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The metal atoms to be measured are placed m the beam of radiatlOn by mcreasmg the temperature of the furnace thereby causmg the mJected speCImen to be volatIhzed A monochromator Isolates the charactenstIc radiatlOn from the hollow cathode lamp and a photosensItIve devIce measures the attenuated transmItted radiatlOn 3 Definition ofTerms 31 3 2 33 Optlffium ConcentratlOn Range A range, defined by llffiItS expressed m concentratlOn, below WhICh scale expanSlOn must be used and above whIch curve correctlOn should be consIdered ThIS range wl1l vary wIth the senSItIvIty of the mstrument and the operatmg condItIon employed SensitIvIty The concentratlOn m ml1hgrams of metal per hter that produces an absorptIon of 1% Detection Llffilt DetectIon hmits can be expressed as eIther an mstrumental or method parameter The hmItmg factor of the former usmg aCId water standards would be the sIgnal to nOlse ratIo and degree of scale expanSlOn used, whl1e the latter would be more affected by the sample matnx and preparatlOn procedure used The SCIentlfic Apparatus Makers AssociatlOn (SAMA) has approved the followmg defimtlOn for detectlOn hmit that concentratIon of an element whIch would yIeld an absorbance equal to tWIce the standard devIation of a senes of measurements of a solutlOn, the concentraton of WhICh IS dIstmctly detectable above, but close to blank absorbance measurement The detectIon hmit values hsted m Table I and on the mdividual analysIs sheets are to be consIdered mmimum workmg hmits achIevable wIth the procedures gIven m thIS manual These values may dIffer from the optImum detectlOn hmit reported by the vanous mstrument manufacturers DIssolved Metals Those constItuents (metals) whIch WIll pass through a 045 u membrane fllter Suspended Metals Those constItuents (metals) whIch are retamed by a 045 u membrane fllter Total Metals The concentratlOn of metals determmed on an unflltered sample followmg VIgorous dIgestion (SectlOn 4 1 3), or the sum of the concentratlOns of metals m both the mssolved and suspended fractIons Total Recoverable Metals The concentratIon ofmetals m an unflltered sample followmg treatment wIth hot dl1ute mmeral aCId (SectlOn 4 1 4) 34 35 36 37 4 Sample Handbng and PreservatlOn 4.1 ForthedetermmatlOnoftracemetals,contammatlOnandlossareofpnmeconcern Dust m the laboratory envIronment, lffipuntIes m reagents and Impunties on laboratory apparatus wmch the sample contacts are all sources of potentIal contammatlOn For hqwd samples, contamers can mtroduce eIther posItive or negatIve errors m the measurement of trace metals by (a) contnbutmg contammants through leachmg or surface desorptlOn and (b) by depletmg concentratlOns through adsorptlOn Thus the collectlOnandtreatmentofthesamplepnortoanalySISreqwrespartICularattentlOn The sample bottle whether boroSIlIcate glass, polyethylene polypropylene or Teflon should be thoroughly washed With detergent and tap water, nnsed wIth 1 1 mtnc aCid, tap MET ALS-4PDF Image | Methods for Chemical Analysis of Water and Wastes
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