Fast determination of Z-ligustilide in plasma by gas chromatography/mass spectrometry following headspace single-drop microextraction

Angelica sinensis (danggui in Chinese) is a common traditional Chinese medicine (TCM), and its essential oil has been used for the treatment of many diseases such as hepatic fibrosis. Z-Ligustilide has been found to be an important active component in the TCM essential oil. In this work, for the first time, headspace single-drop microextraction (HS-SDME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of Z-ligustilide in rabbit plasma after oral administration of essential oil of danggui. The extraction parameters of solvent selection, solvent volume, sample temperature, extraction time, stirring rate, and ion strength were systemically optimized. Furthermore, the method linearity, detection limit, and precision were also investigated. It was shown that the proposed method provided good linearity (0.02-20 microg/mL, R2 = 0.997), low detection limit (10 ng/mL), and good precision (RSD value less than 9%). Finally, HS-SDME followed by GC/MS was used for fast determination of Z-ligustilide in rabbit plasma at different time intervals after oral administration of danggui essential oil. The experimental results suggest that HS-SDME followed by GC/MS is a simple, sensitive, and low-cost method for the determination of Z-ligustilide in plasma, and a low-cost approach to pharmacokinetics studies of active components in TCMs.     

Comparison of tetraethylborate and tetraphenylborate for selenite determination in human urine by gas chromatography mass spectrometry, after headspace solid phase microextraction

Two different derivatizing reagents were tested for the development of a fast and sensitive method for the determination of selenites (Se^IV) in human urine. The reagents were sodium tetraethylborate (NaBEt₄) and tetraphenylborate (NaBPh₄), respectively, and the procedure is based on in situ derivatization of selenites in aqueous medium. Selenite ions are converted to diethylselenide (DESe) or diphenylselenide (DPhSe) and subsequently collected from the headspace by solid phase microextraction using a silica fiber coated with polydimethylsiloxane (HS-SPME). Finally, they are quantitated by GC/MS in SIM mode. Ethylation over phenylation was proved preferable for the headspace extraction because of the higher volatility of the diethyl-derivative of selenites. The optimization of the HS-SPME conditions was performed both in aqueous and urinary solutions. Under the optimum conditions for HS-SPME, the gas chromatographic conditions were also optimized. Between the two alkylation reagents tetraethylborate was proved more efficient and the quantitation was satisfactory. Aqueous certified reference materials were analyzed to evaluate the accuracy of the method. The precision of the method was 4.2% and the calculated detection limit was 0.05 μg L⁻¹ for human urine.     

Derivatization coupled to headspace programmed‐temperature vaporizer gas chromatography with mass spectrometry for the determination of amino acids: Application to urine samples

A new method based on headspace programmed‐temperature vaporizer gas chromatography with mass spectrometry has been developed and validated for the determination of amino acids (alanine, sarcosine, ethylglycine, valine, leucine, and proline) in human urine samples. Derivatization with ethyl chloroformate was employed successfully to determine the amino acids. The derivatization reaction conditions as well as the variables of the headspace sampling were optimized. The existence of a matrix effect was checked and the analytical characteristics of the method were determined. The limits of detection were 0.15–2.89 mg/L, and the limits of quantification were 0.46–8.67 mg/L. The instrumental repeatability was 1.6–11.5%. The quantification of the amino acids in six urine samples from healthy subjects was performed with the method developed with the one‐point standard additions protocol, with norleucine as the internal standard.     

Sensitive and robotic determination of bromate in sea water and drinking deep-sea water by headspace solid-phase micro extraction and gas chromatography–mass spectrometry

A robotic method has been established for the determination of bromate in sea water and drinking deep-sea water. Bromate in water was converted into volatile derivative, which was measured with headspace solid-phase micro extraction and gas chromatography–mass spectrometry (HS-SPME GC–MS). Derivatization reagent and the HS-SPME parameters (selection of fibre, extraction/derivatization temperature, heating time and; the morality of HCl) were optimized and selected. Under the established conditions, the detection and the quantification limits were 0.016 μg L⁻¹ and 0.051 μg L⁻¹, respectively, and the intra- and inter-day relative standard deviation was less than 7% at concentrations of 1.0 and 10.0 μg L⁻¹. The calibration curve showed good linearity with r² = 0.9998. The common ions Cl⁻, NO₃⁻, SO₄²⁻, HPO₄²⁻, H₂PO₄⁻, K⁺, Na⁺, NH₄⁺, Ca²⁺, Mg²⁺, Ba²⁺, Mn⁴⁺, Mn²⁺, Fe³⁺ and Fe²⁺ did not interfere even when present in 1000-fold excess over the active species. The method was successfully applied to the determination of bromate in sea water and drinking deep-sea water.     

