Spectrophotometric determination of trace amounts of cadmium with iodide and methyl violet

445-446A selective spectrophotometric method based on the interaction of an anionic iodo complex of cadmium with methyl violet has been described for the determination of trace amounts of cadmium. The developed method is precise, accurate and has been applied to determination of cadmium at trace levels (25 ppb) in sea water and high purity samples of indium and zinc materials

The host range of Tobacco streak virus in India and transmission by thrips

Tobacco streak virus (TSV) recently caused an epidemic in peanut (= groundnut, Arachis hypogaea) crops in Andhra Pradesh, India. In the epidemic area TSV occurred in many widely distributed weeds of which Parthenium hysterophorus probably plays a major role in its spread by thrips. Three thrips species, Megalurothrips usitatus, Frankliniella schultzei and Scirtothrips dorsalis were vectors in the presence of infected pollen. Of crop species, Helianthus annuus (sunflower) and Tagetes patula (marigold) could act as sources of inoculum. In limited tests, the virus was not seed-transmitted in the peanut cultivar JL-24 or in the sunflower hybrids KBSH-41, -42, -44, and -50, MSFH-17 and ZSH-976. Strategies adopted to reduce the incidence of TSV are discussed

Polymers imprinted with three REG1B peptides for electrochemical determination of Regenerating Protein 1B, a urinary biomarker for pancreatic ductal adenocarcinoma

Three peptides (each containing 13–18 amino acids) were synthesized and used as templates for molecular imprinting and epitope recognition of the Regenerating Protein 1B (REG1B), which is one of the urinary biomarkers for pancreatic ductal adenocarcinoma (PDAC). Poly(ethylene-co-vinyl alcohol)s were employed as the host for molecular imprinting of the peptides. Following their preparation, the molecularly imprinted polymers (MIP) were examined by cyclic voltammetry. The electrochemical responses of a screen-printed gold substrate coated with the MIP were measured at a working voltage of 300 mV (vs. Ag/AgCl); the entire protein and the peptides gave similar responses at concentrations of <1.0 pg⋅mL−1, with detection limits as low as 0.1 pg⋅mL−1. Urine samples from healthy and PDAC patients were then analyzed by using this modified gold electrode, and the results are in agreement with data obtained with ELISA

North American Wild Relatives of Grain Crops

The wild-growing relatives of the grain crops are useful for long-term worldwide crop improvement research. There are neglected examples that should be accessioned as living seeds in gene banks. Some of the grain crops, amaranth, barnyard millet, proso millet, quinoa, and foxtail millet, have understudied unique and potentially useful crop wild relatives in North America. Other grain crops, barley, buckwheat, and oats, have fewer relatives in North America that are mostly weeds from other continents with more diverse crop wild relatives. The expanding abilities of genomic science are a reason to accession the wild species since there are improved ways to study evolution within genera and make use of wide gene pools. Rare wild species, especially quinoa relatives in North American, should be acquired by gene banks in cooperation with biologists that already study and conserve at-risk plant populations. Many of the grain crop wild relatives are weeds that have evolved herbicide resistance that could be used in breeding new herbicide-resistant cultivars, so well-documented examples should be accessioned and also vouchered in gene banks

OFFLINE AND ONLINE SOLID PHASE EXTRACTION/PRECONCENTRATION OF INORGANICS

Solid phase extraction (SPE) is a powerful technique for preconcentration/removal or separation of trace and ultra trace amounts of toxic and nutrient elements. SPE effectively simplifies the labour intensive sample preparation, increase its reliability and eliminate the clean up step by using more selective extraction procedures. The synthesis of sorbents with a simplified procedure and diminution of the risks of errors shows the interest in the areas of environmental monitoring, geochemical exploration, food, agricultural, pharmaceutical, biochemical industry and high purity metal designing, etc. There is no universal SPE method because the sample pretreatment depends strongly on the analytical demand. But there is always an increasing demand for more sensitive, selective, rapid and reliable analytical procedures. Among the various materials, chelate modified naphthalene, activated carbon and chelate functionalized highly cross linked polymers are most important. In the biological and environmental field, large numbers of samples are to be analysed within a short span of time. Hence, online flow injection methods are preferred as they allow extraction, separation, identification and quantification of many numbers of analytes. The flow injection online preconcentration flame AAS procedure developed allows the determination of as low as 0.1 µg/l of nickel in soil and cobalt in human hair samples. The developed procedure is precise and rapid and allows the analysis of 30 samples per hour with a loading time of 60 s. The online FI manifold used in the present study permits high sampling, loading rates and thus resulting in higher preconcentration/enrichment factors of -725 and 600 for cobalt and nickel respectively with a 1 min preconcentration time compared to conventional FAAS signal. These enrichment factors are far superior to hitherto developed on line preconcentration procedures for inorganics. The instrumentation adopted in the present study allows much simpler equipment and low maintenance costs compared to costlier ICP-AES or ICP-MS instruments

