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Determination
of Chromium Emissions from Decorative and Hard Chromium Electroplating
and Chromium Anodizing Operations (Isokinetic Method) – USEPA
Method 306 USEPA Method 306 is used for the determination of chromium (Cr) emissions from decorative and hard chrome electroplating facilities, chromium anodizing operations, and continuous chromium plating operations at iron and steel facilities. An emission sample is extracted isokinetically from the source using an unheated USEPA Method 5 sampling train, with a glass nozzle and probe liner, but with the filter omitted. The sample time is at least two hours. The Cr emissions are collected in an alkaline solution containing 0.1 N sodium hydroxide (NaOH) or 0.1 N sodium bicarbonate (NaHCO3). The collected samples are recovered using an alkaline solution and are then transported to the laboratory for analysis. Total chromium samples with high chromium concentrations (>35 µg/L) are analyzed using inductively coupled plasma emission spectrometry (ICP) at 267.72 nm. The ICP analysis is applicable for this method only when the solution analyzed has a Cr concentration greater than or equal to 35 µg/L or five times the method detection limit. Alternatively, when lower total chromium concentrations (<35 µg/L) are encountered, a portion of the alkaline sample solution is digested with nitric acid and analyzed by graphite furnace atomic absorption spectroscopy (GFAAS) at 357.9 nm. If it is desirable to determine hexavalent chromium (Cr+6) emissions, the samples are analyzed using an ion chromatograph equipped with a post-column reactor (IC/PCR) and a visible wavelength detector. To increase sensitivity for trace levels of Cr+6, a preconcentration system is used in conjunction with the IC/PCR. Components in the sample matrix causes Cr+6 to convert to trivalent chromium (Cr+3) or cause Cr+3 to convert to Cr+6. The chromatographic separation of Cr+6 using ion chromatography reduces the potential for other metals to interfere with the post column reaction. For the IC/PCR analysis, only compounds that coelute with Cr+6 and affect the diphenylcarbazide reaction cause interference. |
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Last Update: October 25, 2006