A novel sample-preparation method for the generic and rapid determination of pesticides and mycotoxins in tea by ultra-performance liquid chromatography-tandem mass spectrometry.

A rapid, simple, and generic analytical method for the simultaneous determination of 140 undesirable low-weight pesticides and mycotoxins from different chemical classes in black tea was developed. The method involved swelling the sample in ammonium acetate buffer, extraction with acetonitrile-dimethyl sulfoxide, cleanup by dual dispersive solid-phase extraction (D-SPE) with the assistance of low-temperature centrifugation, and analysis by ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry using multiple reaction monitoring mode. The interferences in the extract were eliminated by the combination of dual d-SPE using only C18 sorbent and anhydrous magnesium sulfate, which maintained the chromatographic column under the ideal condition for a long time and enabled satisfactory recoveries of hydrophobic and hydrophilic analytes simultaneously. Matrix-matched calibration curves were obtained for most target compounds with linear regression coefficients above 0.9900. The limits of quantification (LOQs) ranged within 0.5-10.0 µg/kg, which were usually sufficient to verify the compliance of products with legal tolerances. Satisfactory recoveries of 64.5%-138.1% were obtained in black ta samples with the relative standard deviation (RSD) values between 1.8 and 25.9%. The inter-day precision ranged within 2.2%-24.9%. For over 90% of the analytes, the recoveries were between 70% and 120%, with RSD values below 15.0%. The application of this method in routine monitoring programs can drastically reduce effort and time.

Generic and rapid determination of low molecular weight organic chemical contaminants in protein powder by using ultra-performance liquid chromatography-tandem mass spectrometry.

A rapid, simple, and generic analytical method that could simultaneously determine 291 undesirable low molecular weight chemical contaminants from different drug families in protein powder, such as veterinary drugs and pesticides, etc, had been developed. This method comprised the extraction with acetonitrile-dimethyl sulfoxide (DMSO), clean-up through dispersive solid phase extraction (D-SPE) and low temperature filtration, and analysis by ultra-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry at multiple-reaction monitoring mode. Acetonitrile-DMSO was more generic than acetonitrile or methanol for the extraction of large-scale organic chemical contaminants with different polarities in protein powder. Most interferences in the extract were eliminated by the combination of D-SPE and low temperature filtration, which simultaneously provided satisfactory recoveries of both hydrophobic and hydrophilic analytes. In particular, besides the purification function, the sorbent of D-SPE also played an important role in grinding samples to improve extraction efficiency during homogenization. This streamlined approach allowed the processes of extraction and the main purification were carried out in one-step, and dramatically reduced sample preparation turnaround times and solvent consumption. For quantification, matrix-fortified calibration curves showed competent linearity for most of the target compounds with linear regression coefficients (r) higher than 0.9900, except for two analytes. The limits of quantification ranged from 0.1 µg/kg to 50 µg/kg, which was usually sufficient to verify the compliance of products with legal tolerances. The average recoveries for spiked protein powder ranged from 65.6% to 142.2% with associated RSD values between 0.5% and 28.5%. For over 90% of the analytes, the recoveries were between 70% and 120% with RSD values in the range of 1%-15%. Applying this method in routine monitoring programs would drastically reduce both effort and time.