Qualitative screening of 116 veterinary drugs in feed by liquid chromatography–high resolution mass spectrometry: Potential application to quantitative analysis

Qualitative Multiresidue Screening Method for 143 Veterinary Drugs and Pharmaceuticals in Milk and Fish Tissue Using Liquid Chromatography Quadrupole-Time-of-Flight Mass Spectrometry

A wide-scope screening methodology has been developed for the identification of veterinary drugs and pharmaceuticals in fish tissue and milk using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS). The method was validated using a qualitative approach at two concentration levels. The detection of the residues was accomplished by retention time, accurate mass, and the isotopic fit using an in-house database. Product-ion spectra were used for unequivocal identification of the compounds. Generic sample treatment was applied. The majority of the compounds were successfully detected and identified at concentration levels of 150 ng mL(-1) in milk and 200 μg kg(-1) in fish (>80% of the compounds in both matrices), whereas satisfactory results were also obtained at concentration levels of 15 ng mL(-1) in milk and 20 μg kg(-1) in fish (>60% of the compounds detected and identified).

Analysis of veterinary drug and pesticide residues in animal feed by high-resolution mass spectrometry: comparison between time-of-flight and Orbitrap

The use of medium-high-resolution mass spectrometers (M-HRMS) provides many advantages in multi-residue analysis. A comparison between two mass spectrometers, medium-resolution (MRMS) time-of-flight (TOF) and high-resolution (HRMS) Orbitrap, has been carried out for the analysis of toxic compounds in animal feed. More than 300 compounds belonging to several classes of veterinary drugs (VDs) and pesticides have been determined in different animal feed samples using a generic extraction method. The use of a clean-up procedure has been evaluated in both instruments, and several validation parameters have been established, such as the matrix effect, linearity, recovery and sensitivity. Finally, both instruments have been used during the analysis of 18 different feed samples (including chicken, hen, rabbit and horse). Some VDs (sulfadiazine, trimethoprim, robenidine and monensin sodium) and one pesticide (chlorpyrifos) have been identified. In general, better results were obtained using the Orbitrap, such as sensitivity (1-12.5 µg kg(-1)) and recovery values (60-125%). Moreover, this analyser had several software tools, which reduced the time for data processing and were easy to use, performing quick screening for more than 450 compounds in less than 5 min. However, some disadvantages such as the high cost and a decrease in the number of detected compounds at low concentrations must be taken into account.

Reliability of veterinary drug residue confirmation: high resolution mass spectrometry versus tandem mass spectrometry

Confirmation of suspected residues has been a long time domain of tandem triple quadrupole mass spectrometry (QqQ). The currently most widely used confirmation strategy relies on the use of two selected reaction monitoring signals (SRM). The details of this confirmation procedure are described in detail in the Commission Decision 93/256/EC (CD). On the other hand, high resolution mass spectrometry (HRMS) is nowadays increasingly used for trace analysis. Yet its utility for confirmatory purposes has not been well explored and utilized, since established confirmation strategies like the CD do not yet include rules for modern HRMS technologies. It is the focus of this paper to evaluate the likelihood of false positive and false negative confirmation results, when using a variety of HRMS based measurement modes as compared to conventional QqQ mass spectrometry. The experimental strategy relies on the chromatographic separation of a complex blank sample (bovine liver extract) and the subsequent monitoring of a number of dummy transitions respectively dummy accurate masses. The term "dummy" refers to precursor and derived product ions (based on a realistic neutral loss) whose elemental compositions (CxHyNzOdCle) were produced by a random number generator. Monitoring a large number of such hypothetical SRM's, or accurate masses inevitably produces a number of mass traces containing chromatographic peaks (false detects) which are caused by eluting matrix compounds. The number and intensity of these peaks were recorded and standardized to permit a comparison among the two employed MS technologies. QqQ performance (compounds which happen to produce a response in two SRM traces at identical retention time) was compared with a number of different HRMS(1) and HRMS(2) detection based modes. A HRMS confirmation criterion based on two full scans (an unfragmented and an all ion fragmented) was proposed. Compared to the CD criteria, a significantly lower probability of false positive and false negative findings is obtained by utilizing this criterion.