Hollow-fiber liquid-phase microextraction of amphetamine-type stimulants in human hair samples

A fast method was optimized and validated in order to quantify amphetamine-type stimulants (amphetamine, AMP; methamphetamine, MAMP; fenproporex, FPX; 3,4-methylenedioxymethamphetamine, MDMA; and 3,4-methylenedioxyamphetamine, MDA) in human hair samples. The method was based in an initial procedure of decontamination of hair samples (50 mg) with dichloromethane, followed by alkaline hydrolysis and extraction of the amphetamines using hollow-fiber liquid-phase micro extraction (HF-LPME) in the three-phase mode. Gas chromatography-mass spectrometry (GC-MS) was used for identification and quantification of the analytes. The LoQs obtained for all amphetamines (around 0.05 ng/mg) were below the cut-off value (0.2 ng/mg) established by the Society of Hair Testing (SoHT). The method showed to be simple and precise. The intra-day and inter-day precisions were within 10.6% and 11.4%, respectively, with the use of only two deuteratecl internal standards (AMP-d5 and MDMA-d5). By using the weighted least squares linear regression (1/x(2)), the accuracy of the method was satisfied in the lower concentration levels (accuracy values better than 87%). Hair samples collected from six volunteers who reported regular use of amphetamines were submitted to the developed method. Drug detection was observed in all samples of the volunteers. (c) 2012 Elsevier B.V. All rights reserved.

LIQUID-PHASE MICROEXTRACTION FOR SIMULTANEOUS CHROMATOGRAPHIC ANALYSIS OF THREE ANTIDEPRESSANT DRUGS IN PLASMA

A method using Liquid Phase Microextraction for simultaneous detection of citalopram (CIT), paroxetine (PAR) and fluoxetine (FLU), using venlafaxine as internal standard, in plasma by high performance liquid chromatography with fluorescence detection was developed. The linearity was evaluated between 5.0 and 500 ng mL(-1) (r > 0.99) and the limit of quantification was 2.0, 3.0 and 5.0 ng mL-1 for CIT. PAR and FLU, respectively. Therefore, it can be applied to therapeutic drug monitoring, pharmacokinetics or bioavailability studies and its advantages are that it necessary relatively inexpensive equipment and sample preparation techniques.

Automated analysis of lidocaine and its metabolite in plasma by in-tube solid-phase microextraction coupled with LC-UV for pharmacokinetic study

A sensitive, selective, and reproducible in-tube solid-phase microextraction and liquid chromatographic (in-tube SPME/LC-UV) method for determination of lidocaine and its metabolite monoethylglycinexylidide (MEGX) in human plasma has been developed, validated, and further applied to pharmacokinetic study in pregnant women with gestational diabetes mellitus (GDM) subjected to epidural anesthesia. Important factors in the optimization of in-tube SPME performance are discussed, including the draw/eject sample volume, draw/eject cycle number, draw/eject flow rate, sample pH, and influence of plasma proteins. The limits of quantification of the in-tube SPME/LC method were 50 ng/mL for both metabolite and lidocaine. The interday and intraday precision had coefficients of variation lower than 8%, and accuracy ranged from 95 to 117%. The response of the in-tube SPME/LC method for analytes was linear over a dynamic range from 50 to 5000 ng/mL, with correlation coefficients higher than 0.9976. The developed in-tube SPME/LC method was successfully used to analyze lidocaine and its metabolite in plasma samples from pregnant women with GDM subjected to epidural anesthesia for pharmacokinetic study.

Solid phase microextraction and LC-MS/MS for the determination of paliperidone after stereoselective fungal biotransformation of risperidone

The present work describes for the first time the use of SPME coupled to LC-MS/MS employing the polar organic mode in a stereoselective fungal biotransformation study to investigate the fungi ability to biotransform the drug risperidone into its chiral and active metabolite 9-hydroxyrisperidone (9-RispOH). The chromatographic separation was performed on a Chiralcel OJ-H column using methanol:ethanol (50:50, v/v) plus 0.2% triethylamine as the mobile phase at a flow rate of 0.8 mL min(-1). The SPME process was performed using a C18 fiber, 30 min of extraction time and 5 min of desorption time in the mobile phase. The method was completely validated and all parameters were in agreement with the literature recommendations. The Cunninghamella echinulata fungus was able to biotransform risperidone into the active metabolite, (+)-9-RispOH, resulting in 100% of enantiomeric excess. The Cunninghamella elegans fungus was also able to stereoselectively biotransform risperidone into (+)- and (-)-9-RispOH enantiomers at different rates. (C) 2012 Elsevier B.V. All rights reserved.

