be arranged to purge the gas purge valve in addition to the analyzer.

According to a further system aspect of the present invention, there is provided a chemical delivery system for a chemical solution having a predetermined chemical component. The chemical control system includes a precision analyzer sample delivery device that delivers samples of the correct amount of liquid chemical. The precision sample is sent to the reaction cell, and the precise amount of the predetermined reagent is delivered to the reaction cell by the precision analyzer reagent delivery device. Sensors typically measure the properties of liquid chemicals during reagent addition. The controller accepts information about the actual characteristics of the liquid chemical measured by the sensor and stores the sample for later analysis. The data is used by a controller to control a refeeder that adds a controlled amount of a predetermined chemical component to the liquid chemical source.

A sample of the chemical solution delivered to the reaction cell by the sample line is provided to a detection device that detects the presence of liquid chemical in the line. In one aspect, the sensor constitutes a proximity or optimal sensor disposed proximate to the sample line. This sensor provides an indication of the utility of liquid chemicals to the controller.

In a highly advantageous aspect of the invention, the precision analyzer sample delivery device comprises a syringe as a component. The syringe is operated with a controllable drive device comprising a drive motor and a controlled circuit. Preferably, the drive motor is in the form of a known stepper.

As pointed out above, after the analysis of the chemical solution is completed, the reaction cell and the sample line are cleaned by a cleaning device using a purge gas. In addition, the cleaning apparatus uses a cleaning solvent. In certain embodiments of the invention the cleaning solvent (water) is applied in the form of a burst that maximizes the cleaning effect. The cleaning device additionally circulates the sample syringe until the previous sample is cleaned.

According to a first method aspect of the present invention, there is provided a method for analyzing a chemical solution in a tank having a first chemical composition. This method

Sending a sample of a chemical solution having a first chemical composition to an assay cell;

A titration analysis is performed in a chemical solution with a first chemical composition sent to the assay cell (the step of performing a titration analysis is

Control the syringe to deliver the titrant to the chemical solution with the first chemical composition sent to the assay cell,

An additional step of analyzing the predetermined chemical characteristics of the chemical solution),

After measuring the end point of the titration analysis,

Performing a cleaning process.

In one aspect of this method aspect of the invention the delivery step comprises a further step of delivering a predetermined sample amount of chemical solution having a first chemical composition to the assay cell. In a further aspect, the delivering step includes varying the rate at which performing the titration assay is performed. This stage of change is sensitive to determining the end point of the titration assay. In a first aspect, titration analysis is performed in inverse proportion to the rate of change of the monitoring signal. However, when the end point of titration analysis is reached, the rate of delivery of the titrant is changed. In essence, during the beginning of the titration, the titrant is delivered at the maximum possible rate without delivering more than the reaction can consume and without exceeding the end point. However, when the end point is reached, the system changes to two stages as indicated by the increased degree of sensor change per unit volume of titrant added. In stage 2, the titrant addition rate is fixed and somewhat slow, and the sensor response changes freely through the inflection point. This is done to promote accuracy throughout the speed, since it has been found that the speed change can affect or change the titer results around the end point somewhat.

In another aspect of the invention, the step of delivering comprises purging all liquid associated with the entire sample from the sample loop. In this method, the subsequent sample to be delivered will be an indication of the current content of the dispensed liquid chemical.

The delivery step includes an additional step of detecting delivery of the chemical solution sample having the first chemical composition to the assay cell. In a particular aspect, this step is performed using a proximity or optical sensor as described above. In addition, the delivery of the sample is timed. If the sample fails to become available within the scheduled maximum time, the condition is incorrect.

In a further aspect of the invention, performing the titration assay comprises delivering a controlled reagent. In some embodiments, this delivery of the regulated reagent is performed via a controlled gravity feeder.

In certain embodiments, the step of controlling the syringe to deliver the titrant includes controlling the stepper drive arrangement coupled with the syringe. Advantageous use of the syringe in the present invention allows precise control over the amount of titrant or sample to be delivered to the reaction cell. In addition, the use of a controlled stepper drive enables control over the transfer rate.

In a further aspect of this aspect of the method of the present invention, the step of monitoring the predetermined chemical characteristics of the chemical solution and the end point measuring step of each titration analysis are repeated. This step is repeated until the results of the titration assays are assured within the predetermined parameters in which they are repeated. In one aspect, this step is performed approximately three to nine times.

As described above, after performing the analysis, a specific step of execution is performed including purging the air through a filter through which the chemical solution having the first chemical composition flows. In certain embodiments, all sample lines and reaction cells are also purged. In addition, the sample syringe is circulated until the entire sample is removed. In one aspect, the pressure of the purging gas is monitored and an error alert sounds when this pressure drops below the predetermined pressure. In addition, the cleaning solvent, which may be water, causes a flow through the filter and the associated sample line.

