Quantitative determination of furocoumarins in samples of “Carapiá” by capillary gas chromatography

Summary The occurrence of furocoumarins in the Moraceae has already been demostrated. We present here the results concerning the chemical composition and quantification of furocoumarins from “carapiá” (Dorstenia species, Moraceae) employed in Brazil because of its medicinal properties against skin diseases. A capillary gas chromatographic procedure is described for the simultaneous determination of the furocoumarins (psoralen, bergapten, pimpinellin, and isopimpinellin) in rhizomes and aerial parts ofDorstenia tubicina, Dorstenia asaroides andDorstenia vitifolia and in commercial samples. The method is shown to be sensitive and reproducible, and may have application in the analysis of “carapia” crude drugs.     

Quantitative determination of capsaicinoids by liquid chromatography–electrospray mass spectrometry

Eight naturally occurring capsaicinoids have been determined in Capsicum by use of high-purity standards, with norcapsaicin as an internal standard. The solid standards were rigorously checked for purity. The sensitivity of electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and coordination ion-spray (CIS; with silver) toward the capsaicinoids were measured and compared. The highest sensitivity was found for positive-ion ESI. Method validation of the liquid chromatography–ESI-mass spectrometry (LC–ESI-MS) determination is reported, including tests for repeatability (4%), detection limit (5 pg injected), linear range (20–6 ng injected), quantitation (excellent linearity; <2% relative standard deviation), and recovery (99–103%). The major and minor capsaicinoids in a commercial plant extract and in chili pepper fruits were quantified.Electronic Supplementary Material Supplementary material is available for this article at     

Analytical determination of nicotine in tobacco leaves by gas chromatography–mass spectrometry

A preliminary investigation using gas chromatography–mass spectrometry (GC–MS) to analyze the nicotine contained in tobacco leaves was carried out. Nicotine is an alkaloid and tobacco leaves was extracted with methanol and determined by GC–MS. The detection limit for nicotine was at the ppm level for non selective monitoring and the nanogram level for selective detection. This is a simple chromatography–mass spectrometry method for the analysis of nicotine in tobacco leave. Compared to other currently utilized methods for the detection of nicotine in tobacco leaves, the GC–MS provided advantages of high sensitivity, nicotine specific detection and lower instrumentation cost.     

Novel sensitive determination of steryl glycosides in biodiesel by gas chromatography–mass spectroscopy

A new method was developed for the quantitative analysis of steryl glycosides in biodiesel (fatty acid methyl esters). This method is much more sensitive than existing methods and has minimum limits of quantification of 50 μg/kg, compared to previously published minimum limits of quantification of about 15 mg/kg. The analysis is based on gas chromatography–mass spectroscopy determination of simple pre-treated and silylated samples via single ion monitoring at 147, 204, 217 m/z, which are specific ions for the silylated sugar moiety. Quantification was carried out using cholesteryl β-d-glucopyranoside as internal standard. The modified synthesis and purification of the internal standard is also presented as well as the characterization by NMR and mass spectroscopy. The advantage of the method compared with other approaches is the simplified sample preparation avoiding extra pre-treatment steps coupled with complete derivatization of the sugar hydroxyl groups by using N,O-bis(trimethylsilyl)acetamide with 5% trimethylchlorosilane as derivatization reagent. On the given conditions high recovery rates ≥89% can be obtained. Evaluation of lab specific variance and intermediate precision underline the robustness of the method which will be further assessed by Round robin tests.     

Simple approach based on ultrasound-assisted emulsification-microextraction for determination of polibrominated flame retardants in water samples by gas chromatography–mass spectrometry

