CN2570785Y

CN2570785Y - Suppression conductance cell

Info

Publication number: CN2570785Y
Application number: CN 02259822
Authority: CN
Inventors: 陈敬强
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2003-09-03
Anticipated expiration: 2012-09-30

Abstract

The utility model relates to a detecting component, which is used on ion chromatographs. The utility model is mainly characterized in that an inlet of a conductance detecting cell is directly connected with a suppressor, and an outlet of the suppressor and the inlet of the conductance cell are combined into integration, i.e., a suppression unit and a conductance unit are made into integration. Therefore, the effect that the outside temperature variation acts on eluate conductance values can be reduced, and simultaneously, the problem that the shapes of chromatographic peaks are wide stretched because of pipelines can be reduced to the minimum.

Description

Inhibition conductance cell

The technical field that belongs to the utility model relates to a utilize in detection part on ion chromatograph.

Background art currently, a known ion chromatograph is composed of six parts, namely a high-pressure pump, a sample injection valve, a separation column, a suppression unit, a conductivity detection unit and a data processing unit. In the conventional ion chromatographic analysis, the components to be detected flow out along with the mobile phase after being separated and inhibited, and enter a conductivity detection cell for detection. The conductivity detection cell continuously measures the concentration of the eluted part in the chromatographic column along with the change of the mobile phase, continuously converts the concentration into an electric signal, and inputs the electric signal into the data processing device to obtain a chromatogram of the separated component along with the change of the time.

An ideal detector can accurately, timely and continuously reflect the change of chromatographic peaks under the conditions of different sample concentrations and various leachates and has the same response signal to the same sample under different environmental conditions, so that the conductivity detection cell has higher sensitivity, wider quantitative detection linear range, selectivity and reproducibility.

According to kohilraush's lawThe conductivity K is 1/1000&A/L&Sigma Ci lambada i; a is the electrode sectional area, L is the distance between two electrodes, when an actual conductance cell is manufactured, A/L is a fixed value and is called as a conductance cell constant K, Ci is the ion concentration, and lambdai is the authority molar conductance of the ions. In ion chromatography, the ion concentration of the system is lower than 1mmol/L, and in a sufficiently dilute solution, the molar conductance of ions reaches a maximum value, and the conductance value is in direct proportion to the ion concentration. It follows that for a practical conductivity cell, once fabricated, the conductance value it detects theoretically is only related to the concentration of the component being measured. However, the experiment shows that the conductance value increases by 2-2.5% when the temperature rises by 1 ℃, and the temperature has direct influence on the conductance value. It can be seen that a conductivity cell that has been fabricated is only temperature capable of interfering with the conductivity value it detects. In actual detection, the measured conductance value should not generate measurement errors due to temperature changes. Therefore, most of the current ion chromatograph conductance cells have a constant temperature device. In the following we analyze the role these thermostats play. The flow rate commonly used in ion chromatography is generally 1.4ml/min, the pipeline for conveying the leacheate adopts a very thin inner diameter, generally phi 0.1mm, so that the movement speed of the leacheate in the pipeline is calculated to be 2.97 m/s, the flow rate of the leacheate in a commonly used conductance cell is made to be very small for reducing the dead volume, the cell volume is only about 0.5-1 muL, and the time for the leacheate to pass through the conductance cell is as follows: 2.14 to 4.28 x 10^-2In such a short time, it is impossible to heat the rinse solution to the set constant temperature, and the same conclusion can be drawn by measuring the temperature of the rinse solution at the outlet of the conductivity cell. Therefore, the fluctuation of the conductance value generated by the change of the external temperature influencing the change of the temperature of the leacheate cannot be eliminated by the constant-temperature conductance cell, and if the length of a pipeline in the conductance cell is increased to enable the leacheate to reach a constant temperature, the dead volume is inevitably increased, the peak shape is widened, and the final quantitative result is influenced.

In order to overcome the influence that current conductivity cell can not eliminate the change of conductivity value because temperature variation brings effectively, the utility model provides a restrain conductivity cell, this conductivity cell can eliminate the influence of temperature to the conductivity value effectively.

