JPS59212740A - Method and apparatus for measuring concentration of plating solution - Google Patents

Abstract

PURPOSE:To detect rapidly and precisely the concn. of Fe<3+> with a simple apparatus by injecting a fixed amt. of a plating soln. into the stream of a reaction soln. contg. a reaction reagent, allowing to pass the soln. through a small-sized tube, and measuring the change in the absorbance of the reaction soln. CONSTITUTION:A sample of a plating soln. from a sample supply source 1 is sent to an injector 3 through one solenoid valve selected from solenoid valves 2. Meanwhile, a reaction soln. 4 is sent to the injector 3 by a proportioning pump 5. After passing through the injector 3, the reaction soln. which is injected with a sample soln. passes through a small-sized tube 6, and flows into a measuring cell 7. By measuring the absorbance with an absorptiometer consisting of the cell 7, a light source 8, an interference filter 9, and a photodetector 10, the concn. of Fe<3+> can be measured rapidly and precisely with the simple apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for simply and quickly measuring the Fe3+ concentration in an electroplating solution and an apparatus used therefor.

The electroplating solution contains iron ions, either by dissolving the steel sheet in the plating solution or by actively adding an iron source as in the case of alloy plating containing iron. Iron ions include Fe2+ and Fe, and Fe2+ is oxidized to Fe3+ at the anode. Since this Fe'' affects the plating efficiency and the properties of the plating film, it is necessary to maintain a predetermined concentration.

(Prior art) In order to control this Fe3+ to a predetermined concentration,
Self-reliance is measured, and the method of measurement is as follows:
Conventionally, methods such as spectrophotometry and reductive titration have been used. However, these three measurement methods had drawbacks as described below.

1. Absorbance method (at continuous dilution method) A method in which a reaction solution containing a coloring reagent that selectively reacts with Fe3+ is collected and mixed together with a plating solution using a constant flow pump. The mixing ratio is a factor that determines analysis accuracy. Therefore, it is necessary to maintain a constant mixing ratio, that is, the flow rate ratio, for a long period of time.This requires an expensive constant flow pump, and requires frequent maintenance and inspection. In addition, in order to collect the sample solution with high precision, a pump with a flow rate of at least several d/min is used, and on the other hand, in order to flow the reaction solution at a flow rate of at least 10 times the corresponding flow rate,
Too much reaction solution is used.

{l1} Intermittent dilution method This is a method in which a fixed volume of sample solution and a diluted solution containing a reaction reagent are collected in a mixing container and mixed until homogeneous.Then, the solution is introduced into an absorptiometer and the absorbance is measured.One sample Since the time required for each analysis is long, it is not suitable when frequent analyzes are required due to large concentration changes, or when analyzing multiple locations with one device.

2. Reductive titration method A fixed volume of sample solution is taken into a reaction vessel, a sanitary reagent of known concentration is sequentially added dropwise, and the concentration of Fe3+ is determined from the amount of liquid required to reach the equivalence point. This method also has the disadvantage of requiring a long analysis time. Also,
Since the reducing reagent is unstable, it must be replaced and inspected frequently, making it unsuitable for long-term unattended operation.

(Object of the invention) The present invention overcomes these drawbacks in the prior art and
The purpose of this method is to quickly and accurately measure the (Fe''+ concentration) using a simple device.

(Structure of the Invention) In the present invention, instead of completely mixing the reaction solution and sample solution, the reaction solution and the sample solution are mixed with Fe carbon under a transient state of flowing at a constant flow rate in a thin tube. (This ensured reproducibility. When a fixed volume of sample solution is instantaneously injected into a reaction solution flowing at a constant flow rate and flows through a narrow tube with a uniform inner diameter, the sample solution The flowing C gradually disperses and dilutes the reaction solution ζ.In this way, by continuously measuring the absorbance of the mixed solution under certain conditions, it is possible to use a small amount of reagents. The Fe3+ concentration can be measured in a short time (and with high precision).

That is, the method of the present invention involves injecting a certain amount of plating solution into a flow of anti-WhM solution containing a coloring reagent and measuring the change in absorbance of the reaction solution after passing through a thin tube. , to measure Fe.''! in the electrical paint solution.

In addition, in order to expand the quantitative range, measurements should be performed at a wavelength shifted from the peak position of the coloring reagent rather than at its maximum absorption wavelength, and it is desirable to use sulfosalicylic acid or thiocyanate as a suitable reagent for this purpose.

The apparatus for carrying out this method includes a syringe for injecting a certain amount of plating solution into a path along which a reaction solution containing a coloring reagent is sent to the spectrophotometer, and a syringe for injecting a certain amount of the plating solution, and the reaction solution together with the injected plating solution. It is equipped with a thin tube through which water flows.

FIG. 1 shows the device. Sample source 1
By selecting one of the supply lines via the solenoid valve 2, the test bath liquid is sent to the syringe B. On the other hand, the reaction solution 4 is sent to the syringe B by a constant flow pump 5. The injector 6 is equipped with a flow path for flowing the sample solution and a flow path for flowing the reaction solution, and by switching these flow paths to each other, the sampled liquid accumulated in the flow path for the sample slip liquid can be transferred to the flow path for the reaction solution. Inject the medium. Reaction m in which sample liquid was injected
After the liquid leaves the 5 syringe 6, it passes through a thin tube 6 and flows into the absorbance measuring cell. The spectrophotometer comprises an absorption countermeasure cell 7, a light source 8 such as a tungsten lamp, an interference filter 9, and a detector 10 that converts the amount of light into an electrical signal.

