DEVELOPMENT AND VALIDATION OF A STABILITY INDICATING REVERSE PHASEHIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD FOR SIMULTANEOUS DETERMINATION OF CLINDAMYCIN, METRONIDAZOLE, AND CLOTRIMAZOLE IN PHARMACEUTICAL COMBINED DOSAGE FORMS

Objective: The objective of present work was to develop and validate a simple, fast, precise, selective, and accurate reverse phase high-performanceliquid chromatography method for the simultaneous determination of Clindamycine, Metronidazole and Clotrimazole in a pharmaceutical dosage form.Methods: The separation of these three drugs was achieved on ODS 250×4.6 mm, 5 mm C18 column. Mobile phase containing 0.1% ortho phosphoricacid buffer and acetonitrile in the ratio of 55:45 v/v was pumped through column at a flow rate of 1 ml/minute. Temperature was maintained at 30°Cand ultraviolet detection at 238 nm.Results: The retention times were observed to be 2.591, 3.584, and 4.221 minutes for Clindamycine, Metronidazole, and Clotrimazole, respectively.Linearity was found to be 25-150 μg/ml Clindamycine, Metronidazole, and Clotrimazole, respectively. The method was statistically validated forlinearity, recovery, the limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision. The stress testing of the drugs individually andtheir mixture are carried out under acidic, alkaline, oxidation, photostability, and thermal degradation conditions and its degradation products arewell resolved from the analyte peaks.Conclusion: This method was successfully validated for accuracy, precision, and linearity, LOD, and LOQ.Keywords: Clindamycine, Metronidazole, Clotrimazole, Reverse phase-high performance liquid chromatography, Simultaneous determination,Degradation studies

Distributed PV Power Extraction Based on a Modified Interleaved SEPIC for Nonuniform Irradiation Conditions

Nonuniform irradiation of a photovoltaic (PV) source, consisting of series-connected modules with bypass diodes, results in multiple peaks in the power-voltage characteristics. This makes the maximum power point tracking (MPPT) difficult because the conventional MPPT algorithms can only deal with single power peak characteristics. This paper proposes a novel distributed MPPT (DMPPT) scheme based on an interleaved single-ended primary inductor converter (SEPIC) converter configuration for compensating the mismatch in characteristics of series-connected PV modules. The proposed scheme obviates the need for bypass diodes across the modules, resulting in single-peak power-voltage characteristics. The proposed DMPPT circuit is derived from an interleaved SEPIC converter that works on the "return energy" concept. The proposed configuration equalizes the voltages across PV modules of the string, resulting in their operating close to its maximum power point. Discontinuous conduction mode of operation is implemented, obviating the voltage-sensing requirements across modules, eliminating the reverse recovery loss of diodes and the turn-on loss of the main switch. The proposed DMPPT scheme uses a simple circuit with reduced control complexity and needs only a few passive elements and only one switching device, compared with the existing DMPPT schemes. The theoretical claims are validated with simulations and extensive hardware experiments

Novel Control Scheme for an Interleaved Flyback Converter Based Solar PV Microinverter to Achieve High Efficiency

The paper proposes an optimal control strategy for the interleaved flyback based microinverter to improve its efficiency over the entire operating range. This control scheme is based on the choice of an appropriate operating mode [1-converter discontinuous conduction mode (DCM), 1-converter boundary conduction mode (BCM), 2-converter DCM, and 2-converter BCM] at various instantaneous power magnitudes. The proposed control method reduces the fixed losses associated with the gate driver and the transformer at the low power level. It also reduces the switching losses that may result due to the extremely high-frequency operation of the BCM at the low power level. Additionally, it also reduces the conduction losses through low current peak due to BCM and equal current sharing between the two converters at the high power level. Switching losses, due to the low-frequency operation of the BCM at a high power level, are also reduced. Operating mode selection of the interleaved inverter at a particular power level is based on the information of optimal efficiency. Detailed calculations of peak current references have been carried out for the various operating modes of the interleaved flyback based microinverter. Simulation and experimental results have validated that the proposed controlmethod results in better efficiency compared with the conventional (DCM, hybrid DCM/BCM, hybrid 1-converter/2-converter) control methods with the output current total harmonic distortion remaining within the specified limits

