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Problems of stability were found for biomarkers of alcohol consumption: ethyl glucuronide (EtG), ethyl sulfate (EtS), phosphatidylethanols (PEths), and fatty acid ethyl esters (FAEEs) in whole blood. The purpose of this study was to establish a method for the determination of these four kinds of ethanol's non-oxidative metabolites in dried blood spots (DBS) by liquid chromatography tandem mass spectrometry (LC-MS/MS), and to evaluate their stability. In this method, 50 μL of human blood was spotted onto a filter paper for DBS analysis. Samples were extracted by methanol, reconstituted by 2-propanol, and injected into the LC-MS/MS system. Limits of detection were among 0.5–50 ng/mL, and deviations in accuracy and precision were all lower than 15% at three quality control levels. The stability of the four kinds of ethanol non-oxidative metabolites in DBS was investigated during a 90-day range under three temperatures, −20 °C, 4 °C, and 25 °C. EtG and EtS showed a high level of stability in DBS in the 90-day range, regardless of the temperature. FAEEs were unstable after three days. PEths showed stability within 15 days in postmortem DBS and 60 days in antemortem DBS, respectively, at all temperatures.

Background: Dopamine transporter (DAT) and serotonin transporter (SERT) are targets for many psychoactive substances. Functional assays including uptake inhibition and release assays often involve radiolabeled compounds like [3H]-dopamine and [3H]-serotonin to assess drug activity at transporters, which have high requirements on handling radioactive samples. Aims: The aim of this study was to establish a label-free method to assess drug activity at DAT and SERT. Methods: A liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was established using transporter-transfected human embryonic kidney 293T (HEK293T) cells. This method was evaluated by testing the effects of amphetamine and cocaine in the assay procedure. Results: The limits of detection of this method were 0.2 nM for both dopamine (DA) and serotonin (5-HT), with good linearities in the range of 0.5–160 nM. Amphetamine and cocaine’s IC50 and EC50 on DAT and SERT determined by this method were consistent with previous reports. Conclusions: A rapid, reliable and label-free LC-MS/MS method for assessing drug activity was established, which affords an attractive alternative for those laboratories that do not have a radiation license or capabilities.

The lack of systematic studies on the stability of ethanol's non-oxidative metabolites in postmortem specimens restricts their use in forensic cases. This study aimed to compare the stability of ethyl glucuronide (EtG), ethyl sulfate (EtS), phosphatidylethanols (PEths) and fatty acid ethyl esters (FAEEs) in postmortem human blood. Three groups were established based on the level and source of ethanol: the blank group, the ethanol-spiked group and the ethanol-positive group. Each group contained six blood samples from different corpses. The samples in each group were placed at 37, 25, 4 and -20°C. Every 24 h for 7 days, 50 μL was collected from each sample. The levels of EtG, EtS, PEths and FAEEs were determined by liquid chromatography-mass spectrometry, and their stability was evaluated. EtG was not detected in the blank group, but it was found in samples in the ethanol-spiked group placed at 37°C, and it was degraded in the ethanol-positive group at 37 and 25°C. EtS showed no change in any of the groups. PEths were not detected in the blank group, but formation was found in the ethanol-spiked group at all temperatures. In the ethanol-positive group, PEth levels fluctuated at 37°C, decreased at 25°C and increased at -20°C. FAEEs were generated in the blank group and in the ethanol-spiked group at all temperatures. In the ethanol-positive group, FAEEs were degraded at 37 and 25°C but were generated at 4 and -20°C. EtS is a reliable biomarker of ethanol consumption, and EtG could be used as a biomarker at low temperatures (4 and -20°C), but PEths and FAEEs are not appropriate biomarkers of ethanol consumption.

The importance of ethanol non-oxidative metabolites as the specific biomarkers of alcohol consumption in clinical and forensic settings is increasingly acknowledged. Simultaneous determination of these metabolites can provide a wealth of information like drinking habit and history, but it was difficult to achieve because of their wide range of polarity. This work describes development and validation of a simple liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for 4 types of ethanol non-oxidative metabolites (ethyl glucuronide, ethyl sulfate, fatty acid ethyl esters and phosphatidylethanols) in 50 μL of human whole blood. Pretreatment method, column and MS conditions were optimized. For the first time, the four types of ethanol non-oxidative metabolites with enormous discrepancies of property were simultaneously extracted and analyzed in one run within 40 min. The limits of detections (LODs) were among 0.1–10 ng/mL, and good linearity was obtained. Deviations in precision and accuracy were all lower than 15% at three QC levels. This method was then applied to two forensic samples, resulting in information on drinking habits and drinking time which were very useful for the interpretation of the blood alcohol results.

