Yosef Raichlin

Mid-infrared fiber-optic attenuated total reflection spectroscopy of the solid-liquid phase transition of water.

Measurements of mid-infrared (MIR) absorption spectra of water and heavy water were carried out by fiber-optic evanescent wave spectroscopy, using silver halide (AgClBr) infrared fibers. Such measurements were performed for the first time on one sample, during the solid–liquid phase transition. From the variation of the spectra with temperature we found a new isosbestic point (at 3280 cm−1 for H2O or at 2475 cm−1 for D2O) and we identified five components of the O–H (O–D) stretch band. These phenomena have provided new information about the molecular structure of water.

High-sensitivity infrared attenuated total reflectance sensors for in situ multicomponent detection of volatile organic compounds in water

In situ detection of volatile organic compounds (VOCs) in aqueous environments is imperative for ensuring the quality and safety of water supplies, yet it remains a challenging analytical task. We present a high-sensitivity method for in situ analysis of multicomponent VOCs at low concentrations based on the use of infrared attenuated total reflection (IR-ATR) spectroscopy. This protocol uses a unique ATR waveguide, which comprises a planar silver halide (AgClxBr1−x) fiber with cylindrical extensions at both ends to increase the number of internal reflections, and a polymer coating that traps VOCs and excludes water molecules. Depending on the type of VOC and measurement scenario, IR spectra with specific frequency windows, scan times and spectral resolutions are obtained, from which concentration information is derived. This protocol allows simultaneous detection of multiple VOCs at concentrations around 10 p.p.b., and it enables accurate quantification via a single measurement within 5 min without the need for sample collection or sample pretreatment. This IR-ATR sensor technology will be useful for other applications; we have included a procedure for the analysis of protein conformation changes in Supplementary Methods as an example.

Determination of Chlorinated Hydrocarbons in Water Using Highly Sensitive Mid-Infrared Sensor Technology

Chlorinated aliphatic hydrocarbons and chlorinated aromatic hydrocarbons (CHCs) are toxic and carcinogenic contaminants commonly found in environmental samples, and efficient online detection of these contaminants is still challenging at the present stage. Here, we report an advanced Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) sensor for in-situ and simultaneous detection of multiple CHCs, including monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, trichloroethylene, perchloroethylene, and chloroform. The polycrystalline silver halide sensor fiber had a unique integrated planar-cylindric geometry, and was coated with an ethylene/propylene copolymer membrane to act as a solid phase extractor, which greatly amplified the analytical signal and contributed to a higher detection sensitivity compared to the previously reported sensors. This system exhibited a high detection sensitivity towards the CHCs mixture at a wide concentration range of 5~700 ppb. The FTIR-ATR sensor described in this study has a high potential to be utilized as a trace-sensitive on-line device for water contamination monitoring.

Fiberoptic infrared spectroscopy: a novel tool for the analysis of urine and urinary salts in situ and in real time.

OBJECTIVES To use infrared fiberoptic spectroscopy for the analysis of urinary salts in real time and with no sample processing; and to assess the practical role of this method for the quantitative measurement of the composition of urine and for the diagnosis of urolithiasis in patients. METHODS Urine samples were obtained from two groups of patients: 24 patients with stone formation after shock wave lithotripsy and 24 normal subjects of similar age. Infrared absorption measurements were performed in real time, using infrared transmitting silver halide fibers. The absorption data were compared with the infrared absorption spectra of aqueous solutions prepared in our laboratory, with known concentrations of known urinary salts. The results were used for the study of the chemical composition of these salts in the urine samples and for a quantitative analysis of the concentration of the salts. RESULTS We determined the composition of the stones in 20 of the 24 patients on the basis of the characteristic absorption peaks for the oxalates, carbonates, urates, and phosphates observed in their urinary samples. Using the method mentioned above, we found the concentration of different salts in urine with an average error of 20%. CONCLUSIONS Fiberoptic infrared spectroscopy could be used as a new diagnostic tool for detecting different urinary salts in urine, finding their chemical composition, and determining their concentrations, without any sample preparation.

Mid-Infrared Planar Silver Halide Waveguides with Integrated Grating Couplers

Grating couplers for planar silver halide waveguides were designed and fabricated by using focused ion beam (FIB) milling technology, facilitating coupling of mid-infrared radiation from quantum cascade lasers into thin-film waveguide structures. An optimized rectangular grating structure for an emitted wavelength of 10.4 μm, with a grating constant of 16.4 μm was integrated into a silver halide waveguide substrate via an optimized FIB fabrication procedure. Efficient uncoupling and radiation propagation through the waveguide was confirmed by analyzing droplets of acetic acid at different concentrations, deposited at the waveguide surface via evanescent field absorption spectroscopy.

Infrared fiber optic evanescent wave spectroscopy for the study of diffusion in the human skin

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.

Fourier transform infrared spectroscopy on external perturbations inducing secondary structure changes of hemoglobin

The secondary structure of proteins and their conformation are intimately related to their biological functions. In this study, heat-induced changes in the secondary structure and conformation of hemoglobin were investigated via infrared attenuated total reflection (IR-ATR) spectroscopy. The secondary structure changes of hemoglobin were derived from IR-ATR spectra using second derivatives and curve fitting. Thereby, the thermal denaturation temperature ranges and the secondary structure changes with temperature were revealed. More detailed information on the secondary structure and conformation was elucidated via two-dimensional infrared correlation spectroscopy. This study deciphers the detailed conformational behavior of hemoglobin molecular changes along with temperature, and creates a general methodological framework for analyzing the heat-induced behavior of biomacromolecules.

Infrared Spectroscopy for Monitoring Gas Hydrates in Aqueous Solution

The presented work describes first principles for monitoring gas hydrate formation and dissociation in solution by evaluating state-responsive IR absorption features of water with fiberoptic evanescent field spectroscopy. In addition, a first order linear functional relationship has been derived according to Lambert Beer’s law, which enables quantification of percentage gas hydrate within the volume of water directly probed via the evanescent field. Moreover, spectroscopic studies evaluating seafloor sediments collected from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix components, thereby establishing evanescent field sensing strategies as a promising perspective for monitoring the dynamics of gas hydrates in oceanic environments.

New applications of fiber-optic IR spectroscopy in urologic practice

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.

Using Attenuated Total Reflection–Fourier Transform Infra-Red (ATR-FTIR) spectroscopy to distinguish between melanoma cells with a different metastatic potential

The vast majority of cancer related deaths are caused by metastatic tumors. Therefore, identifying the metastatic potential of cancer cells is of great importance both for prognosis and for determining the correct treatment. Infrared (IR) spectroscopy of biological cells is an evolving research area, whose main aim is to find the spectral differences between diseased and healthy cells. In the present study, we demonstrate that Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) spectroscopy may be used to determine the metastatic potential of cancer cells. Using the ATR-FTIR spectroscopy, we can identify spectral alterations that are a result of hydration or molecular changes. We examined two murine melanoma cells with a common genetic background but a different metastatic level, and similarly, two human melanoma cells. Our findings revealed that higher metastatic potential correlates with membrane hydration level. Measuring the spectral properties of the cells allows us to determine the membrane hydration levels. Thus, ATR-FTIR spectroscopy has the potential to help in cancer metastasis prognosis.