Studying the effect of vasopressors on therapeutic drug monitoring of two local anesthetics using hybrid micelle liquid chromatography as an analysis tool.

A hybrid micelle based mobile phase was used to develop and validate a liquid chromatographic method for the separation and quantification of two local anesthetics namely; lidocaine hydrochloride (LID), and bupivacaine hydrochloride (BPV) in presence of the frequently co administered vasopressors phenyl ephrine (PHR) and ephedrine (EPH). Optimization of chromatographic separation conditions was performed applying experimental one factor at a time tool, and design of experiment, where the retention behavior of all analytes using both optimization protocols was in accordance. Chromatographic separation was carried on a C8 column operating at 40 °C at a flow rate of 1.5 mL/min. using a mobile phase consisting of 0.18 M sodium dodecyl sulphate, 10% acetonitrile, containing 0.3% triethyl amine and adjusted to pH 7 using 2 M ortho phosphoric acid, adopting UV detection at 230 nm. The proposed method was fully validated and applied to both in vitro and in vivo analysis of rat blood samples. The pharmacokinetics of both LID and BPV was followed when they were solitary injected or when co administered with either PHR or EPH. Moreover, the in vitro spiked experiment was also subjected to documented bio-analytical validation procedures.

Correlation study between the pharmacokinetics of seven main active ingredients of Mahuang decoction and its pharmacodynamics in asthmatic rats.

The aim of this study was to investigate the pharmacokinetics and pharmacodynamics of seven main active components of Mahuang decoction (MHD) and its time-concentration-effect relationship. The asthmatic rat model was established by the method of ovalbumin (OVA) sensttization. The plasma concentrations of ephedrine, pseudoephedrine, methylephedrine, amygdalin, liquiritin, cinnamic acid, glycyrrhizic acid in asthmatic model rat were investigated by a selective and rapid HPLC/MS-MS method. Simultaneously, the asthma-involved cytokines including leukotrienes B4 (LTB4), thromboxane B2 (TXB2), 6-Keto-Prostaglandin F1α (6-K-PGF1α) and histamine (HIS) levels in rat plasma were determined by using ELISA. A mathematics method was applied to assess the trend of percentage rate of change among different time intervals of the seven components. The sigmoid E max function was used to establish the PK-PD modeling of MHD. The results indicated that MHD could control or ameliorate asthma. There was a hysteresis between the peaked drug concentration and maximum therapeutic effect of MHD. The PK-PD curves of MHD showed clockwise or counter-clockwise hysteresis loop. In addition, amygdalin might exert a more significant influence on regulating cytokines levels in asthmatic rats among the seven components of MHD.

Simultaneous UPLC-MS/MS determination of four components of Socheongryong-tang tablet in human plasma: Application to pharmacokinetic study.

The purpose of this study was to develop a method for simultaneous analysis of schizandrin, ephedrine, paeoniflorin, and cinnamic acid as constituents of Socheongryong-tang tablet in human plasma using UPLC-MS/MS. These four components were separated using water containing 0.01% formic acid and methanol as a mobile phase by gradient elution at a flow rate of 0.3 mL/min with a HALO-C18 column (2.1 mm × 100 mm, 2.7 µm particle size). Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique operated in multiple reaction monitoring mode. Mass transitions were m/z 432.9 → 384.1 for schizandrin, 165.8 → 148.1 for ephedrine, 525.0 → 449.2 for paeoniflorin, 146.8 → 102.9 for cinnamic acid, and 340.0 → 324.0 for papaverine as internal standard. Liquid-liquid extraction and protein precipitation with ethyl acetate-methanol (1:2, v/v) were used to obtain these four components. Chromatograms showed high resolution, sensitivity, and selectivity without interference by plasma constituents. Calibration curves of schizandrin, ephedrine, paeoniflorin, and cinnamic acid in human plasma ranged from 0.02 to 8 ng/mL, 0.5 to 200 ng/mL, 0.2 to 80 ng/mL, and 1 to 400 ng/mL, respectively. Calibration curves of each analyte displayed excellent linearity, with correlation coefficients > 0.99. For all four components, both intra- and inter-day precisions (CV%) were <5.99%. The accuracy was 99.35-103.30% for schizandrin, 98.48-104.38% for ephedrine, 97.06-103.34% for paeoniflorin, and 99.97-104.36% for cinnamic acid. This analytical method developed in this study satisfied the criteria of international guidance. It could be successfully applied to pharmacokinetic studies of schizandrin, ephedrine, paeoniflorin, and cinnamic acid after oral administration of Socheongryong-tang tablet to humans.