Discrimination and characterization of the volatile organic compounds of Acori tatarinowii rhizoma based on headspace-gas chromatography-ion mobility spectrometry and headspace solid phase microextraction-gas chromatography-mass spectrometry

Acori tatarinowii rhizome (ATR) is a Traditional Chinese Medicine (TCM), which has multiple effects, such as neuroprotective activity, antidepressant and other activity. However, the widespread cultivation of ATR has led to it varying quality. Therefore, it is important to find a method to quickly identify the components of ATR. Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) were applied to analyze and characterize the volatile organic compounds (VOCs) of ATR. 33 VOCs were identified by HS-GC-IMS and 95 VOCs were identified by HS-SPME-GC–MS from 15 batches of ATR. Then, quantification of estragole, methyleugenol, γ-asarone, β-asarone and asarone by gas chromatography-mass spectrometry (GC–MS). The fingerprint of HS-GC-IMS and the heatmap of HS-SPME-GC–MS were established. Which compared differential components of ATR. In addition, principal component analysis (PCA) was performed on the results of both instruments. The VOCs in the ATR were significantly correlated with β-asarone and asarone by PatternHunter analysis. It assisted HS-GC-IMS determine ATR quality. It is the first report regarding the method development of HS-GC-IMS and HS-SPME-GC–MS that targets the VOCs characterization of ATR, and the findings obtained would benefit the quality control and distinguish the complex analytical objects of ATR.     

New quantification procedure for the analysis of chlorinated paraffins using electron capture negative ionization mass spectrometry

An improved quantification procedure for the analysis of chlorinated paraffins (CPs) is presented based on electron capture negative ionization mass spectrometry. It compensates differences in response factors between reference CP mixtures and the CP pattern present in environmental samples. The use of a CP standard with a matching degree of chlorination is no longer necessary. It could be shown that the response factors of C10-, C11-, C12- and C13-CP mixtures of both 50 and 60% chlorine content were only slightly influenced by the carbon chain length. A linear correlation (R2 = 0.965) between the total response factor of a CP mixture and its chlorine content was obtained for seven short chain chlorinated paraffin mixtures (SCCP, C10-C13) with different composition and chlorine content (51-69%). Maximum single deviations were <7% for this reference set. It allowed to determine the correct total response factor of the CP composition present in a sample. The deviations were not more than 7-33% for five independent SCCP control samples compared to up to 373% for the conventional procedure. The procedure was tested by quantifying the SCCP and MCCP levels in 10 fish liver samples. The proposed method allowed to compensate the influence of the degree of chlorination of the applied reference standard on the total response factor.     

Rapid determination of methyl tert-butyl ether using dynamic headspace/ion mobility spectrometry

Using an original, experimental set-up named dynamic headspace/IMS (DHS/IMS), ppb levels of methyl tert-butyl ether (MTBE), a gasoline additive and environmental pollutant, were determined in drinking and ground water. A portable IMS (Bruker, Raid-1 model) was connected to the outlet of a Drechsel bottle containing 100 ml of water-based sample. Automatically activated to sample air, the IMS built-in pump was used to produce a continuous and gentle air flow bubbling through the water-based sample. This allowed volatile MTBE to be isolated and transferred into the Drechsel headspace and then into the IMS. Analyses of reference solutions and real samples resulted in MTBE detection limits of 20 ppb, calibration curves in the 20-200 ppb range, and relative standard deviations of 4.7 and 8.4%, respectively, for inter- and intra-day reproducibility tests. Detection limits were further improved to 0.5 ppb by means of a Tenax trap cooled with liquid nitrogen, placed between the sample bottle and the IMS. Overall, DHS/IMS could well become a simple and cost-effective tool for rapid and on-line analysis of volatile organic compounds in water.     

Analysis of organic solvents in printing inks by headspace gas chromatography – mass spectrometry

Static headspace analysis by gas chromatography has been found to be a suitable method for the analysis of organic solvents in printing inks. Experimental conditions for the analysis have been optimized, and the accuracy and relative standard deviation of the method has been determined. The solvent content of 29 printing inks has been measured.     

On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials

We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6–21% for pressed pellets and 3–21% for fused solids were obtained from n = 3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches.     

