ASTM: D6502: Particulate and Dissolved Matter by XRF
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Official Method Name
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Standard Test Method for On-Line Measurement of Low Level Particulate and Dissolved Metals in Water by X-Ray Fluorescence (XRF) |
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Current Revision
| Current edition approved Dec. 10, 1999. Published March 2000. |
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Media
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WATER |
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Instrumentation
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X-Ray Fluoresence |
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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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Brief Method Summary
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The concentrations of particulate, or dissolved metals, or both, in water streams are determined through accumulation on appropriate collection media (filters or ion exchange materials) and detection by x-ray fluorescence spectroscopy, providing real time determination of iron and other metals found in water streams. The water sample delivered into the monitoring system passes through a flow sensor, and then, to a flow cell assembly containing a membrane or resin filter, depending on the application of interest. For an application where only dissolved metals are to be analyzed, the sample needs to be filtered upstream of the sample chamber to prevent particulate contamination of the resin membrane surface. A sample bypass valve is used for flow control through the sample chamber. Two sample chambers in sequence can be used to determine both particulate and dissolved components of the metal(s) of interest. X-ray fluorescence is used to determine the concentration of the captured material. XRF analysis gives a measure of total elemental concentration independent of the oxidation state or molecular configuration of the element. Elements with atomic numbers 13 through 92 can be detected. |
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Scope and Application
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This test method covers the operation, calibration, and data interpretation for an on-line corrosion product (metals) monitoring system. The monitoring system is based on x-ray fluorescence (XRF) analysis of metals contained on membrane filters (for particulate forms) or resin membranes (for dissolved forms). Since the XRF detector is sensitive to a range of emission energy, this test method is applicable to simultaneous monitoring of the concentration levels of several metals including titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, mercury, lead, and others in a flowing sample. A detection limit below 1 ppb can be achieved for most metals. |
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Applicable Concentration Range
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1 and greater ug/L |
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Interferences
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Coincidence of Certain Emission Lines - In XRF, each element emits fluorescence at characteristic wavelengths which makes element identification unambiguous; however, certain pairs of emission lines from different elements occur sufficiently close in energy that the resulting overlap causes difficulties in quantitative analysis. An example of this is the Ka line of cobalt, which occurs at 6.925 keV (average) and the Kb line of iron, which occurs at 7.059 keV (average). In the case of a small amount of cobalt in the presence of a large amount of iron, which is a typical case among corrosion product samples from steam generating plants, the cobalt analysis is hindered by the iron in the sample. Note that iron is not similarly affected by the presence of cobalt since the iron Ka line may be isolated to extract iron emission intensity. |
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Quality Control Requirements
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Sample Handling
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Maximum Holding Time
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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