A Molecularly Imprinted Polymer-based Dye Displacement Assay for the Rapid Visual Detection of Amphetamine in Urine.

The rapid sensing of drug compounds has traditionally relied on antibodies, enzymes and electrochemical reactions. These technologies can frequently produce false positives/negatives and require specific conditions to operate. Akin to antibodies, molecularly imprinted polymers (MIPs) are a more robust synthetic alternative with the ability to bind a target molecule with an affinity comparable to that of its natural counterparts. With this in mind, the research presented in this article introduces a facile MIP-based dye displacement assay for the detection of (±) amphetamine in urine. The selective nature of MIPs coupled with a displaceable dye enables the resulting low-cost assay to rapidly produce a clear visual confirmation of a target's presence, offering huge commercial potential. The following manuscript characterizes the proposed assay, drawing attention to various facets of the sensor design and optimization. To this end, synthesis of a MIP tailored towards amphetamine is described, scrutinizing the composition and selectivity (ibuprofen, naproxen, 2-methoxphenidine, quetiapine) of the reported synthetic receptor. Dye selection for the development of the displacement assay follows, proceeded by optimization of the displacement process by investigating the time taken and the amount of MIP powder required for optimum displacement. An optimized dose-response curve is then presented, introducing (±) amphetamine hydrochloride (0.01-1 mg mL-1) to the engineered sensor and determining the limit of detection (LoD). The research culminates in the assay being used for the analysis of spiked urine samples (amphetamine, ibuprofen, naproxen, 2-methoxphenidine, quetiapine, bupropion, pheniramine, bromopheniramine) and evaluating its potential as a low-cost, rapid and selective method of analysis.

Chiral Plasma Pharmacokinetics and Urinary Excretion of Bupropion and Metabolites in Healthy Volunteers.

Bupropion, widely used as an antidepressant and smoking cessation aid, undergoes complex metabolism to yield numerous metabolites with unique disposition, effect, and drug-drug interactions (DDIs) in humans. The stereoselective plasma and urinary pharmacokinetics of bupropion and its metabolites were evaluated to understand their potential contributions to bupropion effects. Healthy human volunteers (n = 15) were administered a single oral dose of racemic bupropion (100 mg), which was followed by collection of plasma and urine samples and determination of bupropion and metabolite concentrations using novel liquid chromatography-tandem mass spectrometry assays. Time-dependent, elimination rate-limited, stereoselective pharmacokinetics were observed for all bupropion metabolites. Area under the plasma concentration-time curve from zero to infinity ratios were on average approximately 65, 6, 6, and 4 and Cmax ratios were approximately 35, 6, 3, and 0.5 for (2R,3R)-/(2S,3S)-hydroxybupropion, R-/S-bupropion, (1S,2R)-/(1R,2S)-erythrohydrobupropion, and (1R,2R)-/(1S,2S)-threohydrobupropion, respectively. The R-/S-bupropion and (1R,2R)-/(1S,2S)-threohydrobupropion ratios are likely indicative of higher presystemic metabolism of S- versus R-bupropion by carbonyl reductases. Interestingly, the apparent renal clearance of (2S,3S)-hydroxybupropion was almost 10-fold higher than that of (2R,3R)-hydroxybupropion. The prediction of steady-state pharmacokinetics demonstrated differential stereospecific accumulation [partial area under the plasma concentration-time curve after the final simulated bupropion dose (300-312 hours) from 185 to 37,447 nM⋅h] and elimination [terminal half-life of approximately 7-46 hours] of bupropion metabolites, which may explain observed stereoselective differences in bupropion effect and DDI risk with CYP2D6 at steady state. Further elucidation of bupropion and metabolite disposition suggests that bupropion is not a reliable in vivo marker of CYP2B6 activity. In summary, to our knowledge, this is the first comprehensive report to provide novel insight into mechanisms underlying bupropion disposition by detailing the stereoselective pharmacokinetics of individual bupropion metabolites, which will enhance clinical understanding of bupropion's effects and DDIs with CYP2D6.

Metabolism and disposition of bupropion in pregnant baboons (Papio cynocephalus).

