Sensitive Gas Chromatography-mass Spectrometry Research Articles

GC-MS method for simultaneous determination and pharmacokinetic investigation of five volatile components in rat plasma after oral administration of the essential oil extract of Pogostemoncablin

Pogostemon cablin (PC) is a traditional Chinese medicine (TCM) and food as well as an important essential oil plant in China. PC essential oil exerts pharmacological effects such as anti-inflammatory, anti-oxidant, anti-platelet, anti-thrombotic, and anti-depressant. This study established a reliable and sensitive gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of the pharmacokinetics of patchouli alcohol, β-elemene, β-caryophyllene, caryophyllene oxide, and farnesol in the plasma of rats after oral administration of PC essential oil extract. Using ethyl acetate to prepare the plasma samples, and p-menthone was used as the internal standard (IS). An HP5-MS column (0.25 μm × 0.25 mm × 30 m) was used for chromatographic separation, and detection was performed in selected ion monitoring (SIM) mode. The accuracies of intra-day and inter-day for all analytes displayed a range of −6.7 %–9.2 %, with precision below 12.5 %. Extraction recoveries for analytes ranged from 74.0 to 106.4 % and matrix effects ranged from 92.4 to 106.9 %. Stability results have demonstrated that the relative standard deviations (RSD) of analytes were below 12.1 %. Therefore, the developed GC-MS method successfully evaluated the pharmacokinetics of five volatile components in PC essential oil extract administered orally to rats.

Development of qualitative GC MS method for simultaneous identification of PM-CCM a modified illicit drugs preparation and its modern-day application in drug-facilitated crimes

Prescriptions for psychoactive substances such as Pregabalin, Methamphetamine, Caffeine, Clonazepam and Mirtazapine (PM-CCM) are common in the treatment of a variety of disorders. Indeed, the PM-CCM has been used in different therapeutic areas, including insomnia, anxiety, seizure disorders, etc. Unfortunately, these psychoactive substances are present in the illegal street market, leading to a lot of drug abuse among some addicted users, road insecurity and suicide. Hence, it has become essential to validate and develop a rapid and effective method to analyze the PM-CCM, a modified illicit drug, for drug abuse in the forensic sciences. A simple, rapid, specific and sensitive Gas Chromatography-Mass Spectrometry(GC-MS) method has been developed for the identification of Pregabalin, Methamphetamine, Caffeine, Clonazepam and Mirtazapine (PM-CCM) in forensic exhibits. At room temperature, the sample was ultrasonicated for 5 minutes before being extracted with methanol. A highly precise auto-injector is used to inject a very small quantity of samples for analysis. Helium is used as a carrier gas with a flow rate of 1 ml/min. The separation of PM-CCM was performed on SH-RXi-5 MS, ID.25 mm, film thickness. 25 µm, length of 30 m column. The constituents of PM-CCM were identified by the mass-to-charge ratio (m/z ratio) of fragments of the parent compound by comparing them with the NIST-17 MS Library. Separation and identification of PM-CCM were achieved within a 15-minute run. The proposed method has been successfully used for the routine analysis of PM-CCM in complex illicit drug preparations and in forensic exhibits as well. The application of above discussed qualitative analysis method and screening of PM-CCM, modified illicit drug samples demonstrates the potential and applicability of the technique to the fast chemical profiling of illicit samples.

Monitoring the concentration of aldehydes in chicken meat during the storage period after treatment by accelerated electrons

