Official Food Control Authority

Zürich, Switzerland

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Zürich, Switzerland
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Kaufmann A.,Official Food Control Authority | Kaufmann A.,Kantonales Labor Zurich
Analytical and Bioanalytical Chemistry | Year: 2012

High-resolution mass spectrometry (HRMS), which is used for residue analysis in food, has gained wider acceptance in the last few years. This development is due to the availability of more rugged, sensitive, and selective instrumentation. The benefits provided by HRMS over classical unit-mass-resolution tandem mass spectrometry are considerable. These benefits include the collection of full-scan spectra, which provides greater insight into the composition of a sample. Consequently, the analyst has the freedom to measure compounds without previous compound-specific tuning, the possibility of retrospective data analysis, and the capability of performing structural elucidations of unknown or suspected compounds. HRMS strongly competes with classical tandem mass spectrometry in the field of quantitative multiresidue methods (e.g., pesticides and veterinary drugs). It is one of the most promising tools when moving towards nontargeted approaches. Certain hardware and software issues still have to be addressed by the instrument manufacturers for it to dislodge tandem mass spectrometry from its position as the standard trace analysis tool. © Springer-Verlag 2012.


Kaufmann A.,Official Food Control Authority | Butcher P.,Official Food Control Authority | Maden K.,Official Food Control Authority | Walker S.,Official Food Control Authority | Widmer M.,Official Food Control Authority
Analytica Chimica Acta | Year: 2011

Multi-residue methods for veterinary drugs or pesticides in food are increasingly often based on ultra performance liquid chromatography (UPLC) coupled to high resolution mass spectrometry (HRMS). Previous available time of flight (TOF) technologies, showing resolutions up to 15,000 full width at half maximum (FWHM), were not sufficiently selective for monitoring low residue concentrations in difficult matrices (e.g. hormones in tissue or antibiotics in honey). The approach proposed in this paper is based on a single stage Orbitrap mass spectrometer operated at 50,000. FWHM. Extracts (liver and kidney) which were produced according to a validated multi-residue method (time of flight detection based) could not be analyzed by Orbitrap because of extensive signal suppression. This required the improvement of established extraction and clean-up procedures. The introduced, more extensive deproteination steps and dedicated instrumental settings successfully eliminated these detrimental suppression effects. The reported method, covering more than 100 different veterinary dugs, was validated according to the EU Commission Decision 2002/657/EEC. Validated matrices include muscle, kidney, liver, fish and honey. Significantly better performance parameters (e.g. linearity, reproducibility and detection limits) were obtained when comparing the new method with the older, TOF based method. These improvements are attributed to the higher resolution (50,000 versus 12,000. FWHM) and the superior mass stability of the of the Orbitrap over the previously utilized TOF instrument. © 2010 Elsevier B.V.


Kaufmann A.,Official Food Control Authority
TrAC - Trends in Analytical Chemistry | Year: 2014

The coupling of ultra-high-performance liquid chromatography (UHPLC) with high-resolution mass spectrometry (HRMS) has been well received within the analytical community. Both technologies have experienced significant advances in recent years. Not only have the resolution power and sensitivity improved, but the increased robustness, which includes prolonged column lifetime, extended dynamic range, easier mass calibration, and enhanced software handling capabilities, is making this coupling more attractive to a larger user base. In this article, we discuss possibilities and current limitations of the UHPLC-HRMS coupling. We also review the application of UHPLC-HRMS in a variety of fields, where it has been widely accepted or where we anticipate more extensive use in the near future. © 2014 Elsevier B.V.