Recent in vitro data obtained in our laboratory revealed similarities between baboons and humans in the biotransformation of bupropion (BUP) by both hepatic and placental microsomes. These data supported the use of baboons to study BUP biotransformation during pregnancy. The aim of this investigation was to determine the pharmacokinetics of BUP in baboons during pregnancy and postpartum, as well as fetal exposure to the drug after intravenous administration. Pregnant baboons (n = 5) received a single intravenous bolus dose of bupropion hydrochloride (1 mg/kg) at gestational ages 94-108 days (midpregnancy), 142-156 days (late pregnancy), and 6 weeks postpartum. Blood and urine samples were collected for 12 and 24 hours, respectively. The concentrations of BUP, hydroxybupropion (OH-BUP), threohydrobupropion, and erythrohydrobupropion in plasma were determined by liquid chromatography-tandem mass spectrometry. Relative to the postpartum period, the average midpregnancy clearance of BUP trended higher (3.6 ± 0.15 versus 2.7 ± 0.28 l/h per kg) and the average C(max) (294 ± 91 versus 361 ± 64 ng/ml) and the area under the curve (AUC) of BUP values (288 ± 22 versus 382 ± 42 h·ng/ml) trended lower. AUC(OH-BUP) also tended to be lower midpregnancy compared with postpartum (194 ± 76 versus 353 ± 165 h·ng/ml). Whereas the observed trend toward increased clearance of BUP during baboon pregnancy could be associated with a pregnancy-induced increase in its biotransformation, the trend toward increased renal elimination of OH-BUP may overshadow any corresponding change in the hydroxylation activity of CYP2B.

Influence of CYP2B6 genetic variants on plasma and urine concentrations of bupropion and metabolites at steady state.

BACKGROUND: Bupropion, an antidepressant and smoking cessation medication, is metabolized to hydroxybupropion (HB), an active metabolite, primarily by CYP2B6. OBJECTIVES: To compare plasma concentrations of bupropion and metabolites at steady state in healthy volunteers with and without CYP2B6 genetic variants. METHODS: In a genotype-guided study of 42 healthy individuals, we measured the plasma and urine concentrations of bupropion and its metabolites, HB, threohydrobupropion, and erythrohydrobupropion after 7 days of sustained-release bupropion dosing. RESULTS: CYP2B6*6 and *18 gene variants were associated with ~33% reduced concentrations of HB, with no effects on concentrations of bupropion or other metabolites. We could account for 50% of the variation in HB concentrations in a model including genotype and sex. CONCLUSION: As HB is active and its steady-state concentrations are more than 10 times higher than bupropion, CYP2B6 variants are likely to affect pharmacological activity. Because of the large individual variation within the genotype group, the use of therapeutic drug monitoring for dose optimization may be necessary.

Crossreactivity of bupropion metabolite with enzyme-linked immunosorbent assays designed to detect amphetamine in urine.

BACKGROUND: Drug screening is rapid, inexpensive, and is often used in clinical, forensic, and workplace drug testing to gain informative results. This article seeks to determine if bupropion and/or its metabolites is resulting in false-positive amphetamine screening results in our case samples using commercially available enzyme-linked immunosorbent assay tests. METHOD: Fortified urine and forensic case samples were used to determine crossreactivity of bupropion and its main metabolite to four different amphetamine and methamphetamine enzyme-linked immunosorbent assay kits. RESULTS: Two of the enzyme-linked immunosorbent assay kits used to screen for amphetamine may result in false-positive results if bupropion metabolites are present in concentrations greater than 500 ng/mL. Three case samples gave a positive screen results for amphetamine using Amphetamine ULTRA kits, yet no amphetamines were confirmed by gas chromatography-mass spectrometry and all samples were positive for bupropion and metabolites. CONCLUSIONS: Laboratory directors and clinicians should be aware of the characteristic of their chosen laboratory assay and should communicate this to physicians so that results can be interpreted accurately.

Sensitized phosphorescence as detection method for the enantioseparation of bupropion by capillary electrophoresis.

A new CE detection method was developed for the chiral drug bupropion (a second-generation antidepressant), based on phosphorescence both in the direct and in the sensitized mode using pulsed laser excitation at 266 nm. Electrokinetic chromatography using 5 mM sulfated-α-CD as chiral selector in 25 mM phosphate buffer at pH 3 allowed the separation of bupropion enantiomers with a high chiral resolution (Rs>3). In the sensitized phosphorescence detection mode, excitation energy is transferred from the analyte to an acceptor (1-bromo-4-napthhalenesulfonic acid or biacetyl) followed by time-resolved phosphorescence detection under deoxygenated buffer conditions. Using 2 × 10(-4) M biacetyl as the acceptor an LOD of 2 × 10(-7) M was obtained for each enantiomer, about 40 times better than in the direct mode. Under these separation conditions, no significantly different phosphorescence lifetimes (measured on-line) were obtained for the two bupropion enantiomers. The suitability of the method was demonstrated with the quantification of bupropion in a pharmaceutical formulation and its determination in a spiked urine sample.

