To judge whether the standard sample valuation procedure is strict, we can consider multiple dimensions such as the valuation institution's qualifications, valuation methods, quality control, uncertainty assessment, data review and reporting:
Qualification and reputation of valuation institutions
- Professional and authoritative institutions: Strict valuation procedures are usually implemented by professional and authoritative institutions. These institutions have deep technical accumulation and rich experience in related fields, such as national metrology institutes, internationally renowned standard material research institutions, etc. They have advanced equipment, professional technicians and a complete quality management system, which can provide reliable guarantees for valuation work. For example, the National Institute of Standards and Technology (NIST) of the United States is widely recognized worldwide, and the standard sample valuations it issues are highly credible.
- Good reputation record: Check the reputation record of the institution to understand the accuracy and reliability of the standard sample valuations it has published in the past. You can understand its reputation in the industry by consulting relevant industry literature and consulting other laboratories or professionals who have used the institution's standard samples. If an institution has always maintained high standards in its long-term work and rarely has inaccurate or controversial valuations, then its valuation procedures are more likely to be strict.
Scientificity and diversity of valuation methods
- Use recognized methods: Strict valuation procedures will use internationally or domestically recognized and fully validated analytical methods. For example, in the valuation of cholesterol standard samples, isotope dilution mass spectrometry (ID-MS) may be used, which is a high-precision absolute measurement method that can accurately determine the content of substances. In addition, other classical chemical analysis methods, such as high-performance liquid chromatography (HPLC), enzyme method, etc., may be combined to analyze samples from different angles to ensure the accuracy of valuation.
- Mutual verification of multiple methods: In order to improve the reliability of valuation, multiple methods based on different principles will be used to measure standard samples and verify the results with each other. If the results obtained by different methods are consistent with each other within a reasonable error range, confidence in the valuation results can be enhanced. For example, the content of a chemical component is determined by both the gravimetric method and the colorimetric method. If the results of the two methods are consistent, it means that the valuation results are more reliable.
Quality control measures
- Internal quality control: During the valuation process, the implementing agency will implement strict internal quality control measures. This includes regular calibration and maintenance of experimental equipment to ensure the accuracy and stability of the instrument; training and assessment of experimental personnel to ensure the standardization of operations; and detailed records of the experimental process for traceability and review. For example, calibration checks are performed before each use of the instrument, and experimental personnel can participate in the value setting work only after professional training and obtaining the corresponding qualifications.
- Participation in external quality assessment: Authoritative value setting agencies usually actively participate in international or domestic external quality assessment activities, and compare and communicate with other laboratories. By comparing their own value setting results with those of other laboratories, potential problems can be discovered and improved in a timely manner. If an agency performs well in external quality assessments and its value setting results are highly consistent with the results of other excellent laboratories, it means that its value setting procedure has a high reliability.
Uncertainty assessment
- Comprehensive assessment of uncertainty: A strict value setting procedure will conduct a comprehensive and in-depth assessment of the uncertainty of the value setting results. The sources of uncertainty include uncertainty of measurement methods, uncertainty of instruments, non-uniformity of samples, environmental factors and other aspects. By analyzing and quantifying these sources of uncertainty in detail, a reasonable uncertainty range can be given, so that users have a clear understanding of the accuracy of the valued results. For example, when reporting the valued results, information such as the expanded uncertainty and inclusion factor are given at the same time.
- Reasonable uncertainty level: The uncertainty level obtained by the assessment should meet the relevant standards and requirements. Generally speaking, the smaller the uncertainty, the more accurate and reliable the valued result. For high-level standard samples, the uncertainty requirements are more stringent. For example, in the valued values of some key metrological standard samples, the uncertainty may be controlled within a very small range to meet the needs of high-precision measurement.
Data review and reporting
- Strict data review process: The data generated during the valued process will undergo a strict review process. Experienced professionals will carefully check the data, including the accuracy, repeatability, and logic of the data. During the review process, statistical methods will be used to analyze the data to determine whether there are outliers or data with excessive deviations. If problems are found, they will be investigated and handled in a timely manner to ensure that the final valued data is true and reliable.
- Detailed report content: The value report of the standard sample should be detailed and complete, including the value method, measurement data, uncertainty assessment, quality control status and other information. The report should follow the relevant standards and specifications, with a unified format and clear content, so that users can understand the whole process of value determination and the reliability of the results. For example, the report will list in detail the specific operating steps, number of measurements, measurement results and the final value calculation process of each measurement method.