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Unformatted text preview: 1 Calibration check 125 ppb Matrix Effect vs External Calibration Internal Standards A know amount of a compound, different from analyte, that is added to the unknown. When to use: The quantity of sample or the instrument response varies slightly from run to run. The relative response of the detector to the analyte and standard is constant over a wide range of conditions. Useful in chromatography, because the small quantity of sample injected into the instrument is not reproducible. Also useful to correct any loss of analyte during sample preparation. 2 Internal Standards Determine response factor: ) ] [ ( ] [ ) ] [ ( ] [ ) standard of ion Concentrat standard of Signal ( analyte of in Concentrat analyte of Signal S A F X A or S I F X I F S X S X = = = [X] and [S] are the concentrations of analyte and standard after they have been mixed together Ex. Selection of Internal Standards Similar to the drug of interest Something not available to the public....
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- Spring '09