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A rapid method was developed and validated for the simultaneous identification and quantitation of the residues of 5-nitroimidazoles and their metabolites in eggs by isotope dilution-ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted with acetonitrile, purified with octadecylsilane-bonded silica gel as sorbent, and defatted with n-hexane. The target compounds were separated in the LC system by gradient elution, and detected using an electrospray ionization (ESI) source in the positive ion mode with multiple reaction monitoring (MRM). Under the optimal conditions, the calibration curves for seven nitroimidazoles were linear in the concentration range of 0.5–20 ng/mL, with correlation coefficient exceeding 0.999. The limits of detection (LOD) and quantification (LOQ) were 0.1–0.25 and 0.3–1.0 μg/kg, respectively. The average recoveries at three spiked levels (0.5, 1.0 and 5.0 μg/kg) were 96.5%–112.7%, with relative standard deviations (RSDs) (n = 6) of 0.82%–8.14%. The proposed method was used for the determination of nitroimidazoles in egg samples from Food Analysis Performance Assessment Scheme (FAPAS) with satisfactory results. The RSDs between the results and the assigned values were less than 10%. This method could accurately detect the seven nitroimidazoles and was validated to be suitable for 38 batches of commercial eggs. The developed method is convenient, sensitive and accurate, and can be applied for daily monitoring of 5-nitroimidazoles and their metabolites in eggs.

A method for determining human epidermal growth factor (hEGF) in cosmetics was developed using solid-phase extraction with high-performance liquid chromatography – tandem mass spectrometry. The sample was extracted and purified by a mixed anionic solid-phase extraction column (MAX), and the eluent was passed through a nylon filter membrane into a polypropylene vial. The matrix-matched external standard method was used to quantify the analyte in multi-reaction monitoring mode. The analyte had an excellent peak shape within 11 min with a linear range from 5 to 80 ng/mL and a linear correlation coefficient (r) of 0.9995. The limit of detection and limit of quantification were 0.75 and 2.5 μg/kg, respectively. The recovery of the target was from 81.5% to 88.8%, and the relative standard deviation was between 1.16% and 5.07%. The results met the International Organization for Standardization 12787 standard. The established method was successfully applied to 30 cosmetic samples. The proposed method is sensitive, accurate, reliable, and suitable for the quantitative confirmation of hEGF and monitoring its illegal addition to cosmetics. [ABSTRACT FROM AUTHOR]

A simple, rapid and sensitive method for the determination of aflatoxins in peanut oil was developed using MIL-101(Cr) material filled syringe filter for one-step solid-phase extraction (SPE) with high-performance liquid chromatography—tandem mass spectrometry (HPLC-MS/MS) detection. The MIL-101(Cr) sorbent was characterized and its mass, the loading solution, and the eluent were optimized; under these conditions, a matrix matching internal standard method was developed. The linear range was from 0.1 to 20 ng/mL with correlation coefficient (r) exceeding 0.9998. The recoveries were between 94.7% and 105.9% with relative standard deviations from 2.02% 6.88%. The recoveries of inter-day and intra-day measurements were from 93.0% to 98.5% and 97.6% to 100.7%. The precision values for inter-day and intra-day analyses were from 6.09% to 7.68% and 2.56% to 4.30%, respectively. The pretreatment efficiency of the developed method was superior to literature procedures and used to determine aflatoxins in 126 peanut oil samples from local markets. 38 samples had positive results and 1 sample exceeded the allowable limit. Hence, the developed protocol was suitable for the determination of aflatoxins in peanut oil. [ABSTRACT FROM AUTHOR]

The construction of atropisomers with 1,2-diaxes, while maintaining high enantiocontrol, presents a significant challenge due to the dynamic nature of steric hindrance at ortho-aryl substituents. Although various catalytic asymmetric methods have been developed for accessing axially chiral arylpyrroles, the synthesis of axially chiral arylpyrroles with 1,2-diaxes in a catalytic asymmetric manner has remained rare. Herein, the authors report the synthesis of diverse axially chiral arylpyrroles with 1,2-diaxes, and C-C and C-N axes through copper-catalysed asymmetirc [4 + 1] annulation of yne-allylic esters with arylamines via a remote stereocontrol strategy. This approach provides facile access to a broad range of heterobiaryl atropisomers (67 examples) in excellent enantioselectivities, each bearing one or two C-C/C-N axes, demonstrating its versatility and efficiency. The utility of this methodology is further highlighted by the transformation of the product into chiral phosphine ligand, and chiral thioureas for the use in asymmetric catalysis., (© 2024. The Author(s).)