The utility model provides a technical scheme that its technical problem adopted: the suppressor is directly connected with the inlet of the conductance cell, and the outlet of the suppressor and the inlet of the conductance cell are combined into a whole, namely, the suppression unit and the conductance detection unit are integrated into a whole, which is called as a suppression conductance cell. And secondly, a constant-temperature heating device is added in the shell of the inhibition conductivity cell. Because the reaction cavity of the suppressor is large in volume and large in thermal capacity, when the whole suppressor is heated to a constant temperature state, the temperature of the leacheate passing through the reaction cavity of the suppressor can quickly reach a constant temperature state, when the leacheate is subjected to ion exchange in the reaction cavity of the suppressor, the leacheate immediately enters the conductivity cell for conductivity detection, and because the whole suppression conductivity cell is in the constant temperature state, the leacheate also reaches the constant temperature state when entering the conductivity cell, the influence of the external temperature change on the conductivity value of the leacheate is reduced, meanwhile, because the suppressor and the conductivity cell are integrated, the structure is simplified, the problem of leakage caused by movably connecting pipeline parts is reduced, and because the suppressor is directly connected with the conductivity cell, the problem that the chromatographic peak shape is widened due to the pipeline is also reduced to the minimum.

The utility model has the advantages that: the suppressor and the conductance cell are integrated, so that the influence of external temperature change on the conductance value of the leacheate is reduced, and the problem that the chromatographic peak shape is widened due to the pipeline is also reduced to the minimum.

Description of the drawingsthe present invention will be further described with reference to the accompanying drawings and examples.

Fig. 1 is a main sectional view of the overall structure of the present invention.

Fig. 2 is an overall flow chart of the ion chromatograph.

In the figure: 1. an eluent inlet, 2 a shell, 3 an insulating layer, 4 and 18 liquid outlets, 5 a constant temperature heating body, 6 a shell fixing plate, 7 an electrode (anode), 8 a partition plate, 9 an ion exchange membrane, 10 an anode electrolytic chamber, 11 and 14 liquid inlets, 12 a conductivity detection unit, 13 an eluent outlet, 15 a reaction cavity, 16 an cathode electrolytic chamber, 17 an electrode (cathode), 19 an eluent storage bottle, 20 an infusion pump, 21 a sample injection valve, 22 a separation column and 23 an inhibition conductivity cell

In FIGS. 1 and 2, first, the state of anion analysis by an ion chromatograph, i.e., a rinse solution (generally Na), will be described₂CO₃/NaHCO₃System) is conveyed to a sample injection valve (21) by a leacheate storage bottle (19) through a liquid conveying pump (20), a sample to be detected enters a flow path through the sample injection valve (21), passes through an anion separation column (22) and enters an inhibition conductivity cell (23), and a conductivity value is detected, so that the separation, qualitative and quantitative processes of the components of the sample to be detected are completed.

Because the affinity of anions in the sample to be detected is different from that of the functional exchange resin in the separation column, the anions in the sample to be detected are sequentially eluted and separated under the elution effect of the eluent. Due to Na₂CO₃/NaHCO₃The leacheate system has high background conductivity, and the background conductivity is reduced by an inhibition device according to the following documents Z W Tian, R Z Hu, H S Lin, J T Wu.high-performance electrochemical support for chromatography, J.chromatography, 1988, 439: 159 to 163 and Chinese patent CN 1003142B. The electrodialysis principle in industrial water treatment is applied to the inhibition process, ions are directionally transferred and pass through the ions under the action of an electric field and an ion exchange membraneAnd the exchange membrane is used for removing ions with the sign opposite to that of the detected ions in the leacheate, so that the leacheate with high conductivity is converted into a low-conductivity substance, and the conductivity value of the ions in the sample to be detected is displayed in a low-conductivity background to achieve the purpose of detection. In the utility model, the leacheate enters a reaction cavity (15) filled with cation exchange resin from a leacheate inlet (1), two surfaces of the reaction cavity (15) are covered with two cation exchange membranes (9), and the other surfaces of the two cation exchange membranes are covered with two clapboards (8). Besides the sealing and reinforcing functions, the fixing plate (6) has electrodes (7) (anode) and electrodes (17) (cathode) adhered to its inner side with epoxy resin. The separator (8) is made of polyethylene and polypropyleneThe diaphragm (8) is composed of a single-layer or multi-layer woven net made of any one or a mixture of the rare, polyvinyl chloride, ABS, polytetrafluoroethylene and nylon, the mesh number of the woven net is 10-500 meshes, and the diameter of woven filaments used by the woven net is 0.1-3 mm, the diaphragm (8) composed of the woven net has the beneficial effects that ① can uniformly support an ion exchange membrane surface, so that the ion exchange membrane surface is uniformly stressed and is not easily damaged, the service life is prolonged, ② can effectively reduce the water flow resistance and reduce the system pressure, ③ has uniform water flow distribution and good turbulence effect, can effectively eliminate the polarization phenomena of membranes and electrodes generated by electrolysis, meanwhile, in order to reduce the system resistance, the width of the diaphragm is 15-20 mm, and a small amount of smashed and ground cation exchange resin with high exchange capacity (the model is produced by Shanxi provincial resin factories with the exchange capacity of more than or equal to 11 mmol/g) is added into the diaphragm, and the electrolytic cell (16) generates the following reactions when the diaphragm works normally:

