The effect of instrument variables on calculation factors for standardisation of colorimetric analyses.
A number of colorimetric methods, particularly enzyme activity assays, are usually standardised using calculation factors based on the molar absorptivity of a principle reactant or product. Such methods are subject to long-term variation. The relationship between long-term variation in results and instrument variables affecting calculation factors has not been quantitated. In this study, we have shown that, on a centrifugal analyser having a within-run coefficient of variation of less than 1%, instrument variables affecting calculation factor alone could result in changes in results of up to 8.5% over 75 days. We therefore advocate daily use of a solution of potassium dichromate to monitor instrument variables that can independently affect calculation factors and within-run imprecision. This procedure is useful for maintaining long-term performance and for differentiating problems of instrumental or chemical origin.
D001322:Autoanalysis / Q000295:instrumentation; D002498:Centrifugation / Q000295:instrumentation; D008433:Mathematics; D011192:Potassium Dichromate / Q000032:analysis; D012015:Reference Standards; D013048:Specimen Handling; D013053:Spectrophotometry / Q000295:instrumentation / Q000592:standards*
D011192:Potassium Dichromate