USGS-NWQL: I-7229-87: Chromium in Suspend Sediment by Atomic Emission (Calculation)
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Official Method Name
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Chromium, Atomic Emission Spectrometry, DC Plasma |
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Current Revision
| 1993 |
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Media
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WATER |
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Instrumentation
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Inductively Coupled Plasma - Atomic Emission Spectroscopy |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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M.J. Fishman, 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125 |
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Brief Method Summary
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Chromium is determined by a direct-reading emission spectrometer that uses a dc argon plasma as an excitation source (Johnson and others, 1979a, 1979b). A solution of lithium chloride, sulfuric acid, and glycerin is added to samples and standards to provide a common background matrix and to compensate for viscosity changes. The liquid solution then is converted by a ceramic nebulizer into a fine aerosol and introduced into the plasma by way of a plastic spray chamber and Pyrex injection tube. Chromium is determined on the average of three replicate exposures using a 5-second integrated intensity. A standard solution and a blank are used to calibrate the instrument. |
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Scope and Application
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This method is used to analyze samples of finished water, natural water, industrial water, and water-suspended sediment containing from 1 to 10,000 ug/L of chromium. Sample solutions containing more than 10,000 ug/L chromium or with specific conductances greater than 10,000 uS/cm must be diluted. Suspended recoverable chromium is calculated by subtracting dissolved chromium from whole water recoverable chromium. |
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Applicable Concentration Range
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1.0-10,000 |
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Interferences
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Stray-light from calcium emission at 422.7-nm wavelength raises the background at the 425.4-nm chromium wavelength causing positive interference. This interference can be corrected by using a two-point background correction technique. Calcium concentrations as large as 1,500 mg/L can be tolerated. Samples exceeding this concentration need to be diluted. |
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Quality Control Requirements
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Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable. |
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Sample Handling
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Description: 250 mL Polyethylene bottle, acid-rinsed. Treatment and Preservation: Filter through 0.45-um filter, use filtered sample to rinse containers and acidify sample with nitric acid (HNO3) to pH < 2. |
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Maximum Holding Time
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180 days from sampling |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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