Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/28—Electrolytic cell components
  • G01N27/283—Means for supporting or introducing electrochemical probes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/10—Devices for withdrawing samples in the liquid or fluent state
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
  • G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
  • G01N35/10—Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
  • G01N35/10—Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices
  • G01N35/1004—Cleaning sample transfer devices

Definitions

• the present invention relates to a rinsing chamber for a retractable fitting comprising an inlet for rinsing media and an outlet. Furthermore, the invention relates to a retractable housing with a housing and a dip tube, which is displaceable in the housing between an extended removal position and a retracted measuring position. Furthermore, the invention relates to a method for determining the concentration of a substance or several substances in a material to be measured by means of titration in a retractable assembly.
• Titration is an absolute analytical method for determining the concentration of a substance.
• a titrant is added to a sample, the so-called analyte, which reacts unambiguously with the substance to be determined. It determines the volume of added titrant necessary to achieve complete equilibration of the ongoing reaction. This state is reached at the so-called equivalence point, at which equivalent amounts of sample and titrant have reacted. From the consumed amount of titrant, the amount of substance of the substance to be analyzed can be determined.
• titration types which differ in the chemical reactions taking place during the titration, such as acid-base titration, redox titration, precipitation titration or complexometric titration.
• acid-base titration redox titration
• precipitation titration complexometric titration.
• complexometric titration For determining the equivalence point, various methods are known. One possibility is to use a color indicator that changes color as close as possible to the equivalence point, and to visually or metrologically detect that color change. Alternative possibilities are based on the acquisition of a physical quantity which can be used to determine the equivalence point, for example by means of a pH electrode, redox electrode, conductivity probe or a photometric probe, which determines the absorption of the sample at a specific wavelength can be.
• titration Various devices are available on the market, with which a titration can be carried out fully automatically.
• the titrant is automatically added to the analyte and the titration curve is recorded simultaneously with a sensor.
• the titration curve automatically determines the equivalence point of the titration. From the volume of titrant consumed until the equivalence point is reached, such devices calculate the concentration of the analyte.
• titrations can be carried out with the help of fully automated process titrators.
• These devices usually operate in online mode, wherein the sample to be determined is passed through a separate sampling line of an apparatus or a process line to the titrator.
• the design of such sampling lines is often expensive and expensive.
• To completely fill sample lines with sample liquid a minimum amount of sample must be available.
• the available volume of the sample is insufficient or that the sample is too valuable to fill sampling lines.
• Another problem arises in the case of an unstable sample, which changes to such an extent when passing through the sampling lines that the analysis result, which is determined in the process titrator, is no longer representative of the conditions prevailing in the apparatus or the process line.
• the object of the invention was to provide a titration method for use in a production process, in which the abovementioned disadvantages of sample introduction are avoided and which, moreover, can be operated cost-effectively and robustly.
• the titration is carried out in a rinsing chamber of a retractable fitting.
• the retractable assembly is attached directly to a plant part, such as an apparatus or a process line, so omitted from the prior art known sampling lines and the problems associated with it.
• the retractable assembly according to the invention can be advantageously attached to different apparatus in which there is a liquid, such as containers, reactors, columns or heat exchangers.
• the retractable assembly according to the invention can be attached to different, with liquid flowed process lines, for example, lines to, from or between the above apparatus or on lines that lead from a piece of equipment to an analyzer.
• Retractable fittings are known in principle in process analysis.
• the published patent application DE 10 2006 061 815 A1 describes a retractable assembly with an armature housing and with a tubular support for a sensor guided linearly between a first position and a second position in the fitting housing via a lifting movement, wherein the sensor has a physical or chemical Process size determined.
• the sensors may be, for example, pH electrodes, amperometric sensors, gas sensors, conductivity sensors or the like.
• the tubular holder mentioned in the published patent application will also be referred to below as a dip tube.
• Known retractable fittings are used, for example, to attach a sensor to a plant part so that it can be introduced without interruption of the process in a material to be measured in the plant part and led out again.
• pH measurements require regular calibration of the electrode.
• the electrode must be removed from the sample.
• This can be realized with a retractable fitting in which the pH electrode is inserted in the dip tube.
