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Papers by Phillip McDowell

Research paper thumbnail of ChemInform Abstract: PEPTIDES. XXXXI. SYNTHESIS OF THE 38-75 FRAGMENT OF A LYSOZYME ANALOG

Chemischer Informationsdienst, Dec 23, 1980

ChemInform Abstract Das Titelpeptid (V) wird nach 2 verschiedenen Methoden, die von den in den vo... more ChemInform Abstract Das Titelpeptid (V) wird nach 2 verschiedenen Methoden, die von den in den vorstehenden Mitt. beschriebenen Peptid-Fragmenten (Ia), (IIa), (IVa) bzw. (VIa), (VII), (IXa) ausgehen, synthetisiert: 1. Das aus den Fragmenten (Ib) und (IIb) nach N-Schutzgruppenabspaltung erhältliche Produkt (IIIb) wird mit dem Fragment (IVb) kondensiert. 2. Das aus den Unterfragmenten (VII) und (VIb) nach Abspaltung der Estergruppe erhältliche Fragment (VIIIb) wird mit dem Fragment (Xb)-seinerseits zugänglich aus den nterfragmenten (IXb) und (IIb)-kondensiert; das erhaltene Hexacosapeptid (IIIa) wird dann wie beschriebenüber (IIIb) mit (IVb) in (V)übergeführt.

Research paper thumbnail of ChemInform Abstract: PEPTIDES. XXXXVI. STUDIES IN THE SYNTHESIS OF AN ANALOG OF HEN EGG WHITE LYSOZYME

Chemischer Informationsdienst, Dec 8, 1981

Research paper thumbnail of ChemInform Abstract: STEREOSPECIFIC SYNTHESIS OF 4,11-EPOXY-CIS-EUDESMANE, A TRICYCLIC SESQUITERPENE DEFENCE SECRETION FROM THE TERMITE AMITERMES EVUNCIFER

Chemischer Informationsdienst, Aug 2, 1977

www.cheminform.wiley-vch.de Benzothiazole derivatives R 0270 Stereospecific Synthesis of Alkyl Ar... more www.cheminform.wiley-vch.de Benzothiazole derivatives R 0270 Stereospecific Synthesis of Alkyl Aryl Sulfides from Alcohols and 2-Sulfanylbenzothiazole Using Aryl Diphenylphosphinite and Azide Compounds by a New Type of Oxidation-Reduction Condensation.-Chiral secondary and tertiary alcohols (I), (IV) and (VI) are converted into the corresponding sulfides with almost complete inversion of configuration under mild conditions.-(KURODA, K.; MARUYAMA,

Research paper thumbnail of Applications of PTV Injectors for Problem Solving in the Petrochemical Industry. Thermal Desorption with GC and GC-MS

Hrc-journal of High Resolution Chromatography, Aug 1, 2000

Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injec... more Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application as a problem solving tool are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples characterised.

Research paper thumbnail of Peptides-XXXXI

Research paper thumbnail of Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armywormSpodoptera exempta(walker) following topical treatment with the compound

Pesticide Science, 1987

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment ... more No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with precocene 11. [3H]-Precocene I1 penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6 4 % of the applied dose. A maximum titre of precocene of 1.1 x I O-~ M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11-3,4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 x I O-~ at 4 h suggesting metabolism via the 3,4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6-and 7-(0)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to 185 Pesric. Sci.

Research paper thumbnail of Interspecific trail-following and evidence of similarity of trails of Trinervitermes species from different habitats

International Journal of Tropical Insect Science, Sep 1, 1982

In choice tests with well-established natural trails and glandular extract trails, allopatric pop... more In choice tests with well-established natural trails and glandular extract trails, allopatric populations of Trinervitermes hettonianus Sjost followed alien colonies' trails with the same degree of motivation as their own trails. The five Trinervitermes spp. tested readily followed each other's trail. Chromatographs of natural trail extracts showed that the main component of the T. bettonianus trail pheromone also occurs in trails of T. gratiosus (and presumably in the other species); this would account for the observed cross-following of trails among these species.

