In view of the diverse forms and unstable properties of cholesterol oxidation products (COPs) in meat products under specific conditions, a sample pretreatment technology, saponification at room temperature, was established for the accurate detection of 9 COPs in meat products by gas chromatography-quadrupole-time-of-flight mass spectrometry (GC-Q-TOF/MS). The results showed that the optimal pre-treatment conditions were extraction with chloroform/methanol (2:1, V/V), saponification at room temperature for 18 h, re-extraction with ethyl acetate/n-hexane (80:20, V/V), and clean-up using an aminopropyl solid-phase extraction (SPE) cartridge. The linear ranges were 0.002-0.5 μg/mL for 7α-hydroxyl cholesterol and 7β-hydroxyl cholesterol, and 0.02-0.5 μg/mL for 5β,6β-epoxide cholesterol, 5α,6α-epoxide cholesterol, 20α-hydroxy cholesterol, 3β,5α,6β-trihydroxy cholesterol, 25α-hydroxy cholesterol, 7-keto cholesterol and 27α-hydroxy cholesterol. The determination coefficients were ≥ 0.9990 for all analytes, the limits of detection (LOQ) were 0.0001-0.001 mg/kg, and the limits of quantitation (LOQ) were 0.0002-0.002 mg/kg. The method had good accuracy and high precision. The average recoveries from spiked samples were 89.7%-116.1%, with relative standard deviations (RSDs) of less than 8.7%. Compared with high temperature saponification, saponification at room temperature effectively prevented the autoxidation of cholesterol and the degradation of 7-ketocholesterol, and reduced the exogenous introduction and endogenous loss of target substances, thereby enabling the rapid and accurate detection of the 9 COPs.

A method was developed for the determination of 11 N-nitrosamines in animal derived foods by pass-through solid phase extraction coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS). The rehydrated samples were extracted with acetonitrile and rapidly purified by using a Prime HLB solid phase extraction column (200 mg/6 mL). The target compounds were detected in the multiple reaction monitoring (MRM) mode, and quantified by the matrix matched external standard method. The calibration curves for the 11 N-nitrosamines were linear in the concentration range of 0.5–500.0 ng/mL, with correlation coefficients of 0.9994–0.9998. The limits of detection (LODs) and the limits of quantitation (LOQs) were 0.2–0.3 and 0.5–1.0 μg/kg, respectively. The average recoveries at spiked levels of 1, 4 and 10 μg/kg ranged from 80.1% to 97.4%, and the relative standard deviations (RSDs) were between 2.3% and 8.8%. The extraction and purification time required by this method was only 15 min/sample and greatly shortened compared with GB 5009.26-2016, and the detection efficiency was increased by 10 times. This method allows rapid detection of N-nitrosamines residues in animal derived foods.

A method for the determination of indoleacetic acid in meat was established using a single-step, cheap, effective, rugged, and safe (SinChERS) purification and rapid derivatization followed by gas chromatography-mass spectrometry (GC-MS). After adding water and adjusting pH to 3 by formic acid, the samples were extracted with acetonitrile, purified on a SinChERS column, and blown to dryness under nitrogen. The residue was derivatized with concentrated sulfuric acid and methanol for 1 min prior to GC-MS analysis. Quantitative was performed using the matrix external standard method. The results showed that the linear relationship of indoleacetic acid concentration and its response value was good in the range of 0.01-5.0 μg/mL, with a correlation coefficient (r²) greater than 0.999. The limit of detection was 0.003 mg/kg and the limit of quantification was 0.01 mg/kg. The average recoveries of pork, beef, and mutton samples spiked at 0.01, 0.05, and 0.10 mg/kg were 92.1% to 102.1%, with relative standard deviations (n = 6) of 2.6% to 5.7%. The method is characterized by high sensitivity and short pretreatment time, and can be used for the determination of indoleacetic acid in meat.

An ultra-high performance liquid chromatography (UPLC) method was developed for the simultaneous determination of 19 free amino acids and taurine in formulas for special medical purpose intended for infants. The samples were hydrolyzed by α-amylase, and purified by precipitating proteins and other impurities through pH adjustment. The method was based on pre-column derivatization with 6-aminoquinolinyl-N-hydroxysuccinimidate (AQC). Formic acid-ammonium formate (20 mmol/L, pH 2.25), formic acid-ammonium formate (20 mmol/L, pH 3.00), and acetonitrile were used as mobile phases A, B and C for gradient elution, respectively. The analytes were separated on an AccQ-Tag Ultra C₁₈ column, detected with a diode-array detector and quantified by an external standard method. Good linearity was observed for cystine in the range of 5–125 μmol/L and 18 other amino acids and taurine in the range of 10–250 μmol/L with correlation coefficients higher than 0.999. The limit of detection (LOD) was 1.5 μmol/L for cystine, and 3 μmol/L for the other analytes. The limit of quantitation (LOQ) was 5 μmol/L for cystine, and 10 μmol/L for the other analytes. The average recoveries of the method were in the range of 90.16%–109.84% with relative standard deviation (RSD) not more than 4.77%. The method was easy to operate, accurate and highly reproducible, and could be suitable for the determination of 19 amino acids and taurine in formulas for special medical purpose intended for infants, providing strong technical support for enterprise quality control and government regulation.

