The infrared spectra of solid renal stone material have been obtained traditionally by the KBr pellet and mineral oil mull techniques. Both are time-consuming methods for routine work because of the necessity of mixing the solid samples with diluent and forming the pellet or window
film. At our laboratory these methods as well as solid film casting from solutions have been used routinely. We have the need for a rapid infrared screening method to route as many as 100 samples/day to other analytical techniques such as x-ray diffractometry, atomic absorption spectrophotometry,
polarization microscopy, chemical analysis, etc., based upon the presence of gross chemical species and their approximate concentrations in the sample. Renal stones are typically crystalline phases of calcium phosphates, calcium oxalates, uric acid, and calcium carbonates. The specific phases
are apatite, whewellite, weddellite, calcite, struvite, uric acid, and rarely ammonium and sodium urate and cystine. The specimens are always solid and usually inorganic but relatively soft and easily ground to very fine powder. The spectral region of interest is usually 1800 to 650 cm−1
and a rapid scan with little sample preparation is preferred. The KBr pellet was used with very good analytical results for years, but the time involved in sample preparation limited our throughput to 4 samples/h even though the run itself was standardized to a mere 2 min (2000 to 600 cm−1
at 700 cm−1 min−1). The nujol mull technique proved to be much more time efficient with a routine throughput for one operator at 7 to 9/h.
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