Determination of anticonvulsants in human plasma using SPME in a heated interface coupled online to liquid chromatography (SPME-LC)

A simple and sensitive method using solid phase microextraction (SPME) and liquid chromatography (LC) with heated online desorption (SPME-LC) was developed and validated to analyze anticonvulsants (AEDs) in human plasma samples. A heated lab-made interface chamber was used in the desorption procedure, which allowed the transference of the whole extracted sample. The SPME conditions were optimized by applying an experimental design. Important factors are discussed such as fiber coating types, pH, extraction time and desorption conditions. The drugs were analyzed by LC, using a C18 column (150 mm x 4.6 mm x 5 mm); and 50 mmol L-1, pH 5.50 ammonium acetate buffer : acetonitrile : methanol (55 : 22 : 23 v/v) as the mobile phase with a flow rate of 0.8 mL min(-1). The suggested method presented precision (intra-assay and inter-assay), linearity and limit of quantification (LOQ) all adequate for the therapeutic drug monitoring (TDM) of AEDs in plasma.

Liquid-phase microextraction for simultaneous chromatographic analysis of three antidepressant drugs in plasma

A method using Liquid Phase Microextraction for simultaneous detection of citalopram (CIT), paroxetine (PAR) and fluoxetine (FLU), using venlafaxine as internal standard, in plasma by high performance liquid chromatography with fluorescence detection was developed. The linearity was evaluated between 5.0 and 500 ng mL-1 (r > 0.99) and the limit of quantification was 2.0, 3.0 and 5.0 ng mL-1 for CIT, PAR and FLU, respectively. Therefore, it can be applied to therapeutic drug monitoring, pharmacokinetics or bioavailability studies and its advantages are that it necessary relatively inexpensive equipment and sample preparation techniques.

Characterization of volatile composition of Laurencia dendroidea by gas chromatography-mass spectrometry

In this study we report the characterization of the volatile compounds of Laurencia dendroidea. Solvent extracts (dichloromethane and methanol), hydrodistillation extracts and headspace solid-phase microextraction samples were obtained and analyzed by GC-MS. Forty-six volatile components were identified in L. dendroidea, among them hydrocarbons, alcohols, phenols, aldehydes, ketones, acids, esters and terpenes.

Application of headspace solid phase microextraction to qualitative and quantitative analysis of tobacco additives in cigarettes

Cigarettes may contain up to 10% by weight additives which are intended to make them more attractive. A fast and rugged method for a cigarette-screening for additives with medium volatility was developed using automatic headspace solid phase microextraction (HS-SPME) with a 65 microm carbowax-divinylbenzene fiber and gas chromatography-mass spectrometry (GC-MS) with standard electron impact ionisation. In three runs, each cigarette sample was extracted in closed headspace vials using basic, acidic and neutral medium containing 0.5 g NaCl or Na2SO4. Furthermore, the method was optimized for quantitative determination of 17 frequently occurring additives. The practical applicability of the method was demonstrated for cigarettes from 32 brands.

Photophysics and photochemistry of azole fungicides: triadimefon and triadimenol

Photophysics and photochemistry of pesticides triadimefon {1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butanone} and triadimenol {1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butan-2-ol} were studied in the solution. The excited singlet states were identified by comparison with the absorption spectra of adequate model compounds, in several solvents. The first excited singlet state of triadimefon is an n, pi* state localized on the carbonyl group, while higher excited states are localized on the chlorophenoxy group and have a pi, pi* character. The lowest singlet state of triadimenol is pi, pi* state, since a methoxyl group replaces the carbonyl group of triadimefon. Triadimefon shows a weak fluorescence from the n, pi* state, upon excitation at both 310 and 250 nm. This suggests a fast intramolecular energy transfer process from the localized pi, pi* state of the chlorophenoxy group to the n, pi* state of the carbonyl group. The photodegradation quantum yield of triadimefon in cyclohexane at 313 run is 0.022. Triadimenol is photostable, under the same conditions. Two major photodegradation products of triadimefon and triadimenol were identified: 4-chlorophenol and 1,2,4-triazole. 4-Chlorophenoxyl radicals were detected by flash photolysis, suggesting a homolytic cleavage of the C-O bond of the asymmetric carbon. (C) 2001 Elsevier Science B.V. All rights reserved.

