Simultaneous Spectrophotometric Determination of Imipramine Hydrochloride with Chlordiazepoxide and Nortriptyline Hydrochloride with Fluphenazine Hydrochloride

Spectrophotometry was used with multivariate calibration to simultaneously determine compounds in mixtures. Two antidepressant mixtures were investigated: imipramine hydrochloride and chlordiazepoxide and nortriptyline hydrochloride and fluphenazine hydrochloride. Considerable spectral overlap and large differences in component concentrations were challenges. Since this type of analysis is often performed using complex algorithms, a simple strategy was used here for the simultaneous determination of both mixture components by classical least squares, principal component regression, and partial least squares. Experimental design was used to select the optimum parameters including the wavelength range, sampling interval, software, and derivative order. Accuracy was enhanced by proper wavelength selection. In addition, derivatives of the raw spectra improved the selectivity. The standard deviation, deviation of mean recovery from 100%, and prediction ability of the models were used as the responses. In respect to these terms, first-order derivatization of the spectra and a sampling interval of 1?nm provided the best results. In particular, the low concentration compounds in the mixtures (chlordiazepoxide and fluphenazine) were determined more accurately with precision lower than 3%. The strategy was used for the quality control of pharmaceuticals containing the mixtures without chemical pretreatment.     

Stability indicating methods for the determination of norfloxacin in mixture with tinidazole

Three stability indicating assay methods are developed for the determination of norfloxacin (Nor) in the presence of its decarboxylated degradation product and in mixture with tinidazole (Tnd). The proposed methods are reversed phase ion pair liquid chromatography (LC), thin layer densitometry (TLC) and second derivative ratio spectra zero crossing spectrophotometry ((2)DD). Chromatographic separation was achieved on mu-Bondapack C18 column 5 microm (300 mm x 3.9 mm, I.D.) and precoated silica gel TLC stationary phases for LC and TLC methods, respectively. Mobile phases consisting of phosphate buffer pH 3.2 : methanol (3 : 1, v/v) containing 0.005 M pentane sulfonic acid sodium salt and isopropanol : butanol : concentrated ammonia : water (25 : 50 : 5 : 25, v/v/v/v) were used for resolution of Nor and Tnd by both techniques, respectively. Detection was carried at 280 nm. In the ratio spectra method, detection of Nor was carried at 282 nm. Linearity, accuracy and precision were found to be acceptable over concentration ranges of 20-225 microg/ml, 0.8-4 microg/spot and 1-7 microg/ml for Nor by LC, TLC and (2)DD methods and over concentration ranges of 37.5-375 microg/ml and 4.8-20 microg/spot for Tnd by LC and TLC methods respectively. The suggested methods were successfully applied for the determination of both drugs in bulk powder, laboratory prepared mixtures and in commercial samples. Statistical comparison between the results obtained by the proposed and the reference methods was carried out using Student t-test, F ratio and one way ANOVA.     

Enhanced sampling of bacteria and their biofilms from food contact surfaces with robust cationic modified swabs

The swab sampling method combined with detection approaches is a common approach used to monitor pathogenic microbes in food facilities and to determine the adequateness of regular cleaning and sanitation processes. Thus, the efficiency of a swab material for both the capture and release of bacteria has a significant impact on the detection of pathogens. A novel functionalized cotton swab was developed based on cationic functionalization of the cotton swab for improving the sampling of bacteria from surfaces. The cationic modified swab was fabricated using UV-induced grafting of cationic monomer (METAC) onto a regular cotton swab. The prepared cationic cotton swabs displayed a persistent positive charge regardless of the pH conditions. The cationic swabs demonstrated 150–200% enhancement in the swab performance for Gram-positive and Gram-negative bacteria under any sampling conditions compared to the regular cotton swab as well as a significant enhancement in the bacteria sampling at the low bacterial concentrations. Furthermore, the cationic cotton swabs showed significant improvement at least 4 folds in the sampling performance of the bacterial biofilm from the stainless-steel surfaces compared to the cotton swabs. These results illustrate the role of modified swabs in enhancing the sampling of bacteria from contact surfaces and their potential impact on improved monitoring of microbial contamination and verification of surface sanitization.