• the change Selarmatur acts like a sluice and allows the probe from the process to be moved into a rinsing chamber that is completely separated from the process. In this rinsing chamber, the pH electrode can be cleaned and calibrated.
• the present invention makes use of the lock function of a retractable fitting, wherein the known functions of measuring in the material to be measured and rinsing or calibrating in the washing chamber are replaced by the functions of sampling in the material to be measured and titration in the washing chamber.
• the previously known rinsing chambers are not suitable for this purpose.
• a flushing chamber according to the invention has further connections.
• One of these ports is provided as a titrating medium inlet, through which titration medium can be metered into the rinsing chamber.
• titration media all media can be used that are also used in conventional process titrators.
• the concentration of sodium hydroxide in aqueous solution is determined by adding a hydrochloric acid solution as a titration medium.
• concentration of hydroxylamine in water is determined by the method of back titration, with sodium hydroxide being used as the titration medium.
• the measuring device may be any kind of sensor or probe suitable for detecting a variable relevant to the progress of the titration. Examples include pH electrodes, redox electrodes, conductivity probes or photometric probes. In a preferred embodiment, the
• Measuring device an electrochemical measuring chain for the measurement of the pH value for the performance of acid-base titrations.
• the pH-sensitive part of this measuring chain preferably forms a glass electrode or an ion-sensitive sensor.
• the ion-sensitive sensor is particularly preferably an ion-sensitive field-effect transistor, a so-called ISFET chip.
• An ISFET chip offers the advantage of a rapid response to a change in the pH, thereby allowing a short titration time in the context of the method according to the invention.
• the rinsing chamber according to the invention is designed such that its internal volume is preferably from 10 to 200 ml (milliliters), more preferably from 15 to 50 ml, in particular from 20 to 30 ml.
• a choice of the internal volume in one of the preferred ranges proves to be advantageous insofar as a sufficient amount of the sample to be analyzed can be introduced into the rinsing chamber and still sufficient volume for dosing the titration medium is available, so that the probe or probe of Messeinrich - Keep immersed in the liquid throughout the course of the titration.
• the rinsing chamber according to the invention furthermore has a mixing device for mixing a liquid content in the rinsing chamber.
• the liquid content of the rinsing chamber is preferably mixed.
• this mixing is done by a micromixer, which is arranged within the rinsing chamber.
• the mixing takes place in that a gaseous mixed medium is introduced into the rinsing chamber through a further inlet.
• a gaseous mixed medium is introduced into the rinsing chamber through a further inlet.
• gaseous nitrogen is used for mixing the contents of the washing chamber.
• the nitrogen is bubbled via a hollow needle into the liquid to be titrated, wherein the forming gas bubbles lead to a thorough mixing of the liquid.
• the volume flow of the inert gas is preferably selected as a function of the shape and size of the outlet opening so that the resulting gas bubbles have a minimum size for good mixing, but are not so large that the sensor or the probe is no longer completely covered with liquid ,
• volume flows of elemental nitrogen of 5 to 40 l / h have been found to be suitable. Particularly good results were found at a flow rate of 20 l / h.
• flushing media the same substances can be used in the device according to the invention as in known process titrators. Their choice depends on the type of sample and the measuring equipment used. Preference is given to using rinsing media which, on account of their physicochemical properties, are suitable for dissolving measurement material adhering to a wall. For aqueous samples, fully ionized water is preferably used as the rinsing medium. If organic constituents are present in the sample, it is advantageous to use organic rinsing media in which the organic constituents of the sample dissolve, for example acetone.
• auxiliary media can also be introduced into the rinsing chamber via an inlet. If, for example, the equivalence point of the titration is to be detected by a color change of an indicator with the aid of a photometric measuring device, the indicator would be an auxiliary medium in the above sense.
• Another object of the invention is a retractable housing comprising a rinsing chamber according to the invention.
• the retractable housing has a housing in which a dip tube is displaceably arranged between an extended removal position and a retracted measurement position.
• the rinsing chamber according to the invention is connected to the housing of the interchangeable fitting.
• a sampling device is arranged in the dip tube.
• a retractable fitting is attached by means of a nozzle to a plant part, such as an apparatus or a process line.
