Determination of Paraquat Dichloride from Water Samples Using Differential Pulse Cathodic Stripping Voltammetry

Paraquat dichloride commonly used as herbicide was determined by differential pulse cathodic stripping voltammetry technique. Experimental parameters, such as pH, accumulation time, accumulation potential and initial potential were optimized. In this analysis, paraquat dichloride exhibited a well-defined tworeduction peaks at ?0.35 and ?0.90 V in the pH range from 2.0 to 12.0. The 0.04 mol L^–1 BR buffer at pH 2.0 was found a suitable medium for electroanalytical determination of the paraquat dichloride. Interfering ions effect was not significant. Linear calibration plots for standard solutions of paraquat dichloride were obtained in the range of 0.25 to 1.75 × 10^–6 mol L^–1. Detection limit was 3.66 × 10^–8 mol L^–1. The optimized parameters were effectively applied for the determination of commercial paraquat dichloride and in artificial samples. Artificial samples were prepared by spiking paraquat dichloride into tap water and drinking water dispenser samples. The recovery value was 90.5% in drinking water dispenser samples and 91.7% in tap water samples at the concentration range of 1.00 × 10^–6 to 1.75 × 10^–6 mol L^–1.

     

A Study on Nucleate Boiling Heat Transfer Characteristics of Acetone on Smooth and Indented Surfaces

This article presents the nucleate boiling heat transfer characteristics of acetone at one bar on smooth and enhanced circular stainless steel surfaces (SS 316) of 20 mm diameter for heat flux between 1 and 4 W cm^? 2, which mimic the operating condition of a typical immersion electronic cooling system. The experimental heat transfer coefficient from the smooth surface is validated against Borishanski correlation [1] within acceptable limits of ± 5%. The steel smooth surface is enhanced by providing 100 equally spaced indents of 0.5 mm diameter and 0.05 mm depth. The experimental results indicate that the enhanced surface shows a good shift in the boiling curve and thus, enhancing the nucleate boiling heat transfer at a lesser wall super heat when compared to the smooth surface by around 35% for tested condition. The effect of subcooling on nucleate boiling in enhanced surface reveal that the heat transfer coefficient degrade by 40 to 55% for a sub cooling of 5 to 10 K. The influence of material is studied by a similar enhanced surface made of brass and compared for the same working condition. The brass enhanced surface showed an improved of around 50% against the steel-enhanced surface. Also, the influence of fluid is studied by comparing acetone and n-pentane, which showed that the latter an enhancement in heat transfer coefficient of 50% over the former.     

Genotypic Diversity of Mosquitocidal Bacteria (Bacillus sphaericus, B. thuringiensis, and B. cereus) Newly Isolated from Natural Sources

In the present study, to comprehend the genetic diversity of mosquitocidal bacteria, the genotypic analysis of 30 strains of Bacillus species isolated newly from diverse environmental sources has been conducted. Randomly amplified polymorphic DNA polymerase chain reaction was conducted to characterize the genotype diversity between the bacterial strains. The matrix of scores from each bacterial DNA was analyzed, and the correlation between the co-efficients and the similarity matrix data was computed. Clusters from dendrogram showing diversity among isolates could be distinguished genetically based on their origin of isolates. The first major cluster consists of 43 strains grouped under various subclusters (91.489 %). A second cluster contains only four strains (8.511 %). An average similarity value of 0.36 revealed the dendrogram split into 28 distinct “groups” or “clusters,” allowing almost a complete separation of strains within the Bacillus group isolated from various sources and thus facilitating assessment of genetic diversity of species and subspecies level. The conclusion from the result was that there was broad diversity among the mosquitocidal strains, and cluster analysis revealed the associations among the isolates based on their origin. A high level of polymorphism with distinct genetic lineages consequent to the source of origin of bacterial strains is the significant impact of this study.     

Identification of Cellulase Gene from the Metagenome of Equus burchelli Fecal Samples and Functional Characterization of a Novel Bifunctional Cellulolytic Enzyme

The metagenomic approach has been used successfully to isolate novel biocatalyst gene from uncultured microorganisms. The gene encoding exo-1,4-??-glucanase avicelase was amplified from the metagenome of the Equus burchelli fecal sample and cloned. The gene was found to be of 1,007?bp of nucleotide which encodes a protein of 318 amino acids with a calculated MW of 36?kDa. The deduced amino acid sequence was homologous with cellulases belonging to the glycosyl hydrolases 6 superfamily. The expressed protein was active towards the substrates avicel and carboxymethyl cellulose, indicating that it has bifunctional cellulolytic enzyme activity. The recombinant protein showed an activity of 5.23?U with specific activity of 6.8?U?mg^?1 protein with the substrate avicel, while when CMC was used, an activity of 3.0?U with a specific activity of 4.2?U?mg^?1 protein was achieved. Its optimum pH was determined to be 7.0 and optimum temperature of 35°C.     

Direct Chiral HPLC Method for the Simultaneous Determination of Warfarin Enantiomers and Its Impurities in Raw Material and Pharmaceutical Formulation: Application of Chemometric Protocol

Warfarin is a well-known anticoagulant agent that occurs in two enantiomers, (R)-(+)-warfarin and (S)-(?)-warfarin, in which 4-hydroxycoumarin and benzalacetone are commonly found as impurities. Due to the lack of analytical reports for the simultaneous estimation on warfarin and its impurities in bulk drug and pharmaceuticals, we aim at the simultaneous estimation and optimization of the chromatographic separation of warfarin and its related substances employing experimental design. Central composite design was employed to evaluate the influence of two independent variables (concentration of organic modifier and flow rate) on the output responses: capacity factor (k ₁), resolution of the peak (Rs _3,4), and retention time of the last peak (tR ₅), as well as to model these responses. Further, the central composite design results were combined in a multicriteria decision-making approach in order to obtain a set of optimal experimental conditions leading to the most desirable compromise between resolution and analysis time.