Chemical purity reagents shall be selected when preparing common test solutions and cleaning solutions for quantitative or qualitative tests.
The purity of chemical reagents has a great impact on the accuracy of test results, but the higher the purity, the more expensive the price. Therefore, reagents of different specifications should be selected according to the requirements of test tasks, test methods and accuracy of test results.
The selection principle of chemical reagents is that, on the premise of meeting the test requirements, the selection level of reagents should be as low as possible without causing waste, and the level of reagents should not be arbitrarily reduced to reduce the accuracy of test results. The following points are usually considered when selecting reagents.
1. In order to reduce the blank value, reagents with high purity specifications should be selected to reduce the blank value for arbitration detection and detection purity reagents.
2. For the standard titration solution prepared by the intermediate method of titration test, the pure test reagent shall be selected for preparation, and then the reference material shall be used for calibration. If the requirements for the test results are not very high, you can also use the high-grade purity or purity test to replace the reference reagent for calibration. Other reagents used in titration tests are usually pure reagents.
3. Instrument detection generally uses high-grade pure or special reagents, and high-purity reagents should be used when measuring trace components.
4. Chemical purity reagents shall be selected when preparing common test solutions and cleaning solutions for quantitative or qualitative tests. It should be noted that the specifications and marks of imported chemical reagents are different from those of current chemical reagents in China, so the requirements for the level of reagents are very high, and there are also special requirements for the purity of experimental water and containers and the cleanliness of instruments. In addition, because the specifications and marks of imported chemical reagents are different from those of current chemical reagents in China, you can refer to relevant chemical manuals for differences.
The above are the classification and selection methods of chemical water quality testing agents.