Water Quality Analysis Kits "Test Wako" Series

• [Active Cl-Test wako] A residual chlorine test kit based on the color reaction of 2,2’-Azinobis(3-ethylbenzothiazoline-6-sulfonic Acid) (ABTS).
  The kit is easy to use and allows both free and combined chlorine to be measured in the same test tube based on their different color-development rates.​
• [Active Cl-DPD Test wako] A residual chlorine test kit based on the color reaction of N,N-Diethyl-p-phenylenediamine Sulfate (DPD).
  Since DPD tablets are used, no weighing is required, allowing residual chlorine to be measured easily.
• [Phenol-Test wako] A phenol test kit based on the 4-Aminoantipyrine method.
  Simply add a color-developing reagent tablet to the test water for rapid and highly accurate measurement of phenols.
• [Formaldehyde-Test wako] A formaldehyde test kit based on the color reaction of 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole.
  Simply add the reagent solutions in sequence to measure trace amounts of formaldehyde easily, selectively, and with high sensitivity.​

Measurement Procedure

1. (1) Attach the packing (cap seal) to the test tube.

   

2. (2) Add 6 mL of test water (up to the marked line).

   

3. (3) Add one color-developing reagent tablet.

   

4. (4) Cover the mouth of the test tube with the packing and shake for 3 seconds (about 5 times).

   

5. (5) Let stand for 5 seconds, then immediately compare the color with the color chart from a distance of 1–2 cm to determine the free chlorine concentration.

   

6. (6) After the colorimetric comparison, shake the tube to completely dissolve the reagent tablet.

   

7. (7) After 5 minutes, compare the color with the color chart from a distance of 1–2 cm to determine the total chlorine concentration.

   

Precautions for Use

• When measuring free chlorine concentration, perform the colorimetric comparison within 10 seconds after adding the tablet, since a longer standing time will cause the reagent to react with combined chlorine as well. In this case, incomplete dissolution of the color-developing reagent tablet does not affect the measured value.
• Compare the color with the color chart under bright natural light.​
• Use only thoroughly cleaned dedicated test tubes.

References

1. S. Hunig, et al.: Liebigs Ann. Chem., 676, 36 (1964)
2. H. Lang, et al.: Z. Analyt. Chem., 201, 321 (1964)

1. Measurement Procedure for Free Residual Chlorine (as Cl, mg/L)

(1) Attach the packing (cap seal) to the Active Cl-DPD Test Tube* and add 5 mL of test water (up to the marked line).	(2) Add one drop of phosphate buffer solution to the test water.	(3) Add one DPD tablet.
(4) Cover the mouth of the test tube with the packing and shake vigorously for about 5 seconds.	(5) Compare the color developed in the sample with the color chart and read the free residual chlorine concentration. (Read the color of the sample from the side of the test tube.)​

* When using a test tube other than the Active Cl-DPD Test Tube, use a tube with a diameter of 1.5 cm and a height of 10 cm. Ensure that the concentration can be read appropriately by comparing the developed color with the color chart after adding the specified volume of a sample of known concentration.​

2. Measurement Procedure for Total Residual Chlorine (as Cl, mg/L)

(1) Add one KI tablet to the sample obtained in Step 1-(5). Mix gently, then let stand for about 2 minutes.​	(2) Compare the color developed in the sample with the color chart and read the total residual chlorine concentration. (Read the color of the sample from the side of the test tube.)​

3. Calculation of Combined Residual Chlorine (as Cl, mg/L)

Calculate the combined residual chlorine concentration by subtracting the free residual chlorine concentration determined in Procedure 1 from the total residual chlorine concentration determined in Procedure 2.​

Precautions for Use

• If the residual chlorine concentration in the test water exceeds 2 mg/L, dilute the sample so that the residual chlorine concentration falls within the range of 0.05 to 2.0 mg/L before measurement.
• A small amount of anhydrous sodium sulfate contained in the DPD tablet may remain undissolved; however, this does not affect the measurement results.

Reference

Ministry of Health and Welfare, Bureau of Environmental Health, Water Supply and Environment Department (supervised): Standard Methods for Water Examination, 210, (Japan Water Works Association) (1993).

Measurement Procedure

(1) Add the test water to the marked line (about 10 mL).	(2) Add one color-developing reagent tablet.	(3) Cap the test tube with the polyethylene stopper and shake thoroughly until the tablet has completely dissolved.​
(4) Compare the color of the test water with the color chart and read the phenol concentration.

Precautions for Use

• Store the color-developing reagent tablet protected from moisture and light.
• The presence of oxidizing or reducing substances in the test water may affect the measurement results.
• Test water containing turbidity or oil should be filtered prior to measurement. For more accurate determination, pretreat the sample according to the testing methods for industrial waste water (JIS K 0102-1971) before measurement.
• If the phenol concentration in the test water is 10 ppm or higher, dilute the test water to about 5 ppm and then perform the measurement.

Measurement Procedure

(1) Pipette 2.0 mL each of the test sample, standard solution, and distilled water (blank) into separate test tubes.​​	(2) Add 2.0 mL of alkaline solution to each test tube.	(3) Add 2.0 mL of the color-developing solution to each test tube and mix thoroughly.
(4) Let the mixtures stand at 20–35°C for 15 minutes.​	(5) Add 2.0 mL of the oxidizing solution to each test tube.	(6) Shake each test tube until foaming stops (about 15 seconds).​
(7) Measure the absorbance of the test sample and standard solution using the blank as a control. Determine the formaldehyde concentration from the calibration curve prepared using the standard solution.

For details on preparation of the formaldehyde standard solution and construction of the calibration curve, click here.​

Precautions for Use

• The developed color is stable, and absorbance shows no significant change for up to 2 hours after color development.
• Maintain the standing temperature at 20–35°C after adding the color-developing solution.​
• Do not leave any reagent solution open for an extended period. Recap tightly immediately after use and store properly.​
• Because this kit reacts specifically with formaldehyde, the presence of ketones, esters, alcohols, or nitrogen-containing compounds at concentrations of up to about 1,000 ppm has virtually no effect on the measurement.
• In the presence of aldehydes other than formaldehyde, there is no effect at low concentrations (up to 5 ppm), but color development occurs at high concentrations.
• Because the reagent solutions are alkaline, rinse thoroughly with water immediately if they come into contact with the skin.​