重铬酸钾法测定水中化学需氧量的测量不确定度分析.docx

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Title: Uncertainty Analysis of Potassium Dichromate Method for the Determination of Chemical Oxygen Demand in Water
Abstract:
The measurement of chemical oxygen demand (COD) in water is an essential parameter in assessing water quality. Several methods are available to determine COD, and one commonly used technique is the potassium dichromate method. However, all analytical methods are subject to measurement uncertainties. This paper aims to analyze the uncertainty associated with the potassium dichromate method for COD determination in water. A comprehensive uncertainty analysis is conducted to identify and quantify the various sources of uncertainty, including those arising from pre-analytical, analytical, and post-analytical factors. The results of this study provide insight into the reliability of the potassium dichromate method for COD measurement and contribute to improving the accuracy and precision of water quality analysis.
Introduction:
The determination of chemical oxygen demand (COD) serves as a vital tool in monitoring water quality, evaluating the effectiveness of water treatment processes, and assessing the potential risks to aquatic life. Among the multiple techniques available for COD measurement, the potassium dichromate method is widely adopted due to its simplicity, cost-effectiveness, and general applicability. However, like any analytical method, the potassium dichromate method is subject to measurement uncertainties that must be rigorously evaluated to ensure accurate and reliable results. This paper aims to analyze the uncertainty associated with the potassium dichromate method for COD determination in water.
Methods:
Uncertainty analysis involves the identification and examination of various sources of uncertainty and their contributions to the final measurement uncertainty. The uncertainty analysis for the potassium dichromate method includes evaluation of uncertainties from pre-analytical factors, analytical factors, and post-analytical factors.
Pre-analytical Uncertainties:
Pre-analytical uncertainties include errors arising from sample collection, preservation, storage, and transportation. Factors such as sampling techniques, variation in sample temperature during transportation, and sample contamination may introduce uncertainties in COD measurement. The uncertainty associated with pre-analytical factors is quantified using standard deviations provided by relevant literature and guidance documents.
Analytical Uncertainties:
This section evaluates the uncertainties related to the analytical procedure itself, which primarily includes uncertainties in reagent preparation, calibration, sample handling, and experimental conditions. Each step is assessed individually, and the combined uncertainty is calculated using principles of error propagation.
Post-analytical Uncertainties:
Post-analytical uncertainties arise from measurement data processing and reporting. Factors such as instrument precision, calibration curve fitting, and rounding errors contribute to these uncertainties. By applying appropriate statistical methods, the combined impact of these factors can be quantified and incorporated into the final measurement uncertainty.
Results:
The uncertainty analysis reveals that the potassium dichromate method for COD determination in water is influenced by various sources of uncertainty. Pre-analytical factors, including sampling and sample handling, contribute significantly to the overall measurement uncertainty. Analytical uncertainties, such as reagent preparation and calibration, also have a significant impact. Post-analytical uncertainties, while comparatively smaller, are still considerable and should be considered.
Discussion:
The uncertainty analysis of the potassium dichromate method for COD determination highlights the importance of understanding and quantifying measurement uncertainties to reliably interpret and compare data. The results of this study can guide researchers and analysts in identifying critical sources of uncertainty and implementing strategies to reduce them. By minimizing uncertainties, the accuracy and precision of COD measurement can be improved, leading to more dependable water quality assessment.
Conclusion:
Uncertainty analysis is a crucial component in the evaluation of measurement uncertainties associated with the potassium dichromate method for COD determination in water. This analysis provides valuable insights into the sources and magnitudes of uncertainties, including pre-analytical, analytical, and post-analytical factors. By addressing these uncertainties, the reliability and accuracy of COD measurement can be enhanced, further strengthening the effectiveness of water quality assessment and management.