Woodfin V. Ligon

Understanding the glycerol surface as it relates to the secondary ion mass spectrometry experiment. A review

Abstract A detailed understanding of the physical processes which can occur at the glycerol surface is essential to understanding the secondary ion mass spectra obtained from glycerol solutions. Because of differences in surface activity, the relative contribution of two solutes to the surface composition can differ dramatically with profound effects on the SIMS spectrum. Both first-order and secondary effects of this type are discussed. Also discussed is the preparation of surface active derivatives, the use of surfactants of opposite charge, and the use of surfactants as reagents and complexing agents.

The use of surfactants to modify molar response factors in the secondary ion mass spectrometry of liquid surfaces

Abstract Differences in the relative molar response observed for a series of closely related analytes in glycerol solution using secondary ion mass spectrometry are attributable largely to differences in surface activity. These differences can be minimized if a relatively large quantity of a surfactant of opposite charge is added to the solution before analysis. This added surfactant is chosen to dominate the surface selectively with the result that differences in surface activity among the species of interest become unimportant. The added surfactant does not interfere because its complementary charge state ensures very low response relative to the species of interest. It is further demonstrated that, in much the same way, surfactants can be used to enhance the response of an analyte relative to a matrix such as glycerol. This paper describes the first reported application of surfactants as reagents to modify the secondary ion mass spectra of liquid solutions.

Isomer specific analysis of selected chlorodibenzofurans

Abstract Two-dimensional gas chromatography has been used to provide full chromatographic resolution of three chlorodibenzofuran isomers. The materials studied were: 2,3,7,8-tetrachlorodibenzofuran, 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,7,8,9-hexachlorodibenzofuran. The materials were detected using medium resolution mass spectrometry.

The analysis of inorganic anions from liquid solutions using cationic surfactants and negative secondary ion mass spectrometry

Small inorganic anions such as nitrate, nitrite, iodate, bromate, cyanate, thiocyanate, chlorate, perchlorate, iodide, bromide, chloride, and tetrafluoroborate can be analyzed at low levels from glycerol solution using negative secondary ion mass spectrometry provided a long chain cationic surfactant such as tetradecyltrimethylammonium hydroxide is present in the solution. Sensitivities are directly related to the extent of association of the anion with the surface monolayer generated by the surfactant. Strongly interacting anions such as nitrate are detectable as intact ions at the 1 ng level (10−5 M in glycerol, two μl of solution). The degree of interaction between the anion and the monolayer parallels the behavior of the same ions on quaternary ammonium ion exchange resins. Fluoride and hydroxide do not interact strongly and do not give signals of useful intensity. Quantification can be readily obtained using stable isotope dilution techniques. The technique has been applied to the analysis of nitrate anion in natural precipitation.

Target compound analysis by two-dimensional gas chromatography—mass spectrometry

Abstract The use of two-dimensional gas chromatography 1 for the analysis of specific target compounds in complex matrices in combination with mass spectrometry has been investigated. The combination of a high capacity, high polarity packed first gas chromatography column followed with a low capacity, low polarity, high resolution second column has been found useful. A component of interest is switched from the first column into a cold trap and then flash-evaporated into the second column. This combination allows part per billion analyses in complex mixtures such as soil extracts, crude oils, and biological extracts without any prior sample cleanup whatever. Two important advantages arise naturally therefore from this approach: a significant reduction in analysis time and a major improvement in the specificity of the analysis. The method offers a relatively inexpensive yet powerful alternative to mass spectrometry—mass spectrometry.

High-resolution field-desorption mass spectrometry utilizing multichannel scaling techniques☆

Abstract The use of a Tracor—Northern Model 1700 multichannel analyzer operated in the multichannel scaling mode has been shown to simplify greatly the acquisition of high-resolution field-desorption mass spectra for very high masses (>1000 daltons). The data are acquired using voltage scanning, and an equation is derived which converts the masses obtained by linear interpolation into true mass values.

Azeotropic distillation as an enrichment strategy for determination of aromatic hydrocarbons

Abstract A wide variety of environmentally significant aromatic hydrocarbons have been found to undergo azeotropic distillation with glycerol and related hydroxylic azeotroping agents. This classical but previously neglected separation method is often quicker and more efficient than Soxhlet extraction for many sample types. In addition, many interfering substances typically encountered in environmental analyses such as large triglycerides do not form azeotropes and therefore are cleanly excluded from the analysis. Azeotropic distillation is much faster and often more complete than solvent extraction. Additionally, this approach significantly minimizes the use of organic solvents in the environmental laboratory while introducing only relatively benign materials such as glycerol.