A method of food radiation treatment can address a number of problems in the food industry, including the suppression of pathogenic microbial contamination, preservation of the nutritional value of the prod­uct, and extension of the food shelf life. When combined with a highly sensitive gas chromatography-mass spectrometry, the method provides detection of biochemical markers of radiation processing in meat prod­ucts with a low content of fat, such as chicken and turkey. We present the results of studying the depend­ ence of the content of volatile organic compounds in chilled chicken meat treated with 1 MeV accelerated electrons in a dose range from 250 Gy to 20 kGy during two weeks of storage. Concentrations of volatile organic compounds in the irradiated and control samples of food samples were determined on the zeroth, 1 st , 4 th , 6 th , 8 th , 11 th and 13 th days after irradiation. Concentrations of aldehydes, namely, hexanal, heptanal, and pentanal identified in poultry meat samples exposed to radiation demonstrated a similar behavior during two weeks of product storage. Samples exposed to irradiation in a dose range from 500 Gy to 10 kGy exhibited an increase in the aldehyde content on days 1-4 after irradiation. It is shown that the time of aldehydes accumulation in irradiated meat shifts towards a shorter period of the product storage with an increase in the dosage of irradiation. Thus, aldehydes can be considered potential markers of the radiation treatment of chicken meat during the first four days after irradiation.

In-vitro and in-silico antibacterial activity of Azadirachta indica (Neem), methanolic extract, and identification of Beta.d-Mannofuranoside as a promising antibacterial agent

BackgroundAntimicrobial resistance became the leading cause of death globally, resulting in an urgent need for the discovery of new, safe, and efficient antibacterial agents. Compounds derived from plants can provide an essential source of new types of antibiotics. A. indica (neem) plant is rich in antimicrobial phytoconstituents. Here, we used the sensitive and reliable gas chromatography-mass spectrometry (GC–MS) approach, for the quantitative and quantitative determination of bioactive constituents in methanolic extract of neem leaves grown in Sudan. Subsequently, antibacterial activity, pharmacokinetic and toxicological properties were utilized using in silico tools.ResultsThe methanolic extract of neem leaves was found to have antibacterial activity against all pathogenic and reference strains. The lowest concentration reported with bacterial activity was 3.125%, which showed zones of inhibition of more than 10 mm on P. aeruginosa, K. pneumoniae, Citrobacter spp., and E. coli, and 8 mm on Proteus spp., E. faecalis, S. epidermidis, and the pathogenic S. aureus. GC–MS analysis revealed the presence of 30 chemical compounds, including fatty acids (11), hydrocarbons (9), pyridine derivatives (2), aldehydes (2), phenol group (1), aromatic substances (1), coumarins (1), and monoterpenes (1). In silico and in vitro tools revealed that.beta.d-Mannofuranoside, O-geranyl was the most active compound on different bacterial proteins. It showed the best docking energy (-8 kcal/mol) and best stability with different bacterial essential proteins during molecular dynamic (MD) simulation. It also had a good minimum inhibitory concentration (MIC) (32 μg/ml and 64 μg/ml) against S. aureus (ATCC 25,923) and E. coli (ATCC 25,922) respectively.ConclusionThe methanolic extract of A. indica leaves possessed strong antibacterial activity against different types of bacteria. Beta.d-Mannofuranoside, O-geranyl was the most active compound and it passed 5 rules of drug-likeness properties. It could therefore be further processed for animal testing and clinical trials for its possible use as an antibacterial agent with commercial values.

Validation of a Microwave-Assisted Derivatization Gas Chromatography-Mass Spectrometry Method for the Quantification of 2-Hydroxybutyrate in Human Serum as an Early Marker of Diabetes Mellitus.

Circulating levels of 2-hydroxybutyrate (2HB) are highly related to glycemic status in different metabolomic studies. According to recent evidence, 2HB is an early biomarker of the future development of dysglycemia and type 2 diabetes mellitus and may be causally related to the progression of normal subjects to impaired fasting glucose or insulin resistance. In the present study, we developed and validated a simple, specific and sensitive gas chromatography-mass spectrometry (GC-MS) method specifically intended to quantify serum levels of 2HB. Liquid–liquid extraction with ethyl acetate was followed by 2 min of microwave-assisted derivatization. The method presented acceptable accuracy, precision and recovery, and the limit of quantification was 5 µM. Levels of 2HB were found to be stable in serum after three freeze-thaw cycles, and at ambient temperature and at a temperature of 4 °C for up to 24 h. Extracts derivatized under microwave irradiation were stable for up to 96 h. No differences were found in 2HB concentrations measured in serum or plasma EDTA samples. In summary, the method is useful for a rapid, precise and accurate quantification of 2HB in serum samples assessed for the evaluation of dysglycemia and diabetes mellitus.

