HIGHLIGHTS Arsenic is considered as one of the highly hazardous elements in the environment and a serious carcinogen for the human health. An enzymatic method has been described by using arsenite oxidase for arsenic detection. Residual activity of the immobilized enzyme was 43% of the initial activity after being recycled 10 times.

The aim of the present work was to study a simple colorimetric and potentiometric biosensor based on urease inhibition by Pb (II) ions for its estimation in milk samples. Urease immobilized on nylon membrane by hydrosol gel method was used as the biocomponent to demonstrate the metal effect on the enzyme activity using phenol red as the pH indicator. A lower limit detection of 38.6µm was achieved in the milk and the enzyme membranes were stable for more than two months at 4ºC. In potentiometric approach, response of an ion selective electrode (ISE) to changing ammonium ion concentration as a consequence of urease inhibition by Pb (II) ions was explored to achieve a detection limit of 9.66 µm. Lead specificity was attained by means of masking agents 1,10 - phenanthroline and sodium potassium tartarate. Validation of the developed biosensors was carried out with spiked milk samples.

To optimize nursery practices for efficient plant production procedures and to keep up to the ever growing demand of seedlings, identification of the most suitable species of arbuscular mycorrhizal fungi (AMF), specific for a given tree species, is clearly a necessary task. Sixty days old seedlings of Neem (Azadirachta indica A. Juss) raised in root trainers were inoculated with six species of AMF and a mixed inoculum (consortia) and kept in green house. Performances of the treatments on this tree species were evaluated in terms of growth parameters like plant height shoot collar diameter, biomass and phosphorous uptake capabilities. Significant and varied increase in the growth parameters and phosphorous uptake was observed for most of the AMF species against control. Consortia culture was found to be the best suited AMF treatment for A.indica, while Glomus intraradices and Glomus mosseae were the best performing single species cultures. It is the first time in the state of Gujarat that a wide variety of AMF species, isolated from the typical semi-arid region of western India, were tested for the best growth performance with one of the most important tree species for the concerned region.

The aim of this work was to study the isolation of glucose oxidase (GOx) from Aspergillus niger in aqueous two phase system consisting of PEG 7500 (150g l-1), potassium phosphate (175 g l-1, K2HPO4 +KH2PO4) and glucose (10 gl-1), the enzyme was partitioned in polymer phase. By sequential extraction GOx (69.2%) was recovered in polymer phase by 11.8 fold purification, giving a yield of 129U mg protein-¹.

Neste trabalho foi desenvolvido um procedimento espectrofotométrico derivativo para a determinação de etilenobisditiocarbamato de zinco(II), Zineb, com base na formação do complexo azul de molibdato de sódio em meio ácido. A lei de Beer é obedecida até 40 µg mL-1 de Zineb no comprimento de onda de 956 nm. O limite de detecção foi de 0,006 µg mL-1 de Zineb para a razão S/N = 3 considerando diversos parâmetros como o efeito da concentração de ácido. A interferência de diversos íons na determinação de Zineb foi avaliada. A maioria dos metais alcalinos e sais metálicos não causou interferências. O procedimento tem boa sensibilidade e foi empregado para a determinação de Zineb em amostras comerciais de alimentos contendo Dithane Z 78 e Hexathane 75% W.P.. Os resultados foram comparados com procedimentos previamente propostos. Zineb foi determinado com sucesso sem a ocorrência de interferências na presença de outros ditiocarbamatos, tais como Ziram, Thiram, Ferbam etc.

A derivative spectrophotometric procedure was developed for the determination of zinc(II) ethylenebisdithiocarbamate, Zineb, after formation of its blue colored complex with sodium molybdate in acidic medium. The Beer's law is obeyed up to 40 µg mL-1of Zineb at 956 nm. The detection limit was 0.006 µg mL-1 for Zineb when S/N ratio is 3 taking into account various parameters, such as the effect of acid concentration. The interference of a large number of ions on the determination of Zineb was evaluated. Most of the alkaline metals and metal salts did not interfere. The procedure presented proper sensitivity and it was applied for determining Zineb in food stuffs and commercial samples of Dithane Z 78 and Hexathane 75% W.P.. Results were compared with earlier reported methods. Zineb was successfully determined without any interferences in the presence of other dithiocarbamates like ziram, thiram, ferbam etc.