Before performing the titration assay, a calibration step of the pH electrode is provided. This step of calibrating the pH electrode reads the first pH into the pH electrode using the first pH buffer; Reading the second pH with the pH electrode using the second pH buffer; An additional step of determining the slope and the upper bound for the pH electrode is included. In another aspect, an ORP electrode is provided. In this embodiment, performing the titration assay includes performing the fraction titration assay. Further provided is a step of measuring the sensitivity of the ORP electrode.

In some embodiments, the endpoint measurement of the titration assay comprises measuring the clouded endpoint. This involves the use of a turbidity sensor to determine the cloudiness end point of the titration. Typically, this embodiment includes an additional step of titrating a solution of unknown cyanide concentration and may use silver ions. The use of a turbidity sensor to determine the turbidity end point of a titration may additionally include measuring a change in the rate of turbidity change of the chemical solution.

According to one further method of the invention, a method for analyzing a chemical solution in a tank having a first chemical composition is provided. According to the present invention, there is provided a step of delivering a sample of a chemical solution having a first chemical composition to an assay cell, and performing an ion selective analysis on a chemical solution having a first chemical composition delivered to the assay cell, The performing of the assay may include delivering a predetermined amount of a plurality of standard solutions having a known concentration of analyte to a chemical solution having a first chemical composition delivered to an assay cell; Measuring an electrode potential of an ion-selective electrode reactive to a predetermined chemical characteristic of a chemical solution having a first chemical composition delivered to an assay cell after each delivering a predetermined amount of standard solution; And an additional step of measuring the amount of analyte in the chemical solution having the first chemical composition delivered to the assay cell, wherein the step of measuring the analyte amount adds an extrapolation of a plurality of measured electrode potential values to a predetermined analyte concentration value. Steps.

In one aspect of a further method of the invention, the step of delivering the plurality of predetermined amounts of the expanded solution comprises delivering about two to six times the predetermined amount of standard solution. In another embodiment, the amount of standard solution having a known concentration of analyte is pre-determined to deliver each of the predetermined amounts of standard solution, followed by the ion to be reactive to the predetermined chemical characteristics of the chemical solution having the first chemical composition delivered to the assay cell. In the step of measuring the electrode potential value of the selective electrode, an additional step is provided wherein the electrode potential difference between successive measurements is approximately 5 mV to 40 mV. Preferably the electrode potential difference is approximately 5 mV to 30 mV and most preferably approximately 20 mV.

In a further aspect of this additional method aspect of the present invention, there is provided a step of reducing the speed of execution of delivering a plurality of predetermined amounts of standard solution. As explained, this will improve the accuracy of the end point measurement of the titration.

In a further aspect, the extrapolation step includes extrapolating a plurality of measured electrode potential values to analyte concentration zero. In a further embodiment, in the delivery of a plurality of predetermined amounts of standard solution having a known concentration of analyte, the concentration of the analyte in the standard solution is greater than the concentration of the analyte in the chemical solution having the first chemical composition. This reduces the dilution possibility of the chemical solution having the first chemical composition.

Relationship to Other Applications

The present invention claims the benefit of US Provisional Application No. 60 / 081,240, filed April 9, 1998, and is a partial serial application thereof.

Technical Field

The present invention generally relates to a chemical treatment system, and more particularly to a system for automatically monitoring and resupplying liquid volumes in chemical treatment systems such as chemical baths. In addition, the invention described herein relates to an automatic on-line chemical bath control system that can be used, for example, as an automatic chemical bath control device for chemical mechanical planarization processes.

The understanding of the invention is achieved by reading the following detailed description, in conjunction with the accompanying drawings, wherein

1 is a schematic diagram of a coupling device useful in the practice of the present invention;

2 is a schematic of an analyzer device that draws samples from multiple chemical tanks;

3 is a schematic diagram of an apparatus for combining the purging gas apparatus and cleaning solvent of FIG. 2;

4 is a schematic diagram of an analyzer / controller aspect of the present invention illustrating a control method;

5 is a schematic diagram of the fluidic interconnection between the various components of the invention, on the first side of the installation panel;

6 is a schematic diagram of a particular additive fluid interconnect between various electrical components of the present invention;

FIG. 7 is a schematic diagram further illustrating the stepper motor control board, on the nitrogen gas circulation and on the second side of the installation panel shown in FIG. 5.

In one aspect of the invention, the analyzer performs sensor differential tracking and alarming. The analysis uses "discrimination" endpoints to avoid being dependent on absolute or calibrated sensor values. When chemical equilibrium is reached during the titration, large swings occur in sensor readouts. This differentiation or increased speed change is required to determine that the end point has been reached. Tracking, reporting and, if necessary, alarming of sensor discrimination allows the user to ameliorate potential problems and decide to perform cleaning or preventive preservation when needed.

