期刊
APPLIED SPECTROSCOPY
卷 70, 期 6, 页码 983-994出版社
SAGE PUBLICATIONS INC
DOI: 10.1177/0003702816641263
关键词
Attenuated total reflection Fourier transform infrared spectroscopy; ATR FT-IR; Mid-infrared spectroscopy; Mid-IR; Urea; Hydration; Creatinine; Medical diagnostics
资金
- Biotechnology and Biological Sciences Research Council [BB/K001094/1]
- Wellcome Trust/Medical Research Council
- Biotechnology and Biological Sciences Research Council [BB/K001094/1] Funding Source: researchfish
- Medical Research Council [1032772] Funding Source: researchfish
- BBSRC [BB/K001094/1] Funding Source: UKRI
When analyzing solutes by Fourier transform infrared (FT-IR) spectroscopy in attenuated total reflection (ATR) mode, drying of samples onto the ATR crystal surface can greatly increase solute band intensities and, therefore, aid detection of minor components. However, analysis of such spectra is complicated by the existence of alternative partial hydration states of some substances that can significantly alter their infrared signatures. This is illustrated here with urea, which is a dominant component of urine. The effects of hydration state on its infrared spectrum were investigated both by incubation in atmospheres of fixed relative humidities and by recording serial spectra during the drying process. Significant changes of absorption band positions and shapes were observed. Decomposition of the CN antisymmetric stretching ((as)) band in all states was possible with four components whose relative intensities varied with hydration state. These correspond to the solution (1468cm(-1)) and dry (1464cm(-1)) states and two intermediate (1454cm(-1) and 1443cm(-1)) forms that arise from specific urea-water and/or urea-urea interactions. Such intermediate forms of other compounds can also be formed, as demonstrated here with creatinine. Recognition of these states and their accommodation in analyses of materials such as dried urine allows more precise decomposition of spectra so that weaker bands of diagnostic interest can be more accurately defined.
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