Quantitative analysis of clonidine and ephedrine by a microfluidic system: On-chip electromembrane extraction followed by high performance liquid chromatography.

In this work, a microfluidic device was developed for on-chip electromembrane extraction of trace amounts of ephedrine (EPH) and clonidine (CLO) in human urine and plasma samples followed by HPLC-UV analysis. Two polymethylmethacrylate plates were used as substrates and a microchannel was carved in each plate. The microchannel channel on the underneath plate provided the flow pass of the sample solution and the one on the upper plate dedicated to a compartment for the stagnant acceptor phase. A piece of polypropylene sheet was impregnated by an organic solvent and mounted between the two parts of the chip device. An electrical field, across the porous sheet, was created by two embedded platinum electrodes placed in the bottom of the channels which were connected to a power supply. The analytes were converted to their ionized form, passed through the supported liquid membrane, and then extracted into the acceptor phase by the applied voltage. All the effective parameters including the type of the SLM, the SLM composition, pH of donor and acceptor phases, and the quantity of the applied voltage were evaluated and optimized. Several organic solvents were evaluated as the SLM to assess the effect of SLM composition. Other parameters were optimized by a central composite design. Under the optimal conditions of voltage of 74V, flow rate of 28µLmin-1, 100 and 20mM HCl as acceptor and donor phase composition, respectively, the calibration curves were plotted for both analytes. The limits of detection were less than 7.0 and 11µgL-1 in urine and plasma, respectively. The linear dynamic ranges were within the range of 10-450 and 25-500µgL-1 (r2˃0.9969) for CLO, and within the range of 20-450 and 30-500µgL-1 (r2˃0.9907) for EPH in urine and plasma, respectively. To examine the capability of the method, real biological samples were analyzed. The results represented a high accuracy in the quantitative analysis of the analytes with relative recoveries within the range of 94.6-105.2% and acceptable repeatability with relative standard deviations lower than 5.1%.

Electromembrane extraction of polar basic drugs from plasma with pure bis(2-ethylhexyl) phosphite as supported liquid membrane.

Electromembrane extraction (EME) of polar basic drugs from human plasma was investigated for the first time using pure bis(2-ethylhexyl) phosphite (DEHPi) as the supported liquid membrane (SLM). The polar basic drugs metaraminol, benzamidine, sotalol, phenylpropanolamine, ephedrine, and trimethoprim were selected as model analytes, and were extracted from 300 µL of human plasma, through 10 µL of DEHPi as SLM, and into 100 µL of 10 mM formic acid as acceptor solution. The extraction potential across the SLM was 100 V, and extractions were performed for 20 min. After EME, the acceptor solutions were analyzed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). In contrast to other SLMs reported for polar basic drugs in the literature, the SLM of DEHPi was highly stable in contact with plasma, and the system-current across the SLM was easily kept below 50 µA. Thus, electrolysis in the sample and acceptor solution was kept at an acceptable level with no detrimental consequences. For the polar model analytes, representing a log P range from -0.40 to 1.32, recoveries in the range 25-91% were obtained from human plasma. Strong hydrogen bonding and dipole interactions were probably responsible for efficient transfer of the model analytes into the SLM, and this is the first report on efficient EME of highly polar analytes without using any ionic carrier in the SLM.