Research paper thumbnail of Mono- and sesquiterpenoid constituents of the defence secretion of the termite amitermes evuncifer

Tetrahedron Letters, 1978

Research paper thumbnail of Selective chemical ionization of nitrogen and sulfur heterocycles in petroleum fractions by ion trap mass spectrometry

Journal of the American Society for Mass Spectrometry, 1993

Research paper thumbnail of Peptides-XXXXVI

Tetrahedron, 1981

Abstract The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) f... more Abstract The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) fragments of the analogue were combined making extensive use of the DCCI/HONSu method. The final coupling involved the (1–75) and (76–129) sub-fragments. Aggregation of the latter fragment caused problems in purification by routine gel filtration methods employing Enzacryl K2 or Sephadex LH60. The fully protected (1–129) product was partially purified by washing, then deprotectcd and purified by gel filtration and ion exchange chromatography. Satisfactory removal of the acetamidomethyl group used for cysteine protection could not be achieved.

Research paper thumbnail of Analysis of airborne volatiles of cowpea

Phytochemistry, 1989

Airborne volatiles of cowpea (Mgna unguiculata) plants were analysed by drawing air over the plan... more Airborne volatiles of cowpea (Mgna unguiculata) plants were analysed by drawing air over the plants in a glass chamber, trapping the airborne volatiles on Tenax TA adsorbent, and releasing the trapped volatiles into a GC-MS by heating the Tenax trap. Eleven volatile compounds; hexanal, 1-nonene, a-pinene, /I-pinene. (Z)-3-hexen-l-01 acetate, hexyl acetate, l&cineole, limonene, (E)+ocimene, nonanal and a-cedrene, were identified.

Research paper thumbnail of The isolation and identification of the cuticular sex-stimulant pheromone of the tsetse Glossina pallidipes Austen (Diptera:Glossinidae)

International Journal of Tropical Insect Science, 1981

ABSTRACT

Research paper thumbnail of Constituents of Commiphora rostrata and some of their analogues as maize weevil, Sitophilus zeamais repellents

International Journal of Tropical Insect Science, 1992

ABSTRACT

Research paper thumbnail of Interspecific trail-following and evidence of similarity of trails of Trinervitermes species from different habitats

International Journal of Tropical Insect Science, 1982

... cated that worker castes of different age groups exhi-bit significant differences in their po... more ... cated that worker castes of different age groups exhi-bit significant differences in their potential trail-laying capacity, and that it is the ... M. (1974) An unusual caste polymorphism of the sternal gland and its trail phero-mone production in the termite Trinervitermes betto-nianus. ...

Research paper thumbnail of Applications of PTV Injectors for Problem Solving in the Petrochemical Industry. Thermal Desorption with GC and GC-MS

Journal of High Resolution Chromatography, 2000

Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injec... more Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application as a problem solving tool are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples characterised.

Research paper thumbnail of Mono- and sesquiterpenoid constituents of the defence secretion of the termite amitermes evuncifer

Tetrahedron Letters, 1978

Research paper thumbnail of Volatile resin exudate from stem bark of Commiphora rostrata: Potential role in plant defence

Phytochemistry, 1988

The volatile resin exuded from the stem bark of Commiphora rosfrata has been examined and 22 oxyg... more The volatile resin exuded from the stem bark of Commiphora rosfrata has been examined and 22 oxygenated alkane components identified by GC and mass spectrometry. The potential value of this material in the defence of the plant against predators and fungal pathogens is discussed.

Research paper thumbnail of Activity of the diastereoisomers of 13,23-dimethylpenta-triacontane, the sex pheromone of Glossina pallidipes, and comparison with the natural pheromone

Physiological Entomology, 1985

All three synthetic diastereoisomers of 13,23-dimethylpentatriacontane, the pheromone of Glossina... more All three synthetic diastereoisomers of 13,23-dimethylpentatriacontane, the pheromone of Glossina pallidipes (Austen), have been tested in the G.pa1lidipes sex pheromone bioassay, together with one of the four diastereoisomers of 13,17-dimethylpentatriacontane, originally proposed as a candidate pheromone of G.pallidipes. Of the three isomers of 13,23-dimethylpentatriacontane only the (13R,23S) isomer was active with an ED-50 of 4.47f1.09yg (meankSD). The (13R,17R)-13,17-dimethylpentatriacontane was inactive. The diastereoisomeric mixtures of 13,17-and 13,23-dimethylpentatriacontane were active with ED-50 values of 17.88k1.25 yg and 8.88k1.15 yg respectively. The natural pheromone was active with an ED-50 of 8.07-t 1.17 p g indicating it to be a diastereoisomeric mixture.

