Journal of Bioanalysis & Biomedicine

A novel high-performance thin-layer chromatographic method has been developed for the resolution of fi ve-coexisting nucleobases (adenine, guanine, cytosine, thymine, and uracil). The nucleobases were separated on aluminum-backed cellulose 60 F 254 plates with the aid of 5.0% aqueous sodium deoxycholate (NaDC)-acetonitrile (AcN), 1:3 (v/v) as mobile phase. All the nucleobases were viewed on HPTLC plates under 254nm UV light. The order of R F value given in parentheses was guanine (0.12) < adenine (0.44) < cytosine (0.50) < uracil (0.72) < thymine (0.84). The effect of pH (acidity or basicity) of the mobile phase on the retention of individual nucleobases was examined. Furthermore, the effect of interference of mono- (Li + , Na + ), and bivalent (Mg 2+ , Ba 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Pb 2+ ) cations; mono- (Br - , CH 3 COO - , NO 3 - , IO 4 - ) , and bivalent (CO 3 2- , SO 4 2- MoO 4 2- ) anions, and complexing ligands (urea, and EDTA) on the retention behavior of nucleobases were also assessed. The chromatography of nucleobases was also performed on silica 60 F 254 , RP-18 F 254 , and kieselgel 60 F 254 HPTLC plates. These TLC plates failed to separate the coexisting purines and pyrimidines. The detection limit of all nucleobases on cellulose 60 F 254 layers was 5.4 × 10 -2 μ g spot -1 . The proposed method is rapid, easy, and reliable. It can be applied for routine analysis of DNA, and RNA nucleobases.

The purpose of this study was to determine naproxen concentrations in rat plasma samples by HPLC and to compare the bioavailability of a generic and two compounded naproxen sodium suspensions (test 1 and test 2). Analysis was run at a fl ow rate of 1.2 mL.min^-1 with a mobile phase of acetonitrile: NaH2PO4 0.01 M pH 4.00 (50:50, v/v) at 280 nm, using a C18 column (150 mm x 4.6 mm, 5 μm). The calibration curve was linear (R2 = 0.9987) over the range of 0.25 - 200 μg.mL^-1. The precision for inter and intra-day analysis ranged from 2.46% to 12.39%. C_max, T_max and AUCt were 191.25 ± 11.17 μg.mL^-1, 1.00 ± 0.106 h and 2438.16 ± 291.34 μg.h.mL^-1 for the reference drug, 188.22 ± 24.78 μg.mL^-1, 1.06 ± 0.092 h and 1755.02 ± 228.90 μg.h.mL^-1 for test 1, and 160.50 ± 10.58 μg.mL^-1, 0.66 ± 0.102 h and 1955.28 ± 142.80 μg.h.mL^-1 for test 2. No signifi cant differences were found based on analysis of variance, with mean values and 90% CI of test2/reference ratio (C_max 83.92% and AUCt 80.19%). For test1/reference ratio, the result was C_max 98.41% and AUCt 71.98%. Based on these results, it can be concluded that the validated method was successfully applied to this study; the test 1 formulation failed to demonstrate a bioequivalence to the reference drug; however, the test 2 and reference naproxen sodium suspension were bioequivalent in terms of the rate and extent of absorption under these conditions.

Disposition kinetic studies of gatifl oxacin (GAT) was conducted after single i.v. dose (10 mg/kg) in six healthy and six mastitic Black Bengal lactating goats. Mastitis was induced by coagulase positive S. aureus. The concentration of the drug was estimated by HPLC. The maximum milk concentration was found to be signifi cantly (p< 0.05) higher in mastitic goats (12.78 ± 3.11 μg/ml) than healthy (9.17 ± 1.41 μg/ml). The therapeutic milk concentration in mastitic goats (0.13 ± 0.05 to 12.41 ± 2.99 μg/ml) was maintained for 48 h which was signifi cantly (p<0.01) longer than in healthy goats (24 h). The elimination half-life in plasma and milk of mastitic goats (5.82 ± 0.67 and 8.20±0.21 h) was signifi cantly (p<0.01) higher than healthy (4.54 ± 0.75 and 3.67±0.09 h).It indicates that GAT persisted in the body of mastitic goats for a longer duration. The AUC_milk/AUC_plasma ratio was 5.82. The t½ milk /t½ plasma ratio was 1.41. MIC in this experiment was considered to be 0.1 μg/ml. The AUC/MIC ratio of plasma and milk of mastitic goats were 180 and 1049 respectively. On the basis of the results obtained it was concluded that GAT exhibited improved pharmacokinetic parameters with good penetration and longer persistence in mastitic milk, which will be of great help in the treatment of mastitis in goats caused by S. aureus.

An accurate and precise LC method using diode array detection for the determination of voriconazole in human serum/plasma samples has been developed and validated for use in pharmacokinetic studies.

A harmonized validation strategy based on the accuracy profiles was used as a suitable tool to guaranty the quality of the results obtained by the use of the analytical validated methodology in a routine setting and to ensure the risk of obtaining the future measurements outside the previously fixed acceptance limits.

As pointed recently the FDA, a weighted 1/x2 linear regression model ranging from 0.25 to 10.35 mg/L was selected as the simplest calibration model that maximized the accuracy all over the range. Relative bias was < 7%, assay imprecision was always < 4% and mean extraction recovery from plasma was > 90%. So, accuracy did not exceed the acceptance limits settled at±15% according to the FDA or Washington conference regulatory requirements for bioanalytical methods.

The validated analytical procedure compliants with strongest regulatory standards and their results are rapid and good enough to enable the laboratory to routinely provide useful and accurate pharmacokinetic data in time to adjust patient regimens.

Casiopeína IIgly is a mixed chelate coordination complex with copper core that have demonstrated high antineoplas- tic activity in vitro and in vivo . In the present work, a de- veloped a nd va lida ted method for mea surement of Casiopeína IIgly in beagle dog and its application in a phar- macokinetic study is reported. The analyte was isolated from blood by solid-phase extraction using Strata X cartridges. The analysis was carried out on a Synergy Polar-RP col- umn (30 X 2.0 mm) using an isocratic elution and MeOH/ HFBA 0.1% (4:6) as the mobile phase. An Agilent LC/ MSD Trap VL equipped with an ionization electrospray source, was operated in selective ion storage (SIS) using stable ion [Cu (II) (F 7 C 3 COO) 4,7-dimethyl phen ] + with 484 m/z for quantification result of ESI reaction between Casiopeína IIgly and HFBA. The method demonstrated to be linear (r = 0.9992) in the range from the 0.1 to 15 μ g/ml with a limit of detection (LOD) of 50 ng/ml. All the param- eters of validation such as selectivity, accuracy, precision and recovery were within the required limits. Pharmacoki- netics assay was carried out at 2 doses, indicated a high elimination rate.