• extended removal position is understood to mean that one end of the immersion tube protrudes into the part of the installation, so that a sample of measured material can be removed Immersion tube is retracted into the housing of the retractable housing.
• the sampling device has at least one sampling opening and a sample container and is mounted in the dip tube in such a way that a sample can be taken from a sample in the removal position through the at least one sampling opening, the sample can be received in the sample container, and in the measuring position, the sample is at least partially dispensable from the sample container through the at least one sampling opening in the rinsing chamber.
• the dip tube has at least one opening at the end, which protrudes into the measured material in the extended removal position, so that the material to be measured can reach the interior of the dip tube.
• the opening can be located on the front side of the dip tube or in the tube wall.
• the end face of the dip tube is closed, and the tube wall has at least one opening.
• the sampling device is arranged such that through the opening in the dip tube the material to be measured can pass through the sampling opening in the sample container.
• the sample container may be completely or partially mounted within the dip tube.
• the sample container can also be located outside the dip tube and be connected via a line to the sampling opening in the dip tube.
• the dip tube and the housing of the interchangeable fitting are designed so that in the retracted measuring position, the rinsing chamber is sealed against the material to be measured in the apparatus part. Furthermore, at least one opening of the dip tube and the sampling opening are positioned such that in the measuring position the sample can be at least partially dispensed from the sample container through the at least one sampling opening into the rinsing chamber.
• the sampling device comprises a hollow needle whose hollow tip forms the sampling opening and whose inner volume functions at least partially as a sample container.
• the sampling device comprises a hollow needle whose lower end is closed and which has an opening laterally as sampling opening, wherein the center of the opening a distance preferably from 0.5 to 10 mm, particularly preferably from 0.8 to 5 mm, in particular from 1 to 3 mm to the lower tip of the hollow needle, and wherein the inner volume of the hollow needle at least partially acts as a sample container.
• the opening may have different shapes, for example circular, elliptical or rectangular.
• the opening is circular.
• the cross-sectional area of the opening is preferably not chosen larger than the cross-sectional area of the hollow needle interior, which is defined by a plane perpendicular to the longitudinal axis of the hollow needle.
• Such a design of the opening in the hollow needle is particularly advantageous if the rinsing chamber is rinsed with a rinsing medium, while the dip tube is in the measuring position with the hollow needle. Due to the lateral arrangement and small size of the opening, the probability that part of the sample is removed from the hollow needle during the flushing process and thus lost for analysis is significantly reduced.
• the opposite end of the hollow needle is also open and connected to a connection of the housing of the interchangeable fitting.
• the hollow needle is dimensioned such that the entire sample required for the titration can be accommodated in the inner volume of the hollow needle. Through the connection in the housing, the removal of the sample can be controlled.
• the hollow needle is dimensioned such that it can accommodate only a portion of the sample volume in its interior.
• the port in the housing is connected to a conduit, for example a flexible hose or rigid pipe section, whose internal volume is sufficient to accommodate the remaining portion of the sample volume.
• the sample container comprises two components, the hollow needle and at least part of the conduit.
• the sample is aspirated using a burette, whereby the drawn volume of the sample can be accurately determined. The burette can also be used to eject the sample into the rinse chamber.
• a further subject matter of the invention relates to a method for determining the concentration of a substance or a plurality of substances in a material to be measured by means of titration in an exchangeable fitting according to the invention, the method comprising the following steps:
• the rinsing chamber is rinsed with a rinsing medium after retraction of the dipping tube into the measuring position and before introduction of the sample into the rinsing chamber.
• the rinsing medium is then removed from the rinsing chamber.
• the outlet is preferably arranged at the lowest point of the dishwashing chamber, so that the flushing medium can be removed from the washing chamber simply by opening the outlet.
• the rinsing agent can also be removed by aspiration or pressing out with a gas from the rinsing chamber.
• material to be measured adhering to a wall of the rinsing chamber, the immersion tube and / or the sampling device from the current or a previously analyzed sample. Be are removed by the rinsing process. This ensures a defined state, in particular a defined sample volume. By this measure, the accuracy of the titration can be significantly increased. If necessary, the rinsing process can be repeated several times, for example in order to further increase the accuracy or in the case of poor solubility of the sample residues in the rinsing medium used.