Optimization of headspace experimental factors to determine chlorophenols in water by means of headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry and parallel factor analysis

In this work an analytical procedure based on headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry (HS-SPME–GC/MS) is proposed to determine chlorophenols with prior derivatization step to improve analyte volatility and therefore the decision limit (CCα). After optimization, the analytical procedure was applied to analyze river water samples. The following analytes are studied: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,4,6-TeCP) and pentachlorophenol (PCP). A D-optimal design is used to study the parameters affecting the HS-SPME process and the derivatization step. Four experimental factors at two levels and one factor at three levels were considered: (i) equilibrium/extraction temperature, (ii) extraction time, (iii) sample volume, (iv) agitation time and (v) equilibrium time. In addition two interactions between four of them were considered. The D-optimal design enables the reduction of the number of experiments from 48 to 18 while maintaining enough precision in the estimation of the effects. As every analysis took 1 h, the design is blocked in 2 days.     

Rapid determination of the volatile components in tobacco by ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction with gas chromatography‐mass spectrometry

An ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction was first employed to determine the volatile components in tobacco samples. The method combined the advantages of ultrasound, microwave, and headspace solid‐phase microextraction. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, several experimental parameters, such as fiber type, ultrasound power, and irradiation time, were optimized to improve sampling efficiency. Under the optimal conditions, there were 37, 36, 34, and 36 components identified in tobacco from Guizhou, Hunan, Yunnan, and Zimbabwe, respectively, including esters, heterocycles, alkanes, ketones, terpenoids, acids, phenols, and alcohols. The compound types were roughly the same while the contents were varied from different origins due to the disparity of their growing conditions, such as soil, water, and climate. In addition, the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method was compared with the microwave‐assisted extraction coupled to headspace solid‐phase microextraction and headspace solid‐phase microextraction methods. More types of volatile components were obtained by using the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method, moreover, the contents were high. The results indicated that the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction technique was a simple, time‐saving and highly efficient approach, which was especially suitable for analysis of the volatile components in tobacco.     

Headspace mass spectrometry methodology: application to oil spill identification in soils

In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment, the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach for oil spill identification in soils. Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for vertisol)     

Analysis of volatile organic compounds in pleural effusions by headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry

Headspace solid‐phase microextraction coupled with cryotrap gas chromatography and mass spectrometry was applied to the analysis of volatile organic compounds in pleural effusions. The highly volatile organic compounds were separated successfully with high sensitivity by the employment of a cryotrap device, with the construction of a cold column head by freezing a segment of metal capillary with liquid nitrogen. A total of 76 volatile organic compounds were identified in 50 pleural effusion samples (20 malignant effusions and 30 benign effusions). Among them, 34 more volatile organic compounds were detected with the retention time less than 8 min, by comparing with the normal headspace solid‐phase microextraction coupled with gas chromatography and mass spectrometry method. Furthermore, 24 volatile organic compounds with high occurrence frequency in pleural effusion samples, 18 of which with the retention time less than 8 min, were selected for the comparative analysis. The results of average peak area comparison and box‐plot analysis showed that except for cyclohexanone, 2‐ethyl‐1‐hexanol, and tetramethylbenzene, which have been reported as potential cancer biomarkers, cyclohexanol, dichloromethane, ethyl acetate, n‐heptane, ethylbenzene, and xylene also had differential expression between malignant and benign effusions. Therefore, the proposed approach was valuable for the comprehensive characterization of volatile organic compounds in pleural effusions.     

Rapid quantification of sucrose esters in oriental tobacco by liquid chromatography-ion trap mass spectrometry

A rapid and sensitive LC-MS/MS method was developed for the quantitative determination of sucrose esters (SEs) in Oriental tobacco samples. The sample preparation involved a 10-min sonication extraction procedure with acetone and five-fold dilution of the extract with methanol. The experiment was carried out in positive ion mode by ESI IT mass spectrometer. Because of lack of authentic standards of SEs, sucrose octa-acetate (internal standard, IS) was used as a surrogate to validate the proposed method. Matrix-matched standard calibration was used for quantification of IS in the spiked samples. Under optimized MS/MS conditions, an LOQ of 3.9 microg/g was achieved for IS, with an LOD of about 1.2 microg/g. Recoveries for IS were 95-97%. Among 19 monitored SEs, the contents of 11 SEs had RSDs lower than 13.7%. The method, with very little sample handling and good sensitivity, was applied to the rapid quantification of SEs in four Oriental tobacco samples. It appears that the sum of contents of the five SEs with MW 650, 664, and 678 Da occupied approximately 80% of the total content of SEs.     