Specific and sensitive GC–MS analysis of hypusine, Nε-(4-amino-2-hydroxybutyl)lysine, a biomarker of hypusinated eukaryotic initiation factor eIF5A, and its application to the bi-ethnic ASOS study

Hypusination is a unique two-step enzymatic post-translational modification of the Nε-amino group of lysine-50 of the eukaryotic initiation factor 5A (eIF5A). We developed a specific and sensitive gas chromatography–mass spectrometry (GC–MS) method for the measurement of biological hypusine (Hyp), i.e., Nε-(4-amino-2-hydroxybutyl)lysine. The method includes a two-step derivatization of Hyp: first esterification with 2 M HCl in CH3OH (60 min, 80 °C) to the methyl ester (Me) and then acylation with penta-fluoro-propionic (PFP) anhydride in ethyl acetate (30 min, 65 °C). Esterification with 2 M HCl in CD3OD was used to prepare the internal standard. The major derivatization product was identified as the un-labelled (d0Me) and the deuterium-labelled methyl esters (d3Me) derivatives: d0Me-Hyp-(PFP)5 and d3Me-Hyp-(PFP)5, respectively. Negative-ion chemical ionization generated the most intense ions with m/z 811 for d0Me-Hyp-(PFP)5 and m/z 814 for the internal standard d3Me-Hyp-(PFP)5. Selected-ion monitoring of m/z 811 and m/z 814 was used in quantitative analyses. Free Hyp was found in spot urine samples (10 µL) of two healthy subjects at 0.60 µM (0.29 µmol Hyp/mmol creatinine) in the female and 1.80 µM (0.19 µmol Hyp/mmol creatinine) in the male subject. The mean accuracy of the method in these urine samples spiked with 1–5 µM Hyp was 91–94%. The limit of detection (LOD) of the method is 1.4 fmol Hyp. The method was applied to measure the urinary excretion rates of Hyp in healthy black (n = 38, age 7.8 ± 0.7 years) and white (n = 41, age 7.7 ± 1.0 years) boys of the Arterial Stiffness in Offspring Study (ASOS). The Hyp concentrations were 3.55 [2.68–5.31] µM (range 0.54–9.84 µM) in the black boys and 3.87 [2.95–5.06] µM (range 1.0–11.7 µM) in the white boys (P = 0.64). The creatinine-corrected excretion rates were 0.25 [0.20–0.29] µmol/mmol (range 0.11–0.36 µmol/mmol) in the black boys and 0.26 [0.21–0.30] µmol/mmol (range 0.10–0.45 µmol/mmol) in the white boys (P = 0.82). These results suggest that there is no ethnic-related difference in the ASOS population in the eIF5A modification. Remarkable differences were found between black and white boys with respect to correlations of urinary Hyp with amino acids and advanced glycation end-products of Lys, Arg and Cys. Deoxyhypusine, formally the direct precursor of Hyp, seems not to be excreted in the urine by healthy subjects.

A new core-shell magnetic mesoporous surface molecularly imprinted composite and its application as an MSPE sorbent for determination of phthalate esters.