Comparison of urine analysis and dried blood spot analysis for the detection of ephedrine and methylephedrine in doping control.

When the misuse of stimulants is determined in doping control tests conducted during the in-competition period, athletes are asked to account for the violation of the rules. This study was designed to evaluate whether the urinary threshold values (10 µg/mL) for ephedrine and methylephedrine set by the World Anti-Doping Agency (WADA) can be exceeded after the oral administration of each substance (25 mg). In addition, the study describes the validity of a liquid chromatography-tandem mass spectrometric method using dried blood spot testing to detect ephedrine and methylephedrine by comparing it to a quantitative laboratory urine assay. After administration of ephedrine, the urinary concentration of ephedrine did not exceed the threshold at 4-10 h in two subjects, whereas the threshold was exceeded in both the subjects at 12 h after administration. For methylephedrine, the urinary concentrations of all the subjects failed to reach the threshold for up to 10 h after administration. The concentrations reached the threshold at 12-24 h after administration in some volunteers. In contrast, the blood concentrations of ephedrine and methylephedrine reached their maximum levels at 2-8 h after administration. The blood concentrations showed a low inter-individual variability, and the results suggested that the urinary excretion of ephedrine and methylephedrine can be strongly affected by urine pH and/or urine volume. These facts suggest that urinary concentrations cannot reflect the psychoactive level of ephedrines in circulation. Thus, dried blood analysis might be suitable for the adequate detection of stimulants during in-competition testing.

Simultaneous quantification and pharmacokinetics of alkaloids in Herba Ephedrae-Radix Aconiti Lateralis extracts.

The combination of Herba Ephedrae (Mahuang in Chinese) and Radix Aconiti Lateralis (Fuzi in Chinese) is a classical preparation in traditional Chinese medicine and used for treating colds and rheumatic arthralgia. However, herbal medicines containing ephedrines and Aconitum alkaloids are strictly regulated because of the potential for adverse effects on the cardiovascular system and the central nervous system. We aimed to investigate the pharmacokinetics of 11 alkaloids in the Mahuang-Fuzi combination and single-herb extracts after oral administration in rats. The alkaloids were norephedrine, norpseudoephedrine, ephedrine, pseudoephedrine, methylephedrine, aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine and benzoylhypaconine. Simultaneous determination of the alkaloids, including two pairs of diastereomers, was achieved in 14.5 min by a simple, rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method. The separation was performed on a Zorbax SB-Aq column (100 mm × 2.1 mm, 3.5 µm) at a flow rate of 0.3 mL/min using acetonitrile-0.1% formic acid aqueous solution as the mobile phase. The validated method demonstrated adequate sensitivity, selectivity and process efficiency for the quantitative analysis of complex herbal components. Compared with single-herb extracts, alkaloids in plasma (except methylephedrine, benzoylmesaconine and benzoylhypaconine) showed slower elimination (the mean residence time or half-life was longer), although the maximum plasma concentration and area under the plasma concentration curve values decreased. Accumulation may occur with continuous drug intake. These results suggest that drug monitoring may be essential for the safe use of the Mahuang-Fuzi combination.

UPLC-MS/MS determination of ephedrine, methylephedrine, amygdalin and glycyrrhizic acid in Beagle plasma and its application to a pharmacokinetic study after oral administration of Ma Huang Tang.

