title: Multi-residue quantification of veterinary drugs in milk with a novel extraction and cleanup technique: salting out supported liquid extraction (SOSLE).
abstract: A quantitative liquid chromatography coupled with high-resolution mass spectrometry method was developed for the determination of more than one hundred compounds belonging to a variety of veterinary drug classes in bovine milk. Salting out supported liquid extraction (SOSLE), a novel extraction and cleanup technique, was introduced to ensure high extraction efficiency and good sample cleanup. The high salt (ammonium sulfate) concentration in the aqueous donor phase permits supported liquid/liquid extraction (SLE) with a relative polar organic acceptor phase (acetonitrile). This is different from traditional SLE, in which the need for phase separation results in the selection of organic solvents with intermediate polarities (e.g., ethyl acetate or dichloromethane). Hence, SOSLE is more efficient in recovering polar analytes than conventional SLE. SOSLE was also compared to classical approaches like solid phase extraction, QuEChERS and ultra-filtration. The proposed technique resulted in extracts of equal or superior cleanliness and with higher average recoveries than those obtained with QuEChERS or SPE. The recovery (median for all compounds) was 73% for QuEChERS, 83% for SPE and 91% for SOSLE. The most significant improvements were observed for polar analytes (penicillines, quinolones and tetracyclines) which are hardly recovered by QuEChERS. The chromatographic separation and detection was based on an ultra-high-performance liquid chromatography Q-Orbitrap system (Q-Exactive plus). The developed analytical method has been validated (based on the commission decision 2002/957/EC) as required for quantitative veterinary drug methods.
authors.affiliation: Official Food Control Authority of the Canton of Zurich, Fehrenstrasse 15, Zürich 8032, Switzerland. Electronic address: anton.kaufmann@klzh.ch.
authors.forename: A
authors.initials: A
authors.lastname: Kaufmann
authors.affiliation: Official Food Control Authority of the Canton of Zurich, Fehrenstrasse 15, Zürich 8032, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Butcher
authors.affiliation: Official Food Control Authority of the Canton of Zurich, Fehrenstrasse 15, Zürich 8032, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Maden
authors.affiliation: Official Food Control Authority of the Canton of Zurich, Fehrenstrasse 15, Zürich 8032, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Walker
authors.affiliation: Official Food Control Authority of the Canton of Zurich, Fehrenstrasse 15, Zürich 8032, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Widmer
mesh_terms: D000818:Animals; D005591:Chemical Fractionation / Q000379:methods*; D002845:Chromatography; D004350:Drug Residues / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification*; D006041:Goats; D059625:Liquid-Liquid Extraction; D013058:Mass Spectrometry; D008892:Milk / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013997:Time Factors; D019155:Veterinary Drugs / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D012997:Solvents; D019155:Veterinary Drugs
keywords: Cleanup; High resolution mass spectrometry; Multi-residue method; Salting out; Supported liquid extraction; Veterinary drugs