Quantitative Impurity Measurement in Organic Crystals by Precise Measurement of THz Absorption Frequencies

We have developed a novel technique for quantitative detection of impurities in organic crystals by precise measurement of THz absorption peak frequencies. Using a highly accurate, high-resolution CW GaP THz spectrometer and measuring the sample at low temperature, the highest sensitivity of 4.51 GHz/% and minimum limit of impurity detection as low as 50 ppm could be obtained. One of the suitable targets for the technique is middle molecular weight (MMW) pharmaceutical which often shows sharp absorption lines in spectrum.