JP2013213789A - Automatic titrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic titrator capable of reducing a measurement time and reducing drainage pump units.SOLUTION: A potentiometer 21 detects an equivalent point by calculating the largest point of the variation (differential value) of potential per unit and, when measurement is completed, supplies cleaning liquid in a tank 24 for cleaning liquid into six cleaning pipes 20 through an L-shaped joint 19 and a resin ring 18 by driving a cleaning pump 23 for a fixed time. Consequently, since the cleaning liquid is ejected from the cleaning pipes 20, a titration nozzle 11, sensors 12, 13, an agitation rod 14 and a drainage tube 16 are cleaned. Since a drainage pump 25 is driven together with the cleaning pump 23, a measured sample and the cleaning liquid are suctioned by the drainage tube 16, and discharged into a drainage tank 26.

Description

  The present invention relates to an automatic titration apparatus, and more particularly to cleaning of a measurement unit of an automatic titration apparatus.

Conventionally, in order to analyze various samples, a titration method is used in which a titration reagent is dropped on a sample placed in a titration vessel to obtain an equivalence point.
The analysis by this titration method includes electro titration and photometric titration, and electro titration includes amperometric titration, polarization titration, potentiometric titration, and the like depending on the detection method of the titration end point.

The amperometric titration method involves immersing a non-polarizable electrode, for example, a silver-silver chloride electrode and a micro indicator electrode, for example, a rotating platinum electrode, in a titration solution, and measuring the current limit during the titration by measuring the limiting current at a constant voltage. Is used to measure many metals.
In addition, the polarization titration method is an electric capacity analysis performed by applying an electric current or voltage to the indicator electrode from the outside to be polarized, and a typical example is a Karl Fischer moisture meter.

On the other hand, potentiometric titration is a method in which the titration end point is detected by potential difference, and there are neutralization titration, oxidation-reduction titration, precipitation titration, and complex titration using pH electrode, ORP electrode, and silver electrode as detection electrodes.
Neutralization titration involves, for example, titrating a hydrochloric acid solution with a sodium hydroxide solution of a known concentration, and the point at which the pH changes rapidly, that is, the inflection point of this curve becomes the equivalence point. The concentration can be calculated from
In addition, the oxidation-reduction titration is performed by titrating a reductant with an oxidant. Since the concentration change and potential change of each chemical species cause a large potential change at the equivalence point, this change is applied to an ORP electrode such as platinum. To track.

For example, precipitation titration is performed by adding a silver nitrate solution to a halogen ion solution and inserting a silver electrode and tracking the potential causes a large change in the potential at the equivalence point. The end point can be determined.
Furthermore, analysis of metal concentration by ethylenediamine is often used in complex titration (chelate titration), and many metals can be analyzed by adjusting pH.

  In a titration apparatus that performs this titration method, a sensor is inserted into a titration cell in order to detect a titration state of a test solution, and the titration state is grasped by an electric signal output from the sensor. In such a titration apparatus, since various types of titration are performed as described above, several sensors such as a glass electrode, a platinum electrode, a silver electrode, or a photometric sensor are prepared as sensors for the purpose of titration. Correspondingly, the most suitable sensor is selected.

  In addition, an automatic titration apparatus that automatically performs titration includes an automatic sampler that includes a plurality of sites where a beaker containing a sample can be set, a sensor that measures potential, a titration nozzle, and a measurement unit that includes a liquid stirring unit. The measurement unit attached to the rotatable arm of the automatic sampler is sequentially immersed in the sample in the beaker to perform measurement (for example, see Patent Document 1).

JP 2000-131328 A

  As described above, the automatic titrator performs measurement by immersing the measurement unit in the sample in the beaker. For example, when continuously measuring samples such as petroleum that are difficult to remove dirt, the next occurrence of dirt is measured. It becomes an error factor of time. For this reason, the automatic sampler has a fixed tank for cleaning the measurement unit, and it was necessary to return the measurement unit to its place after the measurement and clean it. There was a problem that a round-trip time to move to the tank twice was required, and it took time until the next measurement.

  Also, when draining the sample that has entered the beaker, the beaker is moved to the drainage position and then drained at that position, so the pump unit connected to the drainage tube of the measurement unit, the measurement A total of three pump units were required: a pump unit for draining the cleaning liquid at the unit cleaning position and a pump unit for draining at the sample draining position.

  The present invention was devised to solve the above-described problems, and an object thereof is to provide an automatic titration apparatus that can shorten the measurement time and reduce the number of pump units for drainage. .

