Abstract: An alternative method based on an off-line solid phase extraction (SPE) combined with large volume injection-gas chromatography-flame ionization detection (LVI-GC-FID) was developed to determine mineral oil saturated hydrocarbons (MOSH) in infant formula. The MOSH in samples were extracted with n-hexane. The extract was purified by solid phase extraction (SPE) on a column packed with silica gel impregnated silver nitrate and the optimal SPE cartridge was 5 mL glass syringe as indicated by comparison of different length to diameter ratios. Five milliliter of the pooled eluate was concentrated and then injected into the LVI-GC-FID system. The PTV parameters were as follows: the initial temperature was set at 45 ℃ and held for 1 min (split ratio was 200:1), then increased to 360 ℃ at a linear gradient of 250 ℃/min and held for 27 min (split valve was closed for 2 min followed by split ratio of 100:1). The GC column was heated from 35 ℃ (3 min) to 350 ℃ at 25 ℃/min, and then raised to 370 ℃ (10 min) at 5 ℃/min. FID temperature was set at 380 ℃. The GC injection volume was 40 μL. The calibration curve of paraffin oil was linear in the range of 2–500 mg/kg with correlation coefficient of 0.999. The quantification limit (LOQ) of MOSH in infant formula was 0.05 mg/kg. The recoveries from spiked samples were between 92.62% and 102.86%, with relative standard deviation (RSD) of 0.85%–2.57%. This procedure was applied to analyze MOSH in 10 commercial infant formula samples and the contaminant levels ranged from 0.24 to 1.30 mg/kg (0.12-0.85 mg/kg of MOSH between C16 and C35). The results suggested that it is necessary to routinely detect mineral oil contamination in infant formula for infant health.

Key words: infant formula, mineral oil-saturated hydrocarbons (MOSH), SPE, LVI-GC-FID