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.

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.