天然淡水中痕量金属元素检测方案(液相色谱仪)

Authors： Hwan Kim and Paul Field (field@icpms.com) Brief The prepFAST MC is a fully automated low pressure chromatography system that can isolate and collectdiscrete fractions from a dissolved sample. The syringe driven system allows sample loading， elution andcolumn conditioning cycles all with user-defined parameters (time， volume and flow rate). Features： ·Fully automated bioavailability ·Syringe control v Load exact volumevDispense exact volume v Accurate，precise flow rate ·All fluoropolymer flow path ·3 Destination locations ·Flexible chemistry Figure 1. Concentrations for dissolved (blue bars) and bioavailable (red bars) tracemetals are plotted. The percent bioavailable fraction of dissolved metals in CarterLake， IA/ NE (above each red bar) indicates a wide range from 8% (Ni) to 96% (Mn).Large ranges in the bioavailable fraction are expected in natural waters as variableorganic ligand concentration， complexation，pH and ionic strength all affect the colloidalpartitioning of each metal differently. Figure 2. The prepFAST MC system schematic illustrates four steps，1) load sample into loop， 2) push sampleonto column and collect colloidal， 3) elute and collect bioavailable， 4) condition and regenerate. A simple， fully automatedprepFAST MC method is usedto extract bioavailable metalsfrom the total dissolved fractionof natural， fresh waters. Theoperationally defined Chelexlabile fraction is collectedafter a sample at natural pH isexposed to a bed of resin for0.25 seconds (Bowles et al.，2005). Concentrations of Chelexlabile and total dissolved metalsdetermined by ICP-MS are usedto calculate the bioavailabilityof each metal. Excellentreproducibility (rsd=0.7%； n=3)for replicate determinations ofbioavailable Cu in natural watersis achieved through automation.Water collected from CarterLake， IA/NE exhibits a range inbioavailability for a suite of metals(Co=24%， Mn=96%， Fe =35%，Cu =17%， Ni=8%， Zn=23%，Cd=19%and Pb =56%) that istypical of natural waters. Figure 3. The three main steps in processing samples for the determination ofbioavailable metals are illustrated： 1) 10 mL of sample at natural pH is passedthrough a Chelex column (~ 0.25 sec exposure time) retaining bioavailable metalsand collecting the colloidal fraction (Destination 1)， 2) Metals are eluted from thecolumn at low pH (<1) and collected as the bioavailable fraction (Destination 2)， and3) Regenerate / recondition column for next sample (pH 6.7). Figure 4. The bioavailable Cu fraction is plotted as a function of flow rate for inorganic Cu (green diamonds)Cu-NTA (100pg/L Cu， 1mM NTA， pH 6.1； blue diamonds) and Cu spiked lake water (red squares； naturalpH). At a 20 mL/min flow rate (0.25 sec exposure) all inorganic Cu (100%) and approximately 40% of Cu-NTAis retained by the column while flow rate has little effect on the retention of Cu in natural lake water. Theseresults are consistent with the operationally defined bioavailable fraction for Chelex resin (0.25 sec exposuretime； Bowles et al.， 2005). Figure 5. Three replicate determinations of bioavailable Cu in natural waters indicate excellent precision isobtained through automating chemistry. lol Figure 6. SC-4 DX top view with locations for Samples， Destination 1， Destination 2，and Destination 3. Vial sizes， styles and rack configurations are flexible. Benefits： ·Fully automated ·Collect all bioavailable and colloidal fractions ·Routine ·Software controlled ·Excellent reproducibility through automation · Flexible (can be adapted for other resinsor chemistries) ·Inert flow path· Micro column reduces sample/reagent volumes K.C. Bowles， S.C. Apte， G.E. Batley， L.T. Hales，N.J. Rogers. "A rapid Chelex column method forthe determination of metal speciation in naturalwaters."Analytica Chimica Acta. (2005) 7277 World Communications Drive Omaha， NE 68122 USAPhone： 1.402.991.7800 Fax： 1.402.991.7799 Email： sales@icpms.com Web： www.prepFASTMC.com www.icpms.com ElementalScientific prepFAST MC是一个完全自动化的低压色谱系统，可以从溶解的样品中分离和收集离散的组分。该注射器驱动系统允许样品加载、洗脱和柱调节周期，所有参数均由用户定义(时间、体积和流量)。