Method for controlling and eliminating errors
        The magnitude of the error is directly related to the accuracy and accuracy of the analysis results. Measures to reduce errors are as follows:
        1. Select the sample correctly
        The amount of sample is closely related to the accuracy of the analysis result. In constant analysis, too much or too little or too much weight directly affects accuracy. In colorimetric analysis, the content and absorbance tend to be linear in a certain range. This requires measurement when reading within this range to improve accuracy. This can be achieved by increasing the amount of sampling or changing the dilution factor.
        2. increase the number of parallel measurements
       The more the number of accidental errors is measured, the closer the average is to the true value, and the accidental error can be offset, so the analysis is more reliable. Generally requires the number of measurements per sample should not be less than two times, if more accurate determination, the number of analysis should be more.
        3. controlled trial
        Contrast test is an effective method to check system errors. In controlled trials, samples of known results are often performed in exactly the same procedure as tested samples, or by different units and personnel, and finally the results are compared. This can offset the error caused by many unknown factors.
        4. blank test
       In the process of sample determination, the same method of operation and reagents are used, and the blank test is performed without the added substance. When the blank value is deducted from the measured value, the system error caused by impurities and interferences in the reagent can be counteracted.
        5. Calibration instruments and calibration solutions
        All kinds of measurement instruments, such as laboratory electronic balance, Polarimeter, spectrophotometer, and pipette burets volumetric flask, the accurate analysis must be calibrated, and is used in the calculation of positive. A variety of standard solutions (especially those which are susceptible to change) shall be calibrated regularly to ensure the concentration and quality of the standard solution.
        6. strictly abide by the operating procedures
        The technical conditions stipulated in the method of analysis shall be strictly observed. The method of analysis stipulated by the state or the competent department shall not be altered without the consent of the relevant departments.

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