Comparison of Fast GC/MS and conventional GC/MS for the determination of cholesterol oxidation products

Cholesterol oxidation products (COPs) are widely studied because they are likely involved in various chronic and degenerative diseases. The aim of this work was to develop a Fast GC/MS method for COPs analysis and to compare it with a conventional GC/MS method. A mixture of eight COPs standards (7α-hydroxycholesterol, 7β-hydroxycholesterol, 19-hydroxycholesterol (internal standard), 5,6α-epoxycholesterol, 5,6β-epoxycholesterol, cholestanetriol, 7-ketocholesterol and 25-hydroxycholesterol) was silylated and analyzed by Fast GC/MS. A capillary GC column Restek RTX-5 (10 m x 0.1 mm i.d. x 0.1 μm f.t.) coated with 5% diphenyl-polysiloxane was used. The temperature was programmed from 250 to 325°C at 20°C/min. The injector and the ion source temperatures were set at 325°C and 230°C, respectively. Helium was used as carrier gas at 43 cm/s. The injection was performed in the split mode (1:50). The electron energy was 70 eV. A mass range from 50 to 600 m/z was scanned at a rate of 3333 amu/s, which corresponded to 0.2 event time. The method gave a fast (total analysis time= 3.5 min) and satisfactory resolution (R > 1.2) of the COPs standards; the limits of detection and quantitation varied from 2.18 to 5.07 ng/mL and from 6.93 to 16.90 ng/mL, respectively. The interday RSD was < 5.79%, whereas the intraday RSD was < 4.29%, which are similar to those found in conventional GC/MS (< 4.28% and < 5.01%, respectively). COPs recoveries evaluated on spiked mice liver, ranged from 72 to 108% for Fast GC/MS, whereas they varied from 77 to 104% for conventional GC/MS. The analytical performance of the Fast GC/MS method for the determination of COPs, together with the consequent significant reduction of the analysis time and consumables, demonstrates that Fast GC/MS represents a good alternative to conventional GC/MS and evinces its great potential for the analysis of both food and biological samples.