Xiaojun Deng

MULTICLASS RESIDUES SCREENING OF 105 VETERINARY DRUGS IN MEAT, MILK, AND EGG USING ULTRA HIGH PERFORMANCE LIQUID CHROMATOGRAPHY TANDEM QUADRUPOLE TIME-OF-FLIGHT MASS SPECTROMETRY

A high-throughput and robust method for analyzing multiclass residues of veterinary drugs in meat, milk, and egg by ultra-high performance liquid chromatography (UHPLC)–quadrupole time-of-flight mass spectrometry (QTOF) was established. The method successfully applied to the screening, quantification, and confirmation of 105 compounds from 9 different classes of drugs, including beta-agonists, benzimidazoles, corticoides, triphenylmethane, nitromidazoles, quinolones, sulfonamides, tetracylines, and benzodiazepams. The samples are extracted by a single extraction using acetonitrile containing 0.1% formic acid, followed by an easy solid phase extraction (SPE) clean-up on HLB column and finally analyzed by LC/MS QTOF MS. The separation was achieved within 30 min at the optimized chromatographic conditions. More than 92% compounds in this study can be reliably identified based on accurate mass measurement (within the 3 ppm mass error) at the 5 µg/kg concentration levels in the complex food matrix with further MS/MS confirmation. Our study demonstrated a reliable, high-efficient and high-sensitive strategy for the fast and high throughput screening of multiclass of veterinary drugs in foodstuffs of animal origin.

A novel mixed-mode solid phase extraction for simultaneous determination of melamine and cyanuric acid in food by hydrophilic interaction chromatography coupled to tandem mass chromatography.

Utilizing a solid phase extraction column (MCT) containing mixed hydrophilic functional gel and cation exchange sorbent, a sensitive and rapid HPLC-MS/MS method for simultaneously determining the residues of melamine (MEL) and cyanuric acid (CYA) in human foodstuffs was developed. MEL and CYA in egg, pork, liver, kidney and pork, shrimp, sausage casing, honey, soybean milk, soybean powder and dairy product were extracted using acetonitrile/water, defatted with hexane and isolated using MCT solid phase extraction column. The residues were separated upon a hydrophilic interaction liquid chromatography (HILIC) column and analyzed by electrospray ionization under negative-positive switched mode on a triplequadrupole mass spectrometry. The selected reaction monitoring was performed on [M+H](+) of m/z 127.9 to provide the transition of 127>85 and 127>68 (MEL) while the [M-H](-) of m/z 127.1 was selected as the precursor ion for CYA resulting in product ions m/z 85 and 42. Isotope labeled internal standard ((15)N(3)-MEL and (13)C(3)-CYA) and matrix-matched calibration were both used to observe the recovery to be 70.0-129.6% and 70.0-128.9% with RSD of 1.4-23.3% and 1.5-21.7% for MEL and CYA, respectively (n=6). All the LODs and LOQs of MEL and CYA were less than 39.4 and 99.1μgkg(-1), respectively, in 18 matrices, which were sensitive enough for quantitative analysis. This method has been proven effective in simultaneous determination of melamine and cyanuric acid when inspecting unknown and positive samples.

[Determination of glyphosate and aminomethylphosphonic acid residues in foods using high performance liquid chromatography-mass spectrometry/mass spectrometry].

A method for the determination of glyphosate (PMG) and aminomethylphosphonic acid (AMPA) residues in plant products, such as rice, wheat, vegetables, fruits and tea, pig and chicken muscles, aquatic products, chestnut, honey, etc., was developed using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). In this method, PMG and AMPA were extracted with water from samples, defatted using an extraction step with dichloromethane, and purified using a cation-exchange (CAX) solid phase extraction cartridge. Then, these were derived using fluorenylmethylchloroformate (FMOC-Cl) in borate buffer for subsequent HPLC-MS/MS analysis. Isotope-labeled PMG 1, 2(13)- C(15) N was used as the internal standard for the quantitative analysis of two residues. For all samples, the recoveries ranged from 80.0% to 104% and the relative standard deviations (RSDs) ranged from 6.7% to 18.2%. The limit of quantification (LOQ) was determined to be 0.05 mg/kg with a linear range of 0.20-10 microg/L. It is demonstrated that this method is reliable and sensitive for the analysis of PMG and APMA with low concentrations in foods.

[Determination of multi-pesticides in black tea by subcritical water extraction and gas chromatography-tandem mass spectrometry].

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method with subcritical water extraction was developed for the determination of 21 organochlorine and pyrethroid pesticides in black tea. Under the extraction pressure of 5 MPa, the target compounds were extracted with subcritical water at the temperature of 150 degrees C for 15 min, transferred into acetone-n-hexane (1:1, v/v), and cleaned-up by an ENVI-Carb solid phase extraction (SPE) column. The GC separation was performed on a DB-5 capillary column. The pesticides were determined by MS/MS in multiple reaction monitoring (MRM) mode and quantified by matrix-matched internal standard method. The calibration curves showed good linearities in the range of 5.0-320.0 microg/L with the correlation coefficients greater than 0.99. The limit of quantification (S/N > 10) was 50 ng/g, and the limit of detection (S/N > 3) was 10 ng/g. The recoveries of pesticides spiked in the tea at three levels of 50, 100 and 200 ng/g were ranged from 70. 18% to 119.98% with the relative standard deviations (RSDs) of 5.01%-11.76%. The sensitivity, accuracy and precision of the method meet the technical standard of the pesticide determination. The method can be applied to the determination of organochlorine and pyrethroid pesticides in black tea.

[Simultaneous determination of melamine and cyanuric acid in foodstuffs by solid phase extraction-hydrophilic interaction chromatography-tandem mass spectrometry].

A method based on solid phase extraction-liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of melamine and cyanuric acid in foodstuffs is presented. The melamine and cyanuric acid residues were extracted by acetonitrile and water, degreased by hexane, and the extract was cleaned-up by a mixed-mode solid phase-extraction column (MCT) of hydrophilic functional silica gel sorbent and cation exchange resin. The LC separation was performed on a hydrophilic interaction chromatograph, the melamine and cyanuric acid were determined by MS/MS in positive-negative switched electrospray ionization mode, multiple reaction monitoring (MRM) mode, and quantified by isotope internal standard method. The melamine and cyanuric acid were linear in the range of 10-2 500 microg/L with the correlation coefficients (r) higher than 0.99, and the limits of quantification were 25 microg/kg and 50 microg/kg, respectively. The recoveries of melamine and cyanuric acid spiked in animal-derived foods, plant-derived foods, milk and milk products were in the range of 70.0%-129.6% and 70.0%-128.6%, respectively, with the relative standard deviations (RSD) of 1.4%-23.3% and 2.8%-18.7%, respectively. The method can meet the requirement for the determination of melamine and cyanuric acid in foodstuffs simultaneously.