Research paper thumbnail of Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armyworm Spodoptera exempta (walker) following topical treatment with the compound

Pesticide Science, 1987

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment ... more No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with precocene 11. [3H]-Precocene I1 penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6 4 % of the applied dose. A maximum titre of precocene of 1.1 x I O-~ M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11-3,4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 x I O-~ at 4 h suggesting metabolism via the 3,4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6-and 7-(0)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to 185 Pesric. Sci.

Research paper thumbnail of Use of non-volatile ion-pairing agents for liquid chromatographic-mass spectrometric analyses with a moving-belt interface

Journal of Chromatography A, 1991

i i:, J Micro-membrane suppressor systems were employed to allow non-volatile ion-pairing agents ... more i i:, J Micro-membrane suppressor systems were employed to allow non-volatile ion-pairing agents to be used with combined liquid chromatography-mass spectrometry (LC-MS). This enabled the technique to be used with reversed-phase gradient chromatography for the determination of both anionic and cationic species from a range of compounds. The membrane suppressors remove the ion-pairing agent by countercurrent flow regeneration. The determination ofcationic species is demonstrated with the use of pyridinium and imidazolium iodides. Hexanesulphonic acid was used as the chromatographic ion-pairing agent and tetrabutylammonium hydroxide as the regenerant. The determination of anionic species is demonstrated with carboxylic and sulphonic acids, which were chromatographed as the tetrabutylammonium hydroxide ion pair using sulphuric acid as the regenerant. The system described has been used successfully with a moving-belt interface, enabling spectra to be acquired in both electron impact (EI) and chemical ionization (CI) modes, with a magnetic sector instrument. The system is in essence compatible with any LC-MS interface, although some modification may be required if the interface generates a significant back-pressure. e.g., thermospray.

Research paper thumbnail of ChemInform Abstract: PEPTIDES. XXXXI. SYNTHESIS OF THE 38-75 FRAGMENT OF A LYSOZYME ANALOG

Chemischer Informationsdienst, Dec 23, 1980

ChemInform Abstract Das Titelpeptid (V) wird nach 2 verschiedenen Methoden, die von den in den vo... more ChemInform Abstract Das Titelpeptid (V) wird nach 2 verschiedenen Methoden, die von den in den vorstehenden Mitt. beschriebenen Peptid-Fragmenten (Ia), (IIa), (IVa) bzw. (VIa), (VII), (IXa) ausgehen, synthetisiert: 1. Das aus den Fragmenten (Ib) und (IIb) nach N-Schutzgruppenabspaltung erhältliche Produkt (IIIb) wird mit dem Fragment (IVb) kondensiert. 2. Das aus den Unterfragmenten (VII) und (VIb) nach Abspaltung der Estergruppe erhältliche Fragment (VIIIb) wird mit dem Fragment (Xb)-seinerseits zugänglich aus den nterfragmenten (IXb) und (IIb)-kondensiert; das erhaltene Hexacosapeptid (IIIa) wird dann wie beschriebenüber (IIIb) mit (IVb) in (V)übergeführt.

Research paper thumbnail of ChemInform Abstract: PEPTIDES. XXXXVI. STUDIES IN THE SYNTHESIS OF AN ANALOG OF HEN EGG WHITE LYSOZYME

Chemischer Informationsdienst, Dec 8, 1981

Research paper thumbnail of ChemInform Abstract: STEREOSPECIFIC SYNTHESIS OF 4,11-EPOXY-CIS-EUDESMANE, A TRICYCLIC SESQUITERPENE DEFENCE SECRETION FROM THE TERMITE AMITERMES EVUNCIFER

Chemischer Informationsdienst, Aug 2, 1977

www.cheminform.wiley-vch.de Benzothiazole derivatives R 0270 Stereospecific Synthesis of Alkyl Ar... more www.cheminform.wiley-vch.de Benzothiazole derivatives R 0270 Stereospecific Synthesis of Alkyl Aryl Sulfides from Alcohols and 2-Sulfanylbenzothiazole Using Aryl Diphenylphosphinite and Azide Compounds by a New Type of Oxidation-Reduction Condensation.-Chiral secondary and tertiary alcohols (I), (IV) and (VI) are converted into the corresponding sulfides with almost complete inversion of configuration under mild conditions.-(KURODA, K.; MARUYAMA,

Research paper thumbnail of Applications of PTV Injectors for Problem Solving in the Petrochemical Industry. Thermal Desorption with GC and GC-MS

Hrc-journal of High Resolution Chromatography, Aug 1, 2000

Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injec... more Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application as a problem solving tool are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples characterised.

