《检测微量元素方法》由会员分享，可在线阅读，更多相关《检测微量元素方法（11页珍藏版）》请在金锄头文库上搜索。
1、9.2.40 AOAC Official Method 993.14 Trace Elements in Waters and WastewatersInductively Coupled PlasmaMass Spectrometric Method First Action 1993(Applicabletodeterminationof20traceelements,atconcentrations of 0.8200 g/L, in finished drinking water, groundwater, and wastewaters.)Caution:The following
2、reagents are highly toxic: antimony, ar- senic trioxide, beryllium sulfate, cadmium, chromium trioxide, lead nitrate, selenium dioxide, thallium nitrate, and uranium nitrate.Results of interlaboratory study: See Table 993.14A for interlaboratory study data.A. PrincipleMethod describes multielement d
3、etermination of trace elements by inductively coupled plasmamass spectrometry (ICPMS). Ele- ments are digested in a nitrichydrochloric acid solution. Sample material in solution is introduced by pneumatic nebulization into radiofrequencyplasmawhereenergytransferprocessescausedesol- vation, atomizati
4、on, and ionization. Ions are extracted from plasma through differentially pumped vacuum interface and are separated onthebasisofmass-to-chargeratiobyaquadrupolemassspectrom- eter having minimum resolution capability of 1 amu peak width at 5% peak height. Ions transmitted through quadrupole are detec
5、ted by continuous dynode electron multiplier assembly, and ion infor- mation is processed by data handling system.B. Apparatus(a) Inductively coupled plasmamass spectrometer.(1) Instrument capable of scanning mass range 5250 amu with mini- mumresolutioncapabilityof1amupeakwidthat5%peakheightand that
6、 may be fitted with conventional or extended dynamic range de- tection system. (2) Argon gas supply (high-purity grade, 99.99%). (3) Variable-speed peristaltic pump required for solution delivery to nebulizer. (4) Mass-flow controller on nebulizer gas supply may be required.Water-cooledspraychamberb
7、eneficialinreducinginterfer- ences.Operating conditions:Becauseofdiversityininstrumentation, manufacturer-provided operating conditions should be followed.(b) Glassware.Volumetric flasks, graduated cylinders, fun- nels, centrifuge tubes, and calibrated pipets.(c) Beakers.250mLconicalPhillipswith50mm
8、watchglasses and 250 mL Griffin with 75 mm watch glasses.(d) Storage bottles.125 and 250 mL, narrow mouth, Teflon FEP (fluorinated ethylene propylene), with Tefzel ETFE (ethylene tetrafluorethylene) screw caps.(e) Air displacement pipetter.Digital, capable of 102500 L range and disposable pipet tips
9、.(f) Analytical balance.Sensitivity 0.1 mg.(g) Hotplate.Withvariabletemperature,controllableto3C.(h) Centrifuge.Steel cabinet with guard bowl, electric timer, and brake, capable of 2000 g.(i) Drying oven.Gravity convection oven with thermostatic control capable of maintaining 105 5C.C. Reagents (a)
10、Nitric acid (HNO3) solutions.(1) HNO3.Concentrated, specific gravity 1.41. (2) HNO3solution (1 + 1).Add 500 mL HNO3to 400 mL reagent water and dilute to 1 L. (3) HNO3solution (1 + 9).Add 100 mL HNO3to 400 mL reagent water and dilute to 1 L. (4) 1% (v/v) HNO3solution. (5) 2% (v/v) HNO3solution. (b) H
11、ydrochloric acid (HCl) solutions.(1) HCl.Concen- trated,specificgravity1.41.(2)HClsolution(1+1).Add500mL HCl to 400 mL reagent water and dilute to 1 L. (c) Ammonium hydroxide (NH4OH).Concentrated, specific gravity 0.902. (d) Tartaric acid. (e) Reagent water.ASTM type I water (ASTM D1193) is required
12、. Prepare water by distillation, polishing with mixed bed of ionexchangematerial,andfiltrationthrough0.2 mmembranefilter. (f) Standard solutions.Purchase or prepare from ultra high-puritychemicalsormetals(99.9999.999%pure).Picklemet- als (where indicated), to clean surfaces and reduce mass, by addin
13、g 20% excess of metal to acid; dry, weigh, and repeat process until desired weight is achieved. Dry salts 1 h at 105C, except where noted.Usereagentwater,(e),foralldilutionsunlessotherwisespec- ified.StorestocksolutionsinTeflonbottles,B(d).Accuratelyweigh all amounts to nearest 0.1 mg. (1) Aluminum
14、stock solution (1000 mg Al/mL).Pickle Al metal in 7580C (1 + 1) HCl solution, (b)(2), to 0.100 g. Dis- solvemetalin10mLHCl,(b)(1),and2mLHNO3,(a)(1),byheat- ing ca 30 min at 7580C. Continue heating until solution has evaporated to 4 mL. Cool to room temperature and add 4 mL re- agentwater.Evaporateto
15、2mLbyheating.Cooltoroomtempera- ture and dilute to 100 mL. (2) Antimony stock solution (1000 mg Sb/mL).Dissolve 0.100 g Sb powder in 2 mL (1 + 1) HNO3solution, (a)(2), and 0.5 mL HCl. Heat at 7580C to dissolve, cool to room temperature, and add 20 mL reagent water and 0.15 g tartaric acid, (d). Warm
16、 solution to dissolve white precipitate. Cool and dilute to 100 mL. (3) Arsenic stock solution (1000g As/mL).Dissolve 0.1320 g As2O3in mixture of 50 mL reagent water and 1 mL NH4OH, (c), by heating at 7580C; cool to room temperature; and acidify with 2 mL HNO3. Dilute to 100 mL. (4) Barium stock solution (1000g Ba/mL).Dissolve 0.1437 g BaCO3in mixture of 10 mL reagent water and 2 mL HNO3by heat- ing while stiring. Dilute to 100 mL. (5) Bery
