Dynamic Multiple Reaction Monitoring Mode Research Articles

Liquid Chromatography Tandem Mass Spectrometry Detection of Targeted Pyrrolizidine Alkaloids in Honeys Purchased within Ireland

Pyrrolizidine alkaloids (PAs) are naturally occurring plant toxins which can contaminate foods such as honey. Due to this emerging health and food safety risk, there is an increasing need to establish high sample throughput detection methods which are sensitive, selective and robust for PAs. A sensitive and comprehensive method was developed to determine ten PAs and four PA-N-oxides (PANOs) in honey using liquid chromatography-electrospray ionisation tandem mass spectrometry. Target compounds were detected and quantified using mass spectrometry in dynamic multiple reaction monitoring mode (dMRM). The samples were pre-concentrated using a polymeric strong cation exchange (SCX) solid-phase extraction (SPE) which allowed simultaneous screening of PAs and PANOs in honey (87 % mean recovery ± 9 %). The method was validated for selectivity, taking into consideration the matrix effects, specificity, linearity, accuracy and precision. Good linear calibrations were obtained for all ten PAs and four PANOs in spiked honey samples (3.6–357.1 μg L−1; R2 ≥ 0.995). Acceptable inter-day repeatability was achieved for the target analytes in honey with % RSD values (n = 17) less than 8 %. Limits of detection (LOD) and limits of quantitation (LOQ) were achieved with spiked PA and PANO samples, giving an average LOD of 1.0 μg kg−1 and LOQ of 3.4 μg kg−1. This method was successfully applied to 150 honeys purchased within Ireland between the years 2009 and 2011. The results show that PA contamination of honey is significant and comparative to other European studies, with 23 % of the samples testing positive for PA toxins in the range of 2.9 to 545.5 μg kg−1.

Stable isotope dilution assay for the accurate determination of mycotoxins in maize by UHPLC-MS/MS

A fast, easy-to-handle and cost-effective analytical method for 11 mycotoxins currently regulated in maize and other cereal-based food products in Europe was developed and validated for maize. The method is based on two extraction steps using different acidified acetonitrile–water mixtures. Separation is achieved using ultrahigh-performance liquid chromatography (UHPLC) by a linear water–methanol gradient. After electrospray ionisation, tandem mass spectrometric detection is performed in dynamic multiple reaction monitoring mode. Since accurate mass spectrometric quantification is hampered by matrix effects, uniformly [13C]-labelled mycotoxins for each of the 11 compounds were added to the sample extracts prior to UHPLC-MS/MS analysis. Method performance parameters were obtained by spiking blank maize samples with mycotoxins before as well as after extraction on six levels in triplicates. The twofold extraction led to total recoveries of the extraction steps between 97% and 111% for all target analytes, including fumonisins. The [13C]-labelled internal standards efficiently compensated all matrix effects in electrospray ionisation, leading to apparent recoveries between 88% and 105% with reasonable additional costs. The relative standard deviations of the whole method were between 4% and 11% for all analytes. The trueness of the method was verified by the measurement of several maize test materials with well-characterized concentrations. In conclusion, the developed method is capable of determining all regulated mycotoxins in maize and presuming similar matrix effects and extraction recovery also in other cereal-based foods.