Abstract: An alternative method based on an off-line solid phase extraction (SPE) combined with gas chromatography-flame ionization detection (GC-FID) method was developed to determine mineral oil saturated hydrocarbons (MOSH) in Chocolate. The MOSH was extracted with n-hexane. The extract was purified by solid phase extraction (SPE) on a column packed with silica gel impregnated silver nitrate. By comparing the purification effect of silica gel with different silver nitrate content, 0.3% (w/w) silver nitrate silica gel was determined to be the best, and a glass syringe was used as the container for filling silver nitrate silica gel, and the volume of eluent was determined to be 10 mL. The pooled eluate was concentrated and then injected into the GC-FID system. The inject temperature was 275 ℃. The GC column was heated from 50 ℃ to 60 ℃ at 2.5 ℃/min, and then raised to 280 ℃ at 22 ℃/min,and then raised to 320 ℃(12 min) at 30 ℃/min. FID temperature was set at 350 ℃. The GC injection volume was 2 μL. The results showed that the calibration curve of paraffin oil was linear in the range of 1-80 mg/kg with a correlation coefficient of 0.999. The quantification limit (LOQ) of MOSH in chocolate was 0.5 mg/kg. The recoveries from spiked samples were between 90.0% and 99.2%, with the relative standard deviation (RSD) of 6.1%-9.9%. The accuracy, precision and sensitivity of the method are in line with the requirements of saturated hydrocarbon mineral oil detection, and can be used for monitoring the contamination of saturated hydrocarbon mineral oil in chocolate.
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