High-performance liquid chromatography (HPLC) and high-performance liquid chromatography mass spectrometry (HPLC/MS) for the analysis of date rape drugs

The drugs studied in this work have been reportedly used to commit drug-facilitated sexual assault (DFSA), commonly known as "date rape". Detection of the drugs was performed using high-performance liquid chromatography with ultraviolet detection (HPLC/UV) and identified with high performance-liquid chromatography mass spectrometry (HPLC/MS) using selected ion monitoring (SIM). The objective of this study was to develop a single HPLC method for the simultaneous detection, identification and quantitation of these drugs. The following drugs were simultaneously analyzed: Gamma-hydroxybutyrate (GHB), scopolamine, lysergic acid diethylamide, ketamine, flunitrazepam, and diphenhydramine. The results showed increased sensitivity with electrospray (ES) ionization versus atmospheric pressure chemical ionization (APCI) using HPLC/MS. HPLC/ES/MS was approximately six times more sensitive than HPLC/APCI/MS and about fifty times more sensitive than HPLC/UV. A limit of detection (LOD) of 100 ppb was achieved for drug analysis using this method. The average linear regression coefficient of correlation squared (r2) was 0.933 for HPLC/UV and 0.998 for HPLC/ES/MS. The detection limits achieved by this method allowed for the detection of drug dosages used in beverage tampering. This method can be used to screen beverages suspected of drug tampering. The results of this study demonstrated that solid phase microextraction (SPME) did not improve sensitivity as an extraction technique when compared to direct injections of the drug standards.

Quantification of free auxins in semi-hardwood plant cuttings and microshoots by dispersive liquid–liquid microextraction/microwave derivatization and GC/MS analysis

Several studies have suggested that differences in the natural rooting ability of plant cuttings could be attributed to differences in endogenous auxin levels. Hence, during rooting experiments, it is important to be able to routinely monitor the evolution of endogenous levels of plant hormones. This work reports the development of a new method for the quantification of free auxins in auxin-treated Olea europaea (L.) explants, using dispersive liquid–liquid microextraction (DLLME) and microwave assisted derivatization (MAD) followed by gas chromatography/mass spectrometry (GC/MS) analysis. Linear ranges of 0.5–500 ng mL 1 and 1–500 mg mL 1 were used for the quantification of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), respectively. Determined by serial dilutions, the limits of detection (LOD) and quantification (LOQ) were 0.05 ng mL 1 and 0.25 ng mL 1, respectively for both compounds. When using the calibration curve for determination, the LOQ corresponded to 0.5 ng mL 1 (IAA) and 0.5 mg mL 1 (IBA). The proposed method proved to be substantially faster than other alternatives, and allowed free auxin quantification in real samples of semi-hardwood cuttings and microshoots of two olive cultivars. The concentrations found in the analyzed samples are in the range of 0.131–0.342 mg g 1 (IAA) and 20–264 mg g 1 (IBA).

Fingerprinting of complex mixtures with the use of high performance liquid chromatography, inductively coupled plasma atomic emission spectroscopy and chemometrics

The molecular and metal profile fingerprints were obtained from a complex substance, Atractylis chinensis DC—a traditional Chinese medicine (TCM), with the use of the high performance liquid chromatography (HPLC) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) techniques. This substance was used in this work as an example of a complex biological material, which has found application as a TCM. Such TCM samples are traditionally processed by the Bran, Cut, Fried and Swill methods, and were collected from five provinces in China. The data matrices obtained from the two types of analysis produced two principal component biplots, which showed that the HPLC fingerprint data were discriminated on the basis of the methods for processing the raw TCM, while the metal analysis grouped according to the geographical origin. When the two data matrices were combined into a one two-way matrix, the resulting biplot showed a clear separation on the basis of the HPLC fingerprints. Importantly, within each different grouping the objects separated according to their geographical origin, and they ranked approximately in the same order in each group. This result suggested that by using such an approach, it is possible to derive improved characterisation of the complex TCM materials on the basis of the two kinds of analytical data. In addition, two supervised pattern recognition methods, K-nearest neighbors (KNNs) method, and linear discriminant analysis (LDA), were successfully applied to the individual data matrices—thus, supporting the PCA approach.

Metabolic urinary profiling of alcohol hepatotoxicity and intervention effects of Yin Chen Hao Tang in rats using ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry

This paper was designed to study metabonomic characters of the hepatotoxicity induced by alcohol and the intervention effects of Yin Chen Hao Tang (YCHT), a classic traditional Chinese medicine formula for treatment of jaundice and liver disorders in China. Urinary samples from control, alcohol- and YCHT-treated rats were analyzed by ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry (UPLC/ESI-QTOF-MS) in positive ionization mode. The total ion chromatograms obtained from the control, alcohol- and YCHT-treated rats were easily distinguishable using a multivariate statistical analysis method such as the principal components analysis (PCA). The greatest difference in metabolic profiling was observed from alcohol-treated rats compared with the control and YCHT-treated rats. The positive ions m/z 664.3126 (9.00 min) was elevated in urine of alcohol-treated rats, whereas, ions m/z 155.3547 (10.96 min) and 708.2932 (9.01 min) were at a lower concentration compared with that in urine of control rats, however, these ions did not indicate a statistical difference between control rats and YCHT-treated rats. The ion m/z 664.3126 was found to correspond to ceramide (d18:1/25:0), providing further support for an involvement of the sphingomyelin signaling pathway in alcohol hepatotoxicity and the intervention effects of YCHT.