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when resonant energy from another element m a multI-element lamp or a metal Impunty m the lamp cathode falls withm the bandpass of the slIt settmg and that metalISpresentmthesample ThIstypeofmterferencemaysometimesbereduced by narrowmg the slIt wIdth 5.2 Flameless AtomIzation 5 2 1 Although the problem of oXide formation IS greatly reduced wIth furnace 5 2 2 5 2 3 procedures because atomIzatIon occurs m an mert atmosphere, the technIque IS still subject to chemIcal and matnx mterferences The composItion of the sample matnx can have a major effect on the analysIs It IS those effects WhICh must be determmed and taken mto consIderatIon m the analysIs of each dIfferent matrIx encountered To help verIfy the absence of matnx or chemIcal mterference use the followmg procedure WIthdraw from the sample two equal ahquots To one of the alIquots add a known amount of analyte and dIlute both ahquots to the same predetermmedvolume [ThedIlutIOnvolumeshouldbebasedontheanalysIsofthe undIluted sample Preferably, the dIlutIon should be 1 4 whIle keepmg m mmd the optImum concentratIon range of the analysIs Under no CIrcumstances should the dIlutIon be less than 1 1] The dIluted alIquots should then be analyzed and the unspiked results multIplIed by the dIlutIOn factor should be compared to the ongmal determmation Agreement of the results (withm ±10%) mdicates the absence of mterference ComparIson of the actual sIgnal from the spIke to the expected response from the analyte m an aqueous standard should help confirm the findmg from the dilution analysIs Those samples WhICh mdicate the presence of mterference, should be treated m one or more ofthe followmg ways a The samples should be successIvely dIluted and reanalyzed to determme If the mterference can be ehmmated b ThematrIXofthesampleshouldbemodIfiedmthefurnace Examples are the addItIon of ammOnIum nItrate to remove alkalI chlOrIdes, ammOnIum phosphate to retam cadmIum, and nIckel nItrate for arsenIC and selenIum analyses [A TOMIC ABSORPTION NEWSLETTER Vol 14, No 5, p 127, Sept-Oct 1975] The mIxmg of hydrogen WIth the mert purge gas has also been used to suppress chemIcal mterference The hydrogen acts as a reducmg agent and aIds m molecular dIssocIation c Analyze the sample by method of standard addItIons whIle notmg the precautIons and lImItatIons of ItS use (See 8 5) Gases generated m the furnace dunng atomIzatIon may have molecular absorptIon bands encompassmg the analytIcal wavelength When thIS occurs, eIther the use of background correctIon or choosmg an alternate wavelength outsIde the absorptIOn band should elImmate thIs mterference Non-specIfic broad band absorptIon mterference can also be compensated for WIth background correctIon Interference from a smoke-producmg sample matnx can sometImes be reduced by extendmg the charrIng time at a hIgher temperature or utuIzmg an ashmg cycle m MET ALS-8PDF Image | Methods for Chemical Analysis of Water and Wastes
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