Expanding the applicability of biocompatible Salivette® as extraction sorbent in pipette-tip format: Determination of memantine in human urine as proof-of-concept

Sample preparation of complex matrices is commonly performed using either liquid-based or sorbent-based extraction techniques, which have been developed and utilized in numerous variations. Pipette-tip microextraction is a relatively recent technique that has proven to be an effective approach for sample preparation. Various materials have been utilized in this technique including monoliths, silica-based, paper-based, functionalized-inner wall pipette tips and nature-derived materials. However, some of these approaches assist in tip clogging, they still face the issue of prolonged extraction times. In this study, the commercially available Salivette® synthetic material is proposed as a cost-effective extraction sorbent using the pipette tip format. To evaluate the effectiveness of the proposed method, the determination of urinary memantine was chosen as a case study. The sorbent was cut into semicircles and incorporated into 1 mL pipette tip without frits. The proposed approach offers comparable/improved results relative to previous published pipette tip extraction techniques while it minimizes the number of aspirating/dispensing steps, thereby reducing analyst fatigue. The drug was derivatized prior its determination by liquid chromatography and fluorescence detection. Excellent linearity in the range of 5 - 500 ng/mL (r > 0.9920), adequate intra-day and inter-day precision (<14.7 %) and recoveries (ranged between 87.4-115.9 % in all cases) were observed. The limit of detection and the lower limit of quantitation were 1 and 5 ng/mL, respectively. A single washing step of undiluted urine appeared to be sufficient to eliminate the matrix effects. The reported research demonstrated that the biocompatible Salivette® sorbent can be successfully used in pipette tip microextraction. It is commercially available, eliminating the need for the synthesis and characterization of new materials. It requires small amounts of solvents per analysis, supporting the principles of Green Sample Preparation. To enhance sample throughput, a multichannel pipette could also be considered. The innovation and the green character of the analytical scheme were evaluated using the newly developed Violet Innovation Grade Index and AGREEprep tools.