N-Ethylpentylone (NEP) is a popular synthetic cathinone abused worldwide. To obtain more information about its pharmacokinetics and pharmacodynamics, a rapid, simple and sensitive liquid chromatography-tandem mass spectrometry method was developed for the determination of NEP, two important neurotransmitters, dopamine and serotonin, and their metabolites, including 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine and 5-hydroxyindole-3-acetic acid, in rat brain microdialysate. The analytes were separated on a Phnomenex Polar C18 column, with a mobile phase of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B) under gradient elution to shorten the total chromatographic run time. A triple quadruple mass spectrometer coupled with an electrospray ionization source in both positive and negative ion mode was used to detect the analytes. This method showed excellent accuracy (87.4-113.5%) and precision (relative standard deviation

A rapid, simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the qualitative and quantitative analysis of nine barbiturates (barbital, phenobarbital, pentobarbital, amobarbital, secobarbital, thiopental, butalbital, butabarbital, and hexobarbital) in human whole blood. Barbiturates were extracted from 100 μL of human whole blood samples using a simple liquid-liquid extraction (LLE) procedure, and detected by LC-MS/MS. An UPLC C18 (2.1 mm × 100 mm, 1.7 µm) column was used at 40 °C for the separation and acetonitrile/water system was used as the mobile phase with gradient elution. This method showed excellent accuracy (86–111%) and precision (relative standard deviation 0.99 over the range. This method achieved the separation and detection of pentobarbital and amobarbital at the same time in a convenient way. Moreover, it was both simple and sensitive for the determination of nine most commonly used barbiturate drugs, which was meaningful in the field of clinical and forensic toxicology. Copyright © 2016 John Wiley & Sons, Ltd.

Owing to its low cost and admirable luminescent characteristics for use in warm white-light-emitting diode (w-LED) applications, the non-rare-earth Mn4+-activated red phosphor has emerged as a potent competitor of commercial Eu2+-doped nitrides in recent years. In this work, the novel red-emitting phosphor BaMgAl10–2xO17:xMn4+,xMg2+ is successfully synthesized, which exhibits bright and narrow-band luminescence peaking at 660 nm with a full width at half-maximum of merely ∼30 nm upon blue light excitation. The unique structural feature of BMA, i.e., alternating arrangements of Mn4+-doped MgAl10O16/undoped BaO layers in the z direction and Mn4+-doped [AlO6]/undoped [AlO4] groups in the x–y plane, favors efficient Mn4+ luminescence by reducing nonradiative energy loss channels. Unlike previously reported hosts, BMA accommodates Mg2+ in the lattice without destabilizing the crystal structure. Remarkably, partitioning Mg2+ in the host not only greatly enhances Mn4+ luminescence by 1.84-fold but also retards t...

Liquid–liquid extraction (LLE) is the most commonly sample preparation procedure used by forensic toxicologists in China for screening drugs in whole human blood. It extracts numerous substances from blood including targeted drugs and interfering substances, specifically triglycerides (TG). With increasing prevalence of hyperlipidemia, the influences of TG on LLE and on subsequent analysis with gas chromatography–mass spectrometry (GC–MS) may become a major issue for forensic laboratories. This study aims to elucidate the influences of TG on LLE and to provide possible solutions to this problem. Nineteen commonly encountered drugs in forensic cases were spiked to human whole blood with different TG concentrations. Diethyl ether, ethyl acetate/hexane mixed solutions, chlorobutane and several other frequently used solvents were tested for the extraction of drugs from spiked whole blood. The supernatant organic layer was evaporated to dryness and reconstituted with methanol. The resultant products were analyzed by GC–MS, and the extraction recovery was calculated. LLE with diethyl ether, ethyl acetate/hexane (9:1) and chlorobutane all possessed effective and reliable extraction recoveries for blood sample with low TG concentrations (0.63–6.85 mmol/L). At high TG concentrations, diethyl ether produced a highly turbid substance that could not be further analyzed using GC–MS. Extraction recoveries drastically dropped for ethyl acetate/hexane (9:1) mixture at high TG concentrations, while chlorobutane experienced minimal drops in extraction recoveries. In conclusion, TG levels in whole blood noticeably influence drug recovery to variable extents depending on the LLE solvent. Chlorobutane showed minimal influences from TG content in whole blood and thus is the recommended LLE solvent for forensic drug extraction.