• Achieving the equivalence point can be determined by means of commercially available devices which are suitable for fully automatic titrations. These devices usually offer the possibility of determining the concentration of the analyte from the volume of titration medium consumed until reaching the equivalence point.
• titration medium can be introduced into the rinsing chamber before the sample is introduced into the rinsing chamber, so that in the next step correspondingly less titration medium has to be added until an equivalence point is reached.
• the sampling device comprises a hollow needle.
• a predefined amount of material to be measured is sucked as a sample into the inner volume of the hollow needle, and in the measuring position, a further predefined amount of the sample is introduced into the rinsing chamber.
• the sucked amount of material to be measured agrees with the amount introduced into the washing chamber within the scope of the measuring accuracy.
• the introduced into the washing chamber amount is advantageously from 0.1 to 10 ml, more preferably from 0.5 to 5 ml, in particular from 0.8 to 1, 2 ml.
• a predefined amount of Substance or a mixture introduced into the washing chamber is advantageously from 0.1 to 10 ml, more preferably from 0.5 to 5 ml, in particular from 0.8 to 1, 2 ml.
• This substance or mixture should be chosen so that it or it does not react with either the material to be measured in the sample or the titration medium so that the result of the titration is not falsified.
• acid-base titrations for example, fully ionized water is suitable.
• the metered addition of the substance or of the mixture takes place as a template before introducing the sample. This ensures that the measuring probe or the probe of the measuring device is sufficiently wetted with liquid from the beginning of the titration, even if only a small sample volume is available. As a result of this measure, the volumes of the wash chamber interior and the sample to be sampled can be decoupled during the design and selected largely freely.
• a method according to the invention is preferred in which a gaseous mixed medium, preferably nitrogen, is introduced into the rinsing chamber for mixing the sample in the rinsing chamber.
• a gaseous mixed medium preferably nitrogen
• the device according to the invention and the inventive method has many advantages.
• the titration in the retractable fitting is carried out directly at the process, eliminating the need for the conventional approach required lines, the installation costs are reduced.
• the short paths also mean that the time intervals between analyzes can be shortened. Providing analysis results at shorter intervals can be advantageously used for diagnostic purposes or automation applications such as online regulation.
• analysis in the immediate vicinity of the process can increase the accuracy of the analysis because the sample has little opportunity to change its properties during transport to the point of analysis.
• the required amount of sample to be taken from the material to be measured can be significantly reduced, which has a positive effect in particular on valuable items to be measured, since the sample usually has to be disposed of after the analysis.
• Fig. 1 inventive retractable assembly in three-dimensional plan view
• FIG. 2 shows a longitudinal section through an interchangeable fitting according to the invention in the removal position
• FIG. 3 shows a longitudinal section through an interchangeable fitting according to the invention in the measuring position
• Fig. 1 shows a preferred embodiment of a retractable assembly 20 according to the invention in the non-installed state in three-dimensional plan view.
• a rinsing chamber 10 according to the invention is fixedly connected to the housing 21 of the interchangeable fitting. Housing 21 and rinsing chamber 10 are designed substantially cylindrical. The diameter of the rinsing chamber 10 is chosen to be so much larger than the diameter of the housing 21 that inputs and Outlets on the housing 21 radially outwardly projecting top of the washing chamber 10 can be arranged. The top of the washing chamber 10 has more inlets and outlets in this example than required for the function of the interchangeable fitting 20 according to the invention. The unneeded openings are sealed by blind plugs 16.
• the rinsing chamber has an inlet 1 1 for rinsing media and an outlet 12, furthermore a titration medium inlet 13, an inlet 14 for a mixing medium and a measuring device 15.
• the connections for rinsing media, titration medium and mixing medium are designed such that hose or pipe connections, the Manufacturers of fully automatic titrators can be used and connected directly.
• the terminals may also be provided with further components, for example nozzles or hollow needles through which e.g. the mixed medium can be selectively introduced into the washing chamber. In the illustrated example, a hollow needle is inserted in the inlet for the mixing medium 14.
