Stability of arsenic speciation in fish muscle samples, under different storage and sample preparation conditions

As part of a major survey investigating the levels of total and inorganic arsenic in a range of fish, shellfish and seaweed, a stability study was undertaken so as to ensure that the arsenic speciation profile in samples which had been stored for a number of months was likely to have remained unchanged. The potential for different sample preparation regimes to impact on arsenic speciation profiles was also assessed.The data from an initial time-based investigation suggested that the relative levels of inorganic arsenic did not vary over the 9 month period of the study. However, as it had taken 10 days to land, transport and process the fish material, prior to starting the stability study, a second study was undertaken, where the death-to-testing time was reduced to 3 days. The data from this second study confirmed that from the first, showing that the speciation profile did not change, even during the early stages, when poorly controlled sample handling was potentially at its maximum.Data from the sample preparation experiment indicated that the preparation format, i.e., “wet” vs. “freeze-dried,” could influence the relative levels of inorganic arsenic, with less being measured in the latter format (0.14% ± 0.08%). Possible explanations were given, including microbiological activity within the “wet” samples. However, it was thought most likely to be due to analytical variation encountered when working at, or below, the methodological LOQ.It is hoped that this information will assist others regarding issues to be considered when performing similar studies.

► Chemical speciation often dictates the toxicity of an element.
► Sample storage conditions can affect metal speciation stability.
► Arsenic species are stable in fish flesh, under different sample preparation formats.
► Arsenic species are stable in fish flesh, under different sample storage conditions.
► Results prove data accuracy, obtained from long-term stored samples, in FSA survey.