We developed a simple and rapid analysis method for the determination of four amphetamines in human whole blood and urine using gas chromatography–mass spectrometry (GC–MS). During the course of sample preparation, the evaporation process was found to be the weak point for amphetamine and methamphetamine analysis. Liquid–liquid extraction in this study was conducted without the evaporation step, and the upper solvent layer was injected directly without derivatization, which effectively prevented the volatile amphetamines from vanishing during evaporation and guaranteed the linearity of the calibration curves. This method showed good selectivity, precision, and accuracy, and at the same time was simple and fast. The limits of detection were 5 ng/ml. As an application of this study, a whole blood sample and urine sample from a drug abuse suspect were analyzed. This method may be able to meet the need for rapid and accurate confirmation of positive immunoassay results as well as quantification in clinical and forensic toxicological cases. To our knowledge, no forensic toxicologists have noted that such a basic and simple method, without evaporation or derivatization, is useful for routine analysis of amphetamines using GC–MS.

The compatibility of Rhizoma Corydalis(Yuanhu,YH) and Radix Angelicae dahuricae (Baizhi,BZ) as a herb pair Yuanhu-Baizhi(YB) can produce synergistic analgesic effect. However, the underlying mechanism of this herb pair compatibility is not elucidated yet. A LC–MS/MS method combined with in vivo microdialysis sampling from awaken rats’ striatum was developed to simultaneously quantitate three endogenous neurotransmitters, dopamine(DA), glutamate (Glu), and 5-hydroxytryptamine (5-HT), and nine components of Yuanhu-Baizhi herb pair in rats. The microdialysates were derivatizated with benzoyl chloride and analyzed on Agilent Poroshell 120EC-C18 column. The mobile phase consisted of aqueous solution with 0.05% formic acid and 2.0 mM ammonium formate (A), and acetonitrile (B) delivered at gradient elution. All the twelve analytes were quantified using an electrospray ionization tandem mass spectrometry in the selective reaction monitoring mode. The method was validated following FDA’s guidance on bioanalytical validation. The standard curves were linear ( r2 > 0.991) over the corresponding concentration ranges. For three neurotransmitters, the intra-day and inter-day precision (RSD) were not greater than 14.9%, and the intra-day and inter-day accuracy (RE) ranged from -14.2∼ 7.2%. The LLOQ of 5-HT, DA and Glu were 0.50 nM, 0.50 nM and 20.00 nM, respectively. For nine components in Yuanhu-Baizhi herb pair, the intra-day and inter-day precision (RSD) were less than 15.0%, and the intra-day and inter-day accuracy (RE) ranged from -12.5 ∼14.8%. The novel developed method was applied to pharmacokinetic (PK) and pharmacodynamic (PD) study of Yuanhu-Baizhi herb pair in rats. The results showed that the pharmacokinetic behavior of nine components in the herb pair was significantly different with that of single herb, mainly referring to the bioavailability of five alkaloids from Yuanhu increased whereas that of four coumarins decreased in rat striatum. Pharmacodynamic study based on Glu, DA, and 5-HT revealed that the content of neurotransmitters varied when rats were administered Yuanhu-Baizhi herb pair or single herb. PD analysis results demonstrated the compatibility of Yuanhu and Baizhi has the synergistic effect and the effect of attenuation from the point of the neurotransmitters’ view. In conclusion, the pharmacokinetic and pharmacodynamic study based on in vivo microdialysis sampling from awaken animals and LC–MS/MS quantitation is in favor of revealing the compatibility mechanism of herb pairs.

Bismuth ferrite thin films were prepared via sol–gel spin-coating method and the effects of annealing temperature on microstructure, optical, ferroelectric and photovoltaic properties have been investigated. The results show that the bismuth ferrite thin films annealed at 550 °C is single phase and the grain size increases with the rise of annealing temperature. The band gap of bismuth ferrite thin films annealed at 550–650 °C is between 2.306 eV and 2.453 eV. With the rise of the annealing temperature, the remnant polarization gradually decreases and the coercive electric field increases. The short circuit photocurrent density decreases with the rise of annealing temperature, and the open circuit photovoltage and the power conversion efficiency of bismuth ferrite thin films annealed at 550 °C are higher than the thin films annealed at higher temperature.