After performing the calibration step, the system of the present invention analyzes and filters the data. Rather than simply accepting an analysis result as a fact, in order to perform the process and then use the results of process control or feedback, certain exemplary embodiments of the inventive analyzer repeat the analysis at least two times to confirm that the values are repeated. . The results are then checked to determine if these values are within a predetermined range and ensure that the values are reasonable. If the value is repeated and makes sense, then the likelihood of illustration is taken largely. Many features of the inventive data filtration method

1. The final result is not simply based on the average of several tests;

2. The allowable difference between tests is limited to a predetermined maximum to allow for selective accuracy;

3. The maximum number of tests is limited (typically nine) to terminate failed attempts and to warn the operator that an instrument failure may or may not occur.

This method protects the process from false consequences under control and informs the user of the machine's performance daily. An increased number of tests to reach the final result is a good warning that sustainability is required.

According to a further aspect of the invention, the automated replenishment volume correction is based on the holding tank liquid volume. The adjustment of the calculated batch amount is advantageously based on the current tank level reading.

The safety of the process is improved by meeting the supplemental volume safety limit. The replenishment amount is limited regardless of the amount indicated by the calculation. In one implementation of this safety feature of the invention, the analyzer / controller meets the target supplement in several increments, especially if the deviation of the result from the target is large.

According to a further aspect of the invention, beaker cleaning and filling is carried out by high speed, low volume (consumption) spraying. Advantageous use of spray cleaning promotes rapid cleaning and filling of the beaker with minimal water consumption. In most industries performing chemical analysis, time and water are important resources that need to be conserved.

The stirring speed in the titration vessel of the chemical going through the system varies depending on the control parameters specified to achieve maximum mixing and maximum cleaning, while minimum foaming and air incorporation. Various stirring rates allow for optimization of various actions through titration and washing procedures. The titration vessel is sealed except for the vent / overflow tube, which is the path through which the overflowed detector drains. The overflow detector detects and warns of a fault.

In a very advantageous aspect of the invention, the level of the titration vessel is continuously monitored or sensed, rather than by discrete measurement techniques. This enables more accurate and continuous delivery of various water and reagents and automatic detection of failures. Such problems may include, for example, insufficient reagents, low water pressure and inoperable valves. By using continuous titration level sensing, a simple low cost valve for delivering and metering liquid to the titration vessel is possible. While not accurate enough for titrations (eg ± 0.001 ml), it is sufficient for control of reagents or buffers (eg ± 0.1 ml).

Air level detection (ie, static liquid head pressure against slowly bubbled impregnated tube tips) is used in a titration vessel to achieve continuous level measurements in confined spaces containing a wide range of corrosive and alkaline solutions. The sensor tube occupies only 0.125 "outer diameter and does not require a" head space ", ie space for installation directly above the solution. The tube can be made of a semi-curable or curable material that is resistant to solution, such as Teflon or glass. .

1 is a schematic diagram of a coupling device 10 useful in the practice of the present invention. The coupling device uses a thread element 11 which applies a compression rod to the flare portion 13 of the tube 14. As shown, the end surface of the flare portion 13 is tightly sealed against the elastomeric cleaner seal 15. It is common to use flare tube connections in today's industry. In known devices, the end of the tube (not shown) is flared and is fully compressed between the tip of the threaded nut (not shown) and the hard mating surface (not shown) to form a leak free connection. The inclusion of a chemically resistant elastomeric cleaner 15 between the flare portion 13 and the mating surface (not shown) 1) reduces the amount of torque required to form the seal, 2) holds the seal and eventually Causing cracking or "cold flow" of the tubing material, and 3) improving coupling by achieving minimal defects in the tubing and mating surfaces. In the practice of this adjustment, it results in sufficient expansion of the washer when forming the seal under compression, but it is important to use suitable washer diameters and thicknesses for very incomplete blocking of the fluid path through the washer's gravity. Proper washer size also facilitates easy and accurate arrangement of the washer in installation. It is noted that elastomeric cleaners have significant performance advantages over conventional Teflon ^R cleaners in that they are not "cold flow", which will eventually cause leakage and require strengthening.