A simple, efficient, innovative and environmentally friendly analytical technique was successfully applied for the first time for the extraction and preconcentration of polybrominated diphenyl ethers (PBDEs) from water samples. The PBDEs selected for this work were those most commonly found in the literature in natural water samples: 2,2′,4,4′-tetraBDE (BDE-47), 2,2′,4,4,5-pentaBDE (BDE-99), 2,2′,4,4,6-pentaBDE (BDE-100) and 2,2,4,4′,5,5′-hexaBDE (BDE-153). The extracted PBDEs were separated and determined by gas chromatography–mass spectrometry (GC–MS). The extraction/preconcentration technique is based on ultrasound-assisted emulsification-microextraction (USAEME) of a water-immiscible solvent in an aqueous medium. Several variables including, solvent type, extraction time, extraction temperature and matrix modifiers were studied and optimized over the relative response the target analytes. Chloroform was used as extraction solvent in the USAEME technique. Under optimum conditions, the target analytes were quantitatively extracted achieving enrichment factors (EF) higher than 319. The detection limits (LODs) of the analytes for the preconcentration of 10 mL sample volume were within the range 1–2 pg mL⁻¹. The relative standard deviations (RSD) for five replicates at 10 pg mL⁻¹ concentration level were <10.3%. The calibration graphs were linear within the concentration range of 5–5000 pg mL⁻¹ for BDE-47 and BDE-100; and 5–10,000 pg mL⁻¹ for BDE-99 and BDE-153, respectively. The coefficients of estimation were ≥0.9985. Validation of the methodology was performed by standard addition method at two concentration levels (10 and 50 pg mL⁻¹). Recovery values were ≥96%, which showed a successful robustness of the analytical methodology for determination of picogram per milliliter of PBDEs in water samples. Significant quantities of PBDEs were not found in the analyzed samples.     

Comparative study of extraction techniques for determination of garlic flavor components by gas chromatography–mass spectrometry

Several sampling techniques based on steam distillation (SD), simultaneous distillation and solvent extraction (SDE), solid-phase trapping solvent extraction (SPTE), and headspace solid-phase microextraction (HS-SPME) have been compared for the determination of Korean garlic flavor components by gas chromatography–mass spectrometry (GC–MS). Diallyl disulfide (57.88%), allyl sulfide (23.59%), and diallyl trisulfide (11.40%) were found to be the predominant flavor components of garlic samples extracted by SDE whereas these components were at levels of 89.77%, 2.43%, and 3.89% when the same sample was extracted by SD, 97.77%, 0.17%, and 0.10% by SPTE, and 97.85%, 0.01%, and 0.01% by HS-SPME using the 50/30-m divinyl benzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber. Thermal degradation of components such as allyl methyl sulfide, dimethyl disulfide, and thiirane were observed for SDE and SD but not for SPTE or HS-SPME. HS-SPME had several advantages compared with SD, SDE, and SPTE—rapid solvent-free extraction, no apparent thermal degradation, less laborious manipulation, and less sample requirement. Five different fiber coatings were evaluated to select a suitable fiber for HS-SPME of garlic flavor components. DVB/CAR/PDMS was most efficient among the five types of fiber investigated.     

Quantitative determination of taurine and related biomarkers in urine by liquid chromatography–tandem mass spectrometry

Current urinary bladder cancer diagnosis is commonly based on a biopsy obtained during cystoscopy. This invasive method causes discomfort and pain in patients. Recently, taurine and several other compounds such as L-phenylalanine and hippuric acid in urine were found to be indicators of bladder cancer. However, because of a lack of sensitive and accurate analytical techniques, it is impossible to detect these compounds in urine at low levels. In this study, using liquid chromatography–tandem mass spectrometry (LC-MS/MS), a noninvasive method was developed to separate and detect these compounds in urine. ¹⁵N₂-L-glutamine was used as the internal standard, and creatinine acted as an indicator for urine dilution. A phenyl-hexyl column was used for the separation at an isocratic condition of 0.2% formic acid in water and 0.2% formic acid in methanol. Analytes were detected in multiple-reaction monitoring with positive ionization mode. The limit of detection range is 0.18–6 nM and the limit of quantitation ranges from 0.6 to 17.6 nM. The parameters affecting separation and quantification were also investigated and optimized. Proper clinical validation of these biomarkers can be done using this reliable, fast, and simple method. Furthermore, with simple modifications, this method could be applied to other physiological fluids and other types of diseases.     