Graphical abstract: - Highlights: • We prepared Nd-doped BTO thin films by sol–gel method. • Addition of Nd to some extent can inhibit the grain growth. • Addition of Nd{sup 3+} ions can decrease band gap. • The remnant polarization of Nd-doped BTO thin films begins to increase and then decreases. • Photovoltaic properties of Nd-doped BTO thin films begin to increase then decrease. - Abstract: Nd-doped barium titanate thin films were prepared via sol–gel spin-coating method and effects of Nd content on microstructure, optical and photovoltaic properties have been investigated. The results show that Nd-doped barium titanate thin films are single tetragonal perovskite phase. Addition of neodymium to some extent can inhibit the grain growth. Substitution of Nd{sup 3+} ions for Ba{sup 2+} on A sites leads to the decrease of band gap. The remnant polarization begins to increase and reach the maximum and then decreases as Nd content increases. The short circuit photocurrent density, open circuit photovoltage and power conversion efficiency of Nd-doped barium titanate thin films begin to increase and reach the maximum and then decrease as Nd content increases.

An ultra performance liquid chromatography coupled to mass spectrometry-based metabonomic approach, combined with pattern recognition methods including PCA, PLS-DA, RF and heatmap, has been developed to characterize the global serum metabolic profile associated with ionizing radiation (IR). As the VIP-value threshold cutoff of the metabolites was set to 2, metabolites above this threshold were filtered out as potential target biomarkers. Nineteen distinct potential biomarkers in rat plasma were identified. To further elucidate the pathophysiology of IR, related metabolic pathways have been studied. It was found that IR was closely related to disturbed fatty acid metabolism, taurine and hypotaurine metabolism, sphingolipid metabolism, purine metabolism, pyrimidine metabolism, phospholipid catabolism, tryptophan metabolism, phenylalanine metabolism, and bile acid metabolism. With the presented metabonomic method, we systematically analyzed the protective effects of Traditional Chinese Medicine Hong Shan Capsule (HSC). The results demonstrated that HSC administration could provide satisfactory effects on IR through partially regulating the perturbed metabolic pathways.

Recreational drugs have large impact on public health and security, and to monitor them is of urgent demand. In the present study, ultrasound-assisted dispersive liquid-liquid microextraction combined with the detection of gas chromatography-mass spectrometry was applied to the determination of seven common recreational drugs, including amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, meperidine, methadone and ketamine in 200μL of human whole blood. A series of factors which would affect the extraction efficiency were systematically investigated, including the nature and the volume of extraction and dispersing solvents, ultrasonication time, salting-out effect and pH value. The method consumed small amount of sample. The limits of detection and limits of quantification for each analyte were 10 and 40ng/mL, respectively, and the linearity was in the range of 0.04-25μg/mL (R2 higher than 0.99). Good specificity, precision (1.5-8.2% for the intra-day study and 2.6-12.8% for the inter-day study), satisfactory accuracy (85.0-117.1%) and extraction recovery (77.0-92.4%) were obtained, which makes it a high performance method for the determination of recreational drugs in human whole blood samples.

Fatty acid ethyl esters (FAEEs) have been widely studied as specific markers of ethanol intake and mediators of ethanol-induced diseases. In the present study, a simple and rapid gas chromatography-mass spectrometry (GC-MS) method was established for the qualitative and quantitative analysis of six fatty acid ethyl esters (FAEEs), including ethyl myristate, ethyl palmitate, ethyl stearate, ethyl oleate, ethyl linoleate, and ethyl arachidonate, in human whole blood. FAEEs were extracted from 200 μL of human whole blood by a modified liquid-liquid extraction, and the hexane layer was injected directly into GC-MS with ethyl heptadecanoate as the internal standard. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 5–50 ng/mL and 15–200 ng/mL, respectively. Linearity ranged up to 10 μg/mL with r 2 higher than 0.998. Accuracy was in the range of 90.3–109.7%, while intra-day and inter-day precision were 0.7–9.3% and 3.4–12.5%, respectively. This method was then applied to 38 real samples from forensic cases. Differences in the most common FAEEs between Chinese and Western subjects were discussed. The relationship of FAEE concentrations with age and gender was also investigated.

