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Abstract
High performance liquid chromatography procedures using non-porous ODS columns were developed for the assay of aspirin-caffeine-butalbital (mixture 1) and acetaminophen-caffeine-butalbital (mixture 2). The separation and quantitation of Mixture 1 were achieved on a 3.0 μm non-porous silica ODS column at ambient temperature using a mobile phase of 98:2 v/v 50 mM phosphate buffer pH 3.0-acetonitrile at a flow rate of 1.5 mL/min with detection at 220 nm. The method showed linearity for aspirin-caffeine-butalbital in the 325–6500, 40–800, and 50–1000 ng/mL ranges, respectively. Intra- and inter-day RSD values were 0.19–1.72% and 1.30–1.49% for aspirin, 0.08–1.17% and 0.06–1.09% for caffeine, and 0.09–1.55% and 0.07–2.10% for butalbital, respectively. Accuracy of intra and inter-day were in the 0.70–1.27% and 0.20–1.13% for aspirin, 0.05–0.06% and 0.004–0.09% for caffeine, and 0.02–0.09 and 0.02–0.05% for butalbital, respectively.
The limits of detection for aspirin, caffeine, and butalbital were 5, 5, and 10 ng/mL, respectively, based on a signal noise ratio of 3 and a 50 μL injection. The separation and quantitation of mixture 2 were achieved on a 3.0 μm non-porous silica ODS column at ambient temperature using a mobile phase of 97:3 v/v 50 mM phosphate buffer pH 2.5-methanol at a flow rate of 2.0 mL/min with detection at 220 nm. The method showed linearity for acetaminophen, caffeine, and butalbital in the 650–6500, 100–800, and 125–1000 ng/mL ranges, respectively. Intra- and inter-day RSD values were 0.06–2.64% and 2.18–4.19% for acetaminophen, 2.24–4.76% and 4.09–4.12% for caffeine, and 1.65–3.94% and 3.33–3.40% for butalbital, respectively. Accuracy of intra and inter-day were in the 1.13–2.86% and 0.08–0.10% for acetaminophen, 1.12–4.62% and 0.04–2.75% for caffeine, and 0.34–3.48% and 0.02–2.30% for butalbital, respectively. The limits of detection for acetaminophen, caffeine, and butalbital were 20, 20, and 35 ng/mL, respectively, based on a signal noise ratio of 3 and a 10 μL injection.
ACKNOWLEDGMENT
The authors thank MICRA Scientific, Inc. for the gifts of the nonporous ODS columns used in this study.