title: Acid digestion, hydride evolution atomic absorption spectrophotometric method for determining arsenic and selenium in foods: Part I. Assessment of collaborative study.
abstract: Results obtained from the recent collaborative study of a hydride evolution atomic absorption spectrophotometric method for determining arsenic and selenium in foods have been studied intensively. Various parameters relating to the method have been considered: accuracy (excellent agreement between reference data and means over all laboratories for both model solutions and food samples; considerable bias for individual laboratories); precision within laboratory (repeatability coefficients of variation of 0.07-0.15) and among laboratories (reproducibility coefficients of variation of 0.13-0.28); frequency of outlying data from model solutions and biological samples (rejection rate from 9 to 29%); and detection limits (estimated as 80 and 120 ng/g for As and Se, respectively). Attempts were made to interrelate these parameters and to relate them to hydride generator characteristics and to other aspects of the procedure, namely, hydride generator type; absorbance-time peak width; standard curve slope, linearity, and precision; sample type; reagent blank magnitude; collaborator experience with sample treatment and hydride generation procedures, and departures from prescribed sample treatment procedure. On the basis of information from 28 laboratories using 16 different types of hydride generation apparatus, conducting 700 complete analyses and 2400 analyte quantitations on reagent blanks, 3 model solutions, and 13 different reference food samples with levels of As  and Se ranging from 0 to 15,000 and 0 to 4,000 ng/g, respectively, the authors conclude that the method suffers from both systematic error and imprecision, and hence recommend that the method not be adopted.
mesh_terms: D000143:Acids; D001151:Arsenic / Q000032:analysis*; D005069:Evaluation Studies as Topic; D005504:Food Analysis / Q000379:methods*; D008433:Mathematics; D012643:Selenium / Q000032:analysis*; D013054:Spectrophotometry, Atomic / Q000379:methods
chemical_list: D000143:Acids; D012643:Selenium; D001151:Arsenic