Determination Of Amoxicillin In Plasma Research Articles

Simple and Rapid LC Method for the Determination of Amoxicillin in Plasma

A rapid, simple, accurate, sensitive and reproducible high performance liquid chromatographic (HPLC) method for the quantitation of amoxicillin in human plasma using cefadroxil as an internal standard (IS) has been developed and validated. The procedure involves an ultrafiltration step prior to a reversed-phase liquid chromatography. The drug and the IS were eluted from Symmetry® C18 stainless steel column (5 μm, 150 × 4.6 mm I.D.) at room temperature with a mobile phase consisting of methanol: 75 mM potassium dihydrogen phosphate buffer solution (10:90,v/v) (pH adjusted to 3.0 with phosphoric acid), at a flow rate of 1.5 mL min−1. The effluent was monitored using a UV detector set at 228 nm. Each analysis required no longer than 10 min. Quantitation was achieved by measurement of the peak area ratio of the drug to the internal standard, and the limit of quantification of amoxicillin in plasma was 0.5 μg mL−1 (RSD% and DEVs% were <15%). The method showed good precision: the intraday RSD% values for amoxicillin were in the range of 1.41–6.86% whereas the values for interday were in the range of 1.13–8.16% at four different concentrations. The method is rapid (total run time <12 min) and accurate (DEVs,% <10%). The mean relative recovery was 99.67% and the mean absolute recovery was 86.68%. Stability testing shows that amoxicillin is stable in plasma for at least 4 weeks when stored at −70 °C. The method was successfully applied in a pharmacokinetic study involving healthy rabbits.

Development and Validation of a Solid-Phase Extraction-Liquid Chromatographic Method for Determination of Amoxicillin in Plasma

A bioanalytic method for the determination of amoxicillin in plasma by hydrophilic interaction solid-phase extraction and liquid chromatography has been developed and validated. Plasma was precipitated with acetonitrile before samples were loaded onto a zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) solid-phase extraction column. Amoxicillin was analyzed by liquid chromatography on an Aquasil (150 x 4.6 mm) LC column with mobile-phase acetonitrile: phosphate buffer (pH 2.5; 0.1 mol/L) (7:93, v/v) and UV detection at 230 nm. A regression model using 1/concentration weighting was found the most appropriate for quantification. The intraassay precision for plasma was 3.3% at 15.0 microg/mL and 10.9% at 0.200 microg/mL. The interassay precision for plasma was 1.8% at 15.0 microg/mL and 7.5% at 0.200 microg/mL. The total-assay precision for plasma over 4 days using a total of 20 replicates was 13.2%, 5.5%, and 3.8% at 0.200 microg/mL, 3.00 microg/mL, and 15.0 microg/mL, respectively. The lower limit of quantification and the limit of detection were 0.050 microg/mL and 0.025 microg/mL, respectively, for 100 microL plasma. Long-term storage stability studies of amoxicillin in plasma indicate that a temperature of -80 degrees C is necessary to prevent degradation of amoxicillin.

Determination of amoxicillin in plasma by high-performance liquid chromatography with fluorescence detection after on-line oxidation

A simplified high-performance liquid chromatographic method for the determination of amoxicillin in plasma is described. Specific and sensitive fluorescence detection was achieved by on-line post-column electrochemical oxidation, using an electrochemical detector. Owing to the high specificity of the detection system, deproteinized plasma samples could be injected directly without prior treatment. This method permits a very fast and reproducible determination of amoxicillin in plasma on a routine basis at levels, down to 50 ng/ml. The absolute detection limit is about 10 pg injected.