No abstract

1:3:12-substantially greater than the 1:2:3 ratio of their relative unsaturation.

Human milk provides the key nutrients necessary for infant growth and development. The objective of this study was to develop and validate a method to analyze the cholesterol content in liquid human milk samples along lactation. Direct saponification of the sample using ethanolic potassium hydroxide solution under cold conditions was applied and unsaponifiable matter was separated by centrifugation. Cholesterol was converted into its trimethylsilyl ether and the derivative analyzed by gas chromatography coupled with a flame ionization detector. Cholesterol was quantified using epicoprostanol as internal standard. The method is suitable for the determination of cholesterol in only 0.3 g of human milk. It has been validated showing good repeatability (CV(r) < 15%) and intermediate reproducibility (CV(iR) < 15%). The method was used to analyze human milk obtained from five mothers collected at day 30(±3), 60 (±3) and 120 (±3) after delivery. The cholesterol content in human milk slightly decreased from 13.1 mg/100 g at 1 month to 11.3 mg/100 g 120 days after delivery. The method can also be used to determine desmosterol, an intermediate in cholesterol synthesis.

Analysis of fatty acid profile in fats and oils is conventionally performed by gas-liquid chromatography (GLC) as their fatty acid methyl ester (FAME) derivatives. Accurate quantification can be achieved by adding internal standard(s) prior to the derivatization step and calibration of the system using certified FAME mixture. GLC instruments equipped with online sample preparation units became recently commercially available and in theory can be used to improve laboratory productivity and safety. However, studies showing that this type of approach can be used to obtain reliable results are scarce. In the present study, we developed a method suitable for quantitative analysis of fatty acids in fats and oils by robotic preparation and online GLC analysis of FAME using methanolic potassium hydroxide as transmethylation reagent. The method has been validated on different fats and oils including milk fat, palm kernel, rapeseed and long-chain polyunsaturated fatty acids containing oil samples. Method performance has been compared to the corresponding manual procedure and results show good repeatability [CV(r) < 5%] and good intermediate reproducibility [CV(iR) < 5%] in accordance with FDA guidelines. The results obtained show that transmethylation and GLC analysis of fats and oils can be robotized while remaining accurate and providing fatty acid data expressed as g of fatty acid per 100 g of sample. Compared to conventional methods, the volume of reagent and solvent is three times lower per sample analyzed with the robotized version which contributes to the reduction of waste and chemical risk exposure.