2 is a schematic diagram of an analyzer 20 illustrating a draw / purge sampling technique useful in the practice of the present invention. The sample fluid provided to the analyzer, as well as the total volume of the tank to be sampled, must be reflected. To accomplish this, the sample is sometimes connected with a recycle loop (not shown) and string in the form of a pressurized pipe, which typically contains a flowing sample. The analyzer achieves this and can additionally draw samples from stationary tanks (not shown) hundreds of feet apart. In a particular illustrative aspect of the invention, the sample is drawn from three tanks (not shown) through one of the valves 22, 23 and 24, respectively. The first purpose here is to obtain a representative sample. Another goal is to achieve this with the simplest or least amount of equipment. A known solution to this problem is to install a pump (not shown) in the tank to form an additional recycle loop (not shown). This has the disadvantage of adding a relatively strictly maintained piece of equipment, namely the addition of a pump and the solution of a steadily recirculating fluid to the plant (not shown). Instead, the analyzer of the present invention uses a relatively simple eductor 26 to create and draw a vacuum in the sample whenever needed across the sample detector 27. In addition, the unused portion of the sample is not blown back into the tank with air or nitrogen pressurized through valve 28 to purge the line and prepare for the next draw. In some aspects of the invention, a pump (not shown) may be used in place of the eductor to create a vacuum to conserve water, which has the advantage of reducing the need to maintain because of intermittent use. In addition, in the case of multiple tanks, less equipment is required as a whole. In a preferred configuration, an analyzer equipped to draw samples from multiple tanks can reduce cost and complexity of the device by using conventional vacuum systems. Samples that arrive at the vacuum system are discarded. However, the sample material that reaches the valve before the vacuum system is not waste.

The aforementioned method of sampling also has the advantage of a regular back flushing sample filter (not shown) that can be installed in the sample line. In conventional systems, sample material flows through the filter in only one direction, causing false contamination and interference.

The present method of sampling also has the advantage of ensuring that fresh samples arrive. Since the sample line is purged with gas after each analysis, the sample detector 27 can be used to confirm the transition from "sample member" to "sample present". This transition confirms the availability and presence of samples and proper operation of the sampling system. As a comparison, the recycle sample system can only have stagnant or non-representative samples in it, in which case a simple detection of sample presence is inadequate to ensure correct analysis results.

FIG. 3 illustrates that in addition to the gas valve 28 described in FIG. 2, a water or solvent cleaning valve 29 may be added to clean the system between sampling of incompatible liquids and to purge the gas valve itself. Schematic diagram. This ability is important because the dried sample may otherwise accumulate in the excitation and other valves and fail. The device of the cleaning valve behind the purging gas valve is important because without it the valve can in particular cause sample accumulation. This combination of air / water (or gas / solvent) is particularly effective for cleaning the device with minimal time and solvent consumption, since high propulsion and stream destruction are caused by the gas. In the practice of the present invention, the gas causes it to appear as a propelled lane in the tube.

The three tank sample valves 22, 23 and 24 described in FIG. 2 may be replaced with a single rotary valve (not shown) with multiple inlets and one outlet in certain embodiments of the present invention. This device minimizes "dead legs" and then facilitates the removal of old samples. This would be particularly advantageous when working with incompatible samples. However, the rotary valve is easily consumed, which can cause premature valve actuation failures, especially when rotating the entire sample. This vulnerability is overcome by the following gas / solvent cleaning system (FIG. 3), and the rotation of the rotary valve can be limited to the period during which the system is cleaned or empty.

The analyzer of the present invention uses a variety of sample volume devices, which achieves a wide range of sample concentrations and enables the achievement of more versatile instruments, eg, successive different chemicals, each requiring a different sample volume. In the form of a syringe or burette, the sampling device only uses the middle of one third of the sample column. This technique settles in air at the top of the third and in the bottom of the third to prevent it from becoming part of the sample to be analyzed. This feature is facilitated by new use of various volume sampling devices.

Waste is discharged from the titration vessel vertically over the path. This allows for minimal incorporation of the sample mixture as compared to horizontal or below path. The vertical path remains filled with air until it is evacuated by waste eductor or pump. This is important because the trapped liquid can deliver or extend the proper end point,

In the practice of the present invention, the flow of electrolyte is intermittently controlled. All electrochemical sensors such as pH and ORP require a reference cell in which the solution is at zero electrical potential. A number of structures have been tried for this, all of which have their advantages and disadvantages. For low persistence, a gel filled reference cell electrolyte was used. The electrolyte does not flow and requires refilling, but is stagnant instead. However, these cell electrolytes will be toxic and depleted and drift over hours because of the ions passing into and out of the gel, so that the potential is not zero. A known alternative is a slowly flowing electrolyte comparison. In this known device, the contents are flushed and the zero potential is maintained. In order to constrain the flow and conserve the electrolyte, a wooden porous plug, ceramic or plastic is fitted to the tip. A disadvantage here is that porosity eventually disrupts and restricts electrolyte flow and / or blocks current paths, reducing electrode stability and reactivity.

In the present invention, the flow restrictor is in the form of a valve instead of a porous plug. The valve is located upstream away from the sample. In this way no flow can be impeded or impeded. The electrolyte flow is stagnant during the measurement and thus improves stability, allowing short flow during the interval between measurements, maintaining a zero potential connection.