An ultra performance liquid chromatography-mass spectrometric (UPLC-MS) method was developed to investigate the pharmacokinetic properties of ephedrine, methylephedrine, amygdalin, and glycyrrhizic acid after oral gavage of Ma Huang Tang (MHT) in Beagles. Beagle plasma samples were pretreated using liquid-liquid extraction, and chromatographic separation was performed on a C18 column using a linear gradient of water-formic acid mixture (0.1%). The pharmacokinetic parameters of ephedrine, methylephedrine, amygdalin, and glycyrrhizic acid from MHT in Beagles were quantitatively determined by UPLC with tandem mass detector. The qualitative detection of the four compounds was accomplished by selected ion monitoring in negative/positive ion modes electrospray ionization-mass spectrometry (ESI-MS). Detection was based on multiple reaction monitoring with the precursor-to-product ion transitions m/z 166.096-116.983 (ephedrine), m/z 179.034-146.087 (methylephedrine), m/z 456.351-323.074 (amygdalin), and m/z 821.606-351.062 (glycyrrhizic acid). The selectivity, sensitivity, linearity, accuracy, precision, extraction recovery, ion suppression, and stability were within the acceptable ranges. The method described was successfully applied to reveal the pharmacokinetic properties of ephedrine, methylephedrine, amygdalin, and glycyrrhizic acid after oral gavage of MHT in Beagles.

Development and validation of a hydrophilic interaction liquid chromatography with tandem mass spectrometry method for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine.

A sensitive hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the simultaneous detection and quantification of etilefrine and oxilofrine in equine blood plasma and urine. The method is highly sensitive and specific with good precision and accuracy. In plasma the limit of detection and limit of quantification are 0.03 and 0.1 ng/mL, respectively, for both analytes. In urine the limit of detection and limit of quantification are 0.3 and 1 ng/mL, respectively, for both analytes. The suitability of the method for doping control analysis in equine species is demonstrated by analyzing postadministration samples collected after a single intravenous administration of 50 mg etilefrine to a standardbred mare. Etilefrine was detected up to 120 h in urine and up to 48 h in plasma. Etilefrine is highly conjugated in equine urine whereas it exists in the free form in equine plasma. Therefore, enzyme hydrolysis prior to sample preparation is recommended for the detection and quantification of etilefrine and oxilofrine in equine urine.

A report of an outbreak of toxicity from a novel drug of abuse: ERIC-3.

BACKGROUND: Novel drugs of abuse are becoming more common in the UK, and they represent particular difficulties in management. We present a case series of toxicity due to a novel substance Eric-3. METHODS: This was a retrospective case note review over a 6-month period. Patients were included if their presentation was due to ingestion of Eric-3. Physiological data, symptoms, outcome and destination of the patient from the ED were collected. Postmortem toxicological analysis was obtained for one of the patients who died. RESULTS: 41 attendances were identified from 18 patients. Two patients died and five were admitted to ITU. Heart rate and temperature on arrival tended to be above normal (mean heart rate was 112 bpm, with an SD of 18; mean temperature was 37.45° with an SD of 0.95°). 63.4% of attendances included agitation and 34.1% choreiform movements. α-Methyltryptamine and 3-/4-flouroephedrine were found in the blood of one of the patients who died. CONCLUSIONS: In this outbreak, Eric-3 gave symptoms similar to other stimulants. It may have been a novel substance 3-/4-flouroephedrine. It underlines the need for prospective data collection and information sharing.

Detection and quantification of new designer drugs in human blood: Part 2 - Designer cathinones.

In recent years, derivatives of cathinone, a naturally occurring beta-keto phenylethylamine, have entered the illicit drug market. These compounds have been marketed over the internet or in so-called head shops as "legal highs" and have gained popularity among drug users. Numerous fatalities due to the abuse of these drugs in recent years have increased the need for their detection in human blood samples. For detection and determination of 25 designer cathinones and their related ephedrines in blood samples, a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed using only 100 µL of blood. The blood was extracted using liquid-liquid extraction with 1 mL of 1-chlorobutane containing 10% of isopropanol. The final extract was analyzed using a Shimadzu 8030 LC-MS-MS system operated in electrospray positive ionization multiple reaction monitoring mode. The method has been validated according to international guidelines and was found to be selective for all tested compounds. Calibration for all 25 studied analytes was satisfactory from 10-1,000 ng/mL. Accuracy data were within the acceptance interval of ±15% [±20% at the lower limit of quantification (LLOQ)] of the nominal values for all drugs. Within-day (repeatability) and intermediate precision data were within the required limits of 15% relative standard deviation (RSD) (20% RSD at LLOQ).