Stereoselective Steady-State Disposition and Bioequivalence of Brand and Generic Bupropion in Adults.

The antidepressant bupropion is stereoselectively metabolized and metabolite enantiomers have differential pharmacologic effects, but steady-state enantiomeric disposition is unknown. Controversy persists about bupropion XL 300 mg generic equivalence to brand product, and whether generics might have different stereoselective disposition leading to enantiomeric non-bioequivalence and, thus, clinical nonequivalence. This preplanned follow-on analysis of a prospective, randomized, double-blinded, crossover study of brand and 3 generic bupropion XL 300 mg products measured steady-state enantiomeric plasma and urine parent bupropion and primary and secondary metabolite concentrations and evaluated bioequivalence and pharmacokinetics. Steady-state plasma and urine bupropion disposition was markedly stereoselective, with up to 40-fold differences in plasma concentrations of the active metabolite S,S-hydroxybupropion vs. R,R,-hydroxybupropion. Urine metabolite glucuronides were prominent, but glucuronidation was metabolite-specific and enantioselective. There were no differences between any generic and brand, or between generics, in plasma enantiomer concentrations of bupropion or the major metabolites. All generic products satisfied formal bioequivalence criteria (peak plasma concentration (Cmax ) and area under the plasma concentration-time curve over 24 hours (AUC0-24 )) using enantiomers for bupropion as well as for metabolites, and generics were comparable to each other, and were considered bioequivalent, based on enantiomeric analysis. Enantiomeric bioequivalence explains the previously observed therapeutic equivalence of bupropion generics and brand in treating major depression. These results have important implications for understanding the clinical therapeutic effects of bupropion based on complex and stereoselective metabolism.

Rapid clinical induction of hepatic cytochrome P4502B6 activity by ritonavir.

Ritonavir is the most potent and efficacious inhibitor of cytochrome P4503A (CYP3A), and it is used accordingly for the pharmacoenhancement of other antiretrovirals. Paradoxically, ritonavir induces the clinical metabolism and clearance of many drugs. The mechanism by which ritonavir inhibits and induces clinical drug metabolism is unknown. Ritonavir induces CYP2B6 in human hepatocytes. This investigation tested the hypothesis that ritonavir induces human CYP2B6 in vivo. Thirteen healthy human immunodeficiency virus-negative volunteers underwent a three-way sequential crossover protocol, receiving racemic bupropion after nothing (control), 3 days of treatment with ritonavir, and 2.5 weeks of treatment with ritonavir (400 mg twice a day). Stereoselective bupropion hydroxylation was used as an in vivo probe for CYP2B6 activity. Plasma and urine (R)- and (S)-bupropion and (R,R)- and (S,S)-hydroxybupropion concentrations were measured by liquid chromatography-mass spectrometry. Racemic, (R)-, and (S)-bupropion plasma ratios of the area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)) (ritonavir/control) were significantly reduced to 0.84, 0.86, and 0.80, respectively, after 3 days of ritonavir treatment and to 0.67, 0.69, and 0.60 after steady-state ritonavir treatment. Apparent oral clearances for racemic, (R)-, and (S)-bupropion all were significantly increased by 1.2-fold after 3 days of ritonavir treatment and by 1.4-, 1.7-, and 1.5-fold after steady-state ritonavir treatment. The plasma (S,S)-hydroxybupropion/(S)-bupropion AUC(0-72) ratio was significantly increased by ritonavir. Formation clearances of both (R,R)- and (S,S)-hydroxybupropion were increased 1.8-fold after 3 days of ritonavir treatment and 2.1-fold after steady-state ritonavir treatment. These results show that ritonavir induces human CYP2B6 activity. Induction is rapid, occurring after only 3 days of ritonavir, and is sustained for at least 2 weeks. The ritonavir induction of CYP2B6 activity may have significant implications for drug interactions and clarify previously unexplained interactions.

Stereoselective analysis of bupropion and hydroxybupropion in human plasma and urine by LC/MS/MS.

