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Accurate wavelength calibration and a high degree of spatial resolution are required of a multichannel detector for atomic emission spectrometry. While our experience has been with inductively coupled plasmas (ICP), the energetic nature of many emission sources produces complex spectra, and it is imperative that an unknown line be correctly identified. It is often the case that lines are observed that are not listed in common wavelength tables (1,2), and a comprehensive listing

Arsenic-accumulation pattern in eight types of vegetables commonly found in Bangladesh were studied using successive irrigation/harvesting technique. The study also included to find the threshold amount of arsenic that leads to exceed the maximum permissible limit (MPL) in those vegetables and several water-soil-plant arsenic concentration models. Total arsenic concentrations were measured by Hydride Generation–Atomic Absorption Spectroscopy (HG-AAS) technique. Arsenic-accumulation decreased in the order: Arum > Arum leaf > Amaranth > Brinjal > Radish > Indian Spinach > Carrot > Okra. A single harvesting of 10 irrigations with water (3.0 L/irrigation) having arsenic concentrations of ?0.45 mg L-1 to 0.071 m2 area (equivalent to 1.89 kg As ha-1) exceeded the MPL in vegetables (1 mg kg-1, wet weight). The concentration of accumulated arsenic in the vegetables increased linearly with time and exponentially with successive harvesting. Regression analyses showed that arsenic concentration in vegetables was positively correlated with that of irrigation water and soil (r = 0.796 for both cases).© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i3.10494 J. Sci. Res. 4 (3), 675-688 (2012)

ABSTMCTCyclic voltammetry of a 0.3 mM I'dCI2, 0.2 mM Na21rClc, 0.2 M K2S04 mixture at a glassy carbon electrode results in the gradual accumulation of a film, which contains Pd(I1) and iridium oxide, that promotes the quasi-reversible oxidation of TI(1). Cyclic voltammetry at 5 mV/s yields a peak potential difference of 35 mV at the modified electrode and about 700 mV at bare glassy carbon. The peak current for the linear scan voltammetric oxidation of 0.2 mM TI(1) in 1.0 M NaCl is directly proportional to the square root of scan rate up to 0.1 V/s. Both cyclic voltammetry and rotating disk voltammetry at modified electrodes provide data consistent with a two-electron oxidation. The modified electrode is suitable for the determination of thallium by differential pulse voltammetry in the micromolar range. INTK ODUCTIONA general problem in electroanalysis is that many species which undergo redox reactions in homogeneous solution are not oxidized or reduced at the usual electrode surfaces. Modification of electrodes by incorporation of redox mediators provides a means of alleviating this problem. Although this approach is now very common in electrochemical investigations [ 11, it has not been widely exploited for the development o f quantitative methods of 'The clescription of practical ailalytical methods that are based upon electrocatalytic modified electrodes has been slowed by two problems. First, in order to achieve a wide linear dynamic range, the measured current should be limited by diffusion of the analyte in the bulk solution t o the electrode surface. Charge propagation in the film, penetration of the analyte into the film, and the kinetics o f the cross-exchange reaction between the analyte and the mediator can be, at most, only minor factors. Second, the modified electrode must be highly stable.We have demonstrated that 3 film which was prepared by cyclic voltammetry of an RuC13, &Ru(CN), mixture at pH 2 at glassy carbon provides both the catalytic and stability properties needed for practical analytical methodology [ 21. This modified electrode yielded a current for the oxidation of As(II1) by linear ' To whom correspondence should be addressed.