In this study, a new core–shell magnetic mesoporous surface molecularly imprinted polymer (Fe3O4@SiO2@mSiO2-MIPs) which has specific adsorption and rapid adsorption rate for phthalate esters (PAEs) was prepared by a convenient method. Based on this composite as a magnetic solid phase extraction (MSPE) material, a rapid, efficient and sensitive matrix dispersion magnetic solid-phase extraction gas chromatography-mass spectrometry method (DMSPE-GC/MS) was developed for the determination of PAEs in multiple liquid samples. It is the first time that Fe3O4@SiO2@mSiO2-MIPs have been prepared by bonding amino groups on the surface of a double layer silicon substrate with diisononyl phthalate (DINP) as virtual template and 3-(2-aminoethyl)-aminopropyl trimethoxymethylsilane (TSD) as functional monomer. FT-IR, TEM, EDS, SEM, XRD, BET and VSM were used to characterize the composite. The adsorption isotherm and kinetics of Fe3O4@SiO2@mSiO2-MIPs showed that it possessed fast adsorption rates (approximately 5 min to reach equilibrium), high adsorption capacities (523.9 mg g−1) and good recognition of PAEs. The real samples were preconcentrated by Fe3O4@SiO2@mSiO2-MIPs, under the optimum DMSPE-GC/MS conditions. Validation experiments showed that the method presented good linearity (R2 > 0.9971), satisfactory precision (RSD < 5.7%) and high recovery (92.1–105.8%), and the limits of detection ranged from 1.17 ng L−1 to 3.03 ng L−1. The results indicated that the novel method had good sensitivity, high efficiency and wide sample application and was suitable for the determination of PAEs in liquid drink samples such as water, alcohol, beverages and so on.

A SIMPLE SENSITIVE AND RAPID GAS CHROMATOGRAPHY METHOD FOR DETECTION AND QUANTIZATION OF METFORMIN IN METFORMIN TABLET FORMULATION, BY DIRECT INJECTION, USING MASS DETECTOR

Metformin (1, 1- dimethyl biguanide) represents the “gold standard” for the treatment of diabetes mellitus type 2. Despite its important role in reducing mortality and morbidity in the diabetic population, metformin is associated with an increased risk of stroke. A simple, novel, specific, and sensitive gas chromatography-mass spectrometry method (GC-MS) for the determination of metformin was developed. Several parameters such as reaction time and temperature were optimized. There was no interfering peak from the blank at the retention time of metformin. Linearity was demonstrated over the concentration range of 4.024–24.144ppm with a coefficient of determination (R2) above 0.9999. Accuracy and precision were within acceptable limits. The method was fully validated using parameters such as specificity, linearity, limits of detection and quantification, precision, accuracy, recovery, range, robustness, and ruggedness. The developed method was successfully applied for the identification and quantification of metformin in the market tablet formulation.

Simultaneous Estimation of Genotoxic Impurities 4-Nitrobenzene Trifluoride, 4-Aminobenzene Trifluoride, and Benzo Trichloride in Cinacalcet Hydrochloride by GC-MS/MS Method

The main objective of this study is to develop and validate a novel, fast, and more sensitive gas chromatography-mass spectrometry (GC-MS/MS) method for the simultaneous estimation of 4-Nitrobenzotrifluoride (4-NBTF), 4-Amino-benzotrifluoride (4-ABTF), and Benzotrichloride (BTC) impurities in Cinacalcet hydrochloride (CH). The chromate-graphic separations were performed on a DB-624, 30m × 0.32mm × 1.8µm column with injector temperature of 150°C, and mode of injection is split with asplit ratio 1: 20. The carrier gas used was helium with a flowrate 1.5 mL/min, and theinjection load was 1.0 µL. Mass spectrometry quantitation was achieved by aquadrupole analyser with EI (Electron Ionization) ion source atasource temperature of 250ºC and interface temperature of 250ºC. The retention times for 4-NBTF, 4-ABTF, and BTC were at 6.13, 6.74and 7.64min, respectively. The calibration curve was linear over the concentration ranging from LOQ level to 150 % level with the correlation coefficient (r) of &gt; 0.99. The percentage recovery was found to be within the specified range, i.e., 70.0 to 130.0 for the three impurities. The limit of detection (LOD) was established to 0.19, 0.19, and 0.18 ppm, whereas thelimit of quantification (LOQ) was obtained to 1.14, 1.12, and 1.11 ppm for 4-NBTF, 4-ABTF, and BTC, respectively. The test solutions with impurities were found to be stable in the diluent for 24 hours. A simple GC-MS/MS method was developed and validated for simultaneous estimation of three impurities in CH. The method was accurate, precise, linear, specific, sensitive, robust, and rugged as per ICH guidelines. The method has been applied to the real-time batch analysis and found to be suitable for routine quality control analysis of CH.

