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1.
Diels-Alder reactions of a range of 1-(alkoxy/alkyl-substituted phenyl)buta-1,3-dienes with methyl vinyl ketone and methyl acrylate carried out in ethanol as the reaction medium under 9 kbar pressure were investigated. The use of high pressure as the activating method of the Diels-Alder reactions allows the efficient and endodiastereoselective generation of a series of cis-cyclohexenyl-benzene cycloadducts, which are selectively converted into their trans-epimers. The cis-cyclohexenyl-benzenes and trans-cyclohexenyl-benzenes produced are useful precursors for accessing substituted privileged cis-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene and trans-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene skeletons. The total syntheses of Δ(9)-cis-tetrahydrocannabinol (THC) and Δ(9)-trans-THC, through the use of selected Diels-Alder adducts, are described. Finally, a route for obtaining Δ(9)-trans-THC in both enantiomeric pure forms based on the (S)-(-)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP)-hydrazone method is also reported. 相似文献
2.
Lott S Henrion A Malz F Kessler A Güttler B Aderjan R 《Analytical and bioanalytical chemistry》2008,391(3):1003-1010
An isotope dilution gas chromatography/mass spectrometry (ID-GC/MS) reference measurement procedure for Δ9-tetrahydrocannabinol
(THC) in serum was developed and validated. The method complies with the concept of a ratio primary reference measurement
procedure. The uncertainty was determined for two concentrations of THC in serum (1 ng/mL and 2.4 ng/mL). The calculation
procedure is based on the Guide to the Expression of Uncertainty in Measurement (GUM). The relative expanded uncertainty was found to be less than 2% for both concentration levels, corresponding to a 95%
confidence interval. For the reference method, it was shown that the measurement of THC within the concentration range covered
by the current threshold values is very accurate. The method has the potential to provide traceability for the methods used
in practical forensics. 相似文献
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S. Ameur B. Haddou Z. Derriche J. P. Canselier C. Gourdon 《Analytical and bioanalytical chemistry》2013,405(10):3117-3123
A cloud point extraction coupled with high performance liquid chromatography (HPLC/UV) method was developed for the determination of Δ9-tetrahydrocannabinol (THC) in micellar phase. The nonionic surfactant “Dowfax 20B102” was used to extract and pre-concentrate THC from cannabis resin, prior to its determination with a HPLC–UV system (diode array detector) with isocratic elution. The parameters and variables affecting the extraction were investigated. Under optimum conditions (1 wt.% Dowfax 20B102, 1 wt.% Na2SO4, T?=?318 K, t?=?30 min), this method yielded a quite satisfactory recovery rate (~81 %). The limit of detection was 0.04 μg?mL?1, and the relative standard deviation was less than 2 %. Compared with conventional solid–liquid extraction, this new method avoids the use of volatile organic solvents, therefore is environmentally safer. 相似文献
5.
《Analytical letters》2012,45(12):917-930
Abstract A technique capable of determining both Δ9-tetrahydrocannabinol and 11-hydroxy-Δ9-tetrahydrocannabinol is described. The method is based on the reactivity of the phenolic functionality common to both compounds, and is sensitive to 5 ng of Δ9-tetrahydrocannabinol and 1 ng of 11-hydroxy-Δ9-tetrahydrocannabinol per ml of plasma. 相似文献
6.
The detection and confirmation of cannabinoids in oral fluid are important in forensic toxicology. Currently, the presence
of Δ9-tetrahydrocannabinol (THC) is used for the detection of cannabis in oral fluid. A low concentration of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) is found in oral fluid, which suggested a convenient and low-sensitivity confirmation assay
can be used in a routine forensic laboratory. In this study, a highly sensitive isotope dilution liquid chromatography–tandem
mass spectrometry method following dansylation was successfully developed for simultaneous determination of THC and THC-COOH
in oral fluid. The dansylated derivatives dramatically demonstrated and enhanced the sensitivity of THC and THC-COOH. To avoid
signal influenced by the matrix, a 5-min liquid chromatography gradient program was evaluated and optimized, which reduced
the sample diffusion and caused sharp peaks (less than 12 s) and thus helped to achieve detection at a low level. The sensitivity,
accuracy, and precision were also evaluated, and high quantitative accuracy and precision were obtained. The limit of quantitation
of this approach was 25 pg/mL for THC and 10 pg/mL for THC-COOH in oral fluid. Finally, the method was successfully applied
to eight suspected cannabis users. Among them, in six oral fluid samples THC-COOH was determined at a concentration from 13.1
to 47.2 pg/mL. 相似文献
7.