The amount of sample to be injected should be as small as possible in order to increase the dilution rate, but from the viewpoint of reproducibility it is required to be 5 μm or more. The injection method is to fill a fixed volume tube 6 attached to the inside or outside of the switching cock with the sample solution, and then switch the flow path to pour the reaction G solution into this part and drain it out. The amount is not affected by pump flow rate, etc.

A suitable inner diameter of the tube used to mix the injected sample solution and reaction solution is 02 to 1-Qmm.If the tube diameter is larger than this value, reproducibility will deteriorate, and conversely, the Yoshinai pressure will decrease and the pump, etc. Failure rate increases. In addition, the length of the tube from the injector 6 to the detector ioI is preferably long in order to increase the dilution rate, but if it is too long, the internal pressure will rise too much and the analysis time will become long, so it is 0.5 to 5 m. is good. Further, the capacity of the flow path through which the sample solution flows and the flow path through which the reaction solution flows, which are provided with 64 injectors, is usually about 15 μm.

The sample injection volume was 15μ, and the inner diameter of the reaction tube was 0.5m.
m and the length is 3 m, the dilution rate is about 1/10 at the detection peak position. On the other hand, the sensitivity of the reagent that develops the color of Fe3+ is several tens of pr) m or less when using a commonly used absorbance measurement cell with an optical path length of 10 mm, and the concentration range of Fe3+ that can be measured as is is several tens of pr).
It is limited to 0 ppm or less.

Therefore, in order to expand the measurement range, the absorption cell was set to 2 mm, and the wavelength at which the absorbance was measured was shifted from the peak position to lower the sensitivity. In general (the method of measuring absorbance at a position other than the peak position of the absorption spectrum often does not follow Beer's law), when thiocyanate or salicylic acid is used as a coloring reagent, It was confirmed that even at a wavelength that is 1/10 or less of the absorbance at the peak position, the deviation from Beer's law is small l/'1.

Next, the features of the present invention will be specifically explained based on a disaster example.

(Example) Ammonium thiocyanate solution 'lfi-4 with a concentration of 1% was sent through a metering bomb 5 to a syringe 6.As a metering bomb 5, a plunger type pump with excellent long-term stability was used, and the flow rate was adjusted. The flow rate of ammonium thiocyanate solution 4 leaving the syringe 6 was 2 mt/min.
After passing through the Teflon tube 6 with a length of 6 m, the optical path length υ
nm absorbance measurement sensor 7

In this case, a 640 nm interference filter 9 was used, and the absorption at this wavelength C2 was measured.

The reason for measuring at that wavelength will be explained using FIG. 2. Figure 2 shows 10M when ioppm Fe3+ is colored with ammonium thiocyanate and sulfosalicylic acid.
The absorption spectrum obtained by absorbance measurement cell C is shown. The former has an absorption peak at 470 nm, and the latter at 500 nm. If absorbance is measured at these absorption peak positions, 4001) I) m and 2000 pp, respectively.
The upper limit of the measurable concentration is about m. However, when measuring the absorption near 64 Onm, which is the tail of the peak, it is 10.0 nm.
The quantitative range extends to 00 ppm.

Figure 6 is an example of a measurement signal detected by the apparatus shown in Figure 1.The peak is detected 25 seconds after sample injection, and the next sample can be injected in at most 50 seconds. , it has been shown that this is an extremely rapid analytical method.

Figure 4 is an example of the calibration curve for the device shown in Figure 1. In the figure, the horizontal axis is the concentration of Fe3+, and the vertical axis is the absorbance of the detected peak, indicating excellent linearity. The reproducibility accuracy of this analytical method is within 0.05% in the short term.
Even after a long period of several months, the accuracy was maintained within 2%.

In the examples described above, ammonium thiocyanate was used as the coloring reagent, but even when sulfosalicylic acid was used as the coloring reagent, high-precision measurements could be made rapidly.

[Brief explanation of the drawing]

Figure 1 shows the apparatus used in the present invention. In the figure, 1 is a sample supply source, 6 is a syringe, 4 is a reaction solution, 6 is a thin tube, and 7 is an absorbance measurement cell. Figure 2 shows the absorption spectrum when 10 ppm Fe3+ is colored with ammonium thiosinophosphate and sulfosalicylic acid. Figure 3 shows an example of the measurement signal detected by the apparatus shown in Figure 1. Fig. 4 shows an example of the calibration curve of the same device. 1 Sample source 2 Solenoid valve 6 Injector 4 Reaction solution 5 Bump 6 Tube 7 Absorbance measurement cell 8 Light source 9 Interference filter 10 Detector -266-

Claims (1)

[Claims] (1) A certain amount of plating solution is injected into the flow of the reaction solution containing the coloring reagent, and after passing through a thin tube,
A method for measuring pes+gfff in an electroplating solution, which measures the change in absorbance of a reaction solution as a % indicator. {2} Claim (11) characterized in that sulfosalicylic acid or thiocyanate is used as a coloring reagent
Method described. (3) A syringe for injecting a certain amount of plating solution and a strainer tube through which the reaction bath solution flows together with the injected plating solution are installed in the middle of the path for sending the reaction solution containing the coloring reagent to the spectrophotometer. Fe in electroplating solution characterized by
Concentration measuring device.