Determination of 2-methylisoborneol and geosmin produced by Streptomyces sp. and Anabaena PCC7120

A new sample preparation and enrichment technique, headspace liquid-phase microextraction (HS-LPME) linked to gas chromatography-mass spectrometry (GC-MS), was developed for the determination of the off-flavor odorants, 2-methylisoborneol and geosmin, produced by Streptomyces sp. and Anabaena PCC7120. Some of the factors that influence the extraction efficiency of HS-LPME, such as the type of extraction solvent, ionic strength of sample solution, and sample agitation rate, were studied and optimized by a single factor test. Other factors, including extraction temperature, extraction time, microdrop volume, and headspace volume were optimized by orthogonal array design. Extraction of 2-methylisoborneol and geosmin was conducted by exposing 2.5 microL of 1-hexanol for 9 min at 50 degrees C in the headspace of a 20 mL vial with a 10 mL of sample solution saturated by NaCl and stirred at 800 rpm. The developed protocol demonstrated good repeatability (relative standard deviations (RSDs) < 5%), wide linear ranges (10-5000 ng/L, r2 > 0.999), and low limits of detection (LODs) for 2-methylisoborneol and geosmin (0.05 ng/L for both analytes). Subsequently, the method was successfully applied to extract the analytes in bacterial cultures with high recoveries (from 94% to 98%). Compared with headspace solid-phase microextraction (HS-SPME), HS-LPME demonstrates better linearity, precision, and recovery. Importantly, the sensitivity is about 1 order of magnitude higher than that of most HS-SPME. The results showed that HS-LPME coupled with GC-MS is a simple, convenient, rapid, sensitive, and effective method for the qualitative and quantitative analysis of 2-methylisoborneol and geosmin.