A sensitive, stereoselective assay using solid phase extraction and LC-MS-MS was developed and validated for the analysis of (R)- and (S)-bupropion and its major metabolite (R,R)- and (S,S)-hydroxybupropion in human plasma and urine. Plasma or glucuronidase-hydrolyzed urine was acidified, then extracted using a Waters Oasis MCX solid phase 96-well plate. HPLC separation used an alpha(1)-acid glycoprotein column, a gradient mobile phase of methanol and aqueous ammonium formate, and analytes were detected by electrospray ionization and multiple reaction monitoring with an API 4000 Qtrap. The assay was linear in plasma from 0.5 to 200 ng/ml and 2.5 to 1000 ng/ml in each bupropion and hydroxybupropion enantiomer, respectively. The assay was linear in urine from 5 to 2000 ng/ml and 25 to 10,000 ng/ml in each bupropion and hydroxybupropion enantiomer, respectively. Intra- and inter-day accuracy was >98% and intra- and inter-day coefficients of variations were less than 10% for all analytes and concentrations. The assay was applied to a subject dosed with racemic bupropion. The predominant enantiomers in both urine and plasma were (R)-bupropion and (R,R)-hydroxybupropion. This is the first LC-MS/MS assay to analyze the enantiomers of both bupropion and hydroxybupropion in plasma and urine.

Cardiogenic shock and status epilepticus after massive bupropion overdose.

BACKGROUND: To describe a profound cardiac dysfunction and a status epilepticus after a massive bupropion overdose. CASE REPORT: A 35-year-old man was admitted in coma following the deliberate ingestion of 12 g of bupropion. The course was marked by the rapid onset of severe and prolonged status epilepticus and cardiogenic shock. Plasma bupropion level determined four hours after the estimated time of ingestion was 1.4 mg/L. All clinical features resolved completely in response to symptomatic treatment. CONCLUSION: Several cases of bupropion overdose, with sinus tachycardia and seizures rapidly corrected by symptomatic treatment, have been reported in the literature. To our knowledge, this case of overdose with bupropion alone, at very high doses, is the first to describe clinical features comprising severe and prolonged status epilepticus and direct cardiotoxicity with the development of cardiogenic shock documented by echocardiogram.

Development, validation and application of a comprehensive stereoselective LC/MS-MS assay for bupropion and oxidative, reductive, and glucuronide metabolites in human urine.

A stereoselective assay was developed for the quantification of bupropion and oxidative, reductive, and glucuronide metabolites (16 analytes total) in human urine. Initially, authentic glucuronide standards obtained from commercial sources were found to be incorrectly labeled with regard to stereochemistry; the correct stereochemistry was unequivocally reassigned. A trifurcated urine sample preparation and analysis procedure was employed for the stereoselective analysis of bupropion, hydroxybupropion, erythrohydrobupropion, and threohydrobupropion enantiomers, and hydroxybupropion, erythrohydrobupropion and threohydrobupropion ß-d-glucuronide diastereomers in urine. Method 1 stereoselectively analyzed bupropion (R and S), and unconjugated free hydroxybupropion (R,R and S,S), erythrohydrobupropion (1R,2S and 1S,2R), and threohydrobupropion (1R,2R and 1S,2S) using chiral chromatography with an α1-acid glycoprotein column. Because no hydroxybupropion ß-d-glucuronide standards were commercially available, method 2 stereoselectively analyzed total hydroxybupropion aglycones (R,R and S,S-hydroxybupropion) after urine hydrolysis by ß-glucuronidase. Hydroxybupropion ß-d-glucuronide (R,R and S,S) urine concentrations were calculated as the difference between total and free hydroxybupropion (R,R and S,S) concentrations. Due to incomplete ß-glucuronidase hydrolysis of erythrohydrobupropion and threohydrobupropion ß-d-glucuronide diastereomers, method 3 stereoselectively analyzed intact erythrohydrobupropion and threohydrobupropion ß-d-glucuronide diastereomers using C18 column chromatography. All analytes were quantified by positive ion electrospray tandem mass spectrometry. The assay was fully validated over analyte-specific concentrations. Intra- and inter assay precision were within 15% for each analyte. The limits of quantification for bupropion (R and S), hydroxybupropion (R,R and S,S), threohydrobupropion (1S,2S and 1R,2R), erythrohydrobupropion (1R,2S and 1S,2R) were 10, 50, 100, and 100ng/mL, respectively. The limits of quantification for (1R,2R)-threohydrobupropion ß-d-glucuronide, (1S,2S)-threohydrobupropion ß-d-glucuronide, and (1R,2R)-erythrohydrobupropion ß-d-glucuronide were each 50ng/mL. Due to the abundance of bupropion and metabolites in human urine, no efforts were made to optimize sensitivity. All analytes were stable following freeze thaw cycles at -80°C. This assay was applicable to clinical pharmacokinetic investigations of bupropion in patients and to in vitro metabolism of the primary bupropion metabolites to their glucuronides.