Virus-induced Volatile Organic Compounds Are Detectable in Exhaled Breath during Pulmonary Infection.

Rationale: Chronic obstructive pulmonary disease (COPD) is a condition punctuated by acute exacerbations commonly triggered by viral and/or bacterial infection. Early identification of exacerbation triggers is important to guide appropriate therapy, but currently available tests are slow and imprecise. Volatile organic compounds (VOCs) can be detected in exhaled breath and have the potential to be rapid tissue-specific biomarkers of infection etiology. Objectives: To determine whether volatile organic compound measurement could distinguish viral from bacterial infection in COPD. Methods: We used serial sampling within invitro and invivo studies to elucidate the dynamic changes that occur in VOC production during acute respiratory viral infection. Highly sensitive gas chromatography-mass spectrometry techniques were used to measure VOC production from infected airway epithelial-cell cultures and in exhaled breath samples from healthy subjects experimentally challenged with rhinovirus (RV)-A16 and from subjects with COPD with naturally occurring exacerbations. Measurements and Main Results: We identified a novel VOC signature comprising decane and other long-chain alkane compounds that is induced during RV infection of cultured airway epithelial cells and is also increased in the exhaled breath from healthy subjects experimentally challenged with RV and from patients with COPD during naturally occurring viral exacerbations. These compounds correlated with the magnitude of antiviral immune responses, viral burden, and exacerbation severity but were not induced by bacterial infection, suggesting that they represent a specific virus-inducible signature. Conclusions: Our study highlights the potential for measurement of exhaled breath VOCs as rapid, noninvasive biomarkers of viral infection. Further studies are needed to determine whether measurement of these signatures could be used to guide more targeted therapy with antibiotic/antiviral agents for COPD exacerbations.

Establishment of GC–MS method for the determination of Pseudomonas aeruginosa biofilm and its application in metabolite enrichment analysis

PA forms a biofilm resistant to antibiotics, hindering antibiotics efficacy and preventing the eradication of PA, has attracted much attention for its biofilm. In this study, we first established and validated an efficient and sensitive gas chromatography-mass spectrometry (GC–MS) method for the quantification of metabolites in biofilm. Decanoic acid was used as the internal standard. The separation of Palmitic acid, stearic acid and Decanoic acid was conducted on an Elite-5 MS column (30 m × 0.25 mm, 0.25 μm) using gradient elution condition at a flow rate of 1 mL/min. Palmitic acid, stearic acid and Decanoic acid were determined under the positive ionization mode, respectively. The calibration curve of Palmitic acid and stearic acid were established in the range of 4 to 128 μg/mL (r2 = 0.999). The recovery of palmitic acid and stearic acid were between 98.76% and 113.91%, RSD ＜ 5%. The well validated method was used to detect the metabolites of Pseudomonas aeruginosa biofilm. 54 metabolites were isolated and identified from biofilm samples, and 7 important signal pathways were identified by KEGG enrichment analysis. ABC transporters and bacterial chemotaxis signaling pathways have an important impact on the growth of PA biofilm among these metabolic pathways. This study provides valuable references for the further study of PA biofilm, especially the change of metabolite content and the search for biomarkers.

HPLC-UV and GC-MS Methods for Determination of Chlorambucil and Valproic Acid in Plasma for Further Exploring a New Combined Therapy of Chronic Lymphocytic Leukemia.