Quantitative determination of 22 primary aromatic amines by cation-exchange solid-phase extraction and liquid chromatography–mass spectrometry

Primary aromatic amines (PAAs) have been broadly studied due to their high toxicity. In this work a method for the analysis of 22 PAAs in aqueous simulants has been developed. The method is based on a solid-phase extraction step using cation-exchange cartridges and the subsequent analysis of the extracts by ultra-high-performance liquid chromatography with mass spectrometric detection. The recoveries obtained for all the amines analyzed ranged between 81 and 109%, linear range was between 0.03 and 75 μg L⁻¹, with the RSD values between 4.5 and 13.4% and an average value of 7.5% and limits of detection at μg L⁻¹ level. The method has been applied to two real samples obtained from migration experiments of polyurethane based laminates to simulant B (water with 3% (w/v) acetic acid) which represents the worst case for the migration of aromatic amines. The main amines found in both samples were methylenedianiline isomers, obtained from the corresponding residual diisocyanates used during polyurethane adhesive polymerization. The total amine concentration found was 26 and 6.3 μg of aniline equivalents per kg of food simulant.     

Quantitative determination of rifampicin in aquatic products by stable isotope-dilution high liquid chromatography–tandem mass spectrometry

Rifampicin is a semi-synthetic broad-spectrum antibiotic obtained from rifamycin B. It is one of the most effective first-line antituberculosis drugs and is widely used in clinical practice. In the present study, we describe a rapid and sensitive method for the determination of rifampin in aquatic products by stable isotope-dilution high liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Samples were extracted with the acetonitrile, degreased by hexane, and then concentrated by nitrogen blowing. After separation using a C₁₈ column with a mixture of acetonitrile and water as mobile phase, it was determined by HPLC–MS/MS using the stable isotope-dilution calibration method. The performance of our method was validated. The limit of detection was 0.25 μg kg⁻¹ and the limit of quantification was 0.5 μg kg⁻¹. At the three spiked levels of 0.5, 1.0 and 5.0 μg kg⁻¹, the average recoveries of rifampicin in different aquatic products were between 75.28 and 107.6%, and the relative standard deviation ranged from 0.81 to 13.23%. This method was successfully applied for the determination of rifampin in different kinds of aquatic products and rifampicin residue was found in aquatic products obtained from markets in Beijing, China.     

Quantitative analysis of two analgesic formulations by micellar electrokinetic chromatography

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Optimization of the separation of a mixture of unknown composition by reversed-phase HPLC

A method is presented for the computer-assisted optimization of mobile phaseselection for the separation of a synthetic intermediate of unknown composition by reversed-phase HPLC.The method is based on recognition of the order of the peaks by comparisonof peak area ratio and followed by the BSOS-L(Binary Solvent Optimization System forHPLC)method.Excellent agreement was obtained between predicted data and experimentalresults.     

One-step extraction and derivatization liquid-phase microextraction for the determination of chlorophenols by gas chromatography–mass spectrometry

A sample pretreatment method for the determination of 18 chlorophenols (CPs) in aqueous samples by derivatization liquid-phase microextraction (LPME) was investigated using gas chromatography–mass spectrometry. Derivatization reagent was spiked into the extraction solvent to combine derivatization and extraction into one step. High sensitivity of 18 CPs derivatives could be achieved after optimization of several parameters such as extraction solvent, percentage of derivatization reagent, extraction time, pH, and ionic strength. The results from the optimal method showed that calibration ranging from 0.5 to 500 μg L⁻¹ could be achieved with the RSDs between 1.75% and 9.39%, and the limits of detection (LOD) are ranging from 0.01 to 0.12 μg L⁻¹ for the CPs. Moreover, the proposed LPME method was compared with solid-phase microextraction (SPME) coupled with on-fiber derivatization technique. The results suggested that using both methods are quite agreeable. Furthermore, the recoveries of LPME evaluated by spiked environmental samples ranged from 87.9% (3,5-DCP) to 114.7% (2,3,5,6-TeCP), and environmental water samples collected from the Pearl River were analyzed with the optimized LPME method, the concentrations of 18 CPs ranged from 0.0237 μg L⁻¹ (3,5-DCP) to 0.3623 μg L⁻¹ (2,3,6-TCP).     