Another feature of the invention is that the sample tube is in contact with the glass beaker wall. This allows for accurate sample volume to destroy and deliver the droplets. Titration tube tips, on the other hand, vortex the liquid directly to minimize mixing time. In addition, the titration vessel level sensor tube is cut at a 45 ° angle to minimize single bounces, such as bubble escape.

4 is a schematic diagram of an analyzer / controller system 40 constructed in accordance with the principles of the present invention and is useful for explaining the control method. As illustrated in this figure, the analyzer 41 integrated with the manager 42 is provided with a sample line 44, an H ₂ O ₂ blend reservoir (from a plurality of sample lines, in particular an H ₂ O ₂ feed storage drum 48). Sample line 45 from 49 and sample line 46 from H ₂ O ₂ dispense tank 50 are received.

The figure additionally outlines the supplemental control 52, the local control device 53 (“LCU 53”) and the level pressure transducer 55. The combination of analyzer 41 and manager 42 performs automatic analysis of the samples delivered under the control of LCU 53. Result analysis is described according to the changed and alarmed operation in parameter history, supplemental print-outs, system features, sensor calibration data, and display 57. In the event of a failure, alarm 59 is activated to introduce a tower light and an audible signaling device.

A replenisher 60 that includes a precise syringe pump 62 that performs automatic replenishment based on the analysis results is outlined in this figure. Supplemental controller 52 is used from a conventional pump (not shown) towards multiple chemical delivery destinations. Adjustment of the replenishment is performed under software control according to a predetermined replenishment formula adjusted based on the analysis results of the H ₂ O ₂ replenishment feed storage drum 48.

The level monitor of the dispensing tank 50 includes hardware and software for monitoring the level of the dispensing tank and automatically adjusting the replenishment volume, as calculated from the analysis. In a particular illustrative embodiment of the invention, the leveling device in the dispensing tank is in the form of a Teflon tube 64 containing NO ₂ at approximately 2 to 10 psi. In a particular illustrative aspect of the invention, the dispensing of the replenished liquid is carried out through the globally described global feed loop 66, which can be pressurized.

5 is a schematic diagram of a fluid interconnection between various components of the present invention. As shown, the reaction cell 80, which may be a glass beaker in the practice of the present invention, contains a pair of chemical sensors 82 and 83. In one aspect of the invention, the chemical sensor 82 is an ion selective electrode (“ISE”) and the chemical sensor 83 is a pH sensor or an ORP electrode. The reaction cell 80 is provided with a mixer 85 installed below it.

Deionized water is delivered from the deionized water source 87 through the valve 88 to the reaction cell. The valve 88 is electrically operated with a two-way valve. The exact amount of sample liquid and delivery of the predetermined reagents are achieved by syringe combinations 90,91,92,93, respectively, and in specific embodiments of the invention, the samples, NaOH, Ag ₂ NO ₃ and Na ₂ S ₂ O, respectively. _Is set to ₃ . The syringe combination is controlled through each associated one of the electric valves 95-98 by a stepper motor (not shown) controlled by the electrons shown in FIG. In this embodiment, purging of the syringe combinations 90, 91, 92, 93 uses nitrogen gas, and cleaning is controlled in the control panel 100. Nitrogen piping associated with the operation of the control panel 100 is shown in FIG. 7 and will be described below.

Waste is discarded from the reaction cell 80 via an electric valve 110 by a drain pump 112 (FIG. 6). 6 is a schematic diagram of certain interconnections between various components of the present invention. Components already described are similarly defined. As shown in this figure, the electric valve 110 is connected to a drain pump 112,

Sample liquid from sampling chamber 155 is received via lines 116 and 117. However, line 117 is arranged adjacent to proximity sensor 118 that will signal a controller (not shown) indicating that the sample has arrived. The sample is then drawn into the syringe combination 90 through the three-way electric valve 95.

6 illustrates a sampling chamber 120 connected through a plurality of sample sources 121-125 and an associated one of the air valves 131-135, respectively. Each air valve is coupled with the air source 140 through each associated one of the electric valves 141-145.

5 and 6 illustrate that deionized water from deionized water source 87 is connected to the top of cell chamber 120 through electric valves 150 and 152. The lower portion of cell chamber 120 is coupled with a conventional line 155 to which sample sources 121-125 are each coupled via an associated one of air valves 131-135. Common line 155 is coupled to drain valve 160. The figure also shows a grab sample source 161 coupled to a common line 155 via an electric valve 163 and, as will be appreciated, is coupled to the bottom of the cell chamber 120. 5 illustrates, in this particular exemplary embodiment of the present invention, grab sample 161 is drawn from trough 165.