High performance liquid chromatography with ultra-violet detection (HPLC-UV) and gas chromatography–mass spectrometry (GC-MS) methods were developed and validated for the determination of chlorambucil (CLB) and valproic acid (VPA) in plasma, as a part of experiments on their anticancer activity in chronic lymphocytic leukemia (CLL). CLB was extracted from 250 µL of plasma with methanol, using simple protein precipitation and filtration. Chromatography was carried out on a LiChrospher 100 RP-18 end-capped column using a mobile phase consisting of acetonitrile, water and formic acid, and detection at 258 nm. The lowest limit of detection LLOQ was found to be 0.075 μg/mL, showing sufficient sensitivity in relation to therapeutic concentrations of CLB in plasma. The accuracy was from 94.13% to 101.12%, while the intra- and inter-batch precision was ≤9.46%. For quantitation of VPA, a sensitive GC-MS method was developed involving simple pre-column esterification with methanol and extraction with hexane. Chromatography was achieved on an HP-5MSUI column and monitored by MS with an electron impact ionization and selective ion monitoring mode. Using 250 µL of plasma, the LLOQ was found to be 0.075 μg/mL. The accuracy was from 94.96% to 109.12%, while the intra- and inter-batch precision was ≤6.69%. Thus, both methods fulfilled the requirements of FDA guidelines for the determination of drugs in biological materials.

Development of a Sensitive Headspace Gas Chromatography-Mass Spectrometry Method for the Simultaneous Determination of Nitrosamines in Losartan Active Pharmaceutical Ingredients.

Nitrosamine impurities in angiotensin II receptor antagonists (sartans) containing a tetrazole group represent an urgent concern for active pharmaceutical ingredient (API) manufacturers and global regulators. Regarding safety, API manufacturers must develop methods to monitor the levels of each nitrosamine impurity before individual batch release. In this study, we developed and validated a sensitive, selective, and high-throughput method based on headspace gas chromatography–mass spectrometry (HS-GC–MS) for the simultaneous determination of four nitrosamines in losartan potassium API with simple sample preparation. N-Nitrosodimethylamine (NDMA, m/z 74), N-nitrosodiethylamine (NDEA, m/z 102), N-nitrosoethylisopropylamine (EIPNA, m/z 116), and N-nitrosodiisopropylamine (DIPNA, m/z 130) levels were quantified using an electron impact, single quadrupole mass spectrometer under a selected-ion-monitoring acquisition method. The method was validated according to the Q2(R1) ICH guidelines. The calibration curves of the assay ranged from 25 to 5000 ng/mL with limits of quantitation of 25 ppb for NDMA and NDEA and 50 ppb for DIPNA and EIPNA. The accuracy of the developed method ranged from −7.04% to 7.25%, and the precision %CV was ≤11.5. Other validation parameters, including specificity, stability, carryover, and robustness, met the validation criteria. In conclusion, the developed method was successfully applied for the determination of nitrosamines in losartan potassium APIs.

Rapid and sensitive analysis of benzyl isothiocyanate in peel, pulp, and seeds of Carica papaya Linn. by headspace gas chromatography-mass spectrometry

A rapid and sensitive headspace gas chromatography-mass spectrometry (HS-GC–MS) method was established for the determination of benzyl isothiocyanate (BITC) in the peel, pulp, and seeds of Carica papaya Linn. Tween 80 solution with a concentration of 0.002% (w/v) was chosen as a headspace medium for solving the poor solubility of BITC in water without using organic solvents and ensuring high headspace efficiencies. Extraction parameters had been evaluated and optimized by using an orthogonal design with an OA9(34) table. Optimal headspace conditions were obtained when vials were equilibrated at 80 °C for 20 min at a stirring speed of 375 rpm. The calibration curve obtained by using GC–MS was linear in a concentration range of 10–320 ng/mL. The recoveries of peel, pulp, and seeds ranged from 97.3 to 100.6% with RSDs less than 3.0%. The method is simple, rapid, sensitive, and environmentally friendly. It is suitable for analyzing BITC in papaya fruit and is expected to have important application potential in the extraction of water-insoluble volatile components in foods, plants, medicines, and other samples.

