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تسجيل

Sample preparation and presentation , Cells

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  416

2026-11-11

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Sample preparation and presentation

Cells

Specimen cells used in fluorescence measure ments may be round tubes or rectangular cells similar to those used in absorption spectrophotometry, except that they are polished on all four vertical sides. A convenient test specimen size is 2 to 3 mL, but some instruments can be fitted with small cells holding 100–300 lL or with a capillary holder that requires an even smaller specimen volume. Temperature regulation is often important in fluorescence spectrophotometry. For some substances, fluorescence efficiency may be reduced by as much as 1–2% per degree of temperature rise. In such cases, if maximum precision is desired, temperature-controlled sample cells are useful. For routine analysis, it may be sufficient to make measurements rapidly enough so that the specimen does not heat up appreciably from exposure to the intense light source.