Quantification of Trans-4-methyl-1-cyclohexane Carboxylic Acid in Culture Media for Microorganisms by GC-MS

An analytical method was developed for the determination of a candidate naphthenic acid compound using GC-MS,specifically trans-4-methyl-1-cyclohexane carboxylic acid(4MCCA) in culture media.The methods for removal of bacteria from the media and pH condition for extraction 4MCCA were optimized.Effective removal of bacteria from 4MCCA-containing media was achieved by vacuum filtration using a 0.45-μm filter and a 0.22-μm filter separately under a pressure of 0.1 kPa.The ideal acidic range for extraction 4MCCA was pH 2-3.Under the optimized conditions,the samples of 4MCCA were extracted using a liquid-liquid extraction process by dichloromethane.The 4MCCA was determined by external standard method under the SIS mode by GC-MS.The linear range was 0.10-100 mg/L(R2=0.9994).The limit of detection and quantification were 0.10 ng and 0.34 ng.The precision of inner-day and inter-day was 2.7%-6.6% and 1.5%-11.3%,respectively.This method was applied to monitor biodegradation for 150 mg/L 4MCCA.The rates of biodegradation of 4MCCA were 24.7%,51.8%and 55.0%by 24,48,and 96 h,respectively.