Gas chromatography–mass spectrometry for quantitative and qualitative analysis of essential oil from Curcuma wenyujin rhizomes

Objectives: A rapid and sensitive gas chromatography–mass spectrometry (GC–MS) method for quantitative and qualitative analysis of essential oil from Curcuma wenyujin rhizomes was established. Methods: The essential oil of C. wenyujin rhizomes was extracted by supercritical CO2 extraction (SFE). Six main bioactive compounds (eucalyptol, β-elemene, curzerene, germacrone, curdione, and curcumol) were analyzed in selected ion monitoring mode (SIM). Results: Curzerene is not originally present in C. wenyujin rhizomes, but is a product of the transformation of furanodiene at high temperature. The six target components demonstrated good linearity (R2 > 0.9979) over a relatively wide concentration range. The interday and intraday variations had relative standard deviation values less than 5% and the average recovery ranged from 96.95% to 100.04%. The limit of quantitation ranged from 0.032 to 0.235 μg/mL. The developed method was successfully used to analyze the six compounds in 17 samples collected from different origins. Significant variation was observed for the concentrations of the six compounds. In addition, 51 constituents were identified in C. wenyujin rhizome essential oil, consisting of 87.66% of the total essential oil, including curdione, curzerene, dehydrocurdione, germacrone, 1,4-bis(2-benzimidazoyl)benzene, neocurdione, curcumenone, and β-elemene. Conclusions: The proposed method will be useful in the quality control of C. wenyujin rhizome essential oil production.

Determination of pentazocine in urine by gas chromatography-mass spectrometry

A sensitive and specific gas chromatography-mass spectrometry (GC-MS) method using selected ion monitoring (SIM) has been developed for quantification of pentazocine in urine. This method uses solid-solid extraction (SPE) and N, O-bis (trimethylsilyl) trifluoroacetamide with 1% trimethylchlorosilane derivatization, followed by GC-MS analysis using dextromethorphan as the internal standard. The method was linear between 125 and 1500 ng/mL (r2 = 0.997). The limit of quantification and limit of detection were 125 and 62.5 ng/mL, respectively. The intraday accuracy and precision were -6.3∼4.7% and 3.6∼11.2%, respectively. The interday accuracy and precision were -7.5∼7.0% and 6.2∼10.0%, respectively. These data showed that the GC-MS method was suitable for the determination of pentazocine in urine. This method was further applied to an interlaboratory study. The collaborative study was given by the Association of Official Analytical Chemists International (AOAC International). Nine drug abuse urine testing laboratories in Taiwan participated to analyze 3 samples in duplicate. The repeatability relative standard deviation (RSDr) and reproducibility relative standard deviation (RSDR) values were 3.0∼5.2% and 6.8∼10.3%, respectively. The method showed acceptable reproducibility, as evidenced by HORRAT values of 1.1 to 1.5. The method recommended for use by the drug abuse urine testing laboratories in Taiwan.

Carbon dots based solid phase microextraction of 2-nitroaniline followed by fluorescence sensing for selective early screening and sensitive gas chromatography-mass spectrometry determination

For decades, researches have been involving in improving and optimizing solid-phase microextraction (SPME) technique to fit the growing environmental analysis demand. But it is more significant now to introduce meaningful information into the analysis line instead of improving every step in SPME. Herein, we design a carbon dots (CDs) based SPME platform and report its unique application in selective early screening and sensitive detection of 2-nitroaniline. The fluorescence quenching state of the CDs fiber after extraction could be used to prejudge whether an environmental sample contains 2-nitroaniline exceeding the maximum permitted level (30 μg L−1) regulated by the Chinese Ministry of Environmental Protection or not. Photo-induced electron transfer (PET) is believed to be the primary quenching route that leads to electron transfer from the electron-rich CDs to the electron-deficient analyte. A preliminary in vivo study on Daphnia magna and a 2-nitroaniline assay in environmental water and biofluid samples suggested the safety and the excellent qualitative ability of the proposed platform. As a result, the innovative incorporation of fluorescence sensing and SPME not only achieves the information imbedding of environmental analysis system, but also combines the advantages of two techniques including early visual-screening, reusability (≥50 times), high specificity and excellent quantitative ability (detection limit: 0.011 μg L−1). We believe this study can open new avenues in the field of environmental toxicant monitoring.

