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Objective The aim of the work was to develop and validate a simple, sensitive and selective Liquid chromatography with Mass spectroscopic method for simultaneous quantification of lidocaine and prilocaine in human plasma. Design and methods Analytes and the internal standards from human plasma were extracted by using solid- phase extraction technique using Waters Oasis® HLB 1 ​cc (30 ​mg) cartridges. The reconstituted samples were chromatographed on Phenomenex Kinetex EVO 4.6*100 ​mm 2.6 μ 100A column by using a mixture of acetonitrile and 5 ​mM ammonium acetate buffer (80:20, v/v) as the mobile phase at a flow rate of 0.6 ​mL/min. Results The method was validated over the concentration range of 0.10–201.80 ng/mL for lidocaine and 0.10–201.66 ng/mL for prilocaine. The calibration curve obtained was linear. Conclusion Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 3.0 min for each sample, make it possible to analyze more than 350 human plasma samples per day. The proposed method was found applicable for pharmacokinetic studies.

A highly sensitive, specific and rapid liquid chromatography-tandem mass spectrometry technique for the quantification of tasimelteon in human plasma has been developed and validated using tasimelteon-d 5 as internal standard. Liquid-liquid extraction technique with ethyl acetate was used for extraction of tasimelteon from the plasma.The chromatographic separation was achieved on an Agilent Zorbax, Eclipse, C 18 (4.6 × 50 mm, 5 μm) column using a mobile phase of acetonitrile and 0.02% formic acid buffer (85:15, v/v) with a flow rate of 0.5 mL/min. A detailed method validation was performed as per the United States Food and Drug Administration guidelines. The linear calibration curve was obtained over the concentration range 0.30-299 ng/mL. The API-4000 liquid chromatography-tandem mass spectrometry was operated under multiple reaction monitoring mode during analysis. The validated method was successfully applied to estimate plasma concentration of tasimelteon after oral administration of a single dose of a 20 mg capsule in healthy volunteers under fasting conditions. The maximum concentration of the drug achieved in the plasma was 314 ± 147 ng/mL and the time at which this concentration was attained was 0.54 ± 0.22 h.

A highly sensitive, specific and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) analytical method has been developed and validated for the determination of ospemifene in human plasma using ospemifene‐d4 as an internal standard. Solid‐phase extraction technique with Phenomenex Strata X‐33 μm polymeric sorbent cartridges (30 mg/1 mL) was used to extract the analytes from the plasma. The chromatographic separation was achieved on Agilent Eclipse XDB‐Phenyl, 4.6 × 75 mm, 3.5 μm column using the mobile phase composition of methanol and 20 mm ammonium formate buffer (90:10, v/v) at a flow rate of 0.9 mL/min. A detailed method validation was performed as per the US Food and Drug Administration guidelines and the calibration curve obtained was linear (r2 = 99) over the concentration range 5.02–3025 ng/mL. The API‐4500 MS/MS was operated under multiple reaction monitoring mode during the analysis. The proposed method was successfully applied to a pharmacokinetic study in healthy human volunteers after oral administration of an ospemifene 60 mg tablet under fed conditions.