Development of simple and sensitive spectrophotometric method for the determination of bendiocarb in its formulations and environmental samples

Facile, selective and sensitive spectrophotometric method has been developed for the determination of bendiocarb in its insecticidal formulations, fortified water, food grains, agriculture wastewater and agriculture soil samples with prepared reagents. The method was based on alkaline hydrolysis of the bendiocarb pesticide, and the resultant hydrolysis product of bendiocarb was coupled with 2,6-dibromo-4-methylaniline to give a yellow color product with λmaxof457 nmorcouplingwith2, 6−dibromo−4−nitroanilinetoproducearedcoloredproductwithλ_max of474~nmorcouplingwith2, 4, 6−tribromoanilinetoformorangeredcoloredproducthasaλ_max of465 nm.Underoptimalconditions, Beer'slawrangefor2, 6−dibromo−4−methylaniline(DBMA)wasfoundtobe0.6−−14.0~μgmL ^-1, 0.8−−10.0 μgmL ^-1 for2, 6−dibromo−4−nitroaniline(DBNA)and0.4−−10.0 μgmL ^-1 for2, 4, 6−tribromoaniline(TBA).Themolarabsorptivityofthecolorsystemswerefoundtobe4.126~×~10⁴ lmol ^-1 cm ^-1 forDBMA, 3.254×10⁴ l~mol ^-1 cm ^-1 forDBNAand2.812×10⁴ lmol ^-1 cm ^-1 forTBA.Sandell'softhecolorreactionsare0.018 μgcm ^-2(DBMA), 0.052 μgcm ^-2(DBNA)and0.065 μgcm ^-2$ (TBA) respectively. The effect of the non-target species on the determination of bendiocarb was studied. The formation of colored derivatives with the coupling agents is instantaneous and stable for 18 h, 30 h, and 12 h. Performance of the proposed methods were compared statistically in terms Student's F and t-tests with the reported methods.     

Toxins and bioactive compounds from cyanobacteria and their implications on human health

Many species of cyanobacteria (blue-green algae) produce secondary metabolites with potent biotoxic or cytotoxic properties. These metabolites differ from the intermediates and cofactor compounds that are essential for cell structural synthesis and energy transduction. The mass growth of cyanobacteria which develop in fresh, brackish and, marine waters commonly contain potent toxins. Cyanobacterial toxins or cyanotoxins are responsible for or implicated in animal poisoning, human gastroenteritis, dermal contact irritations and primary liver cancer in humans. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer to neurotoxicity. Several incidents of human illness and more recently, the death of 60 haemodialysis patients in Caruaru, Brazil, have been linked to the presence of microcystins in water. In response to the growing concern about the non-lethal acute and chronic effects of microcystins, World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L in drinking water. Cyanobacteria including microcystin-producing strains produce a large number of peptide compounds, e.g. micropeptins, cyanopeptolins, microviridin, circinamide, aeruginosin, with varying bioactivities and potential pharmacological application. This article discusses briefly cyanobacterial toxins and their implications on human health.     

Microphytobenthic biomass,species composition and environmental gradients in the mangrove intertidal region of the Andaman Archipelago,India

