Sample filtration as a source of error in the determination of trace metals in marine waters

Adequate performance in interlaboratory proficiency tests using filtered, pre-treated or pre-digested test materials does not necessarily demonstrate that laboratories' data are of adequate comparability. Sample handling can be an important source of error which is not examined by routine proficiency tests. This paper reports a study of sample filtration as a source error in the determination of trace metals in marine water samples. The results indicate that that current practice may need to be reviewed if important contamination errors are to be controlled.