■Waiting time changes with water temperature! The reaction of color development varies depending on the water temperature. Therefore, it is important to adhere to the reaction time specified in the instructions. There are examples of varying waiting times based on water temperature, such as a guideline that states for COD measurement, it should be 6 minutes and 30 seconds for temperatures below 5°C and 4 minutes for temperatures between 26-30°C. The colder the water temperature, such as in winter outdoors, the longer the waiting time will be. Additionally, reading the results after the specified time may lead to discrepancies in the values. ■Is the amount inhaled a cause of discrepancies? The tube contains a fixed amount of reagent and is designed to assume a certain volume of sample water is inhaled. If the amount inhaled is too much or too little, the values read will also be inaccurate. ■Does the method of reading colors cause differences? The standard color and the color in between the standard colors are read as intermediate values. This reading can vary slightly depending on the person or the day. There are also cases where the same water is measured multiple times. ■Be cautious of dirt on hands and containers Dirty containers or hands can significantly affect the results. Wash your hands before measuring and use a clean container to take the sample water.

■What types of water are difficult to handle? 1. Water with color or turbidity: To avoid interference with color determination, respond by diluting, standing, or filtering. 2. Water that is strongly acidic or alkaline: It may fall outside the pH conditions where reagents work. 3. Water that is too concentrated: If it exceeds the range, dilute it and measure again. 4. Water containing many other substances: Reactions may be hindered. For example, in kits for fluoride, fluoride in the form of boron fluoride cannot be measured. ■Is the COD (pack test) value the same as the official method? The COD in the pack test is measured by reacting in alkaline conditions at room temperature for about 5 minutes. This differs from the commonly used JIS CODMn (30 minutes at 100°C). When used for factory wastewater, it is essential to verify the correlation with the JIS method. ■In what situations is it useful? Simple water quality testing kits can be used to detect changes in concentration if conditions are followed. On the other hand, in water where coexisting substances may have an impact, it is also necessary to compare results with the official method. Our company also offers consultations on how to measure water quality, including the rental of measuring devices like COD. Please feel free to contact us first.