Quinoline-8-thiol functionalized solid phase extractant for the preconcentration of ultratrace amounts of mercury (II)

569-572A solid material consisting of quinoline-8-thiol functionalized naphthalene provides a convenient, rapid and economical method for preconcentration of mercury. The mercury-quinolinc-8-thiol complex is quantitatively retained on naphthalene in the pH range 5.0-7.0. The solid mixture consisting of the metal complex together with naphthalene is dissolved in 2 ml of acetone and mercury content established spectrophotometrically. The calibration graphs are linear over the mercury concentration range 0.002-0.2 μg/ml. Ten replicate determinations of 1.0 μg of mercury present in 250 ml of solution gave a mean absorbance of 0.02 with a relative standard deviation of 3.1 %. The detection limit (corresponding to 3 times the standard deviation of the blank) and enrichment factors are found to be 0.001 μg/ml and 125 respectively. The accuracy of the developed preconcentration procedure has been tested by analyzing human hair standard reference material and human hair samples

EXCIMER FLUORESCENCE OF FLUORENONE IN STEADY STATE EXCITATION

1. L. J. Androews, Alain Doroulda and H. Linchitz, Journal of Phy. Chem. 82, 2304 (1978)Author Institution: Indian Institute of Technology, Madras, India 600036We have observed excimer fluorescence spectra of fluorenone in steady state excitation at 308 nm in both polar and non-polar solvents at room temperature. In addition to the monomer fluorescence band in the region of 340-355 nm, we have also observed another fluorescence band at longer wavelengths in the region 480-510 nm in all the solvents with concentration variation. The fluorescence lifetime measurements of these bands of fluorenone in the solvents Benzene and Acetonitrile revealed that the longer wavelength band with shorter lifetime is to be due to the formation of excimer. Combining our results of steady state fluorescence and the measurement of fluorescence lifetimes of monomer and excimer with the reported [1] studies of laser induced fluorescence, the mechanism of excimer formation has been established to be due to the Triplet-Triplet annihilation. The details for the formation of excimer and its mechanism will be presented

Kinetics of toluene alkylation with methanol on HZSM-8 zeolite catalyst

A detailed kinetic study of the alkylation of toluene with methanol on HZSM-8 zeolite was carried out in a fixed bed reactor. The catalyst showed high activity, selectivity, and stability. An attempt has been made to relate the overall changes taking place during the reaction. The experimental data are analyzed, and a reaction mechanism proposed based on the product pattern. The Langmuir-Hinshelwood-Hougen-Watson model with dual-site mechanism was used to derive the rate equation. The unknown parameters in the rate equations are estimated by a nonlinear regression method. The kinetic model based on the proposed reaction mechanism has predicted the conversion values, which are in close agreement with the experimentally observed values

Spectrophotometric determination of trace amounts of palladium(ll) using iodide and rhodamine 6G

342-343A sensitive and highly selective procedure for the spectrophotometric determination of palladium(II) is described. The method is based on the formation of ternary ion-association complex, Pd-I - -rhodamine 6G, in a citrate buffered medium. The colour system absorbs maximally at 575 nm with molar absorptivity of 8.2 x 104 1 mol- 1 cm - 1 and obeys Beer's law in the range 1-10 mg. The method has been applied successfully to the determination of palladium(II) in synthetic mixtures and in standard palladium activated charcoal