Abstract
RationaleDomoic acid (DA) is a potent neurotoxin that accumulates in shellfish. Routine testing involves homogenization, extraction and chromatographic analysis, with a run time of up to 30 min. Improving throughput using ambient ionization for direct analysis of DA in tissue would result in significant time savings for regulatory testing labs.MethodsWe assess the suitability of laser ablation electrospray ionization high‐resolution mass spectrometry (LAESI‐HRMS) for high‐throughput screening or quantitation of DA in a variety of shellfish matrices. The method was first optimized for use with HRMS detection. Challenges such as tissue sub‐sampling, isobaric interferences and method calibration were considered and practical solutions developed. Samples included 189 real shellfish samples previously analyzed by regulatory labs as well as mussel matrix certified reference materials.ResultsDomoic acid was selectively analyzed directly from shellfish tissue homogenates with a run time of 12 s. The limits of detection were between 0.24 and 1.6 mg DA kg−1 tissue, similar to those of LC/UV methods. The precision was between 27 and 44% relative standard deviation (RSD), making the technique more suited to screening than direct quantitation. LAESI‐MS showed good agreement with LC/UV and LC/MS and was capable of identifying samples above and below 5 mg DA kg−1 wet shellfish tissue, one quarter of the regulatory limit.ConclusionsThese findings demonstrate the suitability of LAESI‐MS for routine, high‐throughput screening of DA. This approach could result in significant time savings for regulatory labs carrying out shellfish safety testing on thousands of samples annually. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.
Highlights
Domoic acid (DA; Fig. 1(A)) is a potent neurotoxin that is produced by marine diatoms and accumulates in shellfish
More advanced LC/MS/MS methods are available for DA, including sample preparation using strong anion-exchange solid-phase extraction (SPE)[5] and/or derivatization chemistry,[8,9] that combined have yielded limits of detection as low as 1 μg kgÀ1.[10]. The scope of DA analysis worldwide is large enough that increases in sample throughput would lead to significant cost and time savings, for regulatory labs
We used a linear ion trap (LIT) mass spectrometer to quantitate DA in MS/MS mode using the m/z 266 product ion obtained from the [M + H]+ ion at m/z 312.[22]. This method showed good selectivity and an LOD of 1 mg DA kgÀ1 in spiked wet mussel tissue homogenate
Summary
Domoic acid (DA; Fig. 1(A)) is a potent neurotoxin that is produced by marine diatoms and accumulates in shellfish. The CFIA has developed rapid ultra-high performance LC/UV and LC/MS methods, similar to that reported previously.[12] These methods use a 2.5 min long chromatographic run and have been validated as fully quantitative with limits of detection (LODs) and limits of quantitation (LOQs) of 0.06 and 0.2 mg kgÀ1, respectively, for LC/MS and 0.7 and 2 mg kgÀ1, respectively, for LC/UV. Even compared with these more rapid methods, a screening method that does not require sample extraction or chromatographic separation would lead to a significant increase in sample throughput
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