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A Novel Continuous-Flow Sequential Extraction Procedure for Metal Speciation in Solids

^a Trace Element Lab., Institute of Science and Technology Research and Development, Mahidol Univ., Rama VI Road, Bangkok 10400, Thailand
^b Dep. of Chemistry, Faculty of Science, Mahidol Univ., Rama VI Road, Bangkok 10400, Thailand

View larger version (24K): [in a new window]   Fig. 1. Diagram of a continuous-flow system.

View larger version (27K): [in a new window]   Fig. 2. Extractograms at varying Step II temperatures for a 0.25-g sample of SRM 2710 soil with a 10-mL extraction chamber volume; subfraction volume, 20 mL; ambient temperature (), 65°C () and 80°C (). Temperatures of Steps I and III were kept constant at ambient and 55°C, respectively.

View larger version (16K): [in a new window]   Fig. 3. Change of pH of the extract during continuous-flow extraction. Sample, 0.25 g SRM 2710 soil; chamber volume, 10 mL; subfraction, 20 mL.

View larger version (41K): [in a new window]   Fig. 4. Effect of varying acetic acid concentration on metal fraction distribution in soil (SRM 2710). Sample weight, 0.25 g; chamber volume, 10 mL; temperatures of Steps I, II, and III were ambient, 65°C, and 55°C, respectively.

View larger version (35K): [in a new window]   Fig. 5. Effect of varying hydroxylamine concentration on metal fraction distribution in soil (SRM 2710). Sample weight, 0.25 g; chamber volume, 10 mL; temperatures of Steps I, II, and III were ambient, 65°C, and 55°C, respectively.

View larger version (17K): [in a new window]   Fig. 6. Flow rate of extraction at various sample weight to chamber volume ratios. 1:12, 3-mL chamber (); 1:20, 3-mL chamber (•); 1:20, 10-mL chamber (); 1:40, 10-mL chamber (). Sample, SRM 2710 soil; subfraction volume, 15 mL. Extraction time for three-step procedure is also indicated on each graphical plot.

View larger version (26K): [in a new window]   Fig. 7. Extractograms of sequential extraction of Ca (), Fe (), Mn (), Cu (), and Zn (•) for SRM 2710 soil. Sample, 0.25 g; chamber volume, 10 mL; subfraction volume, 15 mL. Temperature of Steps II and III were 65 and 55°C, respectively.