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1 2 MERCURY Method 245.2 (Automated Cold Vapor Technique) STORET NO. Total 71900 Dissolved 71890 S~spended 71895 Scope and ApplIcatIOn 1 1 This method is applicable to surface waters It may be applicable to salIne waters, wastewaters, effluents, and domestic sewages providmg potential mterferences are not present (See Interference 4) 12 Theworkmgrangeis02to200ugHg/1 Summary of Method 21 The flameless A A procedure is a physical method based on the absorptIOn of radiatIOn at 253 7 nm by mercury vapor The mercury is reduced to the elemental state and aerated from solutIOn The mercury vapor passes through a cell pOSitioned m the light path of an atomiC absorptIOn spectrophotometer Absorbance (peak height) is measured as a functIOn of mercury concentratIOn and recorded m the usual manner 22 In addition to morgamc forms of mercury, orgamc mercunals may also be present These organo-mercury compounds w111 not respond to the flameless 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 Potassmm persulfate has been found to give approXimately 100% recovery when used as the oXidant with these compounds Therefore, an automated persu1fate oXidatIOn step followmg the automated addition of the permanganate has been mcluded to msure that organo-mercury compounds, if present, w111 be oXidlZed to the mercunc ion before measurement Sample Handlmg and PreservatIOn 31 Untl1 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 (1) If only dissolved mercury is to be determmed, the sample should be filtered before the aCid is added FortotalmercurythefiltratIOnISomitted Interference (See NOTE 1) 4 1 Some sea waters and waste-waters high lIi chlondes have shown a positive mterference, probably due to the formatIOn offree chlonne 4 2 Interference from certam volatile orgamc matenals which w111 absorb at this wavelength is also possible A prelimmary run under oXidizmg conditIOns, without stannous sulfate, would determme if this type ofmterference is present 3 4 Approved for NPDES and SDWA Issued 1974 2452-1PDF Image | Methods for Chemical Analysis of Water and Wastes
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