Joseph V. Paukstelis

Application of a Two-Dimensional Hadamard Encoding Mask for the Imaging of Thin-Layer Chromatography Plates by Laser-Induced Fluorescence or Surface-Enhanced Raman Scattering and for Use with a Photoacoustic Detector to Generate Three-Dimensional Photoacoustic Images

Spatial imaging of thin-layer chromatography plates using laser-induced fluorescence and surface-enhanced Raman scattering has been accomplished with a stationary two-dimensional Hadamard encoding mask. Detection of three nanograms of pararosaniline hydrochloride on a thin-layer chromatography plate was made possible by means of the surface-enhanced Raman phenomenon. The imaging capabilities of the stationary two-dimensional Hadamard encoding mask coupled with the depth profiling ability of photoacoustic detection allows for the three-dimensional photoacoustic imaging of a multiple analyte sample.

Temporal systematic errors using stationary Hadamard encoding masks

Abstract Temporal systematic errors result from the use of a stationary Hadamard encoding mask in a Hadamard transform spectrometer when the time between encodements is made too short relative to the mask response time. These errors have been characterized and an empirical method has been developed to correct for the resulting artifacts appearing in the spectra. It is then possible to operate the Hadamard transform spectrometer with a shorter data acquisition time. Typical examples are presented and discussed.

Comparisons of diisopropylfluorophosphate derivatives of chymotrypsin and chymotrypsinogen by phosphorus-31 nuclear magnetic resonance.

Abstract The nature of the differences in the active sites of α-chymotrypsin and chymotrypsinogen has been investigated by phosphorus-31 NMR studies of their diisopropylfluorophosphate derivatives. The phosphorus-31 resonance of the modified zymogen occurs 2 ppm upfield from that for the enzyme. An even greater separation is seen between diisopropylphosphoryl-neo-chymotrypsinogen and -α-chymotrypsin. A plausible interpretation of the chemical shift differences is based on the known structures for α-chymotrypsin, chymotrypsinogen and diisopropylphosphoryl-trypsin.

Near-infrared Hadamard transform Raman spectrometry

Abstract Hadamard transform spectrometry using a liquid crystal optical shutter array (LC-OSA) as a stationary Hadamard encoding mask is shown to be a viable technique for near-IR Raman spectrometry with the 1064-nm line of a Nd:YAG laser. Spectra are presented and discussed and future plans are outlined.

A new stationary Hadamard encoding mask for near- infrared Hadamard transform Raman spectrometry

Abstract Near-infrared Hadamard transform Raman spectrometry was performed to demonstrate the advantages gained using a recently developed 255 element polymer-dispersed-liquid-crystal (PDLC) optical-shutter-array as a stationary Hadamard encoding mask. Spectra presented illustrate the improvements the PDLC encoding mask has made in comparison with a 127 element cholesteric liquid crystal display used previously. Examples of the multiplex advantage and a selective multiplex technique are presented and discussed.

Phenoxazine as a solid monitoring reagent for ozone

Phenoxazine exhibits selectivity for reaction with ozone in concentrations normally found in air to produce a brown color of exceptional stability. It reacts with nitrogen dioxide to form a red-orange product that is visually distinct from the dull brown produced by the reagent with ozone. The solid reagent on cellulose paper is intended for visual comparison to prepared color standards in passive monitoring or warning devices.

Recent developments in Hadamard transform Raman spectrometry

An introduction to Hadamard transform spectrometry in general and Hadamard transform Raman spectrometry in particular is presented. Two generations of Hadamard encoding masks are described. Experimental details are provided for the operation of a Hadamard transform Raman spectrometer utilizing the Hadamard encoding masks described. Near-infrared Hadamard transform Raman spectra are presented to illustrate spectral subtraction, the multiplex advantage and a selective multiplex technique. With the second generation of Hadamard encoding masks available, the Hadamard transform Raman technique is now ready to begin its testing in the analytical world.

Sensitive Solid Reagent For Formaldehyde, And A New Formaldehyde Generator

Abstract A solid reagent of Purpald®-acetone aminal on sodium or potassium bicarbonate responds to formaldehyde in the sub-ppm concentration range. A purple color (λ=560 nm) is developed proportional to concentration of formaldehyde and time of exposure after wetting with a 90% acetone-10% water solution. The reagent should be of value as a semi-quantitative warning device for the presence of formaldehyde. A device is described which generates formaldehyde in air in the sub-ppm concentration range at room temperature with desired relative humidity. This generator could be used in the same manner to generate low concentrations of other substances of low volatility.

Tin(II)-diphenylcarbazide Complex as a Solid Reagent in Monitoring Devices for Atmospheric Oxidants

Abstract The tin(II)-diphenylcarbazide complex, [Sn(C13H14N4O)2]Cl2 or [Sn(C13H14N4O)2Cl2], applied as an acetone solution to cellulose (filter paper) or starch and dried, is oxidized to the red-violet diphenylcarbazone by ozone and nitrogen dioxide - the principal atmospheric oxidants - at concentrations below 1 ppm. The supported reagent is stable indefinitely when kept in a sealed bottle.

Raman studies of thin-layer chromatography

The Hadamard transform technique has been extended to include imaging with a two- dimensional stationary Hadamard encoding mask. Images have been obtained by measuring laser induced fluorescence, Raman scattering, and surface enhanced Raman scattering. Spots on thin-layer chromatography plates have been imaged using laser induced fluorescence and surface enhanced Raman scattering.