Novel derivatisation technique for the determination of chlorophenoxy acid type herbicides by gas chromatography–mass spectrometry

The analytical detection of chlorophenoxycarboxylic-acid-type herbicides (2,4-D, dichloprop, MCPA, etc.) in environmental samples is often a problem in instrumental analysis, as these compounds containing free carboxylic groups require chemical derivatisation prior to gas chromatographic (GC) methods. Nine chlorophenoxy-acid-type herbicide active ingredients have been derivatised successfully with trimethylsilyl N,N-dimethyl carbamate and t-butyldimethylsilyl N,N-dimethyl carbamate by forming their trimethylsilyl (TMS) and t-butyldimethylsilyl (TBDMS) esters, respectively. The detection and determination of the derivatives were performed by capillary gas chromatography–mass spectrometry. The study included determination of retention indices, mass spectral properties and comparison of derivatives produced. The mass spectra of TBDMS derivatives are usually dominated by very characteristic ions [M-57]⁺ resulting from the cleavage of t-butyl moiety during electron impact (EI) ionisation in the mass spectrometer. Limits of detection were 5 to 100 pg applying GC with EI-MS detection in full scan mode. The method, using SPE sample preparation, was applied for the analysis of 115 ground water and surface water samples collected in Békés County, Hungary in 2009.     

Multi-residue determination of organochlorine pesticides in vegetables in Kirklareli,Turkey by gas chromatography–mass spectrometry

The aim of this study was to investigate the level of organochlorine pesticides use for treatment of tomatoes, eggplants and cucumbers in Kirklareli, Turkey. Eighteen organochlorine pesticides were identified in vegetable samples using microwave or Soxhlet extraction, and results were obtained by gas chromatography–mass spectrometry. The optimized conditions were 1 mL/min for flow rate in the mobile phase, 1 μL for injection volume and 70 V for fragmentation potential. The analytical parameters show that the microwave oven extraction procedure provided the best results when compared to the Soxhlet extraction procedure. Samples were prepared for analysis with hexane?dichlormethane (1: 1, v/v, 40 mL) using a solid-phase extraction method. The limits of detection and quantitation for the eighteen analytes were between 0.02–0.26 and 0.06–0.87 μg/L, respectively, and the relative standard deviations of the migration time ranged from 2.4 to 8.9%. The recoveries of surrogate spiked in vegetable samples ranged from 70 to 116%, respectively. The obtained concentrations of pesticides in all vegetables studied were proved in the range of ND–123 μg/kg. The organochlorine pesticide sum was below the legal limit, except for Endrin and Methoxychlor, which requires a further elucidation of the organochlorine pesticides pollution sources in the region. These studies on accumulation of organochlorine pesticides were necessary for accomplishing a comprehensive ecological risk assessment.     

Multiclass determination of 66 organic micropollutants in environmental water samples by fast gas chromatography–mass spectrometry

A multiresidue method has been developed for quantification and identification of 66 multiclass priority organic pollutants in water by fast gas chromatography (GC) coupled to mass spectrometry (MS). Capabilities and limitations of single quadrupole mass spectrometer as detector in fast GC were studied evaluating the chromatographic responses in terms of sensitivity and chromatographic peak shapes, as they were influenced by scan time. The number of monitored ions in a selected ion monitoring (SIM) group strongly conditioned the scan time and subsequently the number of data points per peak. A compromise between peak shape and scan time was adopted in order to reach the proper conditions for quantitative analysis. An average of 10–15 points per peak was attained for most compounds, involving scan times between 0.1 and 0.22 s. The method was validated for mineral, surface, and groundwater. A solid-phase extraction pre-concentration step using C₁₈ cartridges was applied. Four isotopically labeled standards were added to the samples before extraction and used as surrogates to ensure a reliable quantification. Analyses were performed by GC–MS in electron ionization mode, monitoring the three most abundant and/or specific ions for each compound and using the intensity ratios as a confirmatory parameter. With a chromatographic run of less than 10 min, SIM mode provided excellent sensitivity and identification capability due to the monitoring of three ions and the evaluation of their intensity ratio. Limits of detection below 10 ng/L were reached for most of the 66 compounds in the three matrices studied. Accuracy and precision of the method were evaluated by means of recovery experiments at two fortification levels (10 and 100 ng/L), obtaining recoveries between 70% and 120% in most cases and relative standard deviations below 20%. The possibilities of a simultaneous SIM scan method have also been explored for non-target qualitative analysis. The developed method has been applied to the analysis of surface water samples collected from the Mediterranean region of Spain.     