Large-scale quantum and molecular mechanical methods (QM/MM) and QM calculations were carried out on the soluble Δ(9) desaturase (Δ(9)D) to investigate various structural models of the spectroscopically defined peroxodiferric (P) intermediate. This allowed us to formulate a consistent mechanistic picture for the initial stages of the reaction mechanism of Δ(9)D, an important diferrous nonheme iron enzyme that cleaves the C-H bonds in alkane chains resulting in the highly specific insertion of double bonds. The methods (density functional theory (DFT), time-dependent DFT (TD-DFT), QM(DFT)/MM, and TD-DFT with electrostatic embedding) were benchmarked by demonstrating that the known spectroscopic effects and structural perturbation caused by substrate binding to diferrous Δ(9)D can be qualitatively reproduced. We show that structural models whose spectroscopic (absorption, circular dichroism (CD), vibrational and M?ssbauer) characteristics correlate best with experimental data for the P intermediate correspond to the μ-1,2-O(2)(2-) binding mode. Coordination of Glu196 to one of the iron centers (Fe(B)) is demonstrated to be flexible, with the monodentate binding providing better agreement with spectroscopic data, and the bidentate structure being slightly favored energetically (1-10 kJ mol(-1)). Further possible structures, containing an additional proton or water molecule are also evaluated in connection with the possible activation of the P intermediate. Specifically, we suggest that protonation of the peroxide moiety, possibly preceded by water binding in the Fe(A) coordination sphere, could be responsible for the conversion of the P intermediate in Δ(9)D into a form capable of hydrogen abstraction. Finally, results are compared with recent findings on the related ribonucleotide reductase and toluene/methane monooxygenase enzymes. 相似文献
8.
Dorota Czajkowska 《Tetrahedron letters》2009,50(24):2904-2907
Metathesis reactions of Δ22-steroids are studied. The cross metathesis reactions of model Δ22-steroids with excess of simple alkenes are sluggish or do not occur at all. In contrast, derivatives of both trans- and cis-Δ22-cholesterol undergo ring closing metathesis reactions but the former reacts faster. However, the side chain double bond in stigmasterol and ergosterol is too crowded for metathesis reactions promoted by currently available catalysts. 相似文献
9.
Jack Henion Changtong Hao Daniel Eikel Olof Beck Peter Stambeck 《Journal of mass spectrometry : JMS》2024,59(1):e4987
Increased acceptance of cannabis containing the psychoactive component, Δ9-tetrahydrocannabinol (THC), raises concerns about the potential for impaired drivers and increased highway accidents. In contrast to the “breathalyzer” test, which is generally accepted for determining the alcohol level in a driver, there is no currently accepted roadside test for THC in a motorist. There is a need for an easily collectible biological sample from a potentially impaired driver coupled with an accurate on-site test to measure the presence and quantity of THC in a driver. A novel breath collection device is described, which includes three separate sample collectors for collecting identical A, B, and C breath samples from a subject. A simple one-step ethanol extraction of the “A” breath collector sample can be analyzed by UHPLC/selected ion monitoring (SIM) liquid chromatography/mass spectrometry (LC/MS) to provide qualitative and quantitative determination of THC in breath sample in less than 4 min for samples collected up to 6 h after smoking a cannabis cigarette. SIM LC/MS bioanalyses employed d3-THC as the stable isotope internal standard fortified in negative control breath samples for quantitation including replicates of six calibrator standards and three quality control (QC) samples. Subsequent confirmation of the same breath sample in the B collectors was then confirmed by a reference lab by LC/MS/MS analysis. Fit-for-purpose bioanalytical validation consistent with pharmaceutical regulated bioanalyses produced pharmacokinetic (PK) curves for the two volunteer cannabis smokers. These results produced PK curves, which showed a rapid increase of THC in the breath of the subjects in the first hour followed by reduced THC levels in the later time points. A simpler single-point calibration curve procedure with calibrators and QC prepared in ethanol provided similar results. Limitations to this approach include the higher cost and operator skill sets for the instrumentation employed and the inability to actually determine driver impairment. 相似文献
10.
