Determination of EPA and DHA in Cod-liver Oil by GC

OBJECTIVE To establish a method for the determination of EPA and DHA in cod-liver oil by gas chromatography internal standard method with relative correction factor. METHODS The samples were saponified, methyl esterified and extracted with isooctane. The sample was chromatographed on a DB-23 (30 m×0.25 mm, 0.25 μm) capillary column with a FID detector. The column temperature was raised by program (the initial temperature was 170℃ and the temperature was raised to 225℃ at a rate of 1℃ ·min^-1 for 5 min). The injector temperature was 250℃, detector temperature was 280℃, high purity nitrogen was used as carrier gas, flow rate was 1.0 mL·min^-1, split flow was 100:1, methyl ester (C23:0) was used as an internal standard. RESULTS EPA and DHA showed good linear relationships (r=1.000 0) with the peak area ratio and concentration ratio at the range of 0.048 7-9.740 mg·mL^-1, 0.051 0-10.206 mg·mL^-1, respectively. The average recoveries of EPA and DHA were 98.7% (RSD=0.98%), 99.4% (RSD=1.34%). CONCLUSION The method is sample, accurate and reproducible. It can be used for the quality control and adulteration identification of cod-liver oil.