SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences

28

Substituted imidazoles recently came under scrutiny as they may be indirectly introduced into cola beverages via the use of class IV (E150d) caramel colours and may pose health hazards. A LC/MS/MS method was developed for determining 2- and 4-methylimidazole (2-MI, 4-MI) and 2-acetyl-4-(1,2,3,4)-tetrahydroxybutylimidazole (THI) in beverages and caramel colours. The method is very rapid and easy to conduct as it requires only dilution in eluent for sample preparation. For 4-MI, the recovery was between 94 and 102% for spiked cola samples. The limit of detection was 2μg/L in the measuring solution (corresponding to 40μg/L for cola samples diluted 1:20 during sample preparation). 97 cola samples and 13 caramel colours from Germany and France were analysed. From the 3 analytes, only 4-MI was found in the samples with very varying concentrations (non quantifiable traces to 0.6mg/L in colas and 175-658mg/kg in E150d). The exposure for cola drinkers in worst case scenarios is estimated to be 2-5μg/kg bodyweight/day, which is judged as being only a low risk for public health.

Concepts: Measurement, Analytical chemistry, Dilution, Cola

28

Fesoterodine is a non-selective muscarinic-receptor antagonist, used in the treatment of overactive bladder syndrome. A highly sensitive, selective and rapid method has been developed for the simultaneous determination of fesoterodine and its active metabolite, 5-hydroxymethyl tolterodine (5-HMT) in human plasma by liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Due to rapid conversion of parent drug to 5-HMT, ex vivo stability of fesoterodine in human plasma was extensively studied to optimize the extraction protocol. The analytes and their deuterated analogs were quantitatively extracted from 100μL human plasma by liquid-liquid extraction in methyl tert-butyl ether: n-hexane. The chromatographic separation of analytes was achieved on a Kromasil C18 (100mm×4.6mm, 5μm) column under isocratic conditions. The method was validated over a dynamic concentration range of 0.01-10ng/mL for both the analytes. Ion-suppression effects were investigated by post-column infusion of analytes. The precision (% CV) values for the calculated slopes of calibration curves, which would reflect the relative matrix effect, were less than 1.5% for both the analytes. The intra-batch and inter-batch precision (% CV) across quality control levels varied from 1.82 to 3.73% and the mean extraction recovery was >96% for both the analytes. The method was successfully applied to a bioequivalence study of 8mg fesoterodine tablet formulation (test and reference) in 12 healthy Indian subjects under fasted and fed condition. The assay reproducibility estimated by reanalysis of incurred samples showed a change of ±12.0%.

Concepts: Scientific method, Mass spectrometry, Urology, Sociology, Chromatography, Overactive bladder, Liquid chromatography-mass spectrometry, Bioequivalence

28

Tamsulosin, a selective α(1)-adrenoceptor antagonist, is used for the treatment of benign prostatic hyperplasia (BPH). We developed and validated a rapid, sensitive, and simplified liquid chromatography analytical method utilizing tandem mass spectrometry (LC-MS/MS) for the determination of tamsulosin in human plasma. After liquid-liquid extraction with methyl t-butyl ether, chromatographic separation of tamsulosin was achieved using a reversed-phase Luna C(18) column (2.0mm×50mm, 5μm particles) with a mobile phase of 10mM ammonium formate buffer (pH 3.5)-methanol (25:75, v/v) and quantified by MS/MS detection in ESI positive ion mode. The flow rate of the mobile phase was 200μL/min and the retention times of tamsulosin and the internal standard (IS, diphenhydramine) were 0.8 and 0.9min, respectively. The calibration curves were linear over a range of 0.01-20ng/mL (r>0.999). The lower limit of quantification using 500μL of human plasma was 0.01ng/mL. The mean accuracy and precision for intra- and inter-day validation of tamsulosin were both within acceptable limits. The present LC-MS/MS method showed improved sensitivity for quantification of tamsulosin in human plasma compared with previously described analytical methods. The validated method was successfully applied to a pharmacokinetic study in humans.

Concepts: Mass spectrometry, Chromatography, Analytical chemistry, Gas chromatography, Benign prostatic hyperplasia, Chromatography in blood processing, Tandem mass spectrometry, Tamsulosin