• the connection for the measuring device 15 is designed so that the rod-shaped measuring device is fixed by two crushed O-rings. In addition, these two crimped O-rings ensure that the purge chamber is sealed at this point. It can be seen on the extended dip tube 22 that it is in the removal position.
• Fig. 2 shows a longitudinal section through the retractable assembly 20 shown in Fig. 1 along a plane through the cylinder axis, the measuring device 15 and an opposite blind plug 16 (lying in Fig. 1 behind the housing 21 and therefore not visible). The remaining inlets and outlets are therefore not apparent from the longitudinal section.
• a hollow needle is arranged as a sampling device 23 in this embodiment. The lower end of the hollow needle is closed, the sampling opening 24 is located in the side wall of the hollow needle at a distance of about 1 mm to the lower tip of the hollow needle.
• the dip tube 22 is designed to be closed at its lower end. So that nevertheless a sample can get into the dip tube from the material to be measured, the dip tube has at least one opening laterally just above the lower end.
• the dip tube has three openings, which are arranged distributed uniformly in the circumferential direction.
• This design has the advantage that, on the one hand, mechanical protection of the sampling device 23 located in the immersion tube 22 is ensured, and on the other hand, the flow around the sampling device 23 with the material being measured is hardly restricted.
• the sampling opening 24 in the hollow needle is located directly behind the openings in the dip tube 22.
• a process connection device 25 is provided below the rinsing chamber 10.
• the process connection device 25 is a union nut for connection to a threaded flange.
• the same longitudinal section through the retractable fitting 20 shown in Fig. 1 is shown.
• the dip tube 22 is in contrast to FIG. 2 in the measuring position.
• the sampling opening 24 and the openings at the lower end of the dip tube 22 are located. now in the rinsing chamber 10, so that the sample located in the sampling device 23 can be discharged into the rinsing chamber.
• the lower, closed end of the dip tube 22 abuts O-rings in the housing of the interchangeable fitting and thus seals the rinsing chamber 10 against the material to be measured on the process side.
• the replacement fitting 20 used for this application corresponded to the embodiment shown in FIGS. 1 to 3.
• the inner volume of the rinsing chamber 10 was 20 ml.
• As a sampling device 23 was a hollow needle, which was closed at its lower end. At a distance of 1.2 mm from the lower end of the hollow needle was the center of a lateral circular opening with a diameter of 0.4 mm. A hose connected this needle to a burette. The burette, tubing and needle were filled with a mixture of water and acetone.
• the here and below mentioned mixture of water and acetone was in the ratio of 80 to 20 percent by volume.
• elementary nitrogen was introduced into the liquid phase via the inlet 14, which was provided with a hollow needle, as the mixing medium at a flow rate of 20 l / h.
• the measuring device 15 for monitoring the course of the titration comprised a pH electrode which was equipped with an ISFET chip as a pH-sensitive element.
• the addition of hydrochloric acid as a titration medium, the recording of the titration curve and the determination of the equivalence point from the titration curve were carried out with a commercially available automatic titrator.
• the titration was as follows:
• the dip tube 22 with the sampling device 23 located therein was in the measuring position.
• the rinsing chamber 10 was empty.
• a small amount of air (0.1 ml) was sucked into the needle tip by means of the burette connected to the sampling device 23 via a tube. In this way, a small volume of air was generated at the lower end of the hollow needle in its interior cavities.
• the dip tube 22 was moved via a pneumatic drive in the removal position.
• the burette With the help of the burette a volume of one milliliter was taken by suction from the material to be measured.
• the sample volume completely filled the interior of the hollow needle and partially filled the connecting tube between the hollow needle and the burette.
• the sample container thus comprised the interior of the sampling device 23 and a part of the connecting tube.
• the volume of air drawn in in the first step ensured that the sample did not mix with the mixture of water and acetone present in the burette.
• the dip tube 22 was moved to the measuring position.
• the rinse chamber 10 was rinsed three times with 20 mL each of a mixture of water and acetone to clean the dip tube 22 and needle tip of sample residue and debris.
• the rinsing medium was suctioned off. With the help of the acetone in the flushing medium, the organic impurities contained in the sample could also be dissolved.