Kaufmann A.,Official Food Control Authority | Butcher P.,Official Food Control Authority | Maden K.,Official Food Control Authority | Walker S.,Official Food Control Authority | Widmer M.,Official Food Control Authority
Analytica Chimica Acta | Year: 2010

The selectivity of mass traces obtained by monitoring liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was compared. A number of blank extracts (fish, pork kidney, pork liver and honey) were separated by ultra performance liquid chromatography (UPLC). Detected were some 100 dummy transitions respectively dummy exact masses (traces). These dummy masses were the product of a random generator. The range of the permitted masses corresponded to those which are typical for analytes (e.g. veterinary drugs). The large number of monitored dummy traces ensured that endogenous compounds present in the matrix extract, produced a significant number of detectable chromatographic peaks. All obtained chromatographic peaks were integrated and standardized. Standardisation was done by dividing these absolute peak areas by the average response of a set of 7 different veterinary drugs. This permitted a direct comparison between the LC-HRMS and LC-MS/MS data. The data indicated that the selectivity of LC-HRMS exceeds LC-MS/MS, if high resolution mass spectrometry (HRMS) data is recorded with a resolution of 50,000 full width at half maximum (FWHM) and a corresponding mass window. This conclusion was further supported by experimental data (MS/MS based trace analysis), where a false positive finding was observed. An endogenous matrix compound present in honey matrix behaved like a banned nitroimidazole drug. This included identical retention time and two MRM traces, producing an MRM ratio between them, which perfectly matched the ratio observed in the external standard. HRMS measurement clearly resolved the interfering matrix compound and unmasked the false positive MS/MS finding. © 2010 Elsevier B.V.


Kaufmann A.,Official Food Control Authority
Rapid Communications in Mass Spectrometry | Year: 2010

Elemental compositions (ECs) can be elucidated by evaluating the high-resolution mass spectra of unknown or suspected unfragmented analyte ions. Classical approaches utilize the exact mass of the monoisotopic peak (M + 0) and the relative abundance of isotope peaks (M + 1 and M + 2). The availability of high-resolution instruments like the Orbitrap currently permits mass resolutions up to 100000 full width at half maximum. This not only allows the determination of relative isotopic abundances (RIAs), but also the extraction of other diagnostic information from the spectra, such as fully resolved signals originating from 34S isotopes and fully or partially resolved signals related to 15N isotopes (isotopic fine structure). Fully and partially resolved peaks can be evaluated by visual inspection of the measured peak profiles. This approach is shown to be capable of correctly discarding many of the EC candidates which were proposed by commercial EC calculating algorithms. Using this intuitive strategy significantly extends the upper mass range for the successful elucidation of ECs. © 2010 John Wiley & Sons, Ltd.


Kaufmann A.,Official Food Control Authority | Walker S.,Official Food Control Authority
Journal of Chromatography A | Year: 2013

The performance of liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) post-run target screening for veterinary drug residue analysis (sulfonamides, tetracyclines and quinolones) in animal urine has been critically evaluated. It was found that retention time information still remains an essential information and that accurate masses together with relative isotopic abundance data alone are not sufficient for many residue applications. Post-run target screening requires the careful setting of parameters to achieve near zero false negative (above a defined threshold level) and a manageable numbers of false positive findings. HRMS offers many possibilities for the reduction of false positives (e.g. isotopic ratio, isotopic fine structure, exact mass of fragment ions). However, the successful use of such tools requires a sufficient ion intensity. This is often not available when trace level compounds are to be detected. Nevertheless, the proposed method is sufficiently sensitive to detect the veterinary drugs at the relevant concentration levels in urine. This means that the approach is well suited to significantly reduce the number of corresponding meat samples which have to be analyzed in a final step for the regulatory relevant quantification of residue levels in meat. The semi-quantitative screening of many samples for a large number of analytes within a short period of time requires the availability of software tools which provide fast and reliable answers. © 2012 Elsevier B.V.


Kaufmann A.,Official Food Control Authority | Butcher P.,Official Food Control Authority | Maden K.,Official Food Control Authority
Analytica Chimica Acta | Year: 2012

A quantitative LC-MS/MS method was developed for the determination of 13 commonly used aminoglycoside antibiotics in meat (pork muscle, fish, and veal livers and kidneys). The proposed method is sufficiently sensitive and highly selective. Unlike other previously reported methods, it uses a simple clean-up procedure based on a strong cation-exchange solid-phase cartridge that permits high sample extract loading volumes. A unique elution regime based on a volatile buffer at intermediately high pH value in combination with an organic solvent provides quantitative elution of the various aminoglycosides. This methodology ensured that neither a breakthrough of weakly retained aminoglycosides (e.g. spectinomycin) nor the incomplete elution of strongly retained analytes (e.g. neo- and gentamycin) is observed. The single-step clean-up is fast and produces clean extracts that minimize matrix-related signal suppression in the electrospray interface. © 2011 Elsevier B.V.


