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NITROGEN, NITRATE-NITRITE Method 353.3 (Spectrophotometric, Cadmium Reduction) STORET NO. Total 00630 1 Scope and ApphcatlOn 11 Th1s method 1S apphcable to the determmatlOn of mtnte smgly, or mtnte and mtrate combmed m drmkmg, surface and sahne waters, domest1c and mdustnal wastes The I apphcable range of th1s method 1S 001 to 10 mg/l mtrate-mtnte mtrogen The range may be extended w1th sample dl1utlOn 2 Summary of Method 2 1 A filtered sample 1S passed through a column contam~nggranulated copper-cadmmm to reduce mtrate to mtnte The mtnte (that ongmally present plus reduced mtrate) 1S determmed by d1azot1zmg w1th sulfamlam1de and couphng w1th N-(l-naphthyl)- ethylened1amme d1hydrochlonde to form a h1ghly colored azo dye wh1ch 1S measured spectrophotometncally Separate, rather than combmed mtrate-mtnte, values are readl1y obtamed by carrymg out the procedure first w1th, and then w1thout, the Cu-Cd reductlOn step 3 Sample Handlmg and PreservatlOn 31 Analys1s should be made as soon as poss1ble If analys1s can be made w1thm 24 hours, the sample should be preserved by refngeratlOn at 4°C When samples must be stored for more than 24 hours, they should be preserved w1th sulfunc aC1d (2 ml H2S04 per hter) and refngeratlOn CautlOn Samples for reduct10n column must not be preserved w1th mercunc chlor1de 4 Interferences 41 Bul1d up of suspended matter m the reductlOn column w1ll restnct sample flow Smce mtrate-mtrogen 1S found m a soluble state, the sample may be pre-filtered through a glass fiberfilterora045umembranefilter H1ghlyturb1dsamplesmaybepretreatedw1thzmc sulfate before filtratlOn to remove the bulk of part1culate matter present m the sample 42 Low results m1ght be obtamed for samples that contam h1gh concentratlOns of 1ron, copperorothermetals EDTA1Saddedtothesamplestoehmmateth1smterference 43 Samples that contam large concentrat10ns of 011 and grease w1ll coat the surface of the cadmmm Th1s mterference 1S ehmmated by pre-extractmg the sample w1th an orgamc solvent 44 Th1s procedure determmes both mtrate and mtnte If only mtrate 1S des1red, a separate determmatlOn must be made for mtnte and subsequent correctlOns made The mtnte may be determmed by the procedure below w1thout the reductlOn step Approved for NPDES and SDWA Issued 1974 353 3-1PDF Image | Methods for Chemical Analysis of Water and Wastes
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