Determination of Atovaquone in Human Plasma by LC-MS-MS and Its Application to a Bioequivalence Study

A sensitive and selective method for the determination of atovaquone in human plasma was developed and validated. The procedure employed the use of an internal standard (chlorothalidone) and a solvent extraction step. Detection was by electrospray ionization tandem mass spectrometry with multiple reaction monitoring. The method showed a linear range from 50 to 2,000 ng mL^?1. The extraction recovery was determined to be 84.91 ± 6.42% (SD), the intra- and inter-day assay accuracy (relative error) was within 7.57% and precision (RSD) was below 6.06%. The method was successfully employed to analyze plasma samples and evaluate the pharmacokinetics of atovaquone in human volunteers.     

Alternative LC–MS–MS Method for Simultaneous Determination of Proguanil, Its Active Metabolite in Human Plasma and Application to a Bioequivalence Study

An alternative rapid and sensitive liquid chromatography–tandem mass spectrometry method has been developed and validated for simultaneous analysis of proguanil (PRO) and cycloguanil (CYC) in human plasma. The analytes were extracted from human plasma by solid phase extraction. Riluzole (RIL) was used as an internal standard for proguanil and cycloguanil. A HyPURITY Advance C18 column provided chromatographic separation of analytes followed by detection with mass spectrometry. The method involves simple isocratic chromatography conditions and mass spectrometric detection in the positive ionization mode using an API-4000 system. The proposed method has been validated with linear range of 1.5–150.0 ng mL^?1 for PRO and 0.5–50.0 ng mL^?1 for CYC. The inter-run and intra-run precision values are within 2.54, 9.19% for PRO and 1.99, 10.69% for CYC at LOQ levels. The overall recoveries for PRO and CYC were 102.52 and 106.72%, respectively. Total elution time was as low as 2.50 min. This validated method was used successfully for analysis of plasma samples from a bioequivalence study.     

Microwave-assisted aminolytic depolymerization of PET waste

Polyethylene terephthalate (PET) fibre waste and disposable soft drink bottle waste were subjected to depolymerization via aminolysis using excess of ethanolamine. The reaction was carried out under non conventional microwave energy in the presence of different simple chemicals as catalysts namely, sodium acetate, sodium bicarbonate and sodium sulphate. After repeated crystallization, pure bis (2-hydroxyethyl) terephthalamide (BHETA) was obtained with very high yields (nearly 90%). It was subjected to characterization by elemental analysis, melting point, FTIR, NMR and DSC. With the use of microwave energy, the process becomes economically viable since high yields of BHETA (>90%) at very low reaction time (4 min) could be obtained with common and cheap chemicals as catalysts.     

Validated LC-MS/MS method for quantification of agomelatine in human plasma and its application in a pharmacokinetic study

An analytical method based on liquid-liquid extraction has been developed and validated for analysis of agomelatine in human plasma. Fluoxetine was used as an internal standard for agomelatine. A Betasil C18 (4.0?×?100?mm, 5?μm) column provided chromatographic separation of analytes followed by detection with mass spectrometry. The method involves simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using an API-4000 system. The proposed method has been validated with linear range of 0.050-8.000?ng/ml for agomelatine. The intra-run and inter-run precision values are within 12.12% and 9.01%, respectively, for agomelatine at the lower limit of quantification level. The overall recovery for agomelatine and fluoxetine was 67.10% and 72.96%, respectively. This validated method was used successfully for analysis of plasma samples from a pharmacokinetic study.     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.