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MERCURY Method 245.1 (Manual Cold Vapor Technique) STORET NO. Total 71900 Dissolved 71890 Suspended 71895 1 Scope and ApphcatlOn 11 ThIS method IS apphcable to dnnkmg, surface, and sahne waters, domestIc and mdustnal wastes 12 In addItion to morgamc forms of mercury, orgamc mercunals may also be present These organo-mercury compounds WIll not respond to the cold vapor atomIC absorptIOn techmque unless they are first broken down and converted to mercunc IOns Potassmm permanganate oXIdIzes many of these compounds, but recent studIes have shown that a number of orgamc mercunals, mcludmg phenyl mercunc acetate and methyl mercunc chlonde, are only partially oXIdIzed by thIS reagent Potasssmm persulfate has been found to gIve approxImately 100% recovery when used as the oXIdant wIth these compounds Therefore, a persulfate oXIdatIOn step followmg the addItIon of the permanganate has been mcluded to msure that organo-mercury compounds, If present, WIll be oXIdIzed to the mercunc Ion before measurement A heat step IS reqmred for methyl mercunc chlonde when present m or spIked to a natural system For dlst111ed water the heat step IS not necessary 13 The range of the method may be vaned through mstrument and/or recorder expanSIOn Usmg a 100 ml sample, a detectIOn hmlt of0 2 ug Hg/l can be achIeved, concentratIOns below thIS level should be reported as < 0 2 (see AppendIX 11 2) 2 Summary ofMethod 21 The flameless AA procedure IS a physIcal method based on the absorptIOn ofradIatIon at 253 7 nm by mercury vapor The mercury IS reduced to the elemental state and aerated from solutIOn m a closed system The mercUlY vapor passes through a cell posItIoned m the hght path of an atomIC absorptIOn spectrophotometer Absorbance (peak heIght) IS measured as a functIOn of mercury concentratIOn and recorded m the usual manner 3 Sample Handhng and PreservatIOn 3 1 Untll more conclUSIve data are obtamed, samples should be preserved by aCIdIficatIOn wIth mtnc aCId to a pH of 2 or lower ImmedIately at the tIme of collectIOn If only dIssolved mercury IS to be determmed, the sample should be filtered through an all glass apparatusbeforetheaCIdISadded FortotalmercurythefiltrationISomItted 4 Interference 4 1 POSSIble mterference from sulfide IS ehmmated by the addItion of potassmm permanganate ConcentratIOns as hIgh as 20 mg/l of sulfide as sodmm sulfide do not mterfere wIth the recovery ofadded morgamc mercury from dlst1l1ed water Approved for NPDES and SDWA Issued 1974 245 1-1PDF Image | Methods for Chemical Analysis of Water and Wastes
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