In-tube solid-phase microextraction with poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary for direct high-performance liquid chromatographic determination of ketamine in urine samples

Ketamine was used for anaesthesia originally but has emerged as an abused drug in recent years. The prevalence of ketamine abuse demands a direct and rapid determination method. It is known that in-tube solid phase microextraction (in-tube SPME) can perform extraction with a capillary linked directly to a HPLC system, providing an automated and accurate extraction procedure. In this paper, an in-tube SPME coupled to HPLC method was developed for the determination of ketamine in urine samples with a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column as the extraction phase, which is expected to provide higher extraction efficiency than open tubular capillaries. After optimizing the extraction conditions, ketamine was extracted directly from urine samples in a wide dynamic linear range of 50-10,000 ng mL(-1), with the detection limit obtained as 6.4 ng mL(-1). The intra-day and inter-day precision for the method was 1.6% and 1.7%, respectively. The urine samples from suspect addicts have been successfully analyzed within 20 min. The re-usability of the monolithic column was also confirmed as no decrease of the extraction efficiency was shown after urine extraction.