6 shows that KCl electrolyte source 170 is disposed in reagent compartment 171. KCl electrolyte is supplied to the contents of the reaction cell 80 through the electric valve (174). Similarly, the KI source 176 and H ₂ SO ₄ source 177 are also located in the reagent compartment and are delivered to the reaction cell through each of the electric valves 178 and 179. The reagent compartment is also shown to contain a number of reagent sources supplied to each of the syringe assemblies 90, 91, 92, 93. Such reagents have been discussed above. The electric valves 95-98 are three-way valves that are controllable such that each associated syringe assembly receives each reagent or discharges the precisely measured reagent into the reaction cell.

7 is a simplified schematic diagram of a nitrogen gas circuit, further illustrating stepper motor control panel 180 and other electronic systems for generating electrode signals. 5 and 7, nitrogen source 184 supplies nitrogen to pressure regulators 182 and 183, each of which is connected to associated pressure gauges 185 and 186. Pressure regulated nitrogen is led from pressure regulator 183 via line 188 to T coupler 190 inserted between electric valves 150 and 152. Such nitrogen may be used for purging the sampling chamber 120. Additional pressure regulated nitrogen is led to the reaction cell 80 through valve 192 and line 193.

7 also shows three signal conditioning amplifiers 200, 201, and 202 electrically coupled to ISE, ORP, and pH electrode functions, respectively. In a practical aspect of the invention, the signal conditioning amplifier 200 has a rated input voltage of ± 2000 mV, the signal conditioning amplifier 201 has a rated input voltage of ± 1000 mV, and the signal conditioning amplifier 202 has a 420 mV It has a rated input voltage and is ungrounded. A stepper motor (not shown) that controls the syringe assembly is self controlled via the stepper motor control panel 180. In this particular exemplary embodiment of the invention, the stepper motor control panel 180 can control four stepper motors.

Although the present invention has been described with respect to particular aspects and applications, those skilled in the art can, in light of these teachings, create additional aspects without exceeding or departing from the scope of the present invention. Accordingly, the drawings and description herein are provided to assist in understanding the invention and do not limit the scope of the invention.

Claims (77)

