The function and impact of value traceability in chemical analysis measurements

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　　The function and impact of value traceability in chemical analysis measurements Abstract: Various industries such as industrial production, scientific research experiments, medical testing, and food supervision all rely on chemical analysis instruments to analyze raw materials, sample specimens, and products. The accuracy and reliability of the measurement results play a decisive role in product quality and even in human safety. To ensure the accuracy and reliability of chemical measurement results, aside from external factors such as the environment and the operators, it is more important to conduct metrological verification/calibration in order to establish a traceability for the values obtained by chemical analysis instruments and to analyze the measurement results. The existing relevant materials and literature in our country only describe and study the metrological verification/calibration methods for a specific chemical analyzer; there is little analysis regarding whether the measurement data from such an instrument should be traced back to their origins, as well as the impact and effects of such tracing on the measurement data. This article summarizes the role and impact of value traceability in chemical analysis by examining the measurement principles of common laboratory chemical analysis instruments (such as pH meters, conductivity meters, UV-Vis spectrophotometers, turbidimeters, atomic fluorescence photometers, etc.), the methods for metrological verification/calibration, the metrological standards used for value traceability, the changes in measurement data and results before and after verification/calibration, and an assessment of the effects of these changes on industries such as economics, the environment, and food safety. The data in this article come from statistics on the measurement results of common chemical analysis instruments that have undergone metrological verification/calibration in Gansu Province over the past four years, in accordance with **metrological verification regulations or calibration standards. The information is detailed and reliable, the subjects of study are verifiable, and the research findings are both representative and generalizable; thus achieving the ultimate goal of providing strong support for the development of chemical metrology work in our province. 　　Keywords: traceability of measurement values, chemical analysis, measurement, applications. Research on the traceability of measurement values began quite early; since this is a fairly complex system, considerable time and effort are required in the research process. Based on the current results, many aspects of chemical analysis and measurement align with the principles of value traceability. If these two approaches can be effectively combined and harmony can be achieved in other areas as well, it will surely enable chemical analysis and measurement to be carried out more effectively, thereby strengthening the inspection and analysis of products and reducing the influx of hazardous products. Here, this paper mainly discusses the role and applications of value traceability in chemical analysis and measurement. 　　1 Overview of Value Tracing In chemical analysis and measurement, there was a long lack of standards for measurement, which resulted in products having varying performance and characteristics; as a result, it was difficult for them to gain the approval of buyers once they reached the market. At the same time, due to the significant differences in standards, the reliability of many products is low, and they may even pose certain risks. Therefore, research on measurement criteria can provide essential assistance for chemical analysis and measurement. The traceability system for measurement values has yielded very fruitful results in current research efforts. Conceptually, traceability of quantities refers to an uninterrupted chain of comparisons with specified uncertainties; through this chain, it is possible to relate the values of measurement results or measurement standards to established reference standards. We refer to this property as the traceability of quantities. To enable better application of value traceability in practical work, a series of derivative products have been developed, among which value traceability charts are particularly notable. This chart is a hierarchical diagram that illustrates the relationship between the metrological characteristics of a measuring instrument and the metrological standards, enabling a better representation of the standards and characteristics in chemical analysis measurements as well as providing a comprehensive assessment of the object being tested. 　　2 Metrological verification and calibration: The application of value traceability is not carried out arbitrarily based on theory, but rather needs to be implemented in light of objective realities. Currently, the main technical methods for applying value traceability to chemical analysis measurements are metrological verification and calibration. Firstly, calibration work is primarily aimed at assessing the corresponding performance of measuring instruments, in order to ensure that the work being carried out is of satisfactory quality; if it is not, the reasons for the deficiency and the specific aspects involved are analyzed further. Furthermore, when applying metrological verification methods, it is necessary to emphasize the transfer of measurement values in order to avoid inaccuracies and inconsistencies in those values. Secondly, metrological calibration is also extremely important; it plays a significant positive role in ensuring the traceability of measurement values as well as in carrying out chemical analysis measurements. Measurement calibration primarily involves determining the specific numerical values indicated by measuring instruments or appropriate measurement systems under strictly defined conditions. At the same time, measurement calibration can be accompanied by a set of specific operational procedures corresponding to the relationship between quantities as defined by standards, and these procedures can be adjusted in response to changes in objective conditions. 　　3 The role and impact of value tracing in chemical analysis and measurement (1) The impact and role of value tracing on the measurement data from pH meters. pH meters are one of the most commonly used chemical instruments, and they play a significant role in analytical measurements. Generally, when using a pH meter for analysis and testing, conventional methods are employed, resulting in results of high reliability. However, if analysis and measurement are carried out strictly in accordance with traditional standards, the data obtained by pH meters are likely to differ; even if the differences are small, special attention should still be paid to them. In chemistry, even very small differences can lead to significant reactions. For example, in a pH analysis of a water sample, the conventional method yields a pH value of 7.00; however, if this value is questioned, it is necessary to employ value traceability, that is, metrological verification and calibration. 　　Trace the electrode values back to **certified standard pH substances**. As a form of metrological calibration in the value traceability process, it differs from routine laboratory calibration. Metrological calibration requires performing volume determination under controlled environmental conditions, using traceable volumetric flasks to prepare traceable standard buffer solutions. Furthermore, when calibrating the electrode using standard buffer solutions for a two-point calibration, the offset value and slope value are not the empirical value of 7.00 pH; rather, calibration should be carried out based on the different pH values at various temperatures provided in the certificate of analysis for the standard substances. 　　(2) The impact and role of value tracing on UV-Vis wavelength range data. In chemical analysis and testing, UV-Vis wavelength range data is also a commonly used parameter for assessment. By applying value tracing to this data, its impact and role are evident in the following aspects: First, the data regarding UV-Vis wavelength ranges becomes more accurate, eliminating the need for estimates; moreover, it is possible to analyze specific objective conditions in order to ensure that all data correspond to reality. Secondly, when analyzing UV-Vis spectral width data, the analysis steps were simplified by focusing directly on the more important data points. This essentially improved the quality of chemical analysis and measurement tasks, enabling ideal results to be obtained whether testing products or other substances. 　　4 Conclusion This paper discusses the role and impact of value tracing in chemical analysis and measurement. Based on current practices, the application of value tracing provides significant assistance in chemical analysis and measurement; it enables these processes to proceed more rapidly in many aspects, reduces numerous problems, and also helps to meet the requirements for improved accuracy. In the future, in-depth research should be conducted on the traceability of measurement values to understand their greater role in chemical analysis and measurement, and more approaches should be developed to achieve this. 　　References: Guo Aihua, Li Ye, Wang Wei. 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