Dipalmitoylphosphatidylcholine in amniotic fluid quantified by fast-atom-bombardment mass spectrometry.
Dipalmitoylphosphatidylcholine (DPC) is quantified by taking advantage of stable-isotope-labeled d9-DPC as internal standard. Use of a mass spectrometer to measure the ratio of d9/d0 makes this procedure a quantitative one. d9-DPC was synthesized by refluxing dipalmitoylethanolamine with d3-methyl iodide in methanol in the presence of sodium bicarbonate for 26 h. The yield of d9-phosphatidylcholine (d9-lecithin) was 89% after column-chromatographic purification. Fast atom bombardment was used to desorb the preformed phosphatidylcholine ions in a mass spectrometer of Nier-Johnson geometry. In our assessment of accuracy and precision of this technique, we found a correlation coefficient of 0.9994 between signal and sample concentration. The method was less precise when the total d0- plus d9-DPC was less than 0.2 micrograms or when the ratio of d0- to d9-lecithin exceeded 100. The within-run CV was about 1.0%. The amount of DPC in amniotic fluid samples assessed by mass spectrometry was compared with results for total phosphatidylcholine quantified by thin-layer chromatography. The fate of DPC in various laboratory manipulations was also studied.
D000653:Amniotic Fluid / Q000032:analysis*; D002855:Chromatography, Thin Layer; D003903:Deuterium; D005260:Female; D006801:Humans; D013058:Mass Spectrometry; D011247:Pregnancy; D011296:Prenatal Diagnosis; D011663:Pulmonary Surfactants / Q000032:analysis* / Q000138:chemical synthesis; D012015:Reference Standards
D011663:Pulmonary Surfactants; D003903:Deuterium