8 Questions and 8 Answers About Water Used for Food Testing

1. What's the difference between water used for food testing and ordinary tap water?

Ordinary tap water contains impurities such as minerals, microorganisms, and organic matter. These substances can interfere with test results, leading to data distortion. Water used for food testing is specially purified water that removes most contaminants, meeting the purity requirements of testing experiments.

2. How to choose the water quality grade for different testing items?

• Basic physicochemical tests (e.g., pH value, moisture determination): Grade III water is sufficient.

• Precision experiments such as chromatographic analysis (gas chromatography, liquid chromatography), and heavy metal detection: Grade I ultrapure water is required to avoid problems such as impurities and baseline drift.
  

• Microbiological testing: Sterile ultrapure water is required to prevent microbial contamination of the sample.
  

3. Does pure water need to be filtered before use? Why? 

Filtering is recommended, especially for use with precision instruments such as liquid chromatography and ion chromatography. Filtration removes potentially small particles and colloidal substances from the water, preventing clogging of instrument tubing and damage to precision components like the sampler. It also reduces interference from impurities on the detection signal, resulting in more stable results.

4. When testing water quality in-house, which indicators should be the focus?

Four key indicators to focus on: conductivity (reflecting ion content), total organic carbon (TOC, reflecting residual organic matter), microbial content (for water used in microbiological testing), and particulate matter count (for water used with precision instruments). Conductivity alone is insufficient; a comprehensive assessment is necessary.

5. How often should water quality testing be conducted? How should self-testing and external testing be combined?

• Self-testing: It is recommended to test key indicators (such as conductivity and TOC) weekly to ensure stable water quality.

• External testing: Submit water to a third-party testing agency at least once a year. If the laboratory replaces consumables for the pure water system or performs equipment repairs, it is recommended to submit the water for testing again to verify that the water quality meets standards.
  

6. What are the precautions for storing purified water? How long can it be stored?

• Storage Container: Use a sterile, sealed dedicated water storage tank to avoid contamination;

• Storage Environment: Store in a cool, dry, and contaminant-free place, away from chemicals and sources of microbial contamination;
  

7. How long after installation should a newly installed water purifier be inspected for accurate results?

It is not recommended to inspect the equipment immediately after installation. The internal pipes and filter media of the new equipment may contain impurities from the production process. It is recommended to flush the water for 24 hours before conducting water quality testing for more reliable results.

8. How do I determine when the consumables for my water purifier need to be replaced? In addition to equipment prompts, three signals can be used to determine the water quality:

• Changes in water quality indicators: Abnormal conductivity values exceeding the acceptable range;

• Slower water flow rate: Clogged filter cartridges will reduce water purification efficiency;
  

• Usage time: According to the consumables instruction manual and combined with laboratory water consumption, prepare to replace 1-2 weeks in advance (pretreatment columns are recommended every 3-6 months, reverse osmosis every 18-24 months, and ultrapure columns when the water conductivity is ≥0.2 μS/cm; specific details vary depending on the model and water consumption).