Separation and direct detection of long chain fatty acids and their methylesters by the non-aqueous reversed phase HPLC and silver ion chromatography, combined with CO laser pumped thermal lens spectrometry

摘要

The potential of the CO laser pumped dual beam thermal lens spectrometer (TLS) used as the detector of infrared (IR) absorbance in non-aqueous reversed-phase high pressure liquid chromatography (NARP-HPLC) and argentation chromatography (Ag-HPLC-TLS) has been investigated. The linoleic acid C18:2 (9,11) cis, cis, the conjugated linoleic acid C18:2 (9,12) cis, cis, and (9,11) cis, cis and oleic acid C18:1 (9) cis free fatty acids present in the test mixture were separated and detected by NARP-HPLC-TLS directly, i.e., without a need for their prederivatization. The limit of detection (LOD) for the present NARP-HPLC-TLS set-up was determined using either oleic acid C18:1 (9) cis or linoleic acid C18:2 (9,12) cis, cis as the only analyte. The LOD obtained at 1750 cm(-1) for C18:2 (9,12) cis, cis is 0.14% (v/v) with the standard deviation being 3.8% of the measured value. This is comparable to the LOD attainable by the bulk property refractive index detector (RID). For C18:1 (9) cis the LOD is 0.04% (v/v) with a standard deviation of 2.5%. The unique feature of the NARP-HPLC-TLS is its excellent selectivity; this was demonstrated experimentally by adding alcohols (octanol and decanol) that lack the C=O carbonyl group to the aforementioned mixture of three fatty acids.