A rapid and accurate analysis method based on ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight high-resolution mass spectrometry (UPLC-Q-TOF-HRMS) was developed to screen and determine nine antiallergy drugs in emulsion cosmetics. First, a standard library of the target compounds was established. The library contained the TOF-MS information and secondary MS information such as retention time, ion addition mode, mass error, isotope distribution, mass-to-charge ratio of the parent ion, and fragment ion distribution. According to the European Union regulation (SANTE/11945/2015), the standard for the qualitative determination by HRMS was determined; that is, each compound was confirmed by two ions with a mass error below 5%, and the abundance ratio of the two ions was less than 30%. Second, the instrument conditions and sample pretreatment conditions for the determination of different compounds were optimized, and the influence of different levels of quantitative ions on the matrix effect was compared. The following observations were made:(1) the addition of 0.1% formic acid to the water phase improved the response of the chromatographic peaks; (2) among the various solvent amounts tested (4, 5, 6, 8 mL acetonitrile and 4, 5, 6, 8 mL methanol), 4 mL acetonitrile showed the best extraction efficiency; (3) PRiME HLB had a better purification effect than the other two purification columns (C18 and HLB solid-phase extraction cartridges), thus reducing the interference of impurities and ensuring good recovery of the target compounds; (4) the use of two pairs of secondary product ion quantification could significantly reduce the matrix effect of anti-allergic compounds and improve the quantification accuracy. Finally, based on the above findings, the experimental procedure was established. The lotion samples were first ultrasonically extracted with acetonitrile and purified on the PRiME HLB column. Chromatographic separation was performed on a Waters XBridge C18 column with gradient elution using 0.1% (v/v) formic acid in water and acetonitrile. Finally, the sequential window acquisition of all theoretical mass spectra (SWATH), which shows obvious advantages in continuous and high-throughput acquisition, was selected for MS data acquisition. The retention time, mass accuracy, isotope distribution, and fragment ion matching ratio were used for fast qualitative screening, while the peak areas of characteristic product ions were used for precise quantification. All the calibration curves showed good linearity ( r 2 >0.99) within the tested ranges (5-100 μg/L) under the optimum conditions. The limits of quantification (LOQs) were in the range of 0.05-0.10 mg/kg. The recoveries were in the range of 65.3%-107% at three spiked levels (0.10, 0.20, and 0.60 mg/kg), with relative standard deviations (RSDs, n =6) below 20%. Compared with the existing ion exchange column methods, the proposed "one-step" purification method based on PRiME HLB is simpler and more rapid, where the extraction solution is filtered directly after allowing it to pass through the column, without any subsequent washing and elution procedures. In addition, the LOQs of this method are lower than those of other LC-MS/MS methods, indicating that the proposed method has higher sensitivity. The application of SWATH data acquisition makes it possible to achieve quantification with two pairs of product ions, thus reducing the matrix effect and ensuring accuracy of the quantitative results. Therefore, the proposed method is less time-consuming and operationally convenient, and it can be used for the rapid screening and accurate quantification of antiallergics in lotion samples.

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the simultaneous determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils. The plasticizers in the samples were extracted with acetonitrile. The extract was purified by freezing at -20 ℃, and determined by GC-MS/MS in selective reaction monitoring mode. For the two compounds, the limit of detection and limit of quantification were 0.03 mg/kg and 0.1 mg/kg, respectively, and the linear range was 0.1-10 mg/kg. The recoveries of the two compounds ranged from 81.04% to 108.31% at three spiked levels (0.1, 0.3, and 1.0 mg/kg), and the relative standard deviation ranged from 0.70% to 9.91%. The method is simple, accurate, and suitable for the determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils.

An accurate determination of quantitative and confirmative method for sodium cyclamate in liquor by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with linear trap technology has been established. Without pretreatment, the sample was directly injected after filtering through a 0.2 microm micro filter. The HPLC separation was performed on an Atlantis dC18 column (150 mm x 2.1 mm, 3 microm) by gradient elution with methanol and water containing 0.1% (v/v) formic acid. The eluent was determined and confirmed in multiple reaction monitoring-enhanced product ion (MRM-EPI) scan mode. The acquired data from MRM for the quantitative determination, and the product ion spectra were used for library search for qualitative confirmatory analysis. External standard was used for the quantitative determination of sodium cyclamate in liquor, and good linearity (r = 0.9991) was obtained over the range of 1.320 - 132.0 microg/L. The limit of detection (LOD, S/N = 3) for sodium cyclamate was 0.1 microg/L. The average recoveries ranged from 96.38% to 107.2% at the spiked levels of 2.640, 26.40 and 100.0 microg/L with the relative standard deviations (RSDs) less than 9%. The matching degrees of the spectra for all positive samples were higher than 92%. The method is simple, accurate and efficient for the determination of sodium cyclamate in liquor and particularly suitable for confirmatory analysis of positive samples.