28

Herbal smoking mixtures which are sold as incense or potpourri and often referred to as ‘Spice’ are actually inactive plant matter adulterated with alkylamino indole based synthetic cannabinoids such as JWH-018 and JWH-073. Due to the inclusion of five synthetic cannabinoids, including JWH-018 and JWH-073, as Schedule I drugs by the Drug Enforcement Agency (DEA) in March 2011, it has become necessary for forensic laboratories to develop analytical methods to test for the presence of metabolites of synthetic cannabinoids. When a new analyte of interest emerges, most laboratories strive to develop a sample preparation procedure and validate an analytical method as quickly as possible and therefore, rely on effective but time consuming traditional protocols such as solid phase and liquid-liquid extraction. This research focuses on the examination of all aspects of sample preparation and analytical method development to streamline the analysis of four urinary metabolites of JWH-018 and JWH-073. A detailed evaluation of the β-glucuronide hydrolysis step lead to the reduction of time required for hydrolysis from 1h at 50°C to only 10min at room temperature. By utilizing a salting-out assisted liquid-liquid extraction (SALLE) in place of traditional liquid-liquid extraction with a volatile solvent, processing time was saved and waste was reduced. The analysis run time was also shortened to one-third of a typical published run time by utilizing UPLC with isocratic conditions in place of conventional HPLC running a gradient method.

Concepts: Solubility, Benzene, Analytical chemistry, Diethyl ether, Cannabinoid, Cannabinoids, HU-210, Drug Enforcement Administration

27

A sensitive and accurate method based on the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous determination of eight illegal synthetic dyes (Sudan (I-IV), Para Red, Rhodamine B, Chrysoidin and Auramine O) in chili products. A simple sample treatment procedure entailing the use of an extraction step with acetonitrile/H2O (9/1) without further cleanup was developed. HPLC was performed on a C18 column using a multistep gradient elution with 5mM ammonium acetate (pH 3.0 with formic acid) and methanol as the mobile phase. Mass spectral acquisition was done in multiple reaction monitoring (MRM) mode using positive electrospray ionization (ESI). Linear calibrations were obtained with correlation coefficients R(2)>0.99. Limit of detection (LOD) and limit of quantification (LOQ) for the studied dyes were in the ranges of 0.05-0.6μgkg(-1) and 0.3-3.0μgkg(-1) depending on matrices, respectively. The recoveries of the eight synthetic dyes in five matrices ranged from 70.5% to 119.2%. The intra- and inter-day precisions (RSDs) were between 2.3-15.8% and 5.7-15.6%, respectively. The applicability of the method to the determination of eight banned dyes in chili products was demonstrated.

Concepts: Mass spectrometry, Measurement, Analytical chemistry, Acetic acid, Detection limit, Liquid chromatography-mass spectrometry, Rhodamine, Rhodamine dyes

27

The analysis of biomedical samples such as urine and blood can provide evidence of exposure to chemicals for a range of applications including occupational exposure monitoring, detection of drugs of abuse, performance enhancement in sport and investigations of poisoning and incapacitation. This paper reports the development of an analytical method for two suspected urinary metabolites of the riot control agent 2-chlorobenzylidene malononitrile (CS): 2-chlorohippuric acid and 2-chlorobenzyl-N-acetylcysteine. 2-Chlorohippuric acid was identified in all 2h post-exposure samples from a set of urine samples taken from army recruits exposed to low levels of thermally dispersed CS during training. 2-Chlorobenzyl-N-acetylcysteine, a metabolite known to be formed in the rat, was not identified in any of the samples. The lower limit of detection (LLOD) for 2-chlorohippuric acid and 2-chlorobenzyl-N-acetylcysteine was 1ng/ml and 0.5ng/ml in pooled urine from the pre-exposed subjects. 2-Chlorohippuric acid was rapidly excreted but was detectable in the urine of 17 of the 19 subjects tested 20h after exposure.

Concepts: Drug addiction, Riot, Pepper spray, CS gas, Riot control, Water cannon

27

Ultrasound-assisted emulsification microextraction (USAE-ME) procedure coupled with UV-vis spectrophotometric measurement has been developed for determination of thiocyanate ion (SCN(-)) in water and biological fluids samples. The method is based on protonation of SCN(-) ions in acidic medium and extraction of thiocyanic acid into fine droplets of chloroform as an extraction solvent contains rhodamine B (RhB). The RhB was protonated in presence of thiocynanic acid to form highly colored ion-pair complex of [thiocynate][RhBH(+)] in chloroform, which used for subsequent spectrophotometric determination of SCN(-) ions. Experimental parameters for both spectrophotometric reaction and USAE-ME procedure have been optimized. Under optimized conditions the calibration curve for SCN(-) showed good linearity in the range of 38.0-870.0ngmL(-1) (R(2)=0.9967). The limit of detection (S/N=3) and preconcentration factor were 5.0ngmL(-1) and 40, respectively. Relative standard deviation for determination of 200ngmL(-1) of SCN(-) was 2.8% (n=5). The proposed method has been successfully applied for determination of SCN(-) ion in tap water, mineral bottled water and human saliva and urine samples with an average recovery of 99.2%.