Identification of monoacylglycerol regio-isomers by gas chromatography–mass spectrometry

Monoacylglycerols (MAGs) are lipids found in trace amounts in plants and animal tissues. While they are widely used in various industrial applications, accurate determination of the regio-specific distribution is hindered by the lack of stable, commercially available standards. Indeed, unsaturated β-MAG (or Sn-2 MAG) readily undergoes isomerization into α-MAG (acyl chain is attached to the Sn-1 or the Sn-3 position). In the present study, we describe structural elucidation of α- and β-regio-isomers of monopalmitoyl-glycerol (MAG C16:0) as model compounds in their silylated forms using gas chromatography–mass spectrometry (GC–MS) with electronic impact (EI) ionization. MS fragmentation of α-MAG C16:0 is characterized by the loss of methylene(trimethylsilyl)oxonium (103 amu) and the consecutive loss of acyl chain yielding a fragment ion at m/z 205. The fragmentation pattern of β-MAG C16:0 shows a series of diagnostic fragments at m/z 218, 203, 191 and 103 that are not formed from the α-isomer and hereby enable reliable distinction of these regio-isomers. Possible fragmentation scenarios are postulated to explain the formation of these marker ions, which were also applied to characterize the regio-isomer composition of a complex mixture of MAG sample containing n-3 long-chain polyunsaturated fatty acids.     

Development of a gas chromatography — mass spectrometry method for the determination of carbon disulfide in the atmosphere

Carbon disulfide (CS₂), a relevant reduced sulfur compound in air, is well-known for its malodor and its significant effect on global atmospheric chemistry. Therefore, a reliable method for determining CS₂ in atmospheric samples has been developed based on solid-phase sampling and gas chromatography–mass spectrometry (GC–MS). Two types of solid-phase sampling supports (Orbo-32 and SKC) and the elution with organic solvents — hexane and toluene — were evaluated for low-volume outdoor sampling. Recovery studies and the standard addition method were carried out to demonstrate the proper determination of CS₂ in the absence of the influence of interferences such as ozone, hydrogen sulfide or water — important atmospheric pollutants —. The proposed methodology was validated by performing experiments in a high-volume smog chamber and by comparison with two reference optical methods, Fourier Transform Infrared (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) installed in these facilities. Satisfactory analytical parameters were reported: fast analysis, a correct repeatability of 6 ± 1% and reproducibility of 14 ± 3%, and low detection limits of 0.3–0.9 pg m^? 3. Finally, the method was successfully applied to industrial samples near a pulp factory area, where a high correlation between industrial emissions and reported carbon disulfide concentrations were observed.     

Adsorption characteristics of nitric oxide on various adsorbents determined by gas—solid chromatography

The adsorption of nitric oxide on 13X and 5A molecular sieves, alumina (boehmite) and nickel—kieselguhr and copper oxide—zinc oxide catalysts was studied by using a chromatographic technique. Moment analysis was used for determining the adsorption equilibrium constant K_A.The nitric oxide is purely physically adsorbed on 13X molecular sieve and alumina in the ranges of temperature between 50 and 100 °C and between −8 and 50 °C respectively. The adsorption capacities of 13X molecular sieve and alumina are 0.5 cm³ g⁻¹ and 1.0 cm³ g⁻¹ respectively at 50 °C. The nitric oxide reacts with 5A molecular sieve and changes its adsorption capacity with time from 3.4 cm³ g⁻¹ for fresh adsorbent at 100 °C. For the nickel—kieselguhr catalyst the adsorption of nitric oxide at 50 °C and 110 °C takes place on two kinds of active sites with slow and fast reversible adsorption respectively. The total equilibrium constant, for fast and slow adsorption, is 0.90 cm³ g⁻¹ at 50 °C and 0.32 cm³ g⁻¹ at 110 °C. The nitric oxide reacts with the copper oxide—zinc oxide catalyst between 50 and 200 °C and changes the physical properties of the bed probably as a result of shrinkage of the particles. Therefore, quantitative data could not be obtained for this system.