A method for the determination of trimetazidine and clomiphene in animal-derived foods was developed by mixed-mode reversed-phase strong cation exchange solid phase extraction cleanup followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted with 0.5% (V/V) formic acid in acetonitrile, and purified on a mixed-mode reversed phase strong cation exchange column (PRiME MCX). The chromatographic separation was performed on a Waters ACQUITY UPLC HSS T3 column by gradient elution using a mobile phase composed of acetonitrile and 0.1% formic acid. The analytes were detected in the positive ion mode using multiple reaction monitoring (MRM). Quantification was performed by the internal standard method. The results showed that good linearity was observed for trimetazidine and clomiphene in the concentration range of 0.3–100.0 ng/mL with determination coefficients (R²) > 0.999. The average recoveries of this method ranged from 93.4% to 112.1%, with relative standard deviations (RSDs) of 0.68%–4.81% (n = 6). The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.1 and 0.3 μg/kg, respectively. The developed method is sensitive, stable, practical, and suitable for the determination of trimetazidine and clomiphene in animal-derived foods, which can provide effective technical support for food safety assurance for sports events.

To address the difficulty of detecting aminoglycoside (AG) residues in the liver and kidney of livestock and poultry, the extraction solvent and purification method were improved. A rapid and accurate method for the determination of 12 AGs was developed using hydrophilic interaction chromatography-tandem mass spectrometry (HIC-MS/MS). This method employed phosphate buffer solution containing 50 g/L trichloroacetic acid and 50 g/L sodium chloride as the extraction solvent, which significantly improved the recovery of neomycin. After proper dilution, the extract was purified on a PRiME HLB solid phase extraction (SPE) column. Subsequently, the chromatographic separation was performed on an Obelisc R column using gradient elution with a mobile phase composed of acetonitrile and 1.0% formic acid in water (containing 1 mmol/L ammonium formate) before analysis by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The internal standard method was used for the quantitation of apramycin, hygromycin B, neomycin, and tobramycin, while the external standard method was adopted for the quantitation of the remaining eight compounds. The results revealed that the calibration curves for all analytes had good linearity within the corresponding concentration ranges, with determination coefficients of ≥ 0.99. The limits of detection (LOD) and quantitation (LOQ) ranged from 10 to 50 μg/kg and from 20 to 100 μg/kg, respectively. The recoveries for 8 blank liver and kidney matrices at low, medium, and high spiked levels were 78.0%–108.5%, with relative standard deviations (RSDs) ranging from 1.0% to 11.0% (n = 6). Using a single solid-phase extraction cartridge, the method developed herein is simple and easy to operate and can be used for accurate qualitative and quantitative analysis of AG residues in liver and kidney samples.

A high throughput rapid screening and quantitative analysis method based on a new purification method of single-step purification combined with gas chromatography-quadrupole-time of flight-mass spectrometry (GC-Q-TOF-MS) was developed for 46 alternative plasticizers (APs) in meat products, including adipate, citrate, organophosphatate, sebacate and benzoate. Samples were extracted with acetonitrile and purified through a SinChERS-General column, mass spectrometric information was collected in the full scan mode, and a high-resolution MS library of the 46 APs was created for rapid screening and quantitative determination of the target analytes. In order to improve the accuracy of the screening results, the extraction efficiency of different extraction solvents and the impurity removal ability of different purifying agents were investigated. The GC separation conditions and the high-resolution MS screening parameters were optimized, and the quantitative method was validated from the aspects of linear range and accuracy. The calibration curves for the 46 APs showed a good linear relationship (R² > 0.99) in the range of 0.01–0.2 mg/L, the screening detection limit was 0.03–0.05 mg/kg, and the limit of quantitation was 0.05–0.1 mg/kg. The average spiked recoveries were 68.6%–119.3% and the relative standard deviations (n = 6) were 0.6%–8.9% at three different spiked levels (0.1, 0.2, 0.5 mg/kg). The screening strategy was applied to 100 batches of actual samples. Di(2-ethylhexyl)adipate was detected in one batch of porcine head meat, and acetyl tributyl citrate in three batches of sausages. The proposed method is characterized by short detection time, low cost and high detection efficiency and allows rapid screening and quantitative analysis of the 46 APs in meat products, which provides technical support for the monitoring and risk early warning of APs contamination in meat products.

An improved acetyl chloride-methanol method was established for the rapid and accurate determination of linoleic acid, α-linolenic acid, docosahexaenoic acid (DHA) and arachidonic acid (ARA) in infant foods for special medicinal purpose with deeply hydrolyzed milk proteins and amino acids. The results showed that the optimal pretreatment conditions were 6 mL of reaction reagent, reaction for 60 minutes, and use of isooctane as extraction solvent. The linear range of linolenic acid and α-linolenic acid were 0.8–8.0 and 0.2–2.0 mg/mL, respectively. The linear ranges of DHA and ARA were 0.02–0.40 mg/mL, and the determination coefficients for all analytes were greater than or equal to 0.999 7. The limits of detection (LOD) and limits of quantitation (LOQ) of the developed method were 2 and 5 mg/100 g, respectively. This method was characterized by good repeatability (relative standard deviation (RSD) ≤ 3.3%), high precision (RSD ≤ 3.8%), good stability(RSD ≤ 2.6%), and high spiked recovery (ranging from 93.1% to 101.7%). Compared with its original version, the developed method could effectively solve the problem of incomplete reaction due to caking, with an at least 100% higher working efficiency.