JPH0752179B2 - Coulometric detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coulometric detector and a concentration measuring method, and more particularly to a coulometric detector which enables rapid measurement and easy maintenance of the detector, and a concentration measuring method using the coulometric detector.

[0002]

2. Description of the Related Art Conventionally, as a coulometric analysis method capable of rapid measurement, (1) electrolytic solution stirring coulometry method, (2) coulometry method using a carbon felt electrode (Japanese Patent Laid-Open No. 1-195358). Gazette) etc. are known. However, in the former method, it usually takes 10 minutes or more until the electrolysis is completed, and even if the extrapolation method of the current-electrical quantity curve is used, several minutes of measurement time is required. The latter method has a drawback that maintenance of the carbon felt electrode is not easy.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art, to enable quick measurement, to maintain the detector easily, and to use the coulometric detector, and the concentration using the coulometric detector. To provide a measurement method.

[0004]

SUMMARY OF THE INVENTION The invention claimed herein
Ming is as follows. (1) A cathode plate and a cathode plate connected to the power supply and the measuring instrument, respectively.
And an anode plate and a sample holder for holding the sample between the electrode plates.
Equipped with holding holes or sample solution impregnated mat, and during electrolysis
The both electrode plates are the sample holding holes or the sample liquid impregnated mat.
Characterized by facing each other at intervals of 2 mm or less.
-Rometry detector.

FIG. 1 is an explanatory view of a coulometric detector showing an embodiment of the present invention. (A) shows a coulometric detector having a sample holding hole as a means for holding a sample,
(b) shows a coulometric detector equipped with a sample solution-impregnated mat. The coulometric detector 5 shown in FIG. 1 (a) includes an anode plate 1A fitted to the non-conductive plate 6A so that one surface is exposed, and a depth of 2 at the center of the non-conductive plate 6B.
a sample holding hole 2 having a size of not more than mm, and a cathode plate 1B which is a bottom portion of the sample holding hole 2 and is fitted into the surface of the non-conductive plate 6B.
A lead wire 4 for connecting the anode plate 1A and the cathode plate 1B from a power source and a measuring instrument, respectively, and a coupler 7 for connecting the non-conductive plates 6A, 6B in an openable and closable manner.

The coulometric detector 5 shown in FIG. 1 (b) comprises an anode plate 1A and a cathode plate 1B joined to non-conductive plates 6A and 6B, respectively, and one of the two electrode plates 1A and 1B. 2mm or less sample liquid impregnated mat to be placed 3
A lead wire 4 for connecting the anode plate 1A and the cathode plate 1B to a power source and a measuring instrument, respectively, and a connecting member 7 for connecting the anode plate 1A and the cathode plate 1B in an openable and closable manner. A plastic plate or the like is used for the non-conductive plates 6A and 6B. The anode plate 1A and the cathode plate 1B have Pt, A
Plates such as u, plated plates, carbon plates, etc. are used,
It is preferably selected as appropriate depending on the properties of the electrolyte, the electrolysis voltage, the reactivity with the substance to be electrolyzed and the like. In the present invention, the distance between the anode plate 1A and the cathode plate 1B is 2 mm or less, preferably 1 mm.
It is considered as follows. If the electrode interval exceeds 2 mm, it becomes difficult to obtain the extrapolated value of the electric quantity from the relationship between the electric current and the electric quantity or the logarithm of the current and the time.

In such a structure, the absolute quantification of the substance to be electrolyzed in the sample is performed as follows. First, a certain amount of sample is weighed and administered to the sample holding hole 2 or sucked by the sample solution-impregnated mat 3, and then the non-conductive plates 6A and 6B are closed to apply a voltage and electrolyze. In the case of a sample having a large electric resistance during electrolysis, KNO is contained in the sample.
_It is preferable to add a supporting electrolyte such as ₃ . In the present invention, it is not necessary to perform electrolysis until the substance to be electrolyzed in the sample is completely electrolyzed, and the current-electric quantity curve (Fig. 2 (a)) or the logarithmic time curve of current (Fig. 2 (b)) is used. The amount of electricity required for electrolysis of the substance in the sample can be calculated from the extrapolated value of), and the absolute amount of the electrolyte substance in the sample is calculated from the extrapolated value of this amount of electricity based on Faraday's law. be able to. In addition, the quantity of electricity when using the logarithm of current-time curve
The extrapolated value of is an expression that expresses the attenuation of the current during measurement.

[Equation 1] i = e- ^αt (I: current, α: constant, t: time)
Ground level i ₀ The integral value (electric
Quantity) to the background level electricity quantity i ₀ ・ T
It can be calculated by subtracting.

