SIMPLE AND SENSITIVE SPECTROPHOTO¬METRIC ASSAY OF OFLOXACIN IN PHARMACEUTICALS BASED ON ION-PAIR REACTION

Two simple, sensitive, economical and extraction-free spectrophotometric methods have been developed for the determination of ofloxacin (OFX) in pure form and in tablets. The methods are based on the interaction of OFX with two sulphonphthalein dyes, namely, bromothymol blue (method A) and bromophenol blue (method B) in dichloromethane medium to form stable, yellow-colored ion–pair complexes peaking at 410 nm. Under the optimum conditions, OFX could be assayed in the concentration ranges 1.25-20 and 1.0-16 µg mL-1 OFX by methods A and B, respectively, with correlation coefficient of 0.999 in both methods. The apparent molar absorptivity values are calculated to be 1.74104 and 2.18104, L moL-1 cm-1, for method A and B, respectively, with corres¬pond¬ing Sandell sensitivity values of 0.021 and 0.017 µg cm-2. The limits of detec¬tion (LOD) and quantification (LOQ) are also reported. The stoichiometry of the reaction was found to be 1:1 in both cases and the conditional stability cons¬tants (Kf) of the complexes have also been reported. The intra-day and inter-day variation was assessed. The methods were applied to determine OFX from marked tablet formulations. Statistical analysis proved that the proposed methods were both accurate and precise

Spectrophotometric determination of quetiapine fumarate in pharmaceuticals and human urine by two charge-transfer complexation reactions

Two simple, rapid and accurate spectrophotometric procedures are proposed for the determination of quetiapine fumarate (QTF) in pharmaceuticals and in spiked human urine. The methods are based on charge transfer complexation reactions of free base form of the drug (quetiapine, QTP), as n-electron donor (D), with either p-chloranilic acid (p-CAA) (method A) or 2,3-dichloro-5,6-dicyanoquinone (DDQ) (method B) as π-acceptors (A). The coloured charge transfer complexes produced exhibit absorption maxima at 520 and 540 nm, in method A and method B, respectively. The experimental conditions such as reagent concentration, reaction solvent and time have been carefully optimized to achieve the maximum sensitivity. Beer’s law is obeyed over the concentration ranges of 8.0 - 160 and 4.0 - 80.0 μg ml-1, for method A and method B, respectively. The calculated molar absorptivity values are 1.77 × 103 and 4.59 × 103 l mol-1cm-1, respectively, for method A and method B. The Sandell sensitivity values, limits of detection (LOD) and quantification (LOQ) have also been reported. The stoichiometry of the reaction in both cases was accomplished adopting the limiting logarithmic method and was found to be 1: 2 (D: A). The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of QTF in pharmaceutical formulations and spiked human urine

Sensitive and selective spectrophotometric assay of rizatriptan benzoate in pharmaceuticals using three sulphonphthalein dyes

Three simple, rapid, selective and sensitive spectrophotometric methods are described for the determination of rizatriptan benzoate (RTB) in bulk drug and in tablets. The methods are based on the formation of intense yellow colored ion–pair complexes between RTB and sulphonphthalein acid dyes, namely, bromophenol blue (BPB), bromocresol purple (BCP), bromothymol blue (BTB) in chloroform medium. The colored products are measured at 425 nm (RTB–BPB complex, RTB–BCP complex) and 420 nm (RTB–BTB complex). The reactions were extremely rapid at room temperature and the absorbance values remained constant for 90 min (methods A and B) and over 12 h (method C). Beer’s law was obeyed in the concentration ranges of 0.8–16.0, 1.0–20.0 and 1.2–24 μg ml−1 with molar absorptivity values of 1.76 × 104, 1.96 × 104 and 1.63 × 104 l mol−1 cm−1 for BPB, BCP and BTB methods, respectively. The limits of quantification (LOQ) were 0.39, 0.34 and 0.27 μg ml−1 for BPB, BCP and BTB methods, respectively. Other method validation parameters, such as precision, accuracy, robustness, ruggedness and selectivity, were satisfactory. The composition of the ion–pair was found to be 1:1 by Job’s method. The proposed methods were successfully applied to the determination of RTB in commercial tablets. No interference was observed from common tablet adjuvants. Statistical comparison of the results with the reference method showed excellent agreement and indicated no significant difference in accuracy and precision