Research paper thumbnail of Peptides-XXXXI

Research paper thumbnail of Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armywormSpodoptera exempta(walker) following topical treatment with the compound

Pesticide Science, 1987

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment ... more No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with precocene 11. [3H]-Precocene I1 penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6 4 % of the applied dose. A maximum titre of precocene of 1.1 x I O-~ M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11-3,4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 x I O-~ at 4 h suggesting metabolism via the 3,4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6-and 7-(0)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to 185 Pesric. Sci.

Research paper thumbnail of Interspecific trail-following and evidence of similarity of trails of Trinervitermes species from different habitats

International Journal of Tropical Insect Science, Sep 1, 1982

In choice tests with well-established natural trails and glandular extract trails, allopatric pop... more In choice tests with well-established natural trails and glandular extract trails, allopatric populations of Trinervitermes hettonianus Sjost followed alien colonies' trails with the same degree of motivation as their own trails. The five Trinervitermes spp. tested readily followed each other's trail. Chromatographs of natural trail extracts showed that the main component of the T. bettonianus trail pheromone also occurs in trails of T. gratiosus (and presumably in the other species); this would account for the observed cross-following of trails among these species.

Research paper thumbnail of Mono- and sesquiterpenoid constituents of the defence secretion of the termite amitermes evuncifer

Tetrahedron Letters, 1978

Research paper thumbnail of Selective chemical ionization of nitrogen and sulfur heterocycles in petroleum fractions by ion trap mass spectrometry

Journal of the American Society for Mass Spectrometry, 1993

Research paper thumbnail of Peptides-XXXXVI

Tetrahedron, 1981

Abstract The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) f... more Abstract The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) fragments of the analogue were combined making extensive use of the DCCI/HONSu method. The final coupling involved the (1–75) and (76–129) sub-fragments. Aggregation of the latter fragment caused problems in purification by routine gel filtration methods employing Enzacryl K2 or Sephadex LH60. The fully protected (1–129) product was partially purified by washing, then deprotectcd and purified by gel filtration and ion exchange chromatography. Satisfactory removal of the acetamidomethyl group used for cysteine protection could not be achieved.

Research paper thumbnail of Analysis of airborne volatiles of cowpea

Phytochemistry, 1989

Airborne volatiles of cowpea (Mgna unguiculata) plants were analysed by drawing air over the plan... more Airborne volatiles of cowpea (Mgna unguiculata) plants were analysed by drawing air over the plants in a glass chamber, trapping the airborne volatiles on Tenax TA adsorbent, and releasing the trapped volatiles into a GC-MS by heating the Tenax trap. Eleven volatile compounds; hexanal, 1-nonene, a-pinene, /I-pinene. (Z)-3-hexen-l-01 acetate, hexyl acetate, l&cineole, limonene, (E)+ocimene, nonanal and a-cedrene, were identified.

Research paper thumbnail of The isolation and identification of the cuticular sex-stimulant pheromone of the tsetse Glossina pallidipes Austen (Diptera:Glossinidae)

International Journal of Tropical Insect Science, 1981

ABSTRACT

Research paper thumbnail of Constituents of Commiphora rostrata and some of their analogues as maize weevil, Sitophilus zeamais repellents

International Journal of Tropical Insect Science, 1992

ABSTRACT

Research paper thumbnail of Interspecific trail-following and evidence of similarity of trails of Trinervitermes species from different habitats

International Journal of Tropical Insect Science, 1982

... cated that worker castes of different age groups exhi-bit significant differences in their po... more ... cated that worker castes of different age groups exhi-bit significant differences in their potential trail-laying capacity, and that it is the ... M. (1974) An unusual caste polymorphism of the sternal gland and its trail phero-mone production in the termite Trinervitermes betto-nianus. ...

