高锰酸盐指数快速检测试剂显色机制与水环境影响因素分析OA

Permanganate index(CODMn)is a critical indicator for water quality assessment.Rapid test kits based on the permanganate oxidation colorimetric principle are widely used for on-site monitoring due to their operational simplicity and fast response.However,a systematic evaluation of their reaction mechanisms and sources of measurement errors is still lacking.In this study,three representative CODMn rapid test kits were investigated using ultraviolet-visible(UV-Vis)spectrophotometry combined with visual colorimetry,aiming to elucidate their color development mechanisms,quantitative characteristics,and key influencing factors.The results indicated that the rapid test kits exhibited characteristic absorption bands at 512-562 nm and 588-622 nm,which were associated with the conversion of MnO4-to MnO42-.A good linear relationship between absorbance and CODMn concentration was observed in the range of 0-13 mg/L(r2>0.98).Within higher concentration ranges,introducing the absorbance of MnO2 as a compensation term was necessary to improve quantitative accuracy(r2>0.99).Although visual colorimetry showed good correlation with theoretical CODMn values,it was subject to subjective factors,with coefficients of variation(CV)ranging from 7%to 20%,and errors were more pronounced at critical color thresholds.Further analysis revealed that water temperature,pH value,and salinity significantly affected the measurement results by influencing reaction kinetics.Specifically,acidic conditions and high salinity caused systematic deviations of approximately 15%or more.Ca2+may indirectly influence the MnO4-reduction process through hydration effects and changes in the ionic environment.The CODMn values obtained by rapid test kits were generally higher than those determined by the standard method(GB 11892-1989).When glucose was used as the reducing agent,the result from the standard method was approximately 53%of that from the rapid test kits,and this discrepancy was further amplified in complex environmental water matrices.These findings revealed the error sources of CODMn rapid test kits from the perspectives of reaction mechanisms and environmental influences,and proposed a calibration approach,thereby providing a basis for evaluating and optimizing their applicability under different water environmental conditions.