SPE and LC-MS/MS determination of 14 illicit drugs in surface waters from the Natural Park of L'Albufera (ValSncia, Spain)

A simple and robust method using solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of 14 drugs of abuse and their metabolites (cocainics, amphetamine-like compounds, cannabinoids, and opiates) in surface waters has been developed. Seven SPE adsorbents (Oasis HLB, Oasis MCX, Oasis Wax, Supelselect HLB, Strata-X, Strata-XCW), amount of sorbent bed, water volume, and pH were investigated. The highest recoveries, as well as the simplest protocol, were obtained for Oasis HLB cartridges (6 mL/200 mg) using 250 mL of water. The proposed method was linear in a concentration range from 0.03-6 to 300-60,000 ng/L depending on the compound, with correlation coefficients higher than 0.998. Matrix effects have been studied in surface water samples, and several isotope-labeled internal standards have been evaluated as a way to compensate the signal suppression observed. Limits of detection (LODs) and quantification (LOQs) ranged from 0.01 to 1.54 ng/L and from 0.03 to 5.13 ng/L, respectively. Recoveries were 71-102% at the LOQ level and 77-104 at 50 ng/L. The intra-day and intermediate precisions were from 1% to 8% and from 2% to 11%, respectively. The present work reports for the first time the occurrence of drugs of abuse residues in surface water samples from the Natural Park of L'Albufera (Valencia, Spain). Codeine, cocaine, benzoylecgonine, ecgonine methylester, amphetamine, 3,4-methylendioxy methamphetamine, morphine, and methadone were quantified with median values of 11.10, 0.02, 5.59, 0.08, 0.21, 0.75 and 0.14 ng/L respectively, and 11-nor-9-carboxy-Delta 9-tetrahydrocannabinol was detected in one sample at levels < LOQ.