Isolation and Identification of the Scent Volatiles of the Male Kraussaria angulifera

This study presents results on the analysis of the volatile and non-volatile compounds present in the male Kraussaria angulifera. The determination of these chemicals followed a series of operations: Isolation (extraction and separation) of the target chemicals from the samples; Separation and purification of the target chemicals from co-extracted and non-target chemicals (sample clean-up); Sample concentration; Determination of target chemicals by Infra-red spectroscopic analysis and highly selective and sensitive Gas chromatography-Mass spectrometry (GC-MS).

Optimization of morphine extraction method for the assay of its urinary 3-glucuronideconjuguate by gas chromatography-mass spectrometry

In the field of doping, a great interest is carried for the analysis of morphine, a powerful narcotic analgesic opiate which use is prohibited during competitions. In order to confirm the abnormal analytical result in our anti-doping laboratory, a sensitive and selective gas chromatography-mass spectrometry (GC-MS) method was performed for the quantification of urinary morphine. As sample preparation is a key step for the determination of drugs in biological samples, the aim of this work consists of the optimization of the urinary human sample pretreatment conditions before quantification by GC/MS. Enzymatic hydrolysis associated with liquid-liquid extraction constitute the major pre-treatment steps. Our study has first focused on the optimization of the extraction solvents then to enzymatic hydrolysis which morphine is released from its glucuronide conjugated form. Onboard premiums, a study involving the effect of "amount of enzyme", "incubation temperature" and "duration of hydrolysis" was conducted. This univariate study has enabled us to evaluate the influence of each of these operating variables on the area ratio of morphine to the internal standard (Amorphine/AIS) response and to set the experimental fields for each one of them. Based on these results, an experimental design was established using the Box-Behnken model to determine, by multivariate analysis, the optimal operating conditions maximizing the "Amophine/AIS" response. After validation, the analysis of response surface makes it possible to set the optimum operating conditions, which the ratio "Amorphine/AIS" is maximized. The retained conditions for enzymatic hydrolysis are 160μl of Escherichiacoli glucuronidase enzyme during 6hours of incubation at a temperature of 36°C.The solvent mixture Methyl-t-Butyl Ether/isopropanol (4:1, v/v) was selected since it has improved morphine extraction from the urinary matrix allowing a gain of 50% when compared to that used in our routine laboratory. Our developed extraction method can be successfully applied for our forensic anti-doping analysis of morphin in human sample urine.

Development of a highly sensitive gas chromatography-mass spectrometry method preceded by solid-phase microextraction for the analysis of propofol in low-volume cerebral microdialysate samples.

To date, the commonly used intravenous anesthetic propofol has been widely studied, and fundamental pharmacodynamic and pharmacokinetic characteristics of the drug are known. However, propofol has not yet been quantified in vivo in the target organ, the human brain. Here, cerebral microdialysis offers the unique opportunity to sample propofol in the living human organism. Therefore, a highly sensitive analytical method for propofol quantitation in small sample volumes of 30 μL, based on direct immersion solid‐phase microextraction was developed. Preconcentration was followed by gas chromatographic separation and mass spectrometric detection of the compound. This optimized method provided a linear range between the lower limit of detection (50 ng/L) and 200 μg/L. Matrix‐matched calibration was used to compensate recovery issues. A precision of 2.7% relative standard deviation between five consecutive measurements and an interday precision of 6.4% relative standard deviation could be achieved. Furthermore, the permeability of propofol through a cerebral microdialysate system was tested. In summary, the developed method to analyze cerebral microdialysate samples, allows the in vivo quantitation of propofol in the living human brain. Additionally the calculation of extracellular fluid levels is enabled since the recovery of the cerebral microdialysis regarding propofol was determined.