GC-MS studies on acylated derivatives of 3-methoxy-4-methyl- and 4-methoxy-3-methyl-phenethylamines: regioisomers related to 3,4-MDMA

A series of side chain regioisomers of 3-methoxy-4-methyl- and 4-methoxy-4-methyl-phenethylamines have mass spectra essentially equivalent to the controlled drug substance 3,4-methylenedioxymethamphetamine (3,4-MDMA), all have molecular weight of 193 and major fragment ions in their electron ionization mass spectra at m/z 58 and 135/136. The acetyl, propionyl and trifluoroacetyl derivatives of the primary and secondary regioisomeric amines were prepared and evaluated in GC-MS studies. The mass spectra for these derivatives were significantly individualized and the resulting unique fragment ions allowed for specific side chain identification. The trifluoroacetyl derivatives provided more fragment ions for molecular individualization among these regioisomeric substances. These trifluoroacetyl derivatives showed excellent resolution on a non-polar stationary phase such as Rtx-1.     

GC–MS and GC–IRD studies on dimethoxyamphetamines (DMA): Regioisomers related to 2,5-DMA

The mass spectrum of the drug of abuse 2,5-dimethoxyamphetamine (2,5-DMA) is characterized by an imine fragment base peak at m/z 44 and additional fragments at m/z 151/152 for the dimethoxybenzyl cation and radical cation, respectively. Five positional ring isomers of dimethoxyamphetamines (DMA) have an isomeric relationship to 2,5-DMA. All six compounds have the same molecular weight and produce similar EI mass spectra. This lack of mass spectral specificity for the isomers in addition to the possibility of chromatographic coelution could result in misidentification. The lack of reference materials for the potential imposter molecules constitutes a significant analytical challenge. Perfluoroacylation of the amine group reduced the nitrogen basicity and provided individual fragmentation pathways for discrimination between these compounds based on some unique fragment ions and the relative abundance of common ions. GC–IRD studies provided additional structure–IR spectra relationships and yielded confirmation level identification for each of the six regioisomeric dimethoxyamphetamines. The amines and their perfluoroacylated derivatives were resolved by capillary gas chromatography and the amines showed excellent resolution on the more polar stationary phase, Rtx-200.     

GC‐MS and IR Studies on the Six Ring Regioisomeric Dimethoxyphenylpiperazines (DOMePPs)

A number of N‐substituted piperazines have been described as drugs of abuse in recent years. This new drug category includes several series of aromatic ring substituted phenylpiperazines. The wide variety of available precursors makes regioisomerism a significant issue in these totally synthetic compounds. In this study, a complete series of regioisomeric dimethoxyphenylpiperazines were synthesized and evaluated using GC‐MS and FT‐IR. The EI mass spectra show fragments characteristic of both the dimethoxyphenyl and the piperazine portions of the molecules including the dimethoxyphenylaziridinium cation (m/z 180) and dimethoxyphenyl cation (m/z 137). The ion at m/z 56 for the C₃H₆N⁺ fragment is characteristic of the piperazine ring and was observed in all the spectra. The perfluoroacyl derivatives were resolved by GC, and their mass spectra showed some differences in relative abundance of ions. FTIR provides direct confirmatory data for differentiation between the regioisomeric dimethoxyphenylpiperazines, and GC separation was accomplished on an Rtx‐200 phase.     

Synthesis of 2,3- and 3,4-methylenedioxyphenylalkylamines and their regioisomeric differentiation by mass spectral analysis using GC-MS-MS

3,4-methylenedioxyamphetamine (MDA) derivatives are increasingly abused central nervous system stimulants with neurotoxic properties. In recent years a number of controlled substance analogs (designer drugs) with high structural variety reached the illegal market making their identification an arduous task. The underivatized compounds give very similar or even virtually identical electron impact mass spectra containing mainly intense C(n)H(2n+2)N(+) immonium ions. Using tandem mass spectrometry (MS-MS) the additional structural information contained in the collision induced dissoziation (CID) mass spectra of molecular ions using electron impact (EI) and especially chemical ionization (CI) allowed an unequivocal differentiation of 18 studied regioisomeric 1-(methylenedioxyphenyl)-2-propanamines and 1-(methylenedioxyphenyl)-2-butanamines.Further synthetic methods are presented for 1-(3,4-methylenedioxyphenyl)-N-propyl-2-butanamine, N-isopropyl-1-(3,4-methylenedioxyphenyl)-2-butanamine and four 1-(2, 3-methylenedioxyphenyl)-2-butanamines. N-alkylated 1-(3, 4-methylenedioxyphenyl)-2-butanamine compounds (e.g. MBDB) are also known to be abused psychoactive agents (entactogenes) without the sympatomimetic effects of the 3,4-methylenedioxyamphetamines.     