The automatic titration apparatus of the invention according to claim 1 is an automatic sampler provided with a plurality of parts where a container containing a sample can be set, a sensor for measuring potential, a titration nozzle, a liquid stirring unit, and a sample drain An automatic titration apparatus having a measurement unit having a tube is characterized by comprising a cleaning mechanism for cleaning the sensor, titration nozzle, stirring unit, and drainage tube.
An automatic titration apparatus according to a second aspect of the present invention is the automatic titration apparatus according to the first aspect of the present invention, wherein the cleaning mechanism is equipped with a resin ring attached to an arm of an automatic sampler and the resin ring. It is characterized by comprising a washing pipe.

  The automatic titration apparatus of the present invention is provided with a cleaning mechanism for cleaning the sensor, titration nozzle, stirring unit, and drainage tube, and can be cleaned and drained at that position after titration. After completion, there is no need to return the measurement unit to the cleaning position, and the movement time of the measurement unit is only the time for moving up and down once and moving to the next measurement position, and the time until the next measurement can be shortened.

Also, after completion of the titration, the sample can be drained while washing the measurement unit at that position, so a pump unit for draining the cleaning liquid at the conventional measurement unit cleaning position, and for draining the sample at the drainage position. Therefore, the number of necessary pump units can be reduced.
Furthermore, after the titration is completed, the measurement unit can be cleaned at that position, eliminating the need for a cylindrical tank for cleaning the measurement unit, so it is possible to increase the number of locations where sample containers can be placed, and the automatic sampler The number of samples that can be set can be increased.

It is a perspective view which shows the whole image of the apparatus which applied the automatic titration apparatus of this invention to the electric potential difference automatic titration apparatus. It is a perspective view which shows the detail of the measurement unit of the potentiometric automatic titration apparatus of FIG. It is a figure which shows the cross section of the measurement unit of the potentiometric automatic titration apparatus of FIG. It is a block diagram which shows the structure of the electric potential difference automatic titration apparatus of FIG. It is a figure which shows an example of the titration curve by an electric potential difference automatic titration apparatus.

Hereinafter, an embodiment in which the automatic titration apparatus of the present invention is applied to an electric potential difference automatic titration apparatus will be described with reference to the drawings.
FIG. 1 is a perspective view showing an overall image of an apparatus in which the automatic titration apparatus of the present invention is applied to a potentiometric automatic titration apparatus. A plurality of beakers 2 containing measurement samples are set in an automatic sampler 1, and a measurement unit 3 is automatically operated. Then, it moves to each beaker 2 and is immersed in the sample in the beaker 2. When the titrant is dropped on the sample and the end point is determined by the sensor, the measurement result is output by the potentiometer. When the measurement by the potentiometer is completed, the measurement unit 3 moves to the next sample beaker 2.

2 is a perspective view showing details of the measurement unit 3 of the potentiometric automatic titration apparatus of FIG. 1, and FIG. 3 is a diagram showing a cross section of the measurement unit 3 of the automatic potentiometric titration apparatus of FIG.
2 and 3, 11 is a titration nozzle, 12 and 13 are sensors, 14 is a stirring rod, 15 is a motor, 16 is a drain tube, 17 is an arm, 18 is a resin ring, 19 is an L-shaped joint, 20 Is a cleaning pipe.

  The titration nozzle 11 is a nozzle that drops a titration liquid that reacts with the target object of the measurement sample, and the sensors 12 and 13 are sensors for determining the end point in potentiometric automatic titration. The stirring bar 14 is a bar for stirring the measurement sample and the titrant, and the motor 15 is a driving motor for rotating the stirring bar 14. The drainage tube 16 is a tube for draining the sample after measurement and the cleaning liquid, and the arm 17 is a part that fixes and operates the measurement unit 3 and is connected to the automatic sampler 1.

  The resin ring 18 is a part that contains the cleaning liquid and sends the cleaning liquid to the cleaning pipe 20, and the L-shaped joint 19 is a joint that connects the cleaning liquid sent from the cleaning pump to the resin ring 18. The cleaning pipe 20 is for cleaning the titration nozzle 11, the sensors 12 and 13, the stirring rod 14, and the drainage tube 16 by ejecting cleaning liquid from the tip, and includes six pipes. The resin ring 18 is evenly provided.

On the other hand, FIG. 4 is a block diagram showing the configuration of the potentiometric automatic titration apparatus of FIG. 1, wherein 21 is a potentiometric measurement apparatus, 22 is a titration liquid bottle, 23 is a cleaning pump, 24 is a cleaning liquid tank, and 25 is a draining liquid. A pump 26 is a drainage tank.
The potentiometer 21 controls the dropping of the titrant in the titrant bottle 22 onto the sample, the driving of the arm 17, the motor 15, the washing pump 23 and the drainage pump 25, and the signals from the sensors 12 and 13. Based on this, the end point in the automatic potentiometric titration is determined.

The cleaning pump 23 is a pump that sends the cleaning liquid in the cleaning liquid tank 24 to the cleaning pipe 20, and the drainage pump 25 sends the sample and cleaning liquid in the beaker 3 from the drainage tube 16 to the drainage tank 26. It is a pump for.
In FIG. 4, the same reference numerals as those in FIGS. 2 and 3 are the same, and a description thereof will be omitted.

