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SummarySix varieties of rice were exposed to low and high levels of arsenic in the same soil. Their individual responses of expressing phytochelatins have been correlated to inorganic arsenic uptake, transport, and accumulation in the rice grain.

A tungsten carbide±rhodium coating on the integrated platform of a transversely heated graphite atomiser was used as a permanent chemical modi®er for the determination of Pb in sediment slurries by electrothermal atomic absorption spectrometry. Slurries were sonicated for 20 s before being delivered to the previously W±Rh treated platform. The number of sediment particles introduced into the atomiser for delivery of a 20 ml slurry aliquot ranged from 1300 to 3400. The permanent W±Rh modi®er remains stable for approximately 250 ®rings when 20 ml of slurry containing up to 0.5% m/v are delivered to the atomiser. In addition, the permanent modi®er increases the tube lifetime by 50±95% when compared with untreated integrated platforms. Also, there is less degradation of sensitivity during the atomiser lifetime when compared with conventional modi®ers, resulting in a decreased need for re-calibration during routine analysis. Detection limits, based on integrated absorbance for 0.50% m/v slurries, were 61 ng g 21 Pb for the 250 mg Wz200 mg Rh permanent modi®er and 125 ng g 21 Pb for 5 mg Pdz3 mg Mg(NO 3 ) 2 . The RSD for 735 consecutive measurements of 20 ml of a 0.50% m/v sediment slurry was 3.6% for the proposed permanent chemical modi®er. Results for the determination of Pb in sediment slurries using the W±Rh permanent modi®er were in agreement with those obtained with digested solutions by using PdzMg(NO 3 ) 2 , since no statistical differences were found by the paired t-test at the 99% level.

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