Application of polypropylene tubes as single-use and low-cost sorptive extraction materials for the determination of benzodiazepines and zolpidem in water samples

• First low-cost polymeric sorbent extraction for the determination of benzodiazepines in water
• Minimum consumption of organic solvents (less than 1.5 mL)
• High number of samples can be extracted simultaneously in an unattended way.
• Enrichment factors: 574–1204, extraction efficiencies: 41–86%
• LOQs: 0.4–94 ng L− 1, RSD < 20%, relative recoveries 87–117% for (waste)water

This work presents a method for the simultaneous determination in water of 17 benzodiazepines (BZPs) and a related pharmaceutical (zolpidem) by extraction with low-cost polymeric sorbents followed by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Different polymers were considered: polydimethylsiloxane (PDMS), polypropylene (PP), and polyethersulfone (PES), providing the second one (PP) higher responses. Hence, different operational parameters were considered and optimized using PP as polymeric material for the extraction: ionic strength (as NaCl addition), sample pH, sample volume, extraction time, amount of extractant phase, desorption solvent and desorption time. Under the optimized conditions, 70 mL of sample (pH 9) with 30% (w/v) of NaCl was extracted with four PP tubes (10 mm, ≈ 1 mg each) during 14 h at room temperature, the analytes eluted with 1 mL of acetone and the eluate concentrated to dryness, reconstituted in methanol and analyzed by LC–MS/MS. Under these conditions, extraction efficiencies ranged between 41 and 86%, leading to enrichment factors from 574 to 1204. Satisfactory trueness, expressed as relative recoveries, was obtained in the 87–117% range. LOQs ranged from 0.4 to 31 ng L− 1 and from 2 to 94 ng L− 1 for river and influent wastewater, respectively. None of the analytes were detected in river water while 6 of them were detected in wastewater samples in concentrations between 4 and 152 ng L− 1, being lorazepam and oxazepam the analytes detected at the highest concentration level. Thus, PP may become a good alternative to PDMS or PES for the extraction of basic analytes.