an anode electrolysis chamber:

an anion chamber:

under the action of electric field, the H in the electrolytic chamber⁺Passes through the cation exchange membrane (9) to enter the reaction chamber (15) and is mixed with CO in the leacheate^2- ₃、HCO^- ₂Are combined into H₂CO₃Due to H₂CO₃Is a low conductivity substance, and reduces the local conductivity. While Na in the reaction chamber (15)⁺Passes through the cation exchange membrane into the anion chamber (16) to react with OH generated at the cathode^-Together through the outlet (18). The back conductance of the leacheate which is reacted from the reaction cavity (15) is reduced, the conductance of corresponding ions of the sample to be detected is displayed, the conductance detection unit (12) and the inhibition unit are integrated directly, and the ions of the sample to be detected directly enter the conductance detection unit (12) after passing through the reaction cavity to detect the conductance value. The conductivity detection unit (12) is a bipolar conductivity cell or a multipolar conductivity cell. The leacheate passes through the conductivity detection unit, enters the leacheate outlet (13) and is then connected withIs connected to a liquid inlet (11), is discharged froma liquid outlet (4) through an anode electrolysis chamber (10), is connected to a liquid inlet (14), passes through a cathode electrolysis chamber (16) and is finally discharged from a liquid outlet (18). The shell of the inhibition conductivity cell is provided with a constant temperature heating body (5), and the whole inhibition conductivity cell is kept at a certain set temperature (between 25 and 45 ℃). The heating material of the constant temperature heating body can be a heating wire wound on the shell of the inhibition conductance cell body or the inhibition conductance cell is arranged in a constant temperature container device. The shell of the inhibition conductivity cell is covered with a heat-insulating layer.

As described above, the conditions when the ion chromatograph analyzes cations are as follows: the principle and method of the inhibition conductance cell are similar to those described above except that the resin is replaced by anion exchange resin, the membrane is replaced by anion exchange membrane, and the anode electrolysis chamber and the cathode electrolysis chamber are exchanged.

Claims

1. The inhibiting conductance cell consists of inhibiting unit, conductance detecting unit and constant temperature heater, and the inhibiting unit consists of reaction cavity, positive electrolytic chamber, negative electrolytic chamber, partition board, etc. and features that the inhibiting unit and the conductance detecting unit are combined into one integral.

2. The suppression conductance cell according to claim 1, wherein a constant temperature heating body is installed in a housing of the suppression conductance cell, and the whole suppression conductance cell is kept at a constant temperature to a predetermined temperature (between 25 ℃ and45 ℃); the heating material of the constant temperature heating body can be a heating wire wound on the shell of the inhibition conductance cell body or the inhibition conductance cell is arranged in a constant temperature container device.

3. The inhibition conductance cell of claim 1, wherein the inhibition unit comprises a reaction chamber, a positive electrolysis chamber, a negative electrolysis chamber, a partition plate, and the like, wherein the partition plate is made of a single-layer or multi-layer woven mesh made of any one of polyethylene, polypropylene, polyvinyl chloride, ABS, polytetrafluoroethylene, nylon, or a mixture thereof, and the mesh number of the woven mesh is as follows: 10 to 500 meshes and the diameter of the knitting silk for the knitting net is between 0.1 and 3 millimeters.