Kathryn S. Kalasinsky

Rapid and Convenient Sampling Accessory for Diffuse Reflectance Spectroscopy

Griffiths and co-workers demonstrated that diffuse reflectance infrared spectroscopy (DRIFTS) can be used to study solids as mixtures with KCl and as samples deposited from solutions, and we have devised a sampling accessory for obtaining DRIFT spectra of multiple samples which is more convenient than making KBr pellets, cast films, or even thin films. Very often the analyst is required to obtain spectra of a large number of samples, and generally these samples must be prepared and analyzed one at a time. The multiple sample accessory shown in Fig. 1 enables us to complete the sample preparation prior to recording any spectra. In this way, valuable instrument time is more efficiently utilized, and the necessity of disruputing the instruments purge between each sampling is minimized. The accessory is small enough to fit through a f

Quantitative Analysis of Cellulosic Fillers Using Infrared Reflectance Spectroscopy

For production of a cellulosic filler that is compatible with thermoplastic polymers, a primarily nonpolar or lignin surface is needed. In order to allow quantitative measurement of the cellulose-to-lignin ratio on the surface of the fillers, infrared reflectance techniques and computer curve-fitting were employed. By the use of this method of analysis, relative quantitation was obtained, and it was possible to determine that careful control of certain parameters during the production of thermomechanical pulps produced a more nonpolar lignin-like surface that was compatible with the thermoplastic polymers.

Double lightpipe system for analytical GC/FT-IR and spectral libraries

A GC/FT-IR accessory has been configured with two lightpipes in order to allow flexibility in chromatographic separations. A capillary column is connected to a 15-cm lightpipe (1.5-mm bore) and is used for analytical GC/FT-IR. The second lightpipe (42-cm, 3-mm bore) is connected to a packed column and is configured with valves to provide a stopped-flow capability. This lightpipe is used when the sample size is not limited or when signal-averaging and high resolution are necessary. Broad-band MCT detectors are generally used because they are not adversely affected by unmodulated blackbody radiation from the heated lightpipe. In those instances when a narrow-band MCT detector is needed, an aperture and one additional mirror are used to discriminate against the unmodulated radiation. Applications of both systems are discussed.

Vibrational frequency patterns for hydrogen-substituted degradation products of the pesticide mirex

Abstract A complete vibrational study has been made of a number of the hydrogen-substituted derivatives of the pesticide mirex, C 10 Cl 12 . Although a complete vibrational assignment was not possible owing to the large number of allowed transitions and the small number of observed bands, peak patterns based on substitution were determined and identifications made based on these trends. The spectral data provided should make it possible to identify the various hydrogen-substituted derivatives.

Fourier transform infrared spectroscopy techniques for the analysis of drugs of abuse

Cryogenic deposition techniques for Gas Chromatography/Fourier Transform Infrared (GC/FT-IR) can be successfully employed in urinalysis for drugs of abuse with detection limits comparable to those of the established Gas Chromatography/Mass Spectrometry (GC/MS) technique. The additional confidence of the data that infrared analysis can offer has been helpful in identifying ambiguous results, particularly, in the case of amphetamines where drugs of abuse can be confused with over-the-counter medications or naturally occurring amines. Hair analysis has been important in drug testing when adulteration of urine samples has been a question. Functional group mapping can further assist the analysis and track drug use versus time.

Aqueous Reversed-Phase HPLC/FT-IR Using Diffuse Reflectance Detections

Solvent-elimination HPLC/FT-IR has become a viable combination of two important techniques, and we have been developing a system which is adaptable to both normal and reversed-phase liquid chromatography. The interface involves the deposition of HPLC eluites onto a KCI-laden train with subsequent analysis via diffuse reflectance spectroscopy, and with minor modifications, the system can be used with microbore and analytical columns. With aqueous solvents, the water is converted to methanol and acetone in a post-column reaction with 2,2-dimethoxypropane before the eluites are deposited. A number of different samples have been used to demonstrate the interface and its flexibility. Steroids, analgesics, and other pharmaceutical preparations have been separated with reverse-phase solvents and identified by their infrared spectra. For some of the compounds studied, different infrared spectra of a given compound have been found to exhibit intensity variations, which arise from different crystalline states. The differences can be concentration dependent and may be useful in obtaining semi-quantitative information from the infrared spectra. Applications involving both gradient elution and isocratic separations have been successful. The former provides the same advantages for HPLC/FT-IR as one finds in conventional HPLC. More recent work has been applied to the use of buffers such as those frequently used in bioanalytical separations. In trying to simplify the post-column reaction with water, we have immobilized dehydration reagents onto silica particles and packed these materials into a column which is inserted in-line after the analytical column. Of the reagents utilized to date, 3,3-dimethoxypropyltrimethoxysilane has been found to perform most efficiently. It has advantages over the simpler reagents because it can be regenerated in the reaction column. Results and the efficiency of the dehydration process and its relation to the type of reagent and its coverage will be discussed.

Gas Chromatography-Infrared (GC-IR) Applications In Pesticide Chemistry

After pesticides in bait formulation have been applied in the field, it is important that the fate of that amount of toxicant which has not been consumed by the pest is known. Many of these substances are not compatible with the environment and it is also important that their biodegradation be understood and controlled to a certain extent. In efforts to monitor and direct these reactions GC-IR has been found to be an invaluable tool.