We have been developing a novel infrared fiberoptic system for on-line monitoring of toxic materials in water. The system is based on fiberoptic evanescent wave spectroscopy (FEWS) and it operates in the middle infrared (Mid-IR) spectral range 3µm - 30µm. This spectral range covers the “fingerprint” region where many molecules have characteristic absorption. The system is based on silver halide (AgClBr) fibers which are flexible, non-toxic, non-hygroscopic and highly transparent in the Mid-IR. A short segment of unclad AgClBr serves as a sensing element, which is coupled to a tunable IR source (e.g. FTIR or tunable IR laser) via two long IR fibers. This setup makes it possible to carry out absorption measurements on water, in a remote location (in situ) and in real time. By flattening the short sensor element one can increase the sensitivity. Using this system we have already monitored pollutants in water in concentrations of the order of 1ppm. The system allows a highly sensitive and selective detection of several pollutants, simultaneously. With additional improvement this fiberoptic sensor system will be more sensitive, selective, affordable, robust and easy to operate. Such a system could to detect the presence of toxic chemicals, such as pesticides, in drinking water at levels lower than 1ppm.
Fiberoptic Evanescent Wave Spectroscopy (FEWS) has been used for measurements of the absorption of very small (0.1mg) fragments of urinary calculi in the mid-IR. Such measurements were used for the determination of the chemical composition of each fragment. When large urinary stones are fragmented, it is possible to use this method for determining the chemical composition of the inner part and the outer part of the stone. We examined 40 urinary calculi and found that in 1/3 of them the inner part and the outer parts are identical. In 2/3 the inner part is different than the outer part. This change is not revealed by standard chemical methods that provide an average chemical composition. The novel FEWS method would be useful for the analysis of urinary calculi.
Fiber Evanescent Wave Spectroscopy (FEWS) is a very useful method for non-invasive and non-destructive biomedical diagnosis. We have developed a FEWS system that makes use of a Fourier Transform Infrared (FTIR) spectrometer and IR transmitting AgBrxCl1-x fibers. The FTIR-FEWS system is compact and easy to use, and it is ideal for the study of the spectroscopy of the skin in the mid-IR. The evanescent wave penetration depth in the mid-IR is comparable with the thickness of the stratum corneum, and therefore the vibrational spectra of lipids, proteins and water can be easily analyzed. We have used FTIR-FEWS for a clinical study of the skin of 60 patients, who had some suspicious skin lesions. Preliminary measurements were carried out both on the lesion and on neighboring healthy areas of the skin, showing some differences in the IR absorption. More data is needed in order to determine the possibility of diagnosis of skin cancer and its type from mid-IR spectral data.
The objective of this work was to use infrared (IR) fiberoptic spectroscopy for the analysis of urinary salts. Urine samples were obtained (with no sample preparation) from two groups of patients: 24 stone forming patients, after shock wave lithotripsy, and 24 normal subjects of similar ages. IR absorption measurements were performed in real time, using Fiberoptic Evanescent Wave Spectroscopy system, based on IR transmitting silver halide fibers. The absorption data were compared with the IR spectra of aqueous solutions with known concentrations of known urinary salts. The results were then used for the study of the chemical composition of salts in urine samples and for a quantitative analysis of the concentration of these salts. We established the composition of the stones in 20 of the 24 stone forming patients, based on the characteristic absorption peaks for oxalates, carbonates, urates and phosphates observed in their urinary samples. We also determined the concentrations of these salts in the urine samples with average error of 20 percent.
Fourier Transform Infrared (FTIR) spectroscopic systems make use of Attenuated Total Reflection (ATR) elements for the study of skin in dermatology. FTIR - ATR allows real time and reagent-less analysis of several components, simultaneously. The potential for skin studies is increased by the development of the flexible fiber optic sensor made from infrared transparent polycrystalline silver halide. Segments of fibers can replace the ATR sensing elements inside an FTIR system. Moreover a Fiberoptic Evanescent Wave Spectroscopy (FEWS) can also be used for real time in vivo measurement on skin, in situ. We used FEWS to study the diffusion of UV sunscreen lotions from the outer skin layer into the dermis and epidermis, and used the various absorption bands to differentiate between the behavior of the organic and the water molecules in the lotion. FEWS can be a powerful tool for studying the transport of drugs and cosmetic creams through the skin from the stratum corneum to the dermis and epidermis and for studying the lateral diffusion of various molecules into the skin, in vivo and in real time.