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the digestlOn IS complete, generally mdicated by a lIght colored digestate Evaporate to near dryness (DO NOT BAKE), add 5 ml dIstIlled HCI (11) and warm the beaker gently to dIssolve any soluble matenal (If the sample IS to be analyzed by the furnace procedure, 1 ml of 1 1 dIstIlled HN03 per 100 ml dIlutlOn should be substituted for the dIstilled 1 1 HCI) Wash down the watch glass and beaker walls wIth deIomzed dIstIlled water and filter the sample to remove SIlIcates and other msoluble matenal that could clog the atomIzer Adjust the volume to some predetermmed value based on the expected concentratlOns of metals present ThIS volume WIll vary dependmg on the metal to be determmed The sample IS now readyforanalySIS ConcentratlOnssodetermmedshallbereportedas"suspended" (See Note 4 ) NOTE 4: Certam metals such as antimony arsemc, gold, mdIUm, mercury, osmIUm, palladIUm, platmIUm, rhemum, rhodIUm, ruthemum, selemum, sIlver, thallIum, tm and tItamum requIre modificatlOn of the digestlOn procedure and the tndividual sheets for these metals should be consulted 4 1 3 For the determmatlOn of total metals the sample IS aCIdIfied WIth 1 1 redIstilled HN03 to a pH of less than 2 at the tIme of collectlOn The sample IS not filtered before processmg Choose a volume of sample appropnate for the expected level of metals If much suspended matenaiis present, as lIttle as 50-100 ml of well mIxed sample WIll most probably be suffiCIent (The sample volume reqUIred may also vary proportIonally WIth the number ofmetals to be determmed ) Transfer a representatIve alIquot of the well mIxed sample to a Gnffin beaker and add 3 ml of conc redIstIlled HN03 Place the beaker on a hot plate and evaporate toneardrynesscautlOusly,makmgcertamthatthesampledoesnotboll (DONOT BAKE) Cool the beaker and add another 3 ml portlOn of conc redIstIlled HN03 Cover the beaker WIth a watch glass and return to the hot plate Increase the temperatureofthehotplatesothatagentlerefluxactlOnoccurs Contmueheatmg, addmg addItIonal aCId as necessary, untIl the dIgestIon IS complete (generally mdicated when the digestate IS lIght m color or does not change m appearance WIth contmued refluxmg) Agam, evaporate to near dryness and cool the beaker Add a small quantIty ofredIstIlled 11 HCI (5 m1/100 ml offmal solutlOn) and warm the beaker to dIssolve any preCIpItate or reSIdue resultmg from evaporatlOn (If the sample IS to be analyzed by the furnace procedure, SubstItute dIstilled HN03 for 1 1 HCI so that the final dilutlOn contams 05% (v/v) HN03 ) Wash down the beaker walls and watch glass WIth dIstIlled water and filter the sample to remove SIlIcates and other msoluble matenal that could clog the atomIzer Adjust the volume to somepredetermmedvaluebasedontheexpectedmetalconcentratlOns Thesample IS now ready for analySIS ConcentratlOns so determmed shall be reported as "total" (see Note 4) 4 1.4 To determme total recoverable metals, aCIdIfy the entIre sample at the tIme of collection WIth conc redIstIlled HN03, 5 mIll At the tIme of analYSIS a 100 ml alIquotofwellmIxedsampleIStransferredtoabeakerorflask FIvemlofdIstIlled HCI (l 1) IS added and the sam~leheated on a steam bath or hot plate untIl the MET ALS-6PDF Image | Methods for Chemical Analysis of Water and Wastes
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