Development of the New Infrared Spectrophotometer Using the Vacuum-dried Attenuated Total Reflection (ATR) Method for the Water-Containing Samples: Study for Amniotic Fluid

Infrared spectral analysis gives the information originated in both molecules and radicals. But the existing infrared spectrophotometer has only the lowest sensitivity and detectivity and it has been used only for qualitative analysis. We have developed a new spectrophotometric device and studied its availability for quantitative analysis of water-containing samples of minute amount.(1)We developed the chamber designed for the Attenuated Total Reflection (ATR) method with the vacuum-drying technic and set a prism horizontally in it. This chamber was installed in the infrared spectrophotometer and we could successfully obtain the solid components spectra from water-containing samples firmly attached to the prism surface. (2) We used the HgCdTe detector in the measuring part of the spectrophotometer to improve the detectivity. The results were as follows; (1)Both the sensitivity (44 times in the case of hialuronic acid solution (2 g/dl))and the detectivity were markedly improved. (2) Consequently, we could successfully obtain the solid components spectra from water-containing samples such as the amniotic fluid, from which we have not been able to obtain any information by using conventional spectrophotometers. With this technique, a new quantitative analysis has become possible. This new apparatus needs only a very small amount of samples (60 μl in the case of amniotic fluid) and takes only 8 min to measure. Therefore, it is hoped that this new modality will be widely used in many fields of our medical specialities.