Total Cholesterol and Desmosterol Contents in Raw, UHT, Infant Formula Powder and Human Milks Determined by a New Fast Micro-HPLC Method

Abstract

A simple, fast, sensitive, and environmental friendly micro-method is described for the determination of desmosterol and cholesterol in milk samples using isocratic normal phase high performance liquid chromatography and diode array detection. After sample micro-saponification, the chromatographic separation is achieved in 10 min, further reduced to 6 min when only cholesterol is expected to be present. The method is accurate, presenting cholesterol and desmosterol recoveries >96% and inter-day RSD lower than 3%. Quantification limits were clearly below the requirements for any milk sample, with 40 and 20 μg/100 mL for cholesterol and desmosterol, respectively. Several raw and UHT commercial milk samples, infant powder formulas, and human breast milks were analyzed, with cholesterol and desmosterol (present only in the latter) contents within reported amounts. The proposed method proved to be simple and feasible for determination of a large number of samples, requiring less solvent consumption (9–13 mL of hexane for all saponification/extraction/chromatographic steps) and simpler equipment than most ones reported, and a further possibility of partial solvent recycling due to the isocratic chromatographic mode.