A sequential injection system for on-line sorbent extraction preconcentration in electrothermal atomic absorption spectrometry was developed for the determination of trace cadmium in seawater and other water samples. The system is characterized by simple manifold design and improved robustness. The Cd-APDC complex was sorbed on a. 15-ml micro-column located at the tip of the furnace sampling probe packed with C. After sequentially metering 18 segments of ethanol, washing acid, sample and APDC complexing reagent into a 2.5-m-long, 1-mm-i.d. holding coil, the flow was reversed and directed to the column. The complexing reaction, sample loading and column washing were then achieved within the single reversed syringe stroke. The sorbed analyte was then eluted into the furnace with 50ml ethanol. Mutual mixing between sample, washing acid, and eluent were prevented by separating the zones with small air segments during metering. Progressive tightening of the column was avoided by a short back-suction through the column after each operational cycle. With 1ml sample loaded, and 50ml eluate introduced into the y1. furnace, an enrichment factor of 19 was obtained with a detection limit of 0.5ng l Cd 3s, a precision of 2.1%. y1 R.S.D. ns11, and a throughput of 12h. Good recoveries were obtained for spiked water samples and good agreement of results with standard reference seawater and river water samples were achieved.

Volatile species of gold in acidified medium were generated at room temperature by the reduction of NaBH using 4 a flow injection vapor generation (FI-VG) system, and trapped in situ on the graphite furnace inner wall to get ETAAS detection. Reaction coil inner-wall and inside of the gas-liquid separator were conditioned by passing through a liquid containing micro amounts of Pd(II) and sodium diethyldithiocarbamate (DDTC) and NaBH. The FI manifold 4 design, the precondition of the FI-VG system and the effect of temperature parameters for ETAAS are discussed. Optimization of the FI and chemical parameters, such as effect of sample acidity, effect of sodium tetrahydroborate concentration, effects of the flow rates for sample, reagent and carrier gas, effects of HCl and DDTC concentration in rinsing solution were investigated. A detection limit of 0.8 ngyml (3s) was obtained with a 40 s trapping time and a sampling frequency of 50yh. The precision of 2.2% R.S.D. (ns11) was obtained at 50 ngyml level. The method was used for the determination of gold in ore sample digest solution. The recoveries of gold in ore sample digest dilute solution by spiking of 25 ngyml gold were 90-106%. The results obtained were in good agreement with those obtained from direct ETAAS.

Volatile species of Cu, Au and Tl were generated at room temperature by the reduction of NaBH4 in acidified aqueous medium using a flow injection vapor generation atomic absorption spectrometric (FI-VGAAS) system. 1, 10-phenanthroline, sodium diethanlydithiocarbonate (DDTC) and palladium (or combined with Rodamne B) ware used as enhancement reagents respectively. The normal flow injection peak shape wase obtained and the sensitivity were enhanced by 1-2 magnitude. The detection limits of 0.34-24ng/ml (3σ) were obtained with 300 or 500µl sample solution. The precision of 2.6-1.8% RSD were obtained with the sampling frequencies were of 120-180/h. The FI-VGAAS methods were used for the determination of copper in hair and rice sample and gold in the ore sample digests.

A flow injection microsample introduction system for flame atomic absorption spectrom-etry is developed based on air-transported sample loading and hydrodynamic injection. An augmenting water stream was used between sample loop and nebulizer to prevent distur-bances from nebulizer suction during sample loading. A total of 0.8ml of sample was sufficient for triplicate measurements, including washout between samples, and achieving the sensitivity of conventional steady-state measurements. The system was applied to the determination of copper in serum samples at a sampling frequency of 100/h and with a presision of about 2% rsd.

Gold in ores was determined by flame atomic absorption spectrometry following on-line preconcentration by sorbent extraction in a flow-injection system. The medium polarity adsorption resin Amberlite XAD-8 packed in a 220μ1 micro-column was used to collect gold (II1) from hydrochloric acid sample solutions for 40 s at 7.6ml/mm. Ethanol was used to elute the adsorbed analytes into the nebulizer. Optimization studies were made on sample loading rate, elution rate and sample acidity. Some possible interferences on the determination are discussed. A 35-fold enrichment was achieved at a sampling frequency of 60h-1 and with an RSD of 1.48. The detection limit (30) and 2. bg 1-l. Results for gold in ore samples showed good agreement with those obtained using activated carbon adsorption preconcentration. The recoveries were 97-108s.