For the detection of the major active component of cannabis, Δ9-tetrahydrocannabinol (THC) in aqueous samples, a homogeneous competitive immunoassay based on fluorescence quenching induced by fluorescence resonance energy transfer (FRET) has been developed. The fluorescence of anti-THC-antibody, labeled with fluorescence dye DY-481XL, can be quenched after its binding to THC-BSA-quencher conjugate (bovine serum albumin coupled with THC and another fluorescence dye, DYQ-661, as quencher). This quenching effect is inhibited when the antibodies bind to free THC in aqueous sample, thus competing for binding sites with the THC-BSA-quencher conjugate. The extent of the inhibition corresponds to the concentration of THC in the samples. The assay principle is simple and the test duration is within 10 min. The detection limit for THC in buffer was 2 ng mL−1. In pooled saliva samples a detection limit of 50 ng mL−1 was achieved. 相似文献
11.
Chongxiao Tan Nenad Gajovic-Eichelmann Rainer Polzius Niko Hildebrandt Frank F. Bier 《Analytical and bioanalytical chemistry》2010,398(5):2133-2140
The detection of the major active component of cannabis, Δ9-tetrahydrocannabinol (THC), becomes increasingly relevant due
to its widespread abuse. For control purposes, some easy-to-use, sensitive and inexpensive test methods are needed. We have
developed a fluorescence immunoassay utilising THC–fluorescein conjugate as tracer. Fluorescence spectroscopy of the conjugate
revealed an unusual property: The relatively weak fluorescence of a dilute tracer solution was increased by a factor of up
to 5 after binding of a THC-specific antibody. Fluorescence lifetime measurements in aqueous solutions suggested two different
tracer conformations both associated with quenching of fluorescein fluorescence by the intramolecular THC moiety. After antibody
binding, the tracer enters a third conformation in which fluorescence quenching of fluorescein is completely suppressed. Utilising
this property, we established a homogeneous competitive immunoassay (homogeneous increasing fluorescence immunoassay) with
low detection limits. The test requires only two reagents, the new tracer molecule and an anti-THC antibody. A single test
takes only 8 min. The dynamic detection range for THC is 0.5 to 20 ng/mL in buffer, with a limit of detection (LOD) of 0.5 ng/mL.
The test also works in diluted saliva samples (1:10 dilution with buffer) with an LOD of 2 ng/mL and a dynamic range of 2–50 ng/mL. 相似文献
12.
Rudolf Brenneisen Pascale Meyer Haithem Chtioui Martial Saugy Matthias Kamber 《Analytical and bioanalytical chemistry》2010,396(7):2493-2502
Since 2004, cannabis has been prohibited by the World Anti-Doping Agency for all sports competitions. In the years since then,
about half of all positive doping cases in Switzerland have been related to cannabis consumption. In doping urine analysis,
the target analyte is 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), the cutoff being 15 ng/mL. However, the wide urinary detection window of the long-term metabolite
of Δ9-tetrahydrocannabinol (THC) does not allow a conclusion to be drawn regarding the time of consumption or the impact on the
physical performance. The purpose of the present study on light cannabis smokers was to evaluate target analytes with shorter
urinary excretion times. Twelve male volunteers smoked a cannabis cigarette standardized to 70 mg THC per cigarette. Plasma
and urine were collected up to 8 h and 11 days, respectively. Total THC, 11-hydroxy-Δ9-tetrahydrocannabinol (THC-OH), and THC-COOH were determined after hydrolysis followed by solid-phase extraction and gas chromatography/mass
spectrometry. The limits of quantitation were 0.1–1.0 ng/mL. Eight puffs delivered a mean THC dose of 45 mg. Plasma levels
of total THC, THC-OH, and THC-COOH were measured in the ranges 0.2–59.1, 0.1–3.9, and 0.4–16.4 ng/mL, respectively. Peak concentrations
were observed at 5, 5–20, and 20–180 min. Urine levels were measured in the ranges 0.1–1.3, 0.1–14.4, and 0.5–38.2 ng/mL,
peaking at 2, 2, and 6–24 h, respectively. The times of the last detectable levels were 2–8, 6–96, and 48–120 h. Besides high
to very high THC-COOH levels (245 ± 1,111 ng/mL), THC (3 ± 8 ng/mL) and THC-OH (51 ± 246 ng/mL) were found in 65 and 98% of
cannabis-positive athletes’ urine samples, respectively. In conclusion, in addition to THC-COOH, the pharmacologically active
THC and THC-OH should be used as target analytes for doping urine analysis. In the case of light cannabis use, this may allow
the estimation of more recent consumption, probably influencing performance during competitions. However, it is not possible
to discriminate the intention of cannabis use, i.e., for recreational or doping purposes. Additionally, pharmacokinetic data
of female volunteers are needed to interpret cannabis-positive doping cases of female athletes. 相似文献
13.
