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NITROGEN, NITRATE-NITRITE Method 353.2 (Colorimetric, Automated, Cadmium Reduction) STORET NO. Total 00630 1 Scope and ApphcatIOn 1 1 ThIS method pertains to the determinatIOn of nItnte singly, or nItnte and nItrate combined in surface and sahne waters, and domestIC and industnal wastes The apphcable range of thIS method IS 0 05 to 10 0 mg/l nItrate-nItnte nItrogen The range may be extended wIth sample dIlutIOn 2 Summary of Method 21 A filtered sample IS passed through a column contaming granulated copper-cadmIUm to reduce nItrate to nItnte The nItnte (that onginally present plus reduced nItrate) IS determmed by dIaZOtiZing wIth sulfanIlamIde and couphng wIth N-(1-naphthyl)- ethylenedIamine dihydrochionde to form a hIghly colored azo dye whIch IS measured colonmetncally Separate, rather than combmed nItrate-nItnte, values are readIly obtained by carrymg out the procedure first wIth, and then without, the Cu-Cd reductIOn step 3 Sample Handhng and PreservatIOn 31 AnalysIs should be made as soon as pOSSible If analySIS can be made withm 24 hours, the / sample should be preserved by refngeratIOn at 4°C When samples must be stored for more than 24 hours, they should be preserved wIth sulfunc aCId (2 ml conc H2S04 per hter) and refngeratIOn CautIOn Samples for reductIOn column must not be preserved wIth mercunc chlonde 4 Interferences 41 BuIld up of suspended matter m the reductIOn column WIll restnct sample flow Smce nItrate-nItrogen IS found in a soluble state, the sample may be pre-filtered 42 Low results might be obtained for samples that contam hIgh concentratIOns of Iron, copperorothermetals EDTAISaddedtothesamplestoehmmatethISmterference 43 Samples that contain large concentratIons of oIl and grease WIll coat the surface of the cadmIUm ThIs mterference IS ehmmated by pre-extracting the sample wIth an organIc solvent 5 Apparatus 5 1 TechnIcon AutoAnalyzer (AAI or AAII) conSIsting ofthe fohowing components 5 11 Sampler 5 1 2 ManIfold (AAI) or analytIcal cartndge (AAII) 5 1 3 ProportionIng Pump 5 1 4 Colonmeter eqUIpped wIth a 15 mm or 50 mm tubular flow cell and 540 nm filters 5 1 5 Recorder Approved for NPDES and SDWA Issued 1971 Editonal reVISIon 1974 and 1978 3532-1PDF Image | Methods for Chemical Analysis of Water and Wastes
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