Estimation of the Measurement Uncertainty of the High-Performance Anion-Exchange Chromatographic Determination of Carbohydrates in Soluble (Instant) Coffee
The measurement uncertainty of the determination of free and total carbohydrates in soluble (instant) coffee using high-performance anion exchange chromatography with pulsed amperometric detection according to AOAC Method 995.13 and ISO standard 11292 was calculated. This method is
important with regard to monitoring several carbohydrate concentrations and is used to assess the authenticity of soluble coffee. We followed the recommendations of the ISO, Eurachem, and Valid Analytical Measurement (VAM) guides: individual uncertainty contributions u(x) were identified,
quantified, and expressed as relative standard deviations related to each specific source u(x)/x or RSD(x). Eventually, they were combined to yield the standard uncertainty and the relative standard uncertainty of a given carbohydrate concentration, c, that is respectively u(c) and u(c)/c.
As a result of our study, we could demonstrate that the overall repeatability of the carbohydrate determination in duplicate, RSD(r); the repeatability of the integration of the peak area of the carbohydrate standards, RSD(rarea(ST)); and the uncertainty of the linear calibration
model used in our laboratory, RSD (linST), are the most significant contributions to the total uncertainty. The u(c)/c values thus determined differ for each carbohydrate and depend on their concentrations. The least standard uncertainties that can be achieved are about 2.5%. The
question of trueness in the total carbohydrate assay (determination of monosaccharides obtained upon hydrolysis of coffee oligo- and polysaccharides) was addressed. For this purpose, we analyzed the data of 2 different collaborative trials in which our laboratory took part.
Document Type: Research Article
Nestlé Research Centre, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland.
Publication date: May 1, 2004
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The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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