Concepts: Ammonia, Water, Hydrogen, Ethanol, Liquid, Deprotonation, Thiocyanate, Thiocyanic acid

27

A simple and especially rapid method, pressurized liquid extraction, has been developed and applied to the quantitative determination of oxytetracycline, tetracycline, chlortetracycline, minocycline, methacycline, demeclocycline and doxycycline in egg, fish and shrimp. The procedure consisted of a trichloracetic acid/methanol extraction conducted at elevated temperature (60°C) and pressure (65bar), without further clean-up, the extraction solution was concentrated and finally for high-performance liquid chromatography analysis. The limits of detection were 5.0-10.0μg/kg and the limits of quantification were 10.0-15.0μg/kg for tetracyclines in egg, fish and shrimp using UV detection. The analytical limits CCα and CCβ were also calculated. The recoveries of tetracyclines spiked at levels of 15-300μg/kg, averaged 75.6-103.5% with the relative standard deviation values less than 11%. The optimized procedure has been successfully applied to real samples in our laboratories. It demonstrated that the new method was robust and useful for monitoring and quantification of 7 tetracycline residues in food of animal origin.

Concepts: Scientific method, Chromatography, High performance liquid chromatography, Standard deviation, Deviation, Acne vulgaris, Rosacea, Tetracycline antibiotics

27

A HPLC method with on-line solid phase extraction (SPE) and column switching was developed for simultaneous determination of 5-aminoimidazole-4-carboxamide riboside (AICA riboside) and its active metabolite 5-aminoimidazole-4-carboxamide ribotide (AICA ribotide) in nude mice plasma. Plasma sample was deproteinized by adding a half volume of 10% trichloroacetic acid (TCA), and the resulting supernatant was extracted with diethyl ether to remove TCA. 50μl aqueous fraction was injected onto a WAX-1 SPE column, and AICA ribotide was trapped on the SPE column, while AICA riboside was eluted from the SPE column. The chromatographic separation of AICA riboside was achieved on CG16 column, and separation of AICA ribotide was performed on HILIC-10 and WAX-1 column. The columns temperature was maintained at 40°C, and the optimal detection wavelength was 268nm for both AICA riboside and AICA ribotide. The total analytical run time was 40min. The proposed method was linear over the range of 0.1-500μg/ml for AICA riboside and 0.03-50μg/ml for AICA ribotide. The lower limit of quantification (LLOQ) was 100 and 30ng/ml for AICA riboside and AICA ribotide, respectively. The sensitivity, accuracy and precision of this method were within acceptable limits during validation period. The method was successfully applied to investigate the pharmacokinetics characteristics of AICA riboside and its active metabolite AICA ribotide in nude mice bearing MCF-7 cell xenografts.

Concepts: Chromatography, High performance liquid chromatography, Analytical chemistry, Phase, Accuracy and precision, Diethyl ether, Separation process, Solid phase extraction

27

A specific and sensitive LC-MS/MS method for analysis of F(2)-isoprostanes (F(2)-IsoPs) and prostaglandins (PGs) in urine was developed and validated to examine the levels of F(2)-IsoPs and prostaglandin F(2α) (PGF(2α)), in human urine in patients undergoing cardiac surgery. The rapid extraction for F(2)-IsoPs and PGs from urine was achieved using a polymeric weak anion solid phase extraction cartridge. The base-line separation of 8-iso-PGF(2α), 8-iso-15®-PGF(2α), PGF(2α), and 15®-PGF(2α) was carried out on a Hydro-RP column (250mm×2.0mm i.d., Phenomenex, CA) using a linear gradient of methanol:acetonitrile (1:1, v/v) in 0.1% formic acid at a flow rate of 0.2mL/min. The method was proved to be accurate and precise for simultaneous quantification of each analyte over a linear dynamic range of 0.05-50ng/mL with correlation coefficients greater than 0.99. The intra-day and inter-day assay precision at the lowest quality control (0.07ng/mL) level were less than 17%. The mean extraction recoveries of F(2)-IsoPs and PGs were in a range of 79-100%. In applications of this method to patients undergoing cardiac surgery, post-surgery urinary concentrations of 8-iso-PGF(2α) increased significantly in patients (n=14) who did not develop acute kidney (AKI) (pre-surgery 0.344±0.039 vs. post-surgery 0.682±0.094ng/mg creatinine, p<0.01), whereas there was no significant change in this isoprostane in the patients (n=4) who developed AKI (pre-surgery 0.298±0.062 vs. post-surgery 0.383±0.117ng/mg creatinine, NS). Therefore, the method is suitable for the analysis of individual F(2)-IsoPs and PGF(2α)'s in both clinical and research studies.

Concepts: Kidney, Urine, Gradient, Ureter, High performance liquid chromatography, Analytical chemistry, Prostaglandin, Separation process