Six voltaic cells have been evaluated for their suitability in the determination of thermodynamic parameters. The cells were prepared with all species present at conditions that approximate standard-state conditions and cell potentials were measured as a function of temperature. From these measurements graphs of voltage versus temperature were prepared. From these graphs it was possible to determine the standard heats of reaction (IIrxn), standard change in entropy or disorder (S°rxn), and the Gibbs free energy (G°rxn) for the spontaneous oxidation-reduction reactions. The standard cell potential (E°cell values were also calculated. Two cells with opposite temperature dependence of the cell potential were found to produce good agreement with the literature values of G°rxn, H°rxn, S°rxn and E°cell. Criteria for identifying additional cells that may be suitable for potentiometric studies of thermodynamic parameters are also included. 相似文献
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E. Lendoiro A. de Castro H. Fernández-Vega M. C. Cela-Pérez J. M. López-Vilariño M. V. González-Rodríguez A. Cruz M. López-Rivadulla 《Analytical and bioanalytical chemistry》2014,406(15):3589-3597
The use of molecularly imprinted polymers (MIPs) for solid phase extraction (MISPE) allows a rapid and selective extraction compared with traditional methods. Determination of Δ9-tetrahydrocannabinol (THC) and 11-nor-Δ9-tetrahydrocannabinol carboxylic acid (THC-COOH) in oral fluid (OF) and urine was performed using homemade MISPEs for sample clean-up and liquid chromatography tandem mass spectrometry (LC-MS/MS). Cylindrical MISPE shaped pills were synthesized using catechin as a mimic template. MISPEs were added to 0.5 mL OF or urine sample and sonicated 30 min for adsorption of analytes. For desorption, the MISPE was transfered to a clean tube, and sonicated for 15 min with 2 mL acetone:acetonitrile (3:1, v/v). The elution solvent was evaporated and reconstituted in mobile phase. Chromatographic separation was performed using a SunFire C18 (2.5 μm; 2.1?×?20 mm) column, and formic acid 0.1 % and acetonitrile as mobile phase, with a total run time of 5 min. The method was fully validated including selectivity (no endogenous or exogenous interferences), linearity (1–500 ng/mL in OF, and 2.5–500 ng/mL in urine), limit of detection (0.75 and 1 ng/mL in OF and urine, respectively), imprecision (%CV <12.3 %), accuracy (98.2–107.0 % of target), extraction recovery (15.9–53.5 %), process efficiency (10.1–46.2 %), and matrix effect (<?55 %). Analytes were stable for 72 h in the autosampler. Dilution 1:10 was assured in OF, and Quantisal? matrix effect showed ion suppression (<?80.4 %). The method was applied to the analysis of 20 OF and 11 urine specimens. This is the first method for determination of THC and THC-COOH in OF using MISPE technology. 相似文献
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Tian K Hu D Hu R Wang S Li S Li Y Yang G 《Chemical communications (Cambridge, England)》2011,47(36):10052-10054
A highly luminescent compound, stilbene-2,4-dimethyl-6-(1,2,2,4-tetramethyl-1,2-dihydroquinolin-6-yl)-1,3,5-s-triazine (MQT), exhibits solvent polarity-induced emission enhancement. A fluorescent sensor array was fabricated with MQT and porous polymer substrates. The colorimetric changes of the array exposed to VOCs can be readily distinguished by the naked eye. Post-processing procedures proved the high selectivity of the array for VOCs. 相似文献
19.
Standard Gibbs free energies, enthalpies, and entropies for the dissociation of various aliphatic carboxylic acids are obtained through potnetiometric and calorimetric measurements in water-tert-butyl alcohol mixtures. Results are discussed in terms of solvent structural effects for the proton exchange reaction and in terms of the compensation law to explain enthalpic and entropic effects.Part I, ref 4; Part II,Thermochimica Acta
6, 283 (1973). 相似文献