The FIA manifold used in this work is shown in Fig. 1. A peristaltic pump (Rainin) was used to draw sample, carrier, and reagents through 0.8 mm i.d. Teflon tubing. The entire FIA manifold was constructed with Toflon tubing with the exception of the pump tubing and the detector flow cell coil, which were Tygon (PVC). Sample/carrier and reagent flow rates were 0.7 and 1.0 ml/min, respectively. All lines were cleaned thoroughly with 10% reagent grade HCl for 10 min followed by rinsing with Milli-Q1 water (MQ) before and after sample analyses. With the six-port Teflon injection valve (Valco Instrument, S/N224) in the load position, sample was loaded into the injection loop for 60 s while MQ carrier and reagents flowed to the detector and onto the waste. The volume of the injection loop was increased from 20 ml used by Coale et al. [15] to 120 ml to enhance detection. After the sample loop was ®lled, the valve was switched by the electronic actuator (Valco Instrument) to the inject position for 30 s. The carrier stream was diverted through the sample loop, pushing the sample slug through the system to the juncture of the sample and reagent