Nonuniform cardiac denervation observed by 11C-meta-hydroxyephedrine PET in 6-OHDA-treated monkeys.

Parkinson's disease presents nonmotor complications such as autonomic dysfunction that do not respond to traditional anti-parkinsonian therapies. The lack of established preclinical monkey models of Parkinson's disease with cardiac dysfunction hampers development and testing of new treatments to alleviate or prevent this feature. This study aimed to assess the feasibility of developing a model of cardiac dysautonomia in nonhuman primates and preclinical evaluations tools. Five rhesus monkeys received intravenous injections of 6-hydroxydopamine (total dose: 50 mg/kg). The animals were evaluated before and after with a battery of tests, including positron emission tomography with the norepinephrine analog (11)C-meta-hydroxyephedrine. Imaging 1 week after neurotoxin treatment revealed nearly complete loss of specific radioligand uptake. Partial progressive recovery of cardiac uptake found between 1 and 10 weeks remained stable between 10 and 14 weeks. In all five animals, examination of the pattern of uptake (using Logan plot analysis to create distribution volume maps) revealed a persistent region-specific significant loss in the inferior wall of the left ventricle at 10 (P<0.001) and 14 weeks (P<0.01) relative to the anterior wall. Blood levels of dopamine, norepinephrine (P<0.05), epinephrine, and 3,4-dihydroxyphenylacetic acid (P<0.01) were notably decreased after 6-hydroxydopamine at all time points. These results demonstrate that systemic injection of 6-hydroxydopamine in nonhuman primates creates a nonuniform but reproducible pattern of cardiac denervation as well as a persistent loss of circulating catecholamines, supporting the use of this method to further develop a monkey model of cardiac dysautonomia.

Simultaneous identification of the enantiomers and diastereomers of N,O-di-trifluoroacetylated ephedrine and norephedrine in blood plasma using chiral capillary gas chromatography-mass spectrometry with selected ion monitoring.

A method for identifying the enantiomers of N,O-di-trifluoroacetylated ephedrine (EP) and norephedrine (NE) and the enantiomers of pseudoephedrine (PEP) and pseudonorephedrine (PNE) in plasma was developed using chiral capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). N,O-Di-trifluoroacethyl (TFA) derivatization was accomplished in a dried hydrochloride extract of plasma (minimum quantity of 0.2 mL). An SIM GC-MS method with a ß-cyclodextrin chiral capillary column allowed the successful and simultaneous detection of each TFA-derivatized stereoisomer of EP, NE, PEP, PNE, and an internal standard (IS; S-(+)-ethylamphetamine). Each TFA-drivatized stereoisomer was identified using four mass fragment ions (m/z 140, 154, 168, and 230). The TFA-derivatized stereoisomers of EP, NE, PEP, PNE, and IS were separated completely and were detected with sufficient sensitivity. The assay allowed the stereoisomers to be determined in a linear range of 12.5-1250 ng/mL for the EP stereoisomers and a linear range of 5-1250 ng/mL for the PEP, NE, and PNE stereoisomers. The detection limits were 7.5 ng/mL for the EP stereoisomers and 2.5 ng/mL for the PEP, NE, and PNE stereoisomers. The intra- and interday precisions were less than 5.9% and 8.2%, respectively. This chiral capillary SIM GC-MS method was sufficiently effective in the analysis of plasma from users of over-the-counter cold medicines and was also fully applicable to the plasma analysis of guinea pigs following their treatment with racemic EP.

Pharmacokinetic determination of ephedrine in Herba Ephedrae and Wu Tou Tang decoctions in rats using ultra performance liquid chromatography tandem mass spectrometry.

A rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry method was developed and validated for the determination and quantification of ephedrine in rat plasma samples. An Acquity UPLC BEH C18 column (1.7 µm, 2.1 mm × 50 mm) was used for chromatographic separation. Electrospray ionization in the positive mode was used, and the precursor-fragment ion pairs of m/z 166/148 and m/z 289/97 were adopted to characterize ephedrine and testosterone (internal standard), respectively. The method was validated using 10, 100 and 500 ng/mL of ephedrine. It demonstrated adequate levels of precision and accuracy, matrix effect, extraction recovery and stability. Linearity over the concentration range of 0.5-2000 ng/mL was acceptable with a correlation coefficient (r²) better than 0.990. To determine the pharmacokinetic behaviour of this sympathomimetic compound in the Sprague-Dawley rats, ephedrine hydrochloride, Herba Ephedrae single-herb and Wu Tou Tang decoctions were administered orally, and ephedrine hydrochloride was also administered by intravenous injection, and blood samples were collected over 24 h. Ephedrine was measured in plasma and pharmacokinetic parameters were determined by using the standard non-compartmental method and calculated by using Practical Pharmacokinetic Program-Version 87/97. The AUC(0-t) and T(max) values were significantly different (p < 0.05). Ephedrine AUC(0-t) values were significantly lower following the Wu Tou Tang decoction compared to the other oral treatments, suggesting that some components in the decoction may reduce the bioavailability of ephedrine.

Monolithic molecular imprinted polymer fiber for recognition and solid phase microextraction of ephedrine and pseudoephedrine in biological samples prior to capillary electrophoresis analysis.

A novel capillary electrophoresis (CE) method coupled with monolithic molecular imprinted polymer (MIP) fiber based solid phase microextraction (SPME) was developed for selective and sensitive determination of ephedrine (E) and pseudoephedrine (PE). With in situ polymerization in a silica capillary mold and E as template, the MIP fibers could be produced in batch reproducibly and each fiber was available for 50 extraction cycles without significant decrease in extraction ability. Using the MIP fiber under optimized extraction conditions, CE detection limits of E and PE were greatly lowered from 0.20 to 0.00096 µg/mL and 0.12 to 0.0011 µg/mL, respectively. Analysis of urine and serum samples by the MIP-SPME-CE method was also performed, with results indicating that E and PE could be selectively extracted. The recoveries and relative standard deviations (RSDs) for sample analysis were found in the range of 91-104% and 3.8-9.1%, respectively.

Simultaneous determination of codeine, ephedrine, guaiphenesin and chlorpheniramine in beagle dog plasma using high performance liquid chromatography coupled with tandem mass spectrometric detection: application to a bioequivalence study.

A rapid and sensitive method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of codeine, ephedrine, guaiphenesin and chlorpheniramine in beagle dog plasma has been developed and validated. Following liquid-liquid extraction, the analytes were separated on a reversed-phase C(18) column (150 mm × 2.0 mm, 3 µm) using formic acid:10 mM ammonium acetate:methanol (0.2:62:38, v/v/v) as mobile phase at a flow rate of 0.2 mL/min and analyzed by a triple-quadrupole mass spectrometer in the selected reaction monitoring (SRM) mode. The method was linear for all analytes over the following concentration (ng/mL) ranges: codeine 0.08-16; ephedrine 0.8-160; guaiphenesin 80-16,000; chlorpheniramine 0.2-40. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. It is the first time that the validated HPLC-MS/MS method was successfully applied to a bioequivalence study in 6 healthy beagle dogs.

Comparison of conventional hollow fiber based liquid phase microextraction and electromembrane extraction efficiencies for the extraction of ephedrine from biological fluids.