GC-IRD studies on regioisomeric ring substituted methoxy methyl phenylacetones related to 3,4-methylenedioxyphenylacetone

The methoxy methyl phenylacetones share an isobaric relationship (equivalent mass but different elemental composition) to the controlled precursor substance 3,4-methylenedioxyphenylacetone (3,4-methylenedioxyphenyl-2-propanone; 3,4-MDP-2-P). The ten ring substituted methoxy methyl phenylacetones are resolved by capillary gas chromatography on a modified cyclodextrin stationary phase. All ten regioisomeric ketones eluted before the controlled precursor substance 3,4-methylenedioxyphenylacetone. The vapor phase infrared spectra generated from the capillary column effluent clearly differentiated 3,4-MDP-2-P from the various methoxy methyl phenylacetones. Additionally the methoxy methyl phenylacetones provide unique individual infrared spectra. Infrared absorption frequencies and patterns confirmed the relative position of the methoxy-group and the acetone side-chain for the regioisomeric ketones.     

Isomeric fluoro-methoxy-phenylalkylamines: a new series of controlled-substance analogues (designer drugs)

An impressively large number of clandestinely produced controlled-substance analogues (designer drugs) of amphetamine with high structural variety have been encountered in forensic samples in recent years. The continuous designer drug exploration and their widespread consumption results in an increasing number of reports regarding abuse and intoxication. This study presents the analytical properties of a series of new fluoro-methoxy-substituted controlled-substance analogues of amphetamine. Three ring positional isomeric fluoroamphetamines, two isomeric fluoromethoxyamphetamines, two N-alkyl 4-fluoroamphetamines, and one 4-fluorophenylbutan-2-amine were identified and differentiated by gas chromatography-mass spectrometry (GC-MS), 1H- and 13C-nuclear magnetic resonance (NMR), and gas chromatography-infrared spectroscopy (GC-IR). The regioisomeric 2-, 3-, and 4-fluoroamphetamines and the regioisomeric fluoro-methoxyamphetamines show virtually identical mass spectra so that this method is insufficient to discriminate between these closely related compounds. The mass spectra of the acetylated compounds allowed a differentiation of the 4-fluoroamphetamine from its regioisomeric 2- and 3-fluoroamphetamines. The gas chromatographic properties of the three regioisomeric fluoroamphetamines and their acetylated and trifluoroacetylated derivatives are also so similar that a complete separation of these compounds could not be achieved under GC-MS conditions. The two isomeric compounds 5-fluoro-2-methoxyamphetamine and 3-fluoro-4-methoxyamphetamine on the other hand showed significant different gas chromatographic retention times so that a separation was uncomplicated. The trifluoroacetylation of these compounds proved to be an effective method for their mass spectral differentiation. Gas chromatography-infrared spectroscopy and 1H- and 13C-nuclear magnetic resonance allowed an unequivocal differentiation of all studied regioisomeric fluoroamphetamines and fluoro-methoxyamphetamines.     

Differentiation of methylenedioxybenzylpiperazines (MDBPs) and methoxymethylbenzylpiperazines (MMBPs) By GC-IRD and GC-MS

The substituted benzylpiperazines, 3,4-methylenedioxybenzylpiperazine (3,4-MDBP), its regioisomer 2,3-methylenedioxybenzylpiperazine (2,3-MDBP) and four isobaric ring substituted methoxymethylbenzylpiperazines (MMBP) have almost identical mass spectra. Perfluoroacylation of the secondary amine nitrogen of these isomeric piperazines gave mass spectra with differences in relative abundance of some fragment ions. However, the spectra did not yield any unique fragments for specific identification of one isomer to the exclusion of the other compounds. Gas chromatography coupled with infrared detection (GC-IRD) provides direct confirmatory data for the structural differentiation between the six isomers. The mass spectra in combination with the vapor phase infrared spectra provide for specific confirmation of each of the isomeric piperazines. The underivatized and perfluoroacyl derivative forms of the ring substituted benzylpiperazines were resolved on the polar stationary phase Rtx-200.     