In a chemical control system for a chemical solution having a predetermined chemical composition, An analyzer for measuring the proportion of one of the predetermined chemical components in the chemical solution to be delivered, Precision analyzer sample delivery batch for delivering chemical solution samples to the analyzer, A controller for receiving information about the measurement by an analyzer of the proportion of one of the predetermined chemical components in the chemical solution to be delivered, and A chemical control system comprising a replenisher responsive to a controller for dispensing a controlled amount of a predetermined chemical component. The chemical control system of claim 1, wherein the analyzer is a titrator system. The method of claim 1 wherein the analyzer is A reaction cell for receiving a chemical solution sample from the precision analyzer sample delivery batch; And A chemical control system comprising a sensor for selectively measuring a predetermined characteristic of the chemical solution and the reaction progress with the chemical solution. 4. The chemical control system of claim 3, wherein the reaction cell comprises a glass beaker. 4. The chemical control system of claim 3, wherein the sensor comprises a pH electrode. 4. The chemical control system of claim 3, wherein the sensor comprises an ORP electrode. 4. The chemical control system of claim 3, wherein the sensor comprises an ion selective electrode. 4. The chemical control system of claim 3, wherein the sensor comprises a turbidity sensor. The chemical control system of claim 1, wherein the chemical solution is a slurry and one of the predetermined chemical components in the slurry is H ₂ O ₂ . The chemical control system of claim 1, further provided with a global loop for chemical solution distribution. The chemical control system of claim 1, wherein the controller is provided with an information display display responsive to the measurement by the analyzer. The chemical control system of claim 11, wherein the display displays information responsive to the plurality of predetermined parameters of the chemical control system. The chemical control system of claim 11, wherein the display displays information responsive to diagnostic conditions of the chemical control system. 12. The chemical control system of claim 11, wherein the display displays information responsive to the replenishment history by the replenisher. 12. The chemical control system of claim 11, wherein the display displays information responsive to the system failure history. The chemical control system of claim 11, further comprising a chemical sensor, wherein the display displays information responsive to the calibration of the chemical sensor. The chemical control system of claim 11, wherein a chemical tank is further provided and the display displays information responsive to the amount of chemical solution in the chemical tank. 18. The chemical control system of claim 17, further provided with a liquid level monitoring arrangement coupled between the chemical tank and the controller. 19. The flow through a orifice in an inert tube of claim 18, wherein the liquid level monitoring arrangement comprises a pressure monitoring system for measuring the pressure of the monitoring gas delivered to the chemical tank by the pressure regulator and the orifice and extending into the tank to be immersed. Chemical control system in which monitoring is achieved in the area. 20. The chemical control system of claim 19, wherein the pressure of the monitoring gas delivered to the liquid level monitoring batch prior to the orifice is approximately 1 to 15 psi. 21. The chemical control system of claim 20, wherein the pressure of the monitoring gas delivered to the liquid monitor batch is preferably between 2 and 10 psi. The chemical control system of claim 1, wherein the precision analyzer sample delivery batch comprises an eductor for drawing the sample to the analyzer. The chemical control system of claim 1, further comprising a purge system for analyzer cleaning. 24. The chemical control system of claim 23, wherein the purge system comprises a gas purge valve for controlling pressurized purge gas for analyzer cleaning. 25. The chemical control system of claim 24, wherein the purge system further comprises a cleaning solvent purge valve for controlling the cleaning solvent for cleaning the analyzer. 27. The chemical control system of claim 25, wherein operation of the cleaning solvent purge valve further cleans analyzer tubing associated with the analyzer and gas purge valve. In a chemical control system for a chemical solution having a predetermined chemical composition, Precision analyzer sample delivery batch for delivering precision samples of chemical solutions, Reaction cell for precise sample acceptance of chemical solutions, Precision analyzer reagent delivery batch to deliver the correct amount of scheduled reagents to the reaction cell, Sensors for measuring the characteristics of chemical solutions, A controller for receiving information about the characteristics of the chemical solution measured by the sensor, and A chemical control system comprising a replenisher responsive to a controller for receiving a controlled amount of a predetermined chemical component. 28. The chemical control system of claim 27, further provided with a second sensor for measuring the availability of the chemical solution. 29. The chemical control system of claim 28, wherein the second sensor comprises a proximity sensor. 28. The chemical control system of claim 27, wherein the precision analyzer sample delivery batch comprises a syringe. 31. The chemical control system of claim 30, further provided with a controllable drive arrangement for driving the syringe. 32. The chemical control system of claim 31, wherein the controllable drive arrangement comprises a stepper motor drive. 28. The chemical control system of claim 27, wherein the replenisher is arranged to deliver a controlled amount of the predetermined chemical component to the chemical solution storage tank. 28. The chemical control system of claim 27, further comprising a sweep batch for cleaning the reaction cell of a preceding sample of chemical solution. 35. The chemical control system of claim 34, wherein the sweep batch comprises a purge gas. 36. The chemical control system of claim 35, wherein the sweep batch comprises a cleaning solvent. 35. The chemical control system of claim 34, comprising a syringe circulation batch for circulating the sample syringe until the sweep batch is removed from the preceding sample. In the analysis method of a chemical solution in a tank having a first chemical composition, Delivering a sample of the chemical solution having the first chemical composition to the assay cell, A titration assay is performed on a chemical solution having a first chemical composition delivered to the assay cell, where performing the titration assay controls the syringe for delivering the titrant to the chemical solution, Monitoring the chemical properties; After determining the end point of the titration analysis, A method comprising performing a cleaning procedure. 39. The method of claim 38, wherein the delivering step comprises the additional step of delivering a predetermined sample amount of chemical solution having a first chemical composition to the assay cell. 40. The method of claim 39, wherein delivering a predetermined sample amount of a chemical solution having a first chemical composition to the assay cell comprises circulating a sample syringe. 39. The method of claim 38, wherein the delivering step comprises an initial phase of rate adjustment wherein the performing the titration analysis is performed inversely proportional to the rate of change of the monitoring signal. The method of claim 38, further comprising a final phase in which the delivery rate is fixed and slowed down as the delivery step approaches the end of the titration assay. The method of claim 38, wherein the delivering step comprises a further step of purging from the sample loop all liquid associated with the preceding sample. 