Next, the operation when the acid value of gasoline is measured by the automatic potentiometric titration apparatus shown in FIG. 1 will be described as an example. In this case, a solution for potassium hydroxide (2-propanol solvent) is used as a titrant, and a solvent of toluene: 2-propanol: water = 500: 495: 5 is used as a solvent.
In addition, an indicator electrode and a comparison electrode are used as the sensors 12 and 13.

  When the measurement is started after the titrant bottle 22 is filled with the titrant, the potentiometer 21 drives the arm 17 to lower the measurement unit 3 to the beaker 2 of the first sample. 3 is immersed. Next, the potential difference measuring device 21 drives the motor 15 to rotate the stirring rod 14 to drop the titration liquid in the titration liquid bottle 22 from the titration nozzle 11 while stirring the sample. The potentiometer 21 determines the state of the solution being titrated based on the potentials of the indicator electrode (sensor 12) and the comparison electrode (sensor 13), controls the titration liquid injection speed based on the amount of potential change, and drops the titrant liquid. Continues to.

  The potential difference measuring device 21 detects an equivalence point (end point) from the amount of change in potential (pH). That is, as shown in FIG. 5, the potential difference measuring device 21 detects the equivalent point by calculating the point where the amount of change (differential value) in potential per unit is the largest.

  When the measurement is completed, the potentiometer 21 supplies the cleaning liquid in the cleaning liquid tank 24 to the six cleaning pipes 20 via the L-shaped joint 19 and the resin ring 18 by driving the cleaning pump 23 for a predetermined time. . Accordingly, since the cleaning liquid is ejected from the cleaning pipe 20, the titration nozzle 11, the sensors 12 and 13, the stirring rod 14, and the drainage tube 16 are cleaned. Since the potential difference measuring device 21 drives the drainage pump 25 simultaneously with the cleaning pump 23, the measured sample and the cleaning liquid are sucked by the drainage tube 16 and discharged to the drainage tank 26.

  When cleaning and drainage are completed, the potentiometer 21 drives the arm 17 to raise the measurement unit 3, moves it to the beaker position of the next sample, and lowers it again to bring the measurement unit into the next sample. 3 is immersed and the next measurement is started.

  As described above, since the cleaning liquid is ejected from the cleaning pipe 20 after the measurement is completed, the titration nozzle 11, the sensors 12 and 13, the stirring rod 14, and the drainage tube 16 are cleaned at the measurement position, and the sample and Since the cleaning liquid can be discharged, there is no need to return the measuring unit 3 to the cleaning position after the completion of the titration. The moving time of the measuring unit 3 is only the time for moving up and down once and moving to the next measuring position until the next measurement. Can be shortened.

  In addition, after completion of the titration, the sample can be drained while cleaning the measurement unit 3 at that position. Therefore, a pump unit for draining the cleaning liquid at the conventional measurement unit cleaning position, for draining at the sample drainage position. The number of pump units required can be reduced, and a cylindrical tank for cleaning the measurement unit 3 is not required, so the number of locations where sample containers can be placed is increased by one. It becomes possible.

  In the above embodiment, an example in which the acid value of gasoline is measured by an automatic potentiometric titration apparatus has been described. However, various other samples can be measured, and in the above embodiment, washing is performed. Although an example in which six cleaning pipes are provided has been described, any number of cleaning pipes can be provided.

  Furthermore, in the above embodiment, an example in which the automatic titration apparatus of the present invention is applied to a potentiometric automatic titration apparatus has been described. However, the automatic titration apparatus of the present invention performs polarization titration, current titration, conductivity titration, or photometric titration. The present invention can also be applied to an automatic titration apparatus to be executed.

DESCRIPTION OF SYMBOLS 1 Automatic sampler 2 Beaker 3 Measuring unit 11 Titration nozzle 12, 13 Sensor 14 Stirring rod 15 Motor 16 Draining tube 17 Arm 18 Resin ring 19 L-shaped joint 20 Washing pipe 21 Potentiometric device 22 Titration liquid bottle 23 Washing pump 24 Tank for cleaning liquid 25 Pump for drainage 26 Tank for drainage

Claims (2)

  In an automatic sampler having a plurality of parts where a container containing a sample can be set, and an automatic titrator having a measuring unit equipped with a sensor for measuring electric potential, a titration nozzle, a liquid stirring unit, and a sample drain tube An automatic titration apparatus comprising a cleaning mechanism for cleaning the sensor, titration nozzle, stirring unit, and drainage tube.   2. The automatic titration apparatus according to claim 1, wherein the cleaning mechanism includes a resin ring attached to an arm of an automatic sampler, and a cleaning pipe mounted on the resin ring.

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