Differentiation of regioisomeric ring-substituted fluorophenethylamines with product ion spectrometry

The electron ionization (EI) of aromatic ring-substituted isomers gives virtual identical mass spectra which seriously affects their analysis. Especially regioisomeric meta- and para-ring-substituted compounds cannot show any ortho-effect reactions making their differentiation by mass spectrometry impossible. Furthermore o-, m- and p-substituted compounds can only be separated insufficiently by chromatography due to their very similar retention that do not allow univocal identification. Product ion mass spectrometry has proved to be a useful tool to differentiate structurally closely related fluorophenethylamines even in the case of the meta- and para-isomers. A series of N-alkylated o-, m- and p-fluoroamphetamines and 1-(4-fluorophenyl)butan-2-amines have been synthesized in microscale and studied by product ion spectrometry. The combination of chemical ionization (CI) and product ion spectrometry of hydrogen fluoride loss ions [M+H?HF]⁺ allows a univocal differentiation of all studied fluoro-substituted phenethylamines without prior derivatization. This method with submicrogram detection limits provides great advantages for the differentiation between aromatic regioisomeric fluorophenethylamine designer drugs where other methods such as nuclear magnetic resonance (NMR) spectrometry lack sufficient sensitivity or might fail because complex mixtures have to be analyzed.     

GC-MS and GC-IRD analysis of 2-, 3- and 4-methylmethamphetamine and 2-, 3- and 4-methylamphetamine

4-Methylmethamphetamine has been detected in samples submitted for analysis in several states throughout Australia. Six ring substituted methyl isomers of methamphetamine and amphetamine were synthesised and analysed. As the regioisomeric 2-, 3- and 4-methylmethamphetamine and 2-, 3- and 4-methylamphetamine have virtually identical mass spectra, the use of MS is an ineffective technique to discriminate between these closely related compounds. We set out to determine whether the regioisomers could be differentiated by a combination of GC-MS, acetyl derivatisation and GC-IRD. We demonstrate that the three isomers of methylmethamphetamine and methylamphetamine can be separated by GC, and a combination of acetyl derivatisation and vapour phase IR can identify the specific ring substituted compound.     

Formation of Trifluoroacetylated Ephedrine During the Analysis of a Pseudoephedrine-Formaldehyde Adduct by TFAA Derivatization Followed by GC-MS

Abstract:  (+)-Pseudoephedrine reacts with formaldehyde to form (4 S ,5 S )-3,4-dimethyl-5-phenyloxazolidine. Gas chromatography–mass spectrometry (GC-MS) analysis after the reaction of this oxazolidine with excess trifluoroacetic acid anhydride (TFAA) shows predominantly N , O- bis(trifluoroacetyl)pseudoephedrine with some of the monotrifluoroacetylated derivative. In addition, variable amounts of N , O- bis(trifluoroacetyl)ephedrine were detected by GC-MS. N , O- bis(trifluoroacetyl)ephedrine was not detected upon trifluoroacetylation of the source (+)-pseudoephedrine, and nuclear magnetic resonance analysis of the (4 S ,5 S )-3,4-dimethyl-5-phenyloxazolidine showed no evidence of the (4 R ,5 S ) isomer. This suggests that the N ,O-bis(trifluoroacetyl)ephedrine is formed by epimerization during the TFAA derivatization and GC-MS analysis of the pseudoephedrine-formaldehyde adduct.     

Identifying reliable ions for the statistical differentiation of structurally similar fentanyl analogs