Research paper thumbnail of Applications of PTV Injectors for Problem Solving in the Petrochemical Industry. Thermal Desorption with GC and GC-MS

Journal of High Resolution Chromatography, 2000

Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injec... more Programmable Temperature Vaporising Injection (PTV) has been used extensively as a means of injecting large volumes of samples to enhance sensitivity. This paper describes the use of PTV injection in the desorption mode for the analysis of a range of solid samples, and four examples of this application as a problem solving tool are described in detail. Detection by mass spectrometry was used extensively as a means of identification of the components in the various samples characterised.

Research paper thumbnail of Mono- and sesquiterpenoid constituents of the defence secretion of the termite amitermes evuncifer

Tetrahedron Letters, 1978

Research paper thumbnail of Volatile resin exudate from stem bark of Commiphora rostrata: Potential role in plant defence

Phytochemistry, 1988

The volatile resin exuded from the stem bark of Commiphora rosfrata has been examined and 22 oxyg... more The volatile resin exuded from the stem bark of Commiphora rosfrata has been examined and 22 oxygenated alkane components identified by GC and mass spectrometry. The potential value of this material in the defence of the plant against predators and fungal pathogens is discussed.

Research paper thumbnail of Activity of the diastereoisomers of 13,23-dimethylpenta-triacontane, the sex pheromone of Glossina pallidipes, and comparison with the natural pheromone

Physiological Entomology, 1985

All three synthetic diastereoisomers of 13,23-dimethylpentatriacontane, the pheromone of Glossina... more All three synthetic diastereoisomers of 13,23-dimethylpentatriacontane, the pheromone of Glossina pallidipes (Austen), have been tested in the G.pa1lidipes sex pheromone bioassay, together with one of the four diastereoisomers of 13,17-dimethylpentatriacontane, originally proposed as a candidate pheromone of G.pallidipes. Of the three isomers of 13,23-dimethylpentatriacontane only the (13R,23S) isomer was active with an ED-50 of 4.47f1.09yg (meankSD). The (13R,17R)-13,17-dimethylpentatriacontane was inactive. The diastereoisomeric mixtures of 13,17-and 13,23-dimethylpentatriacontane were active with ED-50 values of 17.88k1.25 yg and 8.88k1.15 yg respectively. The natural pheromone was active with an ED-50 of 8.07-t 1.17 p g indicating it to be a diastereoisomeric mixture.

Research paper thumbnail of Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armyworm Spodoptera exempta (walker) following topical treatment with the compound

Pesticide Science, 1987

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment ... more No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with precocene 11. [3H]-Precocene I1 penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6 4 % of the applied dose. A maximum titre of precocene of 1.1 x I O-~ M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11-3,4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 x I O-~ at 4 h suggesting metabolism via the 3,4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6-and 7-(0)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to 185 Pesric. Sci.

Research paper thumbnail of Use of non-volatile ion-pairing agents for liquid chromatographic-mass spectrometric analyses with a moving-belt interface

Journal of Chromatography A, 1991

i i:, J Micro-membrane suppressor systems were employed to allow non-volatile ion-pairing agents ... more i i:, J Micro-membrane suppressor systems were employed to allow non-volatile ion-pairing agents to be used with combined liquid chromatography-mass spectrometry (LC-MS). This enabled the technique to be used with reversed-phase gradient chromatography for the determination of both anionic and cationic species from a range of compounds. The membrane suppressors remove the ion-pairing agent by countercurrent flow regeneration. The determination ofcationic species is demonstrated with the use of pyridinium and imidazolium iodides. Hexanesulphonic acid was used as the chromatographic ion-pairing agent and tetrabutylammonium hydroxide as the regenerant. The determination of anionic species is demonstrated with carboxylic and sulphonic acids, which were chromatographed as the tetrabutylammonium hydroxide ion pair using sulphuric acid as the regenerant. The system described has been used successfully with a moving-belt interface, enabling spectra to be acquired in both electron impact (EI) and chemical ionization (CI) modes, with a magnetic sector instrument. The system is in essence compatible with any LC-MS interface, although some modification may be required if the interface generates a significant back-pressure. e.g., thermospray.