In the present study, hollow fiber liquid phase microextraction (HF-LPME) based on pH gradient and electromembrane extraction (EME) coupled with high-performance liquid chromatography (HPLC) was compared for the extraction of ephedrine from biological samples. The influences of fundamental parameters affecting the extraction efficiency of ephedrine were studied and optimized for both methods. Under the optimized conditions, preconcentration factors of 120 and 35 for urine and 51 and 8 for human plasma were obtained using EME and HF-LPME, respectively. The calibration curves showed good linearity for urine and plasma samples by both methods with the coefficient of estimations higher than 0.98. The limits of detection were obtained 5 and 10 ng mL(-1) using EME and 60 and 200 ng mL(-1) by HF-LPME for urine and plasma samples respectively. The relative standard deviations of the analysis were found in the range of 5.2-8.6% (n=3). The results showed that in comparison with HF-LPME based on pH gradient, EME is a much more effective transport process, providing high extraction efficiencies in very short time.

Determination of L-ephedrine, pseudoephedrine, and caffeine in rat plasma by liquid chromatography-tandem mass spectrometry.

A rapid and simple liquid chromatography tandem mass spectrometry method was developed and validated for the simultaneous determination of L-ephedrine, pseudoephedrine, and caffeine in male Fisher-344 rat plasma at nanogram-per-milliliter concentrations for use in support of toxicology studies. Only 25 µL of plasma is required, and extraction is performed using a simple, single-step protein precipitation. The method was validated over a range of 2.09 to 5460 ng/mL for L-ephedrine, 2.09 to 5050 ng/mL for pseudoephedrine and 2.03 to 5340 ng/mL for caffeine. A binary gradient elution at 0.3 mL/min was used with a Waters XBridge Phenyl (2.1 × 150 mm, 3.5 µm) column and a Waters XBridge Phenyl 2.1- × 10-mm guard column at ambient temperature. The mobile phase consisted of 10 mM ammonium acetate in water (pH 5.0) and methanol. Caffeine trimethyl-(13)C(3) was used as the internal standard. The method was evaluated for linearity, recovery, precision, accuracy, and stability, and it was successfully applied in toxicokinetic studies of ephedrine, administered alone, in combination with caffeine, and in the herbal source Ma Huang.

Determination of cathinones and related ephedrines in forensic whole-blood samples by liquid-chromatography-electrospray tandem mass spectrometry.

A liquid-chromatography-tandem-mass-spectrometry method using pneumatically assisted electrospray ionisation (LC-ESI-MS/MS) was developed for the simultaneous determination of cathinone, methcathinone, ethcathinone, amfepramone, mephedrone, flephedrone, methedrone, methylone, butylone, cathine, norephedrine, ephedrine, pseudoephedrine, methylephedrine and methylpseudoephedrine in human live and post-mortem whole blood. The blood proteins were precipitated by the addition of methanol, and the extract was purified by ultrafiltration. The separation of diastereomeric ephedrines was achieved on an ethyl-linked phenyl column. Matrix-matched calibrants combined with the isotope dilution of selected substances were used for quantitative analysis. The relative intra-laboratory reproducibility standard deviations were generally better than 7% at concentrations of 20 µg/L, and the mean true recoveries were 87-106% in the concentration range of 10-250 µg/L. The detection limits were in the range of 0.5-3 µg/L. The cathinones were unstable in whole blood and sample extracts under neutral conditions, but the stability could be improved by the acidification of the sample matrix.

Identification and quantitation of amphetamine, methamphetamine, MDMA, pseudoephedrine, and ephedrine in blood, plasma, and serum using gas chromatography-mass spectrometry (GC/MS).

Amphetamine, methamphetamine, MDMA, pseudoephedrine, and ephedrine are measured in blood, serum, and plasma using gas chromatography coupled to mass spectrometry (GC/MS). Following a simple liquid-liquid extraction, analytes are derivatized with heptafluorobutyric anhydride (HFBA) and 1 microL injected onto a HP-5MS 15-meter capillary column. Quantitation of each analyte is accomplished using a multi-point calibration curve and deuterated internal standards. The method provides a simple, robust, and reliable means to identify and measure these analytes.