Efficient MEG signal decoding of direction in wrist movement using curve fitting (EMDC)

Magnetoencephalography (MEG) can be used as an effective non-invasive interface with the brain to provide movement-related information similar to invasive signal recordings. This paper proposes a reliable and efficient algorithm for classification of wrist movement in four directions from MEG signals of two subjects. Our approach involves signal smoothing, design of a class-specific Unique Identifier Signal (UIS) and curve fitting to identify the direction in a given test signal. Our algorithm is evaluated with the data set provided in BCI competition 2008. Our simulations show the best average prediction accuracy of 88.84 for this four-class classification problem. The results of the proposed model are found to be superior to most other techniques in vogue. © 2011 IEEE

Simple and rapid spectrophotometric assay of levocetirizine in pharmaceuticals through charge-transfer complexation using chloranilic acid and 2,3-dichloro-5,6-dicyanoquinone as π-acceptors

Simple, rapid, selective and fairly sensitive method is described for the determination of levocetirizine (LCTZ) in pure form and in its dosage forms. The method is based on the formation of intensely colored charge-transfer (CT) complexes between LCTZ as donor with two π acceptors, chloranilic acid (CAA) and 2,3-dichloro-5,6-dicyanoquinone (DDQ) in acetonitrile-dioxane medium. The colored products were measured at 520 nm (CAA) and 590 nm (DDQ). Optimization of experimentation conditions is described. Beer’s law is obeyed over the concentration ranges 3-120 and 2-80 µg mL^-1 for CAA and DDQ reagents, respectively, with corresponding molar absorptivity values of 4.0×10³ and 5.5×10³ L mol cm^-1. The limits of quantification (LOQ) are 2.99 and 1.69 µg mL^-1 for above reagents, respectively. Other method validation parameters, such as accuracy, precision, robustness and ruggedness, and selectivity are also reported. The composition of CT complex was found to be 1:1. The proposed method was successfully applied to the determination of the active ingredient in commercial tablets; and the results were in good agreement with those obtained by the official method.DOI: http://dx.doi.org/10.4314/bcse.v26i3.

Determination of raloxifene hydrochloride in human urine by LC-MS-MS

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed to determine raloxifene hydrochloride (RLX) in human urine. After a solid-phase extraction with SPE cartridge, the urine sample was analyzed on a C18 column (Symmetry 3.5μm; 50 mm4.6 mm i.d) interfaced with a triple quadruple tandem mass spectrometer. A positive electrospray ionization was employed as the ionization source. The mobile phase consisted of ammonium acetate (pH 4.0)–acetonitrile (60:40, v/v).The method was linear over a concentration range of 20–1000 ng mL-1. The lower limit of quantitation was 20 ng mL-1. The intra-day and inter-day relative standard deviation across three validation runs over the entire concentration range was <10.5%. The accuracy determined at three concentrations (50, 500 and 850 ng mL-1 RLX) was within ±0.84% in terms of relative errors

Permanganometric determination of etamsylate in bulk drug and in tablets

One titrimetric and two spectrophotometric methods which are simple, selective, sensitive, accurate, precise and economical for the determination of etamsylate (ETM) In bulk drug and In tablets employing permanganate as the oxidimetric reagent are described. In titrimetry, ETM is titrated directly with permanganate in sulphuric acid medium. A direct spectrophotometry (method A) involves treating the aqueous solution of the drug with permanganate in alkaline medium and measuring the bluish green product at 6 10 nm. In indirect spectrophotometry (method 8), the drug solution was treated with a fixed concentration of permanganate in H2SO4 medium, and after a specified time the unreacted permanganate was measured at 545 nm. The molar combining ratio in titrimetry and the optimum assay conditions were studied. Titrimetry is applicable over 1-10 mg range and the calculations are based on a 1:4 (ETM:KMnO4) molar ratio. In spectrophotometry, Beer's law is obeyed over 0.5- 5.0 and 1.5- -15 mu g ml(-1) for method A and B, respectively. The molar absorptivity values are calculated to be 2.79x10(4) and 4.17x10(4) / mol(-1) cm(-1) for method A and B, respectively and the corresponding sandell sensitivity values are 0 0094 and 0.0063 mu g cm(-2). The limits of detection (LOD) and quantification (LOQ) are also reported for spectrophotometric methods. The applicability of the developed methods was demonstrated by the determination of etamsylate in pure drug as well as in commercial dosage forms