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novel chemiluminescence method for the determination of levofloxacin is presented, which is based on the inhibitory effect of levofloxacin on the chemiluminescence reaction between luminol and myoglobin in a flow-injection system. The decrement of chemiluminescence intensity is linear with the logarithm of levofloxacin concentration over the range from 0.07 to 100.0 ng/mL ( r = 0.9994), with the detection limit of 0.02 ng/mL (3σ). At a flow rate of 2.0 mL/min, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% ( n = 5). The proposed procedure was applied successfully to the determination of levofloxacin in pharmaceutical preparations, human urine and serum without any pretreatment procedure. [ABSTRACT FROM AUTHOR]

A sensitive chemiluminescence method based on enhancing the effect of cefetamet pivoxil on the chemiluminescent reaction between luminol and dissolved oxygen in a flow injection system was proposed for the determination of cefetamet pivoxil. The increment of the chemiluminescence intensity was proportional to the concentration of cefetamet pivoxil, which yields a calibration graph that is linear over the concentration from 0.4 to 100.0 ng/mL ( r 2 = 0.991) with the detection limit of 0.1 ng/mL (3σ). At a flow rate of 2.0 mL/min complete determination of cefetamet pivoxil, including sampling and washing, could be accomplished in 40 s with the RSD of less than 0.03 ( n = 5). The proposed method was applied successfully to the determination of cefetamet pivoxil in human urine and human serum. [ABSTRACT FROM AUTHOR]

Abstract  The interaction of lysozyme with bromophenol blue (BPB) in acetate buffer (pH 6.0) was studied by fluorescence quenching method for the first time. It was found that BPB could conspicuously quench the fluorescence of lysozyme by the static quenching process, possibly due to the binding on the active site near Trp62. The binding parameters including the binding constant and the number of binding site were calculated. The thermodynamic parameters ΔH°, ΔS° and ΔG° at different temperatures were obtained. The formation of lysozyme–BPB complex depended on the cooperation of the hydrophobic and electrostatic forces. And the binding average distance between lysozyme and BPB was determined. The effect of common metal ions on the binding constant of lysozyme–BPB was also examined. [ABSTRACT FROM AUTHOR]

Abstract  It was first found that 4-(2-pyridylazo)-resorcinol (PAR) can combine with lysozyme forming a polymolecular complex, with the molar ratio of 1:12 (lysozyme/PAR) in the medium of acetate buffer (pH 6.0). The fluorescence spectra suggested that PAR molecules may produce self-aggregation, and it was suggested that there are interactions between lysozyme and PAR possibly mainly on the cooperation of hydrophobic, electrostatic actions and chelate bond. The coordination complex of lysozyme-PAR can cause an enhanced resonance light scattering (RLS) signal with the scattering peak located at 521 nm. The increment of RLS intensity was linear with the concentration of lysozyme over the range from 1 ng mL-1 to 30.0 μg mL-1, with the limit of detection of 0.3 ng mL−1 (3σ, n = 5). Effect of experimental conditions, including temperature, pH, concentration of PAR, and the ionic strength on RLS were also tested. The proposed RLS method was successfully applied to analyze lysozyme in hen egg white, human saliva and tear samples without any special pretreatment. Compared with other methods, the proposed procedure is of high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

A sensitive chemiluminescence method for the determination of clindamycin is presented. The method is based on the inhibitory effect of clindamycin on the chemiluminescence reaction between luminol and myoglobin in a flow-injection system. The decrement in chemiluminescence intensity is linear with the logarithm of the clindamycin concentration over the range of 0.1–70.0 ng mL−1 ( r 2 = 0.9995), with a detection limit of 0.03 ng mL−1 (3σ). At a flow rate of 2.0 mL min−1, the complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n = 5). The procedure was applied to the determination of clindamycin in human serum and in monitoring the excretion of clindamycin in human urine samples without any pretreatment process. It was found that the excretive clindamycin concentration reached its maximum 3 hours after oral administration. The clindamycin excretive ratio in 9 hours was 10.84% in the body of the volunteer. [ABSTRACT FROM AUTHOR]