NONDESTRUCTIVE AND NONINTRUSIVE DETERMINATION OF CHEMICAL AND ISOTOPIC PURITY OF SOLVENTS BY NEAR-INFRARED THERMAL LENS SPECTROMETRY

A novel instrument which is based on the use of the thermal lens effec t to facilitate the sensitive measurements of the absorption in the ne ar-infrared region has been developed. In this instrument, the near-IR excitation light was provided by a solid-state, spectra-tunable (from 860 to 1060 nm) titanium:sapphire laser. The heat generated as a cons equence of the sample absorption of the excitation beam was monitored in the visible region by a He-Ne laser. The data obtained were analyze d by multivariate calibration methods for the nondestructive, noninvas ive determinations of chemical and isotopic impurities in solvents. Wa ter in D2O and in tetrahydrofuran can be detected at levels as low as 0.006 and 0.3% (v/v). The method can also be used for the simultaneous determination of water and DMSO-h6 in DMSO-d6 and CD3OH in CD3OH, CD2 HOH, and CDH2OH at levels as low as 10(-3)% (w/w).