ABSTRACT
A rapid method based on ultrahigh-performance liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry (UPLC-HRMS) was developed for the screening and confirmation of 20 mycotoxins in grain products. The samples were extracted with acetonitrile containing 2% (v/v) formic acid, and the extracts were cleaned up on Captive EMR-Lipid columns. The analytes were separated on a Thermo Hypersil Gold C18 column (100 mm×2.1 mm, 1.9 µm), and analyzed by UPLC-HRMS. The retention time and accurate mass of the parent ion were used for fast screening in full scan mode, while the accurate masses of the fragment ions were used for confirmation in the two-stage threshold-triggered full mass scan mode. The results revealed that the 20 mycotoxins showed good linear relationships in their respective mass concentration ranges. The correlation coefficients were not less than 0.99, and the limits of quantitation (LOQs) ranged from 0.25 to 20 µg/kg. The recoveries of the 20 mycotoxins in the sample ranged from 72.9% to 117.8% with the relative standard deviations (RSDs) from 2.9% to 15.2% at three spiked levels (n=6). This method has the advantages of high sensitivity and reliability, and is thus suitable for the rapid screening and confirmation of 20 mycotoxins in grain products.
Subject(s)
Edible Grain/chemistry , Mycotoxins/analysis , Chromatography, High Pressure Liquid , Edible Grain/microbiology , Mass Spectrometry , Reproducibility of ResultsABSTRACT
A method for the simultaneous determination of the residues of 11 quinolones in hotpot ingredients by quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and ultra performance liquid chromatography-tandem mass spectrometric method (UPLC-MS/MS) was established. The sample was extracted with acetonitrile (containing 5% formic acid) and followed by stratifying with a salting-out agent. Clean-up of the extracts was processed by C18 and PSA, a modified QuEChERS procedure. The analytes were then separated on a Poroshell 120 EC-C18 column, and finally detected by tandem mass spectrometry in positive ESI mode. The linearity of all the 11 quinolones in the range from 1.0 to 100.0 microg/kg had correlation coefficients greater than 0.998. The limits of detection (LOD) of the method were from 1.8 to 3.1 microg/kg and the limits of quantification (LOQ) were from 6.0 to 10.3 microg/kg. The average recoveries of the 11 quinolones were in the range from 70.1% to 100.3%, with relative standard deviations from 2.42% to 10.88%. The established method is sensitive and of good recoveries. It can be applied as a rapid and reliable method for the determination of the 11 quinolones in hotpot ingredients.
Subject(s)
Chromatography, High Pressure Liquid , Food Contamination/analysis , Quinolones/analysis , Solid Phase Extraction , Tandem Mass Spectrometry , Limit of DetectionABSTRACT
Trimethylamine-N-oxide demethylase (TMAOase) was purified from Jumbo squid (Dosidicus gigas) and characterized in detail herein. The TMAOase was extracted from squid with 20 mM Tris-acetate buffer (pH 7.0) containing 1.0 M NaCl, followed by acid treatment and heat treatment. Then it was purified by deithylaminoethyl-cellulose and Sephacryl S-300 chromatography, subsequently resulting in an 839-fold purification. The molecular mass of the TMAOase was defined to be 17.5 kDa. The optimum pH of the purified TMAOase was 7.0, and its optimum temperature was confirmed to be 55 degrees C. The TMAOase was stable to heat treatment up to 50 degrees C and stable at pH 7.0-9.0. Reducing agents such as DTT, Na2SO3, and NADH were effective at activating TMAOase, and ethylenediaminetetraacetic acid, as well as Mg2+ and Ca2+, could also enhance the activity of TMAOase remarkably, whereas the TMAOase could be significantly inhibited by tea polyphenol, phytic acid and acetic acid. In addition, the TMAOase converted TMAO to dimethylamine and formaldehyde stoichiometrically with a K(m) of 26.2 mM.