Definitive identification of fentanyl analogs based on mass spectral comparison is challenging given the high degree of structural and, hence, spectral similarity. To address this, a statistical method was previously developed in which two electron-ionization (EI) mass spectra are compared using the unequal variance t-test. Normalized intensities of corresponding ions are compared, testing the null hypothesis (H₀) that the difference in intensity is equal to zero. If H₀ is accepted at all m/z values, the two spectra are statistically equivalent at the specified confidence level. If H₀ is not accepted at any m/z value, then there is a significant difference in intensity at that m/z value between the two spectra. In this work, the statistical comparison method is applied to distinguish EI spectra of valeryl fentanyl, isovaleryl fentanyl, and pivaloyl fentanyl. Spectra of the three analogs were collected over a 9-month period and at different concentrations. At the 99.9% confidence level, the spectra of corresponding isomers were statistically associated. Spectra of different isomers were statistically distinct, and ions responsible for discrimination were identified in each comparison. To account for inherent instrument variations, discriminating ions for each pairwise comparison were ranked based on the magnitude of the calculated t-statistic (t_calc) value. For a given comparison, ions with higher t_calc values are those with the greatest difference in intensity between the two spectra and, therefore, are considered more reliable for discrimination. Using these methods, objective discrimination among the spectra was achieved and ions considered most reliable for discrimination of these isomers were identified.     

Identification of 3,4-methylenedioxyamphetamine analogs encountered in clandestine tablets

Recently, 3,4-methylenedioxyamphetamine derivatives have been encountered in the Italian illicit market, mainly in form of tablets. Among this class of substances small modifications of the molecule may result in a wide range of derivatives and analogs some of which are not yet listed as controlled substances in the Italian schedules. Due to the structural similarity some of these molecules have a gas chromatographic behavior and mass spectra that only slightly differ. In the present work, an analytical strategy is proposed to achieve the identification of analogs within this class of molecules. In seized material sent by the Court of Law of Rome to our laboratories a number of tablets engraved with different symbols (e.g., `Dollar', `Fido Dido' and `Bomb') were submitted to analysis in order to establish whether they contained drugs of abuse. The analytical techniques employed for this purpose were UV spectrophotometry and thin-layer chromatography which provided information suggesting that the tablets contained a methylenedioxyamphetamine. Gas chromatography with flame ionization detection indicated that the main ingredient differed from the molecules of the same class already known. Finally, capillary gas chromatographic–mass spectrometric analysis of the native molecules and their pentafluoropropionic acid derivatives, performed with both, electron impact and chemical ionization, allowed the identification, in each tablet, of three molecules: the N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MDP-2-MB, MBDB), the 1-(3,4-methylenedioxyphenyl)-2-butanamine (MDP-2-B) and the N,N-dimethyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MDP-2-MMB).     

GC–MS analysis of eight aminoindanes using three derivatization reagents

Aminoindanes are a class of novel psychoactive substances (NPSs) that have become more prevalent over the past decade. GC–MS is often utilized for identifying seized drugs and is well regarded for its ability to separate mixtures. However, certain aminoindanes have similar mass spectral data and require specific gas chromatographic stationary phases for separation. Derivatization is an alternative method that can be applied to GC–MS to enhance chromatographic results, providing more selective analysis in seized-drug identification. This study investigates derivatization techniques to provide options for forensic science laboratories in accurately identifying aminoindanes. Three derivatization reagents, N-methyl-bis(trifluoroacetamide) (MBTFA), heptafluorobutyric anhydride (HFBA), and ethyl chloroformate (ECF) were evaluated for the analysis of eight aminoindanes by GC–MS using two common gas chromatographic stationary phases, Rxi®-5Sil MS and Rxi®-1Sil MS. All three derivatization methods successfully isolated eight aminoindanes, including the isomers 4,5-methylenedioxy-2-aminoindane (4,5-MDAI), and 5,6-methylenedioxy-2-aminoindane (5,6-MDAI) that could not be differentiated prior to derivatization. Reduced peak tailing and increased abundance were observed after derivatization for all the compounds, and mass spectra of the derivatives contained individualizing fragment ions that allowed for further characterization of the aminoindanes. This excluded 4,5-MDAI and 5,6-MDAI as they shared the same characteristic ions and were only distinguishable by their retention times. All three derivatization techniques used in this study allow for successful characterization of the aminoindanes and give forensic science laboratories flexibility in their analysis approach when they encounter these compounds.     