[0008]

EXAMPLES The present invention will be described in detail below with reference to examples. Examples 1 to 4 and Comparative Example 1 The water content of the dehydrated sludge was measured using the coulometric detector shown in Fig. 1 (a). Electrode spacing of detector (depth of sample holding hole) is 3.0mm, 2.0mm, 1.5mm, 1.0
mm, 0.7 mm and 0.5 mm, and the detector was connected to a potentiostat (constant voltage power supply), a coulomb meter, an XY recorder and a time recorder as shown in FIG. 3 for automatic measurement. A Pt plated plate was used for the anode plate and a carbon plate was used for the cathode plate. First, a small amount of KNO ₃ powder was put in the sample holding hole of the detector, 58 mg of dehydrated sludge was sampled and administered to this, and electrolyzed at an applied voltage of 2.5 V for 70 seconds. current by recorder - creating an electrical quantity curve, current - calculated by comprising a water content in the sample from the outside挿電air amount of electric quantity curve (outer挿電air amount ^{× 18 × 10 3/2 ×} 96500) formula, obtained The water content was calculated by dividing the obtained water content by the sampled amount (58 mg). The current-time curve when the electrode interval is 1 mm is shown in FIG. 4, but the extrapolated value could not be obtained due to the curvilinear decrease of the current, but the current-electric quantity curve shown in FIG. Fell linearly, and the extrapolated value up to the background current level could be easily obtained.
The results obtained are shown in Table 1. The same dehydrated sludge 58mg
The water content by the dry weighing method (Ket infrared drying moisture meter) was 79.8%. From Table 1, it was found that the water content can be accurately measured from the extrapolated value of the current-electricity curve in the detector having the electrode interval of 2 mm or less.

[0009]

[Table 1]

Example 6 The coulometric detector shown in FIG. 1 (b) was connected to the automatic measuring apparatus shown in FIG. 3 to quantify reduced L-ascorbic acid (vitamin C) in orange juice. A filter paper capable of supporting 0.5 ml of the solution is used as the sample solution impregnated mat, and a voltage of 0.8 V is applied to the anode plate (Pt plating plate) and the cathode plate (carbon plate) with an electrode interval of 0.5 mm to 20
Electrolysis was performed for 2 seconds, and vitamin C in orange juice was measured 10 times. Relative standard deviation at this time is 4.3%
The difference between this average value and the average value by the indophenol method was 2.6%.

[0011]

According to coulometry detector of the present invention, it is possible to quickly measure the absolute quantification of the electrolytic substance in the sample from the quantity of electricity extrapolated value, also not using carbon felt electrodes Therefore, maintenance of the detector is easy.

[Brief description of drawings]

FIG. 1 is an explanatory view of a coulometric detector showing an embodiment of the present invention, in which (a) is a detector having a sample holding hole, and (b) is a detector.
Indicates a detector equipped with a sample solution-impregnated mat.

FIG. 2A is a current-electricity curve diagram, and FIG. 2B is a log-time curve diagram of current.

FIG. 3 shows a flowchart of an automatic measuring device using the detector of the present invention.

FIG. 4 shows a current-time curve diagram when the electrode interval is 1 mm.

FIG. 5 shows a current-electrical quantity curve diagram when the electrode interval is 1 mm.

[Explanation of symbols]

1A ... Anode plate, 1B ... Cathode plate, 2 ... Sample holding hole, 3 ... Sample solution impregnated mat, 4 ... Lead wire, 5 ... Coulometric detector, 6A, 6B ... Non-conductive plate, 7 ... Coupler.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Negishi Akira 1-4, Umezono, Tsukuba-shi, Ibaraki Electronic Technology Research Institute, Industrial Technology Institute (72) Osamu Hamamoto 1 Hachiman Kaigan Dori, Ichihara-shi, Chiba Mitsui Shipbuilding Co., Ltd. Chiba Works (72) Inventor Keiichi Watanabe 1 Yawata Kaigan Dori, Ichihara-shi, Chiba Mitsui Shipbuilding Co., Ltd. Chiba Works Inspector Yaichi Inoue (56) Reference JP-A-3-180747 (JP, A) JP-A-2-140655 (JP, A)

Claims (1)

[Claims] 1. A connected to the power source and instrumentation
Comprising a negative electrode plate and the anode plate, and a sample-holding hole or sample liquid impregnated mat for holding a sample to both said electrodes plates, and electrostatic
At the time of solution, the both electrode plates are
A coulometric detector characterized by facing each other at intervals of 2 mm or less through an immersion mat .