• the sample in the sample container was completely discharged into the rinsing chamber 10. Subsequently, 3 ml of the mixture of water and acetone were metered through the hollow needle serving as a sampling device 23, so that no sample remains in the sample container.
• the titration ran automatically and ended when an equivalence point was detected.
• the consumption of hydrochloric acid or the content of caustic soda was determined by means of the automatic titrator.
• the rinse chamber was rinsed with 20 mL of the mixture of water and acetone. The rinsing medium was suctioned off.
• the retractable assembly according to the invention was used to determine the concentration of hydroxylamine in water.
• the method of back titration was used: Hydroxylamine reacts with sulfuric acid to hydroxylammonium sulfate.
• excess sulfuric acid is added to the sample.
• the hydroxylamine contained in the sample reacts completely to hydroxylammonium sulfate.
• a titration curve is recorded using a pH electrode, which has two inflection points.
• the pH electrode used for this step is preferably that which is also used for measuring the pH during sulfuric acid addition. However, another pH electrode may be used.
• the first inflection point of the titration curve marks the complete conversion of the excess sulfuric acid present in the solution to natural sulfate and water.
• the second inflection point marks the complete conversion of the hydroxylammonium sulfate to hydroxylammonium hydrogen sulfate and sodium sulfate.
• the difference between the quantities of added sodium hydroxide solution required to reach the two inflection points of the titration curve corresponds to the molar amount of hydroxylamine present in the sample.
• the amounts of sodium hydroxide solution added can be easily determined, for example, by metering sodium hydroxide solution of known concentration over a burette, the metered quantities being detected.
• the retractable fitting 20 used for this application corresponded to the embodiment shown in FIGS. 1 to 3.
• the inner volume of the rinsing chamber 10 was 20 ml.
• As a sampling device 23 was a hollow needle, which was closed at its lower end. At a distance of 1.2 mm from the lower end of the hollow needle was the center of a lateral circular opening with a diameter of 0.4 mm.
• a hose connected this needle to a burette. The burette, hose and needle were filled with water.
• air was blown into the liquid phase via the inlet 14, which was provided with a hollow needle, as the mixing medium with a volume flow of 10 to 15 l / h.
• the measuring device 15 for monitoring the course of the titration comprised a pH electrode which was equipped with an ISFET chip as a pH-sensitive element.
• the addition of a sufficient amount of sulfuric acid as an auxiliary medium, the sodium hydroxide solution as a titration medium, the recording of the titration curve, the determination of the inflection points of the titration curve and the calculation of the molar amount of hydroxylamine contained in the sample were carried out with a commercially available automatic titrator.
• the titration was as follows: At the beginning, the dip tube 22 with the sampling device 23 located therein was in the measuring position. The rinsing chamber 10 was empty. A small amount of air (0.1 ml) was sucked into the needle tip by means of the burette connected to the sampling device 23 via a tube. In this way, a small volume of air was generated at the lower end of the hollow needle in its interior.
• the dip tube 22 was moved via a pneumatic drive in the removal position.
• a volume of 10 ml was taken as sample from the material to be measured by suction.
• the sample volume completely filled the interior of the hollow needle and partially filled the connecting tube between the hollow needle and the burette.
• the sample container thus comprised the interior of the sampling device 23 and a part of the connecting tube.
• the volume of air aspirated in the first step ensured that the sample did not mix with the water in the burette.
• the dip tube 22 was moved to the measuring position.
• the rinsing chamber 10 was rinsed once with 30 ml of water to clean the dip tube 22 and the needle tip of sample residues and contaminants.
• the rinsing medium was suctioned off.
• the sample in the sample container was completely discharged into the rinsing chamber 10.

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• 2011
  • 2011-10-24 KR KR1020127016945A patent/KR20130122512A/ko not_active Application Discontinuation
  • 2011-10-24 WO PCT/EP2011/068494 patent/WO2012055795A1/de active Application Filing
  • 2011-10-24 JP JP2013535382A patent/JP2013545091A/ja active Pending
  • 2011-10-24 EP EP11773728A patent/EP2502046A1/de not_active Withdrawn
  • 2011-10-24 CN CN2011800087298A patent/CN102753951A/zh active Pending

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