A rapid and accurate method has been developed for the determination of boron in serum, plasma and urine by inductively coupled plasma mass spectrometry. The memory effects of B were examined using different diluents/rinse solutions, including water, nitric acid, Triton X-100, ammonia and mannitol in water, in nitric acid and in ammonia. A combination of ammonia with mannitol, as both diluent and flush solution, gave the best precision, the minimum memory effect and the lowest background. A sample dilution of 20-fold was simply made for serum and plasma and 100-fold for urine for determination with a single calibration curve. Beryllium was employed as the internal standard to control matrix effects and to compensate for possible fluctuation and instrument drift. The isotope B-10(+) was utilised to avoid spectral overlap by the intense C-12(+) isotope. The final solution of blank, standards and samples contained 0.25% w/v mannitol, 0.1 M ammonia and 20 ng ml(-1) of Be. Six samples, including human and horse serum, human and horse plasma, and human urine, were analysed to test the reliability of the method. A limit of detection (3 sigma) of 0.015 ng ml(-1) was obtained and the recoveries of spiked boron (two spiking levels for each matrix) from the selected samples ranged from 98% to 104%. Much higher concentrations of B in urine (approximate to 1 mu g ml(-1)) were found compared to those in serum and plasma samples (32.8-61.1 ng ml(-1))
A new rhodamine-based fluorescent probe for the discrimination of Fe 3+ from Fe 2+ has been designed and investigated. The probe shows an immediate visual color change in response to Fe 3+ and Cu 2+ , while only Fe 3+ triggers the fluorescent change of the probe. The existence of large amount of other metal ions shows negligible interference in the detection of Fe 3+ . The association constant K ass of 4.64 × 10 8 M −2 (R 2 = 0.994) and 5.38 × 10 8 M −2 (R 2 = 0.991) of the complex was derived from UV/Vis and fluorescence titration assuming 1:2 stoichiometry of probe-Fe 3+ complex, respectively.
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