A rapid and simple method for determination of halothane, isoflurane and sevoflurane in blood using gas chromatography

We have developed a technique to determine the concentration of volatile anesthetics (halothane, isoflurane and sevoflurane) in blood that is a modification of a method used for volatile anesthetics in Krebs solution. Methylene chloride was the internal standard and chloroform was used to extract the volatile anesthetic from blood. The congealed blood proteins were separated from the chloroform solvent (containing anesthetic) using a two-compartment vial that filtered out the proteinaceous material during centrifuging. Recovery averaged 102%. Linearity was excellent (r = 0.992-0.999) in the 50-600, 50-300 and 50-300 microg/mL range for halothane, isoflurane and sevoflurane, respectively. Intra-day and inter-day precisions were likewise excellent, with relative standard deviations <5.3 and <7.1%, respectively. Accuracy ranged from 0.8 to 9.5% of the estimated theoretical value. Extracted anesthetic in chloroform solvent was stable over 4-5 days, with <3% variability. The time from obtaining the blood sample to determination of the concentration from the chromatographic peak was 15 min or less.