Owing to its low cost and admirable luminescent characteristics for use in warm white-light-emitting diode (w-LED) applications, the non-rare-earth Mn4+-activated red phosphor has emerged as a potent competitor of commercial Eu2+-doped nitrides in recent years. In this work, the novel red-emitting phosphor BaMgAl10–2xO17:xMn4+,xMg2+ is successfully synthesized, which exhibits bright and narrow-band luminescence peaking at 660 nm with a full width at half-maximum of merely ∼30 nm upon blue light excitation. The unique structural feature of BMA, i.e., alternating arrangements of Mn4+-doped MgAl10O16/undoped BaO layers in the z direction and Mn4+-doped [AlO6]/undoped [AlO4] groups in the x–y plane, favors efficient Mn4+ luminescence by reducing nonradiative energy loss channels. Unlike previously reported hosts, BMA accommodates Mg2+ in the lattice without destabilizing the crystal structure. Remarkably, partitioning Mg2+ in the host not only greatly enhances Mn4+ luminescence by 1.84-fold but also retards t...

Analysis of plasma metabolomic samples by gas chromatography-mass spectrometry always requires comprehensive pretreatment including oximation and silylation. Although heating block (HB) is a commonly used method, it is time consuming. This study describes an extremely time-effective microwave-assisted (MA) oximation and silylation approach for metabolomic study of plasma samples. The Box-Behnken design was employed to optimize the MA conditions by means of oximation at 65 W for 100 s and then silylation through 180 s incubation with 230 W microwave irradiation. The results showed that microwave irradiation decreased the sample preparation time from approximately 180 min to 5 min without loss of information for the metabolites in plasma samples. Both the HB method and the developed MA method were applied in plasma metabolomic study of sulfur mustard intoxication. Partial least-squares discriminant analysis (PLS-DA) was used to globally understand the metabolic changes, and multi-criteria assessment was used to select the most significant and reliable variables as potential biomarkers. The data obtained by the MA method were in good correlation with the HB method. Compared with HB method, the newly developed MA oximation and silylation of plasma metabolome samples was more efficient and time-effective and may prove to be an attractive alternative for high-throughput sample preparation in plasma metabolomics.

Hafnium (Hf)-doped Ba[Zr 0.2 Ti 0.8 ]O 3 (BZT) ceramics were prepared by the conventional solid-state reaction method. The microstructure, dielectric and ferroelectric properties of Hf-doped BZT ceramics have been investigated. Hf 4+ ions enter the perovskite-type cubic structure to substitute for Ti 4+ ions on the B sites and lead to the increase of the lattice parameter. Addition of hafnium can restrain grain growth in the BZT ceramics. Hf-doped BZT ceramics have ferroelectric properties with diffuse phase transition. Hf 4+ ions can reduce dielectric loss of BZT ceramics. As Hf content increases, the remnant polarization begins to increase to the maximum and then decrease, while the coercive field begins to decrease to the minimum and then increase. The remnant polarization, saturation polarization and coercive field decrease with the rise of measurement temperature.

Samarium-doped barium titanate ceramics were prepared by the conventional solid-state reaction method. The microstructure, dielectric and ferroelectric properties of Sm-doped barium titanate ceramics have been investigated. The result indicates that Sm3+ ions enter the perovskite-type structure to substitute for Ba2+ ions on the A sites and lead to the change of the crystal structure from tetragonal to cubic structure. Addition of samarium can restrain the grain growth of barium titanate ceramics and lead to the fall of the Curie temperature. There is diffuse phase transition in Sm-doped barium titanate ceramics. Sm3+ ions can decrease the dielectric loss of barium titanate ceramics on the basis of the Ti-vacancy defect compensation model. The remnant polarization and the coercive field of Sm-doped barium titanate ceramics decrease monotonously with the increase of samarium content. As temperature rises, the remnant polarization and the coercive electric field of Sm-doped barium titanate ceramics decrease...

