Microbeads from recycled polystyrene yogurt cups for the in-syringe micro solid-phase extraction of four opioids from environmental and biological samples

A novel procedure for the extraction and determination of four opioids from environmental and biological fluids is presented. The main goal of this study is to introduce an innovative method for recycling plastic waste (i.e., polystyrene), aiming to achieve a consistent and dependable microstructure. Polystyrene microbeads, deposited on a rounded piece of paper, have been used as a sorbent material in an in-syringe extraction device. For the preparation of the polymeric sorbent, an emulsion solidification technique was optimized, achieving a regular micro material, obtained from second-hand regenerated polystyrene polymer from yogurt cups. This work presents, for the first time, the use of recycled polystyrene as micro-sorbent integrated into a paper-based support, combining waste valorization with effective analyte extraction. Under the optimum conditions, methadone, tramadol, codeine, and morphine were determined by direct injection mass spectrometry in environmental water as well as biofluids as saliva and urine. Limits of detection lower than 8 mu g L-1 and precision better than 14.9 % have been obtained for all the analytes in saliva and environmental water samples. The interference of the endogenous compounds of urine prevents the determination of morphine and codeine in this matrix. The trueness, expressed as relative recovery (RR), ranged from 85 % to 114 %. The extraction device has proved to be a valid and sustainable alternative to traditional sorbents, offering good analytical standards and being transversal for the application to different matrices. The simplicity and environmental friendliness of this approach make it highly adaptable across various research and industrial domains.