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Phosphatidylserine (PS) has received interest for its ability to improve cognitive abilities and behaviors. A new method for determining PS in milk-based nutritional products has been developed. The method includes a quick and simple sample preparation procedure, followed by high-performance liquid chromatography (HPLC) fluorescence detection (FLD) with an on-line 9-fluorenylmethyloxycarbonyl (FMOC) derivatization. The method allows PS to be determined in raw materials, milk powder and liquid milk products. The day-to-day ( n = 3 days) average recovery of over spike-in (at 100% PS content level) was 100%, and the method quantification limit is 53 mg per kg milk powder.

The selectivity and sensitivity of high-performance liquid chromatographic analysis for the determination of vitamin D3 and D2 content in medical nutritional products were improved with the aid of electrochemical detection in internal standard—oxidation/reduction mode. The relative standard deviation at the 13-nmol level for the analysis of vitamin D in products was 3.6% (n = 5). Recovery rates of added vitamin D3 were 97.5 ± 3.0% (mean ± S.D.). It is concluded that this method is much more selective and accurate for detection of vitamin D at the nanomolar level than ultraviolet detection methods.