Monthly sampling in mangrove intertidal sediments of Andaman Archipelago was carried out during a 1-year study (January to December, 2013) in order to analyse the spatial and temporal distribution of microphytobenthos (MPB) and MPB biomass (sediment chlorophyll-a (chl-a)) in the surficial layer 0–1 cm. The MPB community was mainly composed of diatoms. The MPB biomass concentration in surface sediment (0–1 cm) ranged from 0.7 to 16.98 μg cm^?3. Population density of benthic diatoms varied from 78 to 224 ind cm^?3. This study identified 41 diatom taxa (27 pennate diatoms, 14 centric diatoms) in the sediment, and among all the diatom taxa, we distinguished few true planktonic species—Coscinodiscus centralis, Coscinodiscus marginatus, Leptocylindricus danicus, Planktoniella sol, Thalassiosira decipiens, Thalassionema nitzschioides and Thalassiothrix longissima. Overall, a high percentage of diatoms were pennate (81%) as opposed to centric. Based on benthic diatom abundance, species composition and distribution, MPB assemblages of sampling stations were grouped into two distinct clusters: one with St. 1 and St. 3 and another one with St. 2 and St. 4. Canonical correspondence analysis (CCA) revealed seasonality as the most important factor determining variability in diatom species composition among sampling sites. There was a distinct seasonal pattern in MPB biomass distribution and benthic diatom cell density during monsoon and post-monsoon seasons. Our results suggest that among various physical and chemical variables studied, greater levels of overlying water nutrients and sediment textures significantly correlated and were conducive factors for MPB. This is the first detailed study on the MPB from these mangrove sediments, providing benchmark data for future studies about these remote groups of Andaman and Nicobar Islands.     

Facile and Sensitive Spectrophotometric Determination of Carbosulfan in Formulations and Environmental Samples

Facile, selective and sensitive spectrophotometric method has been developed for the determination of carbosulfan in insecticidal formulations, fortified water, food grains, agriculture wastewater and soil samples with newly synthesized reagents. The method was based on acid and alkaline hydrolysis of the carbosulfan pesticide, and the resultant hydrolysis product of carbosulfan was coupled with 2,6-dibromo-4-methylaniline to give a yellow color product with λ _max of 464 nm or interaction with 2,6-dibromo-4-nitroaniline to produce yellow colored product with λ _max of 408 nm or coupling with 2,4,6-tribromoaniline to form red colored product has a λ _max of 471 nm. Under optimal conditions, Beer’s law range for 2,6-dibromo-4-methylaniline (DBMA) was found to be 0.2–12.0 μg ml⁻¹, 0.6–16.0 μg ml⁻¹ for 2,6-dibromo-4-nitroaniline (DBNA) and 0.4–15.0 μg ml⁻¹ for 2,4,6-tribromoaniline (TBA). The molar absorptivity of the color systems were found to be 3.112 × 10⁴ l mol⁻¹ cm⁻¹ for DBMA, 3.214 × 10⁴ l mol⁻¹ cm⁻¹ for DBNA and 3.881 × 10⁴ l mol⁻¹ cm⁻¹ for TBA. Sandell’s of the color reactions are 0.013 μg cm⁻² (DBMA), 0.012 μg cm⁻² (DBNA) and 0.011 μg cm⁻² (TBA) respectively. The effect of the non-target species on the determination of carbosulfan was studied to enhance the selectivity of the proposed methods. The formation of colored derivatives with the coupling agents is instantaneous and stable for 28, 30, and 26 h. Performance of the proposed methods were compared statistically in terms Student’s F and t-tests with the reported methods. An erratum to this article can be found at     

Studies of selenium in environmental samples and synthetic mixtures by spectrophotometry

A rapid, highly sensitive and selective spectrophotometric method for the determination of traces of selenium(IV) is described. The method is based on oxidation of p-nitroaniline by selenium(IV) followed by coupling reaction with N-(1-naphthalene-1-yl)ethane-1,2-diamine dihydrochloride (NEDA) in neutral medium to give red colored derivative with lambda(max) 515 nm and is stable for more than 10 days at 35 degrees C. Beer's law is obeyed for selenium(IV) in the concentration range of 0.02-3.2 microg ml(-1) at the wavelength of maximum absorption. The optimum reaction conditions and other analytical parameters were investigated to enhance the sensitivity of the present method. The detailed study of various interferences made the method more selective. The proposed method was successfully applied to the analysis of selenium in polluted water, natural water samples, plant material, soil samples, and synthetic mixtures. The results obtained were agreed with the reported methods at the 95% confidence level. The performance of proposed method was evaluated in terms of Student's t-test and Variance ratio f-test which indicates the significance of proposed method over reported method.