Use of quadrupole GC-MS and ion trap GC-MS-MS for determining 3-hydroxy fatty acids in settled house dust: relation to endotoxin activity

Gas chromatography-mass spectrometry (GC-MS) using a quadrupole instrument and GC-tandem MS (GC-MS-MS) using an ion trap instrument were applied to de termine 3-hydroxy fatty acids (3-OH FAs) with 10-18 carbon chain lengths, s pecific components of the endotoxin (lipopolysaccharide, LPS) of Gram-negat ive bacteria, in 30 house dust samples. The two methods provided similar de tection sensitivity for methyl ester/trimethylsilyl derivatives of the 3-OH FAs and allowed these acids to be distinguished from co-eluting 2-OH FA de rivatives. The correlation coefficients between endotoxin activity (Limulus test) and the combined amounts of 3-OH C-10, 3-OH C-12, and 3-OH C-14 were 0.60 and 0.61 when using GC-MS and GC- MS-MS, respectively. The superior s electivity of CC-MS-MS was illustrated in analyses of sub-milligram amounts of dust, where the chromatograms achieved by GC-MS were difficult to inter pret due to a high background and several closely eluting compounds. GC-MS- MS is therefore preferable to GC-MS for determining 3-OH FAs in minute (sub -milligram) amounts of dust.