Pharmacology of narcotic analgesics in the horse: quantitative detection of morphine in equine blood and urine and logit-Log transformations of this data.

Morphine was detected in equine biological fluids by a combination of liquid-liquid extraction and column chromatography, followed by derivatization and gas-liquid chromatographic assay, using electron capture detector. Recovery of morphine from the equine biological samples was poor. However, despite an overall recovery of less than 20%, this method had a detection limit of 0.2 ng/ml. Addition of 5,000 U of bovine liver beta-glucuronidase/ml of urine enabled detection of the drug in urine for up to 144 hours after horses were given 0.1 mg of morphine/kg of body weight. Morphine was found for at least 24 hours in serum samples. An adaptation of logit-log transformation of gas-liquid chromatographic data for linearization over 3 log units suggested a simple adaptation to existing semiautomated data handling systems.