RAPID ANALYSIS OF GEOSMIN AND 2-METHYLISOBORNEOL IN WATER USING SOLID PHASE MICRO EXTRACTION PROCEDURES STEVEN W. LLOYD*, JEANNE M. LEA, PAUL V. ZIMBA and CASEY C. GRIMM USDA-ARS-SRRC, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, U.S.A. (First received July 1997; accepted in revised form October 1997) AbstractÐGeosmin (GSM) and 2-methylisoborneol (MIB) are algae metabolites with muddy/musty odors which contaminate water supplies and can be absorbed by aquatic organisms. Humans can per- ceive them in water and aquatic food products at ng/l (parts per trillion) concentrations. A rapid method employing solid phase micro extraction (SPME) has been developed for the analysis of GSM and MIB in water. Routine quanti®cation at mg/l concentrations can be accomplished using gas chro- matography and ¯ame ionization detection (FID) on a 6 ml aqueous sample with a total analysis time of less than 15 min. Concentration levels of MIB and GSM at 10 ng/l (parts per trillion) can be detected under optimal conditions employing GC/MS in selected ion monitoring mode. Standard sol- utions and water samples from MIB producing algae cultures were used to compare SPME against purge and trap (P&T) using both ¯ame ionization and mass spectrometric detection. Results obtained from SPME and P&T were similar in terms of reproducibility and sensitivity. This paper reports a simple, rapid method for monitoring the algal production of MIB and GSM at the mg/l range which can be extended to the drinking water levels at the ng/l range of concentrations. Published by Elsevier Science Ltd Key wordsÐaquaculture, 2-methylisoborneol, micro extraction, potable water, SPME, geosmin, o-¯avors, odor, Pseudanabaena NOMENCLATURE SPME: Solid phase micro extraction P&T: Purge and Trap GC: Gas chromatograph FID: Flame ionization detector ITD: Ion trap detector MSD: Mass selective detector S/N: Signal-to-noise ratio Coecient of variation: Ratio of standard deviation to mean, expressed as percent GSM: Geosmin MIB: 2-Methylisoborneol INTRODUCTION Planktonic and benthic algae (particularly cyano- bacteria), fungi, bacteria and actinomycetes are known to produce geosmin (GSM) and 2-methyliso- borneol (MIB). These semi-volatile compounds have a muddy, musty odor discernible by the human nose when present at concentrations >0.004±0.020 mg/l in water (Persson, 1980; Mallevaille and Suet, 1987). Although posing no known health hazard (Dionigi et al., 1993), munici- pal water systems are plagued with consumer com- plaints when these compounds exceed the threshold of human perception. Additionally, both com- pounds are rapidly absorbed from water into the lipid tissue of ®sh and other aquatic organisms and, when present in tissue at concentrations greater than ca. 0.6 mg/kg, render ®sh un®t for retail sale (Persson, 1980). At present, economical means are not available to remove these compounds from aquatic organisms (Widrig et al., 1996). Traditional analytical methods for monitoring MIB and GSM concentrations include closed-loop stripping (McGuire et al., 1981), liquid±liquid extraction (Johnsen and Kuan, 1987), steam distilla- tion (Bartels et al., 1989) and purge and trap (Johnsen and Lloyd, 1992). These techniques are eective, but are expensive, time consuming and labor intensive. Three alternative techniques have recently been introduced but have not gained broad acceptance. Membrane-based extraction (Zander and Pingert, 1997) can detect analytes at the parts per trillion level. Solid phase extraction (Conte et al., 1996) is rapid, inexpensive and can detect con- centrations at the parts per billion level. A third alternative is solid phase micro-extraction (SPME), a method pioneered by Pawliszyn and colleagues (Belardi and Pawliszyn, 1989). Solid phase microextraction is a simple and inex- pensive method for the analysis of volatile and Wat. Res. Vol. 32, No. 7, pp. 2140±2146, 1998 Published by Elsevier Science Ltd Printed in Great Britain 0043-1354/98 $19.00 + 0.00 PII: S0043-1354(97)00444-2 *Author to whom all correspondence should be addressed. [Tel: +1-504-286-4464; Fax: +1-504-286-4419; E-mail: slloyd@nola.srrc.usda.gov]. 2140