Determination of synthesis route of 1-(3,4-methylenedioxyphenyl)-2-propanone (MDP-2-P) based on impurity profiles of MDMA

In our study 1-(3,4-methylenedioxyphenyl)-2-propanone (MDP-2-P or PMK) was prepared by two different routes, i.e. by oxidizing isosafrole in an acid medium and by 1-(3,4-methylenedioxyphenyl)-2-nitropropene reduction. The final product-MDP-2-P was subjected to GC/MS analysis. The intermediates and reaction by-products were identified and the 'route specific' impurities were established. The following impurities are the markers of the greatest importance: 1-(3,4-methylenedioxyphenyl)-1-propanone (compound 10, Table 2), 1-methoxy-1-(3,4-methylenedioxyphenyl)-2-propanone (compound 11, Table 2) and 2,2,4-trimethyl-5-(3,4-methylenedioxyphenyl)-[1,3]dioxolane (compound 13, Table 2) (the 'oxidising isosafrole route') and N-cyclohexylacetamide (compound 3, Table 1), 3-methyl-6,7-methylenedioxyisoquinoline-1,4-dione (compound 15, Table 1) (the 'MDP-2-nitropropene reduction route'). Subsequently, MDMA was prepared by reductive amination of MDP-2-P using NaBH4 as reducing agent (so-called 'cool method'). Impurities were extracted with n-heptane under alkaline conditions. The impurity profiles were obtained by means of GC/MS, some reaction by-products were identified by means of the EI mass spectra including low energy EI mass spectra and 'route specific' impurities were established. 4-Methyl-5-(3,4-methylenedioxyphenyl)-[1,3]dioxolan-2-one (compound 22, Table 2), N-methyl-2-methoxy-1-methyl-2-(3,4-methylenedioxyphenyl)-ethaneamine (compound 18, Table 2), 3-methyl-6,7-methylenedioxyisoquinoline-1,4-dione (compound 15, Table 1) and N-cyclohexyloacetamide (compound 3, Table 1) were found to be the synthesis markers of greatest importance.     

Anion Identification via Complexation with meso‐octamethylcalix(4)pyrrole and Detection Using Electrospray Ionization Mass Spectrometry*

Abstract: The routine identification of controlled substances and adulterants during forensic chemistry analysis often involves the identification of counter ions or salt forms present in an exhibit. Here, the use of the compound meso‐octamethylcalix(4)pyrrole (C4P) during salt‐form identification analysis is presented. C4P is a commercially‐available, anion‐binding agent that can be reacted with a controlled substance or adulterant, resulting in the sequestration of anionic species, usually present as counter ions to the active ingredient. Formation of noncovalent complexes between the cyclic host C4P compound and anionic guests is investigated using electrospray ionization–mass spectrometry (ESI–MS). Complexes with chloride, bromide, iodide, nitrate, and acetate are readily observed and mass spectrometry analysis provides identification via molecular weight characterization. Chloride and bromide complexes are also characterized by the isotopic distribution of their molecular ions. Formation of host–guest complexes is not observed for sulfate and phosphate salts, presumably due to steric hindrance and energetically unfavorable conditions.     

The analytical profile of some 4-methylthioamphetamine (4-MTA) homologues

The 4-methylthioamphetamine (4-MTA) is a sulphur-containing amphetamine-type stimulant (ATS), which appeared on the illicit market in Europe at the end of 90s. For the purpose of this study, several N-alkyl homologues of 4-MTA, including 4-methylthiomethamphetamine (4-MTMA), 4-methylthioethylamphetamine (4-MTEA), 4-methylthiodimethamphetamine (4-MTDMA), 4-methylthiopropylamphetamine (4-MTPA) and 4-methylthiobutylamphetamine (4-MTBA) were synthesized. The homologues were characterized by means of gas chromatography/mass spectrometry (GC–MS), infrared (IR) spectroscopy and the magnetic resonance spectroscopy (¹H and ¹³C NMR). The gas chromatography and mass spectrometry properties of their acetyl, trifluoroacyl (TFA), pentafluoropropionyl (PFP) and heptafluorobutyryl (HFB) derivatives were also investigated and discussed.     

Mass spectrometric data characteristics of commonly abused amphetamines with sequential derivatization at two active sites

