A novel method for the separation and preconcentration of MnVII/MnII with crosslinked chitosan (CCTS) and determination by flame atomic absorption spectrometry (FAAS) has been developed. The adsorption rate of CCTS for MnVII was 98% at pH 3, while MnII was not adsorbed. MnVII was eluted from the CCTS with 10% (m/v) oxammonium hydrochloride and determined by FAAS. MnII was determined from the total manganese present after MnII in the water samples was transformed into MnVII. The detection limit (3 sigma, n = 10) for MnVII was 1.98 micrograms l-1 and the relative standard deviation less than 6.6% at the 10 micrograms l-1 level. The method was applied to environmental water samples with recoveries of between 95-103%.
A fast tunable dual-wavelength laser based on in-fiber acousto-optic Mach-Zehnder interferometer (AO-MZI) with new fabrication process is proposed. Not only could the center wavelength of the output laser be optimized with enhanced tuning range about 30 nm by tuning the polarization and the driving frequency of the radio frequency (RF) signal accordingly, but also the spectral spacing between the two output wavelengths could be tuned from ~0 nm to 2.65 nm by controlling the power of the RF signal. The tuning mechanism was also discussed.
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