Adaptive Velocity PSO for Global Maximum Power Control of a PV Array Under Nonuniform Irradiation Conditions

Nonuniform irradiation conditions (NUIC) of a photovoltaic (PV) array pose a major challenge to optimal power utilization due to multiple power peaks (consisting of multiple local peaks and one global peak) in power-voltage (P-V) characteristics. This paper proposes an adaptive velocity particle swarm optimization (AVPSO) algorithm for tracking the global maximum of the multiple peak P-V characteristics. The AVPSO algorithm continuously adjusts individual particle's weight factor and cognitive acceleration coefficient, depending upon its distance from the global best position during the tracking process. The advantage of the adaptive weight factor is reduced power oscillations in the region of global best position, while adaptive cognitive factor prevents the particles from getting trapped in local minima. Thus, the adaptive nature of the particle's velocity improves the global maximum power point tracking (GMPPT) time and power yield. Another feature involves limiting the particle's velocity to avoid skipping intermediate peaks. Additionally, AVPSO also includes the ability to sort particle's positions in each iteration, which prevents large changes in the PV voltage, thereby reducing the control effort of a PV voltage controller. The effectiveness of the proposed GMPPT algorithm is investigated for static and dynamic performance under different NUIC patterns and mitigation of local minima trapping issues through analysis, simulations, and extensive hardware experiments

Global maximum power point tracking of PV arrays under partial shading conditions using a modified particle velocity-based PSO technique

Modern PV arrays are generally designed with bypass diodes to avoid damage. However, such arrays exhibit multiple peaks in their P-V characteristics under partial shading conditions. Owing to the limitation in the abilities of conventional maximum power point tracking algorithms in such cases, the application of other optimisation algorithms has been explored. This study proposes a modified particle velocity-based particle swarm optimisation (MPV-PSO) algorithm for tracking the global power peak of the multiple peak P-V characteristics. The MPV-PSO algorithm is both adaptive and deterministic in nature. It eliminates the inherent randomness in the conventional PSO algorithm by excluding the use of random numbers in the velocity equation. The proposed algorithm also eliminates the need for tuning the weight factor, the cognitive and social acceleration coefficients by introducing adaptive values for them which adjust themselves based on the particle position. These adaptive values also solve problems like oscillations about the global best position during steady-state operation and particles getting trapped in local minima. The effectiveness of the proposed MPV-PSO algorithm is validated through MATLAB/Simulink simulations and hardware experiments

A RAPID AND SENSITIVE LIQUID CHROMATOGRAPHY- MASS SPECTROMETRY/MASS SPECTROMETRY METHOD FOR ESTIMATION OF PIOGLITAZONE, KETO PIOGLITAZONE AND HYDROXY PIOGLITAZONE IN HUMAN PLASMA

  Objective: The main objective of the work was to develop a straightforward, fast and selective liquid chromatography/tandem mass spectrometry (LC-MS/MS) assay for determination of pioglitazone (PG), keto pioglitazone (KPG), and hydroxy pioglitazone (HPG) in human plasma and to validate as per recent guidelines.Methods: Analyte and the internal standard (IS) were extracted from plasma through liquid-liquid extraction and chromatographed on a Xterra RP18, 100×4.6, 5 μ column using methanol: acetonitrile mixture and 10 mM Ammonium formate buffer (70:30, v/v) as the mobile phase at a flow rate of 0.7 mL/min. The API-3200 Q Trap LC-MS/MS instrument in multiple reaction monitoring mode was used for detection. Diphenhydramine was utilized as IS.Results: The linearity was established in the concentration range of 20.15-1007.58 ng/mL for PG, 20.35-1017.58 ng/mL for KPG, and 19.68-491.22 ng/mL for HPG in human plasma. All the validation parameters were well within the acceptance limits.Conclusion: A new simple LC-MS/MS method was developed for the determination of PG, KPG, and HPG in human plasma. This method can be easily applied for the estimation of pharmacokinetic parameters of PG, KPG, and HPG