There have been reports on improved chromatographic parameters derived from the incorporation of sequential derivatization in preparing biological specimens for the analysis of opiates. This current study was designed to characterize the mass spectrometric data resulting from sequential derivatizations of commonly abused amphetamines (along with all commercially available deuterated analogs) containing two active sites, i.e., amphetamine, methylenedioxyamphetamine, phenylpropanolamine. The first derivatization groups included in this study were trifluoroacetyl, pentafluoropropionyl, and heptafluorobutyryl, while t-butyldimethylsilyl was used as the second derivatization group. Products resulting from the first step and the two-step derivatization processes were analyzed by GC-MS. Full-scan mass spectrometric data were used to select ions with potential for designating the analytes and their respective isotopically labeled analogs in quantitative analysis protocols. Selected ion monitoring data were then collected and assessed to determine the quality of these ions when one or two different derivatization groups were incorporated in the sample preparation processes. A total of 77 full-scan mass spectra and 8 ion intensity cross-contribution tables, representing various forms of derivatization and isotopic analogs of the three amphetamines, are systematically presented for reference. Evaluations of these data concluded that many, but not all, products derived from "double derivatization" (sequential derivatization with two derivatization groups), generate ions of higher quality than those derived from "single derivatization".     

Discriminating Hodgdon Pyrodex® and Triple Seven® Using Gas Chromatography–Mass Spectrometry

Abstract: Pyrodex ^® and Triple Seven ^® are black powder substitutes that often find use as fillers in improvised explosive devices, such as pipe bombs. These propellants have essentially the same overall appearance and oxidizers, but different fuels. For example, Pyrodex ^® contains sulfur, sodium benzoate, and dicyandiamide (DCDA), whereas Triple Seven ^® lacks sulfur but also contains 3‐nitrobenzoic acid. In this method, intact particles and postblast solid residues were reacted with bis(trimethylsilyl)trifluoroacetamide + 1% trimethylchlorosilane in acetonitrile for 30 min at 60°C. The resultant trimethylsilyl derivatives of the organic fuels were then analyzed by gas chromatography–mass spectrometry. Each derivative was clearly resolved from other components, and high‐quality mass spectra were obtained. In addition, characteristic fragments resulting from loss of a methyl radical from the molecular ion (m/z 163 for sulfur, m/z 171 for DCDA, m/z 179 for benzoic acid, and m/z 224 for nitrobenzoic acid) were able to be monitored.     

Differentiation of side chain isomers of ring-substituted amphetamines using gas chromatography/infrared/mass spectrometry (GC/IR/MS).

Common analytical methods used for identifying samples obtained from clandestine laboratories were evaluated for their ability to differentiate between possible amphetamine isomers and homologs. A series of ring-substituted (4-methyl, 4-methoxy, and 3,4-methylenedioxy) amphetamine and N-methylphenethylamine isomers was analyzed using color tests, thin-layer chromatography, gas chromatography/mass spectrometry (GC/MS) and GC/infrared (GC/IR). The N-acetyl derivatives of the isomers were analyzed using GC/IR/MS. GC/IR/MS readily differentiated the 4-methylphenylalkylamine isomers. MS and IR spectra were also obtained for each pair of the 4-methoxyphenylalkylamine isomers and the 3,4-methylenedioxyphenylalkylamine isomers, but differentiation via GC/IR/MS was difficult. The N-acetyl derivatives of each pair of isomers could be readily differentiated using GC/IR/MS. Good library researchable spectra for N-acetylamphetamine could be obtained for IR identification with 10 ng (on-column) and MS identification with 2 ng. The spectrometrically independent IR and MS data obtained for the N-acetyl derivatives indicated that the combination of GC/IR/MS can add a significant level of confidence in the analysis of ring-substituted arylalkylamines.     

Positive- and negative-ion mass spectrometry and rapid clean-up of 19 phenothiazines

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra of 19 phenothiazines are presented. In the PIEI mode, peaks due to M, M minus side chain (M - R1), M - R1 + H, and side chain itself (R1) appeared for most compounds. The M - R1 and R1 ions were very useful for drug screening. In the PICI mode, most spectra showed base or intense peaks due to M + H, and small peaks due to M + C2H5; peaks due to M - R1 + 2H and R1 also appeared in many compounds. In the NICI mode, fragmentation modes were different in different compound groups; molecular or [M - H]- quasi-molecular anions appeared in many compounds with aliphatic side chains. Anions at m/z 98 and 115 were characteristic for compounds with (N-methylpiperazinyl)propyl side chains. Selected ion monitoring in the PIEI mode generally gave much higher sensitivity than in the PICI and NICI modes. Phenothiazines present in urine or plasma could be rapidly isolated by use of Sep-Pak C18 cartridges. Thirteen of 19 phenothiazines could be detected by HP-17 wide-bore capillary gas chromatography with satisfactory separation from impurities in their underivatized forms.