Ultra aq c18 column

A Dionex Ultimate 3000 HPLC system was used (Thermo Scientific) coupled to an API 4000 Qtrap LC–MS/MS (AB Sciex, Toronto, Canada) equipped with a TurboV Ion Spray source operating in positive ion mode. Analyst software (v.1.6.2) from AB Sciex was used for data acquisition and analysis. All MS parameters were optimized by direct infusion of solution of each analyte and source parameters (gas flows and temperatures) by flow injection. The ion source operated with spray voltage set at 5.3 kV, curtain gas at 24, ion source temperature at 550 °C, GS 1 70, GS 2 48; collision gas low. Analytes were detected using scheduled multiple reaction monitoring (MRM) acquisition, using 150 s detection window and 3 s target scan time; two transitions were monitored for each molecule. All the acquisition parameters are listed in the Tables S2 And S3. A Ultra AQ C18 column (100 × 2.1 mm, 3 µm; Restek, USA) was used; eluents were 5 mM AmAc in water (A) and acetonitrile (B), both containing 0.2% FoAc. The column temperature was kept at 35 °C. Chromatographic separation of the analytes was performed using a linear gradient; 10 µL injection volume was used. The column effluent was delivered to the mass spectrometer with no split.

To validate the developed colorimetric ketamine sensing method, a literature method based on LC-MS/MS was performed [32 (link)]. To show the linearity of the LC-MS/MS method, diluted working solutions with a concentration range of 1–30 μg L⁻¹ were prepared from the stock solution of ketamine. LC was carried out using a Restek Ultra-AQ C18 column (100 × 2.1 mm ID, 3 μm particle size) which was kept at 45 °C temperature. The gradient program was carried out the same as in the literature [32 (link)]. The positive ion mode electrospray ionisation method was used for LC-MS/MS analysis. The precursor ion and product ion were m/z 238.1 and 124.8 for ketamine, respectively (collision energy: 29 V). Student’s t- and F-tests were used to statistically compare the outcomes of spectrophotometry and LC-MS/MS.