V-doped barium titante ceramics were prepared by conventional solid state reaction method. XRD patterns show that V 5+ ions have entered into the tetragonal perovskite structure of solid solution to substitute for Ti 4+ ions on the B sites. Addition of vanadium accelerates grain growth of BTO ceramics and there is abnormal grain growth of barium titanate ceramics with higher vanadium concentration. Vanadium doping can increase the Curie temperature and decrease the dielectric loss of barium titanate ceramics. As vanadium concentration increases, the remnant polarization of Vdoped BTO ceramics begins to increase and reaches the maximum and then decreases. The coercive electric field for V-doped barium titanate ceramics decreases with the increasing of vanadium concentration. As temperature rises, the remnant polarization and the coercive electric field of V-doped barium titanate ceramics decrease simultaneously. # 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Clarification of postmortem metabolite changes can help characterize the process of biological degradation and facilitate investigations of forensic casework, especially in the estimation of postmortem interval (PMI). Metabolomics can provide information on the molecular profiles of tissues, which can aid in investigating postmortem metabolite changes. In this study, liquid chromatography-mass spectrometric (LC-MS) analysis was performed to identify the metabolic profiles of rat femoral muscle at ten periods of time after death within 168 h. The results obtained by reversed-phase liquid chromatography (RPLC)- and hydrophilic interaction liquid chromatography (HILIC)- electrospray ionization (ESI±) have revealed more than 16,000 features from all four datasets. Furthermore, 915 of these features were identified using an in-house database. Principal component analysis (PCA) demonstrated the time-specific features of molecular profiling at each period of time after death. Moreover, results from partial least squares projection to latent structures-discriminant analysis (PLS-DA) disclosed a strong association of metabolic alterations of at least 59 metabolites with the time since death, especially within 48 h after death, which expounds these metabolites as potential indicators in PMI estimation. Altogether, our results illustrate the potentiality of metabolic profiling in the evaluation of PMI and provide candidate metabolite markers with strong correlation with time since death for forensic purpose.

Currently, the development of efficient red-emitting persistent phosphor is still an ongoing challenge. Herein, a novel red-emitting LPL phosphor Ca3Ti2O7:Pr(3+) is successfully prepared by a high-temperature solid-state method. XRD Rietveld refinement analyses demonstrate the high phase purity of the sample which crystallizes in an orthorhombic Ccm21 space group with lattice parameters of a = 5.7702(5) A, b = 19.4829(7) A, and c = 5.1214(2) A. Electronic structure of the host matrix is analyzed by the first-principle calculation using CASTEP code. The calculation results show that Ca3Ti2O7 has a direct band gap with CB and VB mainly composed of the Ti-3d and O-2p states, respectively. On the basis of the DR spectrum, the band gap is determined to be 3.6 eV. It is demonstrated that the 612 nm red-emitting persistent luminescence of Ca3Ti2O7:Pr(3+) can be either activated by Ti(4+)-O(2-) → Ti(3+)-O(-) host absorption and Pr(3+)-O-Ti(4+) → Pr(4+)-O-Ti(3+) IVCT in the UV region, or Pr(3+):(3)H4 → (3)PJ transition in the blue region. The red afterglow can last for ∼ 5 min observed by the naked eyes in the dark after ceasing the irradiation source. On the basis of the TL analyses, the trap is found exponentially distributed in the host with the depth of 0.69-0.92 eV. Finally, a possible LPL mechanism for Ca3Ti2O7:Pr(3+) is proposed.

The characterization and quantification of the metabolites of chiral drugs still remain a great challenge due to the complexity of the metabolites and most of them are not commercially available. In this study, a practical approach based on the combinatory liquid chromatography-mass spectrometric techniques has been proposed for the evaluation of metabolism profiles and urinary excretion kinetics of chiral drugs and their metabolites. Racemic tetrahydropalmatine (rac-THP), a biologically active ingredient isolated from a traditional Chinese herb Rhizoma Corydalis, was chosen as the model chiral drug. Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) was applied to characterize the metabolites of THP enantiomers in rat urine after administration of (+)-THP or (-)-THP. Accurate mass measurement was used to determine the elemental composition of metabolites and thus to confirm the proposed structures of these metabolites. More than 30 potential metabolites were found in rat urine, most of which were identified for the first time, and the metabolic pathways in vivo were involved in demethylation, oxidation, glucuronide conjugation and sulfation, etc. And the tridesmethlyzed metabolite and didesmethlyzed coupled with oxidation metabolite were found only in (+)-THP treated rats. Afterwards, a liquid chromatography tandem mass spectrometry (LC-QqQ/MS) assay was developed and validated for the determination of the urine level of THP enantiomers and their metabolites. Semi-quantification of three phase I metabolites and two phase II metabolites were performed. Enantiomeric (-/+) cumulative urinary excretion ratios of THP and its five metabolites were obtained, which indicated the stereoselective aspects of metabolites of THP enantiomers in vivo. The study demonstrated the enormous potential of this strategy for the qualitative characterization, quantitative assay and the stereoselectivity of chiral drugs and their metabolites.