39. The method of claim 38, wherein the delivering step comprises a further step of using a continuous air level sensor to detect and confirm delivery of all reagents to the assay cell, including samples of the chemical solution having the first chemical composition. 45. The method of claim 44, wherein the delivering step comprises an additional step of timing delivery of each chemical solution to the assay cell to monitor the suitability of reagent supply and equipment operation. 39. The method of claim 38, wherein performing the titration assay comprises an additional step of delivering a conditioning reagent. 47. The method of claim 46, wherein the conditioning reagent delivery step comprises an additional step of controlling the gravity feed batch. 47. The method of claim 46, wherein the conditioning reagent delivery step comprises an additional step of controlling the pump. 39. The method of claim 38, wherein the syringe control step for titrant delivery comprises a further step of controlling a stepper drive motor coupled with the syringe. 39. The method of claim 38, wherein the predetermined chemical characteristic analysis step of the chemical solution comprises adding an analog readout of the predetermined chemical characteristic. 51. The method of claim 50, wherein analyzing the predetermined chemical characteristics of the chemical solution and determining the end point of each titration assay. 53. The method of claim 51, wherein analyzing the predetermined chemical characteristics of the chemical solution and determining the end point of each titration assay until the repeatability of the titration assay results is set within the predetermined parameters. The method of claim 52, wherein analyzing the predetermined chemical characteristics of the chemical solution and determining the end point of each titration assay are repeated approximately two to nine times. 39. The method of claim 38, wherein performing the cleaning procedure comprises an additional step of forcing a gas purge back through the filter through which the chemical solution having the first chemical composition delivered to the assay cell during the sample delivery step is flowed. 55. The method of claim 54, wherein an error warning step is further provided when it is determined that the gas pressure during the gas purge forced step is above a predetermined pressure. 55. The method of claim 54, further comprising propagating the wash water by purge gas through a filter through which a chemical solution having a first chemical composition delivered to the assay cell is performed during the sample delivery step. 59. The method of claim 56, wherein the propelled wash water constitutes a high speed low volume spray. 59. The method of claim 56, further comprising agitating the titration vessel at a maximum agitation rate that results in less foaming to optimize titration and agitation. 59. The method of claim 56, further comprising the step of circulating the sample syringe until flushed. 39. The method of claim 38, wherein prior to performing the titration assay step, a pH electrode calibration step is provided. 61. The method of claim 60, wherein the pH electrode calibration step is A first pH reading is made with the pH electrode using the first pH buffer, A second pH reading is made with the pH electrode using the second pH buffer, and then and a further step of measuring the slope and the upper bound for the pH electrode. 39. The method of claim 38, wherein an ORP electrode is provided and performing titration analysis comprises performing differential titration analysis. 63. The method of claim 62, further comprising the step of measuring the sensitivity of the ORP electrode prior to performing the step of performing the differential titration analysis. 39. The method of claim 38, wherein measuring the endpoint of the titration assay comprises measuring the cloudy endpoint of the titration assay, and further comprising using a turbidity sensor for measuring the cloudiness endpoint of the titration. 65. The method of claim 64, wherein performing a titration analysis on the chemical solution having the first chemical composition delivered to the assay cell comprises titrating an unknown cyanide concentration solution. 66. The method of claim 65, wherein titrating the unknown cyanide concentration solution uses silver ions. 65. The method of claim 64, wherein using the turbidity sensor to determine the turbidity end point of the titration comprises measuring the change in the rate of change in turbidity of the chemical solution and titrating until the rate drops to near zero. In the analysis method of a chemical solution in a tank having a first chemical composition, Delivering a sample of the chemical solution having the first chemical composition to the assay cell, Perform ion selectivity analysis on a chemical solution having a first chemical composition delivered to the assay cell (wherein the performing ion selectivity analysis step comprises a plurality of known concentrations of the analyte in the chemical solution having a first chemical composition delivered to the assay cell). Delivering a predetermined amount of a standard solution, measuring an electrode potential value of an ion-selective electrode responsive to a predetermined chemical characteristic of a chemical solution having a first chemical composition delivered to the assay cell after each predetermined amount of standard solution is delivered Includes; Measuring the amount of analyte in the chemical solution having the first chemical composition delivered to the assay cell, wherein the step of measuring the amount of analyte further extrapolates the plurality of measured electrode potential values back to a predetermined point of analyte concentration. How to include. 69. The method of claim 68, wherein the step of delivering the plurality of predetermined amounts of standard solution comprises the delivery of approximately two to six predetermined amounts of standard solution. The method of claim 68, wherein delivering a plurality of predetermined amounts of standard solution knowing the concentration of the analyte comprises an additional step of prescribing the amount of standard solution knowing the concentration of the analyte. Measuring the electrode potential value of the ion-selective electrode responsive to the predetermined chemical characteristic of the chemical solution having the first chemical composition delivered to the assay cell after delivery, wherein the electrode potential difference between successive measurements is approximately 3 to 40 mV. The method of claim 70, wherein the electrode potential difference between successive measurements is approximately 5 to 30 mV. 72. The method of claim 71, wherein the electrode potential difference between successive measurements is approximately 20 mV. 69. The method of claim 68, further comprising reducing the rate at which the plurality of predetermined amounts of standard solution delivery steps are performed. 69. The method of claim 68, wherein extrapolating comprises extrapolating the plurality of measured electrode potential values back to zero analyte concentration points. 69. The method of claim 68, wherein in a plurality of predetermined amounts of standard solution delivery steps wherein the concentration of the analyte is known, the concentration of the analyte in the standard solution is high relative to the concentration of the analyte in the chemical solution having the first chemical composition delivered to the assay cell, Thus dilution of the chemical solution having the first chemical composition is reduced. In the fitting for tubing coupling, Flared tube end with toroidal surface, A compression washer for axial contact with the flare end, and A fitting comprising a compression fitting with a threaded portion for forcing a flare tube to axial compression against a compression washer. 77. The fitting of claim 76, wherein the compression washer is formed of an elastomer.