Intraventricular conduction delay after bupropion overdose.

Bupropion overdose mainly is characterized by tachycardia, agitation, and seizures. The few reports of QRS complex widening after bupropion overdose that have been published in peer-reviewed literature are notable for failure to have confirmed elevated plasma bupropion concentrations or failure to have excluded other causes of QRS widening. We describe two patients in whom bupropion overdose was confirmed with elevated plasma bupropion concentrations and in whom other cardiotoxic ingestions were excluded with comprehensive analytical toxicology testing. Our findings are in keeping with ex vivo studies in which bupropion antagonizes cardiac voltage-gated sodium channels. Bupropion overdose should be considered in the differential diagnosis of unexpected QRS widening.

Bupropion in breast milk: an exposure assessment for potential treatment to prevent post-partum tobacco use.

OBJECTIVES: To assess potential infant exposure to bupropion and its active metabolites in breast milk such as would occur during treatment to prevent post-partum relapse to tobacco use, and to compare the concentrations of bupropion in urine and saliva with plasma and breast milk. DESIGN AND SETTING: Cohort study, outpatient clinical research centre. SUBJECTS: Ten healthy post-partum volunteers who agreed to take bupropion for seven days, pump and discard their breast milk, and have samples of breast milk, plasma, saliva, and urine analysed. INTERVENTION: Bupropion 150 mg a day for three days and then 300 mg a day for four days. MAIN OUTCOME MEASURES: Concentrations of bupropion and its active metabolites (hydroxybupropion, erythrohydrobupropion, threohydrobupropion) in breast milk, plasma, saliva, and urine. Determination of average infant exposure. RESULTS: The calculated average dosage of bupropion in breast milk was 6.75 microg/kg/day. Therefore, the average infant exposure is 0.14% of the standard adult dose of bupropion, corrected for the difference in body weight. Considering the sum of bupropion and its active metabolites, the average infant exposure is expected to be 2% of the standard maternal dose on a molar basis. The concentration of bupropion and its active metabolites in breast milk was not associated with age, body mass index, use of oral contraceptive pills, age of infant, or the frequency of breast feeding at the time the study was initiated. The coefficient of determination (r2) between the concentration of bupropion in breast milk and in urine was 0.77 (p < 0.01). CONCLUSIONS: Bupropion and its active metabolites are present in the breast milk of lactating women. The concentrations of bupropion in breast milk and urine were highly correlated. These results indicate that the daily dose of bupropion and metabolites that would be delivered to an infant of a woman taking a therapeutic dose of bupropion is small. These results suggest that the effectiveness of bupropion to prevent post-partum relapse to tobacco use should be evaluated without excluding women who plan to breast feed.

Bupropion and alcohol fatal intoxication: case report.

A fatality due to the ingestion of bupropion and ethanol is presented. Bupropion and its metabolites were extracted from several tissues and identified using gas chromatography with nitrogenphosphorus and mass spectrometry detection. The concentrations of bupropion, hydroxybupropion and the erythroamino and threoamino alcohol metabolites in heart blood were 4.2, 5.0, 0.6 and 4.6 mg/l, respectively. The heart blood ethanol concentration was 0.27 g/dl. In addition, bupropion was distributed as follows: subclavian blood, 6.2 mg/l; bile, 1.4 mg/l; kidney, 2.4 mg/l; liver, 1.0 mg/kg; stomach contents, 16 mg and urine, 37 mg/l.

Determination of bupropion using liquid chromatography with fluorescence detection in pharmaceutical preparations, human plasma and human urine.

A novel pre-column derivatization reversed-phase high-performance liquid chromatography with fluorescence detection is described for the determination of bupropion in pharmaceutical preparation, human plasma and human urine using mexiletine as internal standard. The proposed method is based on the reaction of 4-chloro-7-nitrobenzofurazan (NBD-Cl) with bupropion to produce a fluorescent derivative. The derivative formed is monitored on a C18 (150 mm × 4.6 mm i.d., 5 µm) column using a mobile phase consisting of methanol-water 75:25 (v/v), at a flow-rate of 1.2 mL/min and detected fluorimetrically at λ(ex) = 458 and λ(em) = 533 nm. The assay was linear over the concentration ranges of 5-500 and 10-500 ng/mL for plasma and urine, respectively. The limits of detection and quantification were calculated to be 0.24 and 0.72 ng/mL for plasma and urine, respectively (inter-day results). The recoveries obtained for plasma and urine were 97.12% ± 0.45 and 96.00% ± 0.45, respectively. The method presents good performance in terms of precision, accuracy, specificity, linearity, detection and quantification limits and robustness. The proposed method is applied to determine bupropion in commercially available tablets. The results were compared with an ultraviolet spectrophotometry method using t- and F-tests.