Kaufmann A.,Official Food Control Authority | Widmer M.,Official Food Control Authority | Maden K.,Official Food Control Authority
Rapid Communications in Mass Spectrometry | Year: 2010

Signal suppression is a common issue when analyzing compounds by liquid chromatography coupled to mass spectrometry (LC/MS/MS). Suppression of signals is caused by co-eluting matrix compounds and is thought to take place in the interface. This paper reports strong signal suppression effects which were observed when using a single-stage Orbitrap instrument which was coupled by an electrospray interface to a liquid chromatograph. This type of signal suppression (often the complete loss of certain analyte signal) is observed in addition to signal suppression originating in the electrospray interface. The location of where this phenomenon occurs was shown to be clearly beyond the interface region. It was suspected that not the Orbitrap cell itself, but the C-trap, which is an integral part within the Orbitrap instrument, was the probable location. Such post-interface signal suppression was observed - and could be experimentally induced - when multiply charged ions (e.g. electrospray protonated proteins) were co-eluting with the analytes. High concentrations of proteins, yet not exceeding the maximum ion capacity of the trap, can cause a complete loss of all low m/z masses. This paper describes the practical implication when analyzing heavy matrix samples and discusses strategies to reduce such detrimental effects. © 2010 John Wiley & Sons, Ltd.


Borras S.,University of Barcelona | Kaufmann A.,Official Food Control Authority | Companyo R.,University of Barcelona
Analytica Chimica Acta | Year: 2013

Monitoring of common diagnostic fragments is essential for recognizing molecules which are members of a particular compound class. Up to now, unit resolving tandem quadrupole mass spectrometers, operating in the precursor ion scan mode, have been typically used to perform such analysis. By means of high-resolution mass spectrometry (HRMS) a much more sensitive and selective detection can be achieved. However, using a single-stage HRMS instrument, there is no unequivocal link to the corresponding precursor ion, since such instrumentation does not permit a previous precursor selection. Thus, to address this limitation, an in silico approach to locate precursor ions, based on diagnostic fragments, was developed. Implemented as an Excel macro, the algorithm rapidly assembles and surveys exact mass data to provide a list of feasible precursor candidates according to the correlation of the chromatographic peak shape profile and other additional filtering criteria (e.g. neutral losses and isotopes). The macro was tested with two families of veterinary drugs, sulfonamides and penicillins, which are known to yield diagnostic product ions when fragmented. Data sets obtained from different food matrices (fish and liver), both at high and low concentration of the target compounds, were investigated in order to evaluate the capabilities and limitations of the reported approach. Finally, other possible applications of this technique, such as the elucidation of elemental compositions based on product ions and corresponding neutral losses, were also presented and discussed. © 2013 Elsevier B.V.


Kaufmann A.,Official Food Control Authority | Widmer M.,Official Food Control Authority
Analytica Chimica Acta | Year: 2013

A quantitative LC-MS/MS method was developed for the determination of five polypeptide antibiotics (bacitracin, colistin A, colistin B, polymyxin B1 and polymyxin B2) in a variety of food matrices (muscle, liver, kidney, egg and milk). The described method is sufficiently sensitive, selective and provides acceptable recoveries for all compounds. The extraction is based on acidified methanolic solvent. This is followed by a reversed phase solid phase extraction step to clean-up and concentrate the extracts. The use of a modern core shell column in combination with an eluent consisting of trifluoroacetic acid, formic acid and acetonitrile provides chromatographically well resolved analyte peaks The single-step clean-up is fast and produces a sufficiently clean extract in order to control matrix-related signal suppression in the electrospray interface. © 2013 Elsevier B.V.

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