Wide-Scope Screening Method for Multiclass Veterinary Drug Residues in Fish, Shrimp, and Eel Using Liquid Chromatography–Quadrupole High-Resolution Mass Spectrometry

Abstract

A screening method for veterinary drug residues in fish, shrimp, and eel using LC with a high-resolution MS instrument has been developed and validated. The method was optimized for over 70 test compounds representing a variety of veterinary drug classes. Tissues were extracted by vortex mixing with acetonitrile acidified with 2% acetic acid and 0.2% p-toluenesulfonic acid. A centrifuged portion of the extract was passed through a novel solid phase extraction cartridge designed to remove interfering matrix components from tissue extracts. The eluent was then evaporated and reconstituted for analysis. Data were collected with a quadrupole-Orbitrap high-resolution mass spectrometer using both nontargeted and targeted acquisition methods. Residues were detected on the basis of the exact mass of the precursor and a product ion along with isotope pattern and retention time matching. Semiquantitative data analysis compared MS1 signal to a one-point extracted matrix standard at a target testing level. The test compounds were detected and identified in salmon, tilapia, catfish, shrimp, and eel extracts fortified at the target testing levels. Fish dosed with selected analytes and aquaculture samples previously found to contain residues were also analyzed. The screening method can be expanded to monitor for an additional >260 veterinary drugs on the basis of exact mass measurements and retention times.

Application and evaluation of a high-resolution mass spectrometry screening method for veterinary drug residues in incurred fish and imported aquaculture samples

“…Tissues were stored at − 20 °C until used. The samples were extracted according to a method previously described [13]. Briefly, homogenized tissue (2.0 g) was extracted with 8 mL of extraction solution consisting of 0.2% p -toluene sulfonic acid monohydrate ( w / v ) and 2% glacial acetic acid ( v / v ) in 100% acetonitrile.…”

“…The positive control sample was fortified with the test compounds used previously to validate the screening method [13]. These included 70 analytes representing a wide range of analytes and target testing levels.…”

“…If the response for one of these test compounds found in an incurred or imported sample was at least 50% of that in the positive (1× target testing level, TTL) control and met identification criteria [17], then the sample was considered to be presumptive positive for that compound. The threshold cutoff level of 50% as compared to a positive control was established previously based on the measured variance of the response for analytes fortified in fish at the 1× TTL level [13]. Each test sample was extracted and analyzed in duplicate.…”

“…When that occurs, the quadrupole filters the precursor ion into the HCD cell using a limited m / z window to produce fragment ions related to that compound. A more detailed description of these MS methods have been described previously [13]. Due to an upgrade in software from the original method, some settings, particularly for DDMS 2 , were changed slightly.…”

“…Our laboratory recently developed and validated a screening method [13] for veterinary drug residues in fish, shrimp, and eel using LC with a quadrupole-Orbitrap HRMS. This screening method can monitor for over 300 veterinary drugs using an in-house compound database that includes exact mass measurements and retention times.…”