Simultaneous microwave digestion for total arsenic and inorganic arsenic in local shrimp and prawn commodities of Brunei Darussalam for regulatory and safety monitoring

TL;DR

This study shows that using total arsenic alone for seafood safety in Brunei can lead to incorrect rejections, and suggests using inorganic arsenic data for better regulation.

Contribution

The study introduces a validated method for simultaneous analysis of total and inorganic arsenic in shrimp and prawn samples for regulatory compliance.

Findings

Samples with high total arsenic were found to be compliant when inorganic arsenic was analyzed.

Aquaculture samples had the highest total arsenic in flesh, while capture samples correlated with highest weight fractions.

Risk assessment showed no health risk from inorganic arsenic levels in the tested seafood.

Abstract

The data gap in food safety regulations have created misinformation leading to the rejection of commodities for trade. The evidence presented is the local regulation of arsenic in sea produce which is based on total arsenic, tAs, instead of toxic inorganic arsenic, iAs. Furthermore, tAs data in animal origin seafood has been widely proven to be dominated by the non-toxic Arsenobetaine, AsB. Therefore, if arsenic regulatory limit was set based only on tAs without reference to iAs data, seafood products might be wrongfully rejected for trade because of non-compliance to tAs limit. We provided analysis of tAs and iAs of 14 local prawn and shrimp commodities from three shrimp/prawn sector namely aquaculture (n = 3), capture (n = 5) and processed (n = 6) using effective extraction, as well as, a fit-for-purpose analytical method for iAs. A HVG-AAS method was developed and validated for iAs with LoQ of 1.6 ppb, analytical range of 0–6 ppb, repeatability RSDr of 0.5–3.1 %, coefficient of determination R2 of 0.9975, and percentage recovery of 90.9 %, while an existing method using ICP-MS was used to verify the tAs. Based on the AOAC Official Method 999.10 2005 with minor adjustments, seafood samples were digested with concentrated nitric acid and hydrogen peroxide under pressure in a closed vessel heated by a microwave digester. An additional step for iAs determination was necessary to ensure compatibility in HVG-AAS analysis. Further subdivision of the aquaculture and capture samples was done by dividing them into 3 fractions, namely head, flesh and peel. Comparison of tAs in all the three fractions indicated that for aquaculture sector, the highest tAs were found in the flesh (2nd highest in % weight) whereas for the capture sector, the highest amount of tAs correlated with the highest % weight of the fraction. On regulatory aspects, speciation analysis on the iAs indicated samples with quantifiable iAs value were in-compliance despite tAs were initially found to be higher than the national limits. Risk assessment of iAs indicated there were no risk for human daily intake based on the BDML0.5 value of 3.0 μg/kg b.w per day for an average 70 kg man. All findings concluded the need for doing arsenic speciation analysis of iAs along with tAs for routine monitoring of prawn/shrimp samples and to revise the local limits from tAs to iAs particularly for seafood commodities.

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