Frequency of false positive amphetamine screens due to bupropion using the Syva EMIT II immunoassay.

Bupropion is a commonly prescribed, monocyclic antidepressant often used as an aid for smoking cessation. Several case reports have described false positive amphetamine urine drug screens (UDS) associated with bupropion. We sought to determine whether false positive amphetamine UDS due to the use of bupropion would be a frequent occurrence. We conducted an IRB-approved, retrospective chart review of all emergency department patients who underwent UDS between 1 January 2006 and 31 July 2007. All urine samples were screened using Syva EMIT II Plus immunoassay reagents. All positive screens underwent confirmation by gas chromatography (GC). We reviewed the records of patients with positive amphetamine UDS. We documented prescription use of bupropion, other antidepressants, stimulants, antipsychotics, and anti-hypertensives. We recorded evidence of polysubstance abuse (PSA) as patients who had had a documented diagnosis or laboratory evidence of abuse of at least two substances (drugs or ethanol). Of 10,011 urine drug screens, 362 (3.6%) were positive for amphetamine. GC confirmed amphetamines in 234 (65%), but failed to confirm in 128 (35%). Among the 234 confirmed, records reflected use of bupropion in three (1.3%), other antidepressants in 38 (16%), antipsychotics in 17 (8%), and amphetamine in 50 (21%). Records indicated evidence of PSA in 55 (24%). Among the 128 which failed to confirm, records reflected prescription use of bupropion in 53 (41%). None whose drug screen failed to confirm had evidence of PSA. Therapeutic use of bupropion appears to be the most frequent cause of false positive urine drug screens for amphetamines in our population.

Identification of bupropion urinary metabolites by liquid chromatography/mass spectrometry.

Human urinary metabolism of the antidepressant bupropion was studied using liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). A total of 20 metabolites were detected and identified. The phase I metabolism included formation of morpholinohydroxybupropion, threo- and erythrohydrobupropion, aromatic hydroxylation, butyl group hydroxylation with ketone hydrogenation and dihydroxylation. These metabolites were detected either as the free form or as glucuronide and/or sulphate conjugates. In addition also m-chlorohippuric acid was detected. Of the phase I metabolites, a dihydroxylation to the aromatic ring and to the methyl group in the middle of the substrate molecule was reported here for the first time, as well as eight of the glucuronide conjugates (to hydroxy, dihydroxy, hydroxy and hydrogenation metabolites) and three of the sulphate conjugates (to aromatic hydroxy and hydroxy and hydrogenation metabolites).

Analysis of benzene ethylamine derivatives in urine using the programmable dynamic liquid-phase microextraction (LPME) device.

An automated LPME device for a dynamic LPME method was manufactured and its extraction efficiency was tested using spiked urine samples. The developed home-made LPME device was a programmable automated syringe dispenser to overcome deteriorating precision and difficulties in manually manipulating the plunger repeatedly. To establish the optimum parameters for benzene ethylamines, the effects of sampling volume, solvent volume, pH, salt-effect, choice of solvents, plunger speed, and number of samplings were investigated. Good repeatabilities for the extraction of mephentermine, ephedrine, methoxyphenamine, selegiline, and bupropion were obtained and the RSD values were 2.4, 1.9, 1.3, 1.6 and 1.5% at a concentration of 3 microg mL(-1) in spiked urine samples, respectively. The limit of detection was below 0.05 microg mL(-1) for the investigated drugs. This developed device for LPME analysis gave good validation results and improved convenience.

Mass spectrometric investigation of 2-aminopropiophenones and some of their metabolites.

Complex metabolic mixtures of 2-aminopropiophenones, obtained both after in vitro and human in vivo metabolism of these compounds, have been investigated using both mass spectrometry and gas chromatography/mass spectrometry. The mass spectrometric fragmentation schemes of the compounds have been proposed and verified. The schemes are based on the characteristic fragments obtained by alpha-cleavage of these compounds using direct inlet mass spectrometry or gas chromatography/mass spectrometry. These findings were confirmed with chemical ionization mass spectrometry, when quasi-molecular (MH+) ions were obtained as the highest relative abundance ions for all the compounds investigated, and were used in metabolic investigations of 2-aminopropiophenones.