David E. Games

Supercritical fluid chromatographic and supercritical fluid chromatographic―mass spectrometric studies of some polar compounds

Abstract Silica and amino-bonded silica columns (4.6 mm I.D.), with carbon dioxide modified with methanol or methoxyethanol, have been used to effect supercritical fluid chromatographic separations of mixtures of xanthines, carbamates, sulphonamides, steroids and ergot alkaloids. Combined supercritical fluid chromatography—mass spectrometry has been accomplished using a moving belt high-performance liquid chromatographic—mass spectrometric interface with a modified thermospray deposition device. The applicability of the technique is illustrated with mixtures of xanthines, sulphonamides and an extract from Claviceps purpurea .

Applications of high-pressure liquid chromatography and field desorption mass spectrometry in studies of natural porphyrins and chlorophyll derivatives

Mixtures of porphyrins derived from natural sources can be readily separated by high-pressure liquid chromatography both analytically and on a preparative scale. A variety of procedures have been developed not only for the esters but also for free acids, and on the analytical scale quantitation is easily achieved by visible absorption. The retention times are largely characteristic of the number of carboxylic acid side chains (or other polar groups) but further information can be obtained by mass spectrometric studies of the various fractions. Field desorption mass spectrometry is particularly useful for this purpose because the emitter wire can be dipped directly into the eluates. The field desorption spectra of porphyrin free acids and esters as well as their metal complexes give essentially molecular ions with little or no fragmentation in most cases, whereas electron-impact mass spectrometry, particularly of free acids, is impeded by the low volatility of porphyrins. Mixtures can also be analysed by field desorption mass spectrometry, and this provides not only a rapid qualitative assessment of the components of a mixture, but also a check on the subsequent chromatographic separations.

Analysis of drug residues in tissue by combined supercritical-fluid extraction-supercritical-fluid chromatography-mass spectrometry-mass spectrometry

The combination of supercritical-fluid extraction-supercritical-fluid chromatography-tandem mass spectrometry has been evaluated for the detection of residues of a small group of veterinary drugs in freeze-dried pigs kidney. During extraction with supercritical CO2 the drugs were retained by the column while non-polar endogenous material was not retained and thus passed to waste. Subsequent changes to the mobile phase composition eluted the drugs which were detected with high specificity by tandem mass spectrometry. Although the sensitivity in this preliminary study was not adequate for surveillance or enforcement, there is potential for further development of the approach.

High-performance liquid chromatography-mass spectrometry with transport interfaces

Abstract The utility of various types of transport interface for high-performance liquid chromatography-mass spectrometry is reviewed, together with areas in which the technique has been applied. The advantages of using microbore high-performance liquid chromatography systems with interfaces of this type are described, and the relative merits of mass spectrometry-mass spectrometry and liquid chromatography-mass spectrometry for studies of complex mixtures are discussed.

Use of circular dichroism as a high-performance liquid chromatography detector

Abstract A circular dichroism (CD) spectrophotometer has been coupled to a high-performance liquid chromatograph. Natural pyrethrins, tryptophan, rotenoids and Amaryllidaceae alkaloids have been used to evaluate the system. Monitoring at selected wavelengths has enabled detection levels in the low μg range to be obtained. By using stopped-flow techniques, full CD spectra can be obtained, and the system has been used in conjunction with combined high-performance liquid chromatography-mass spectrometry to study an extract of timbo powder.

Analysis of pepper and capsicum oleoresins by high-performance liquid chromatography-mass spectrometry and field desorption mass spectrometry

Using a combination of high-performance liquid chromatography-mass spectrometry with a moving-belt interface, field desorption mass spectrometry and high-resolution accurate mass electron impact mass spectrometry, the major components of the oleoresins of black pepper and capsicum have been identified. Nordihydro-, dihyro- and homo-capsaicin together with capsaicin and a series of fatty acids were found in the capsicum oleoresin. A series of N-isobutyltrienamides and dienamides, together with piperettin and piperine isomers and piperolein A and B, piperanine and piperylin were identified in the black pepper oleoresin. ?? 1984.

Studies of combined liquid chromatography-mass spectrometry with a moving-belt interface

Abstract The advantages and limitations of a moving-belt interface for liquid chromatography-mass spectrometry are discussed using examples of combined liquid chromatography-mass spectrometry of natural coumarins, alkaloids, rotenoids, sugars, nucleosides, peptides and pesticides and drugs and their metabolites. Preliminary data obtained using a micro high-performance liquid chromatograph interfaced to the moving belt are reported.

Analysis of sulphonamides using supercritical fluid chromatography and supercritical fluid chromatography—mass spectrometry

Packed-column supercritical fluid chromatography has been used for the separation of mixtures of sulphonamides on silica and amino-bonded stationary phases utilizing carbon dioxide with methanol modifier as the mobile phase. The effect of modifier concentration, column pressure and modifier identity on retention was also studied. Packed-column supercritical fluid chromatography-mass spectrometry (SFC-MS) of these mixtures utilizing both moving-belt and modified thermospray interfaces was also studied. The identification of sulphamethazine in a spiked porcine kidney extract was performed by SFC-MS using the moving-belt interface.

Field desorption mass spectrometry of organometallic complex salts

Abstract The field desorption spectra of [(L)M(CO) 3 ] + BF 4 − [M = Fe, L = cyclo-C 6 H 7 , cyclo-C 7 H 9 , cyclo-C 10 H 11 , 2-MeO-cyclo-C 6 H 7 ; M = W, L = cyclo-C 7 H 7 ], [(Ar)Fe(C 5 H 5 )] + PF 6 − [Ar = C 6 H 6 , CH 3 C 6 H 5 , (CH 3 ) 3 C 6 H 3 ], [(cyclo-C 8 H 11 )Co(C 5 H 5 )] + BF 4 − and [(C 6 H 6 )Cr(CO) 3 ] have been obtained. In all cases molecular or quasi-molecular ions for the cations were present, usually as the base peaks in the spectra. Fragment ions corresponding to metal—ligand cleavages were also found in most cases.

Supercritical fluid chromatography of Fusarium mycotoxins

Capillary- and packed-column supercritical fluid chromatography has been used for the separation of Fusarium mycotoxins of various structure types such as the trichothecenes including deoxynivalenol and its acetylated derivatives and T-2 toxin, as well as butenolide, culmorin, sambucinol and zearalenone. The effect of modifier concentration and column temperature and pressure was also studied. Retention indices based on alkylphenones were determined for these mycotoxins on two of the capillary columns employed.