Profiling of 19-norsteroid sulfoconjugates in human urine by liquid chromatography mass spectrometry

19-Nortestosterone (nandrolone) major metabolites in human urine are excreted as sulfoconjugated and glucuroconjugated forms. A sensitive and selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method in negative ESI mode was developed for direct quantification of 19-norandrosterone sulfate (19-NAS) and 19-noretiocholanolone sulfate (19-NES). For both sulfoconjugates, the [M−H]⁻ ion at m/z 355 and the fragment ion at m/z 97 were used as the precursor and product ions, respectively. The purification method involved a complete and rapid separation of sulfates and glucuronides in two extracts after loading the sample on a weak anion exchange solid phase extraction support (SPE Oasis^® WAX). Then, sulfates were separated by LC (Uptisphere^® ODB, 150 mm × 3.0 mm, 5 μm) and analyzed on a linear trap and a triple quadrupole mass spectrometer. The lower limit of detection (LLOD) and lowest limit of quantification (LLOQ) were of 100 pg mL⁻¹ and 1 ng mL⁻¹, respectively. Assay validation demonstrated good performances in terms of trueness (92.0-104.9%), repeatability (0.6-7.2%) and intermediate precision (1.3-10.8%) over the range of 1-2500 ng mL⁻¹. Finally, 19-NAS and 19-NES in urine samples collected after intake of 19-norandrostenedione (nandrolone precursor) were quantified. This assay may be easily implemented to separate glucuronide and sulfate steroids from urine specimens prior to quantification by LC/MS/MS.     

Isotope pattern deconvolution-tandem mass spectrometry for the determination and confirmation of diclofenac in wastewaters

Isotope dilution mass spectrometry (IDMS) based on isotope pattern deconvolution (IPD) has been applied here to MS/MS (QqQ) in order to carry out the quantification and confirmation of organic compounds in complex matrix water samples without the use of a methodological IDMS calibration graph. In this alternative approach, the isotope composition of the spiked sample is measured after fragmentation by SRM and deconvoluted into its constituting components (molar fractions of natural abundance and labeled compound) by multiple linear regression (IPD). The procedure has been evaluated for the determination of the pharmaceutical diclofenac in effluent and influent urban wastewaters and fortified surface waters by UHPLC (ESI) MS/MS using diclofenac-d₄ as labeled compound. Calculations were performed acquiring a part and the whole fragment cluster ion, achieving in all cases recoveries within 90–110% and coefficients of variation below 5% for all water samples tested. In addition, potential false negatives arising from the presence of diclofenac-d₂ impurities in the labeled compound were avoided when the proposed approach was used instead of the most usual IDMS calibration procedure. The number of SRM transitions measured was minimized to three to make possible the application of this alternative technique in routine multi-residue analysis.     

Determination of pyrimethanil and kresoxim-methyl in soils by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method using headspace solid-phase microextraction (HS-SPME) then gas chromatography–mass spectrometry with selected ion monitoring (GC–MS, SIM) has been developed for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in soil and humic materials. Both fungicides were extracted on to a fused-silica fibre coated with 85 m polyacrylate (PA). Response-surface methodology was used to optimise the experimental conditions. For soil samples the linear dynamic range of application was 0.004–1.000 g g^–1 for pyrimethanil and 0.013–1.000 g g^–1 for kresoxim-methyl. The detection limits were 0.001 g g^–1 and 0.004 g g^–1 for pyrimethanil and kresoxim-methyl, respectively. HP-SPME–GC–MS analysis was highly reproducible—relative standard deviations (RSD) were between 6.7 and 12.2%. The method was validated by analysis of spiked matrix samples and used to investigate the presence of pyrimethanil and kresoxim-methyl above the detection limits in soil and humic materials.     

电感耦合等离子体质谱测定钼矿石中的铼

以三酸消解钼矿石中的铼, 不经分离富集, 用电感耦合等离子体质谱法直接测定钼矿石样品中的铼。方法检出限可达0.012μg/g , 通过对国家岩石一级标准样品的测试, 测定结果一致;对GBW07285标准样品11 次测定的相对标准偏差(RSD) 为1.13%。     

Headspace solid-phase micro-extraction and gas chromatography-ion trap tandem mass spectrometry method for butyltin analysis in sediments: Optimization and validation

In this work, headspace solid-phase micro-extraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) method for analysis of butyltin compounds in sediment samples was upgraded by the introduction of tandem mass spectrometry (MS/MS). Optimization and validation of this method based on an one step procedure, tetraethylborate in situ ethylation with simultaneous extraction by headspace SPME, combined with tandem mass spectrometry is described. A simple leaching/extraction step of mono-(M), di-(D) and tri-(T) butyltin (BT) compounds from the sediment is required as sample pre-treatment. The combination of the two techniques headspace SPME and MS/MS, led to very little matrix interference which permitted to attain limits of detection three or more orders of magnitude lower than those attained in previous methods: 0.3 pg g^− 1 for MBT, 1 pg g^− 1 for DBT and 0.4 pg g^− 1 for TBT. Linear response range was from 0.02–1260 ng g^− 1 for MBT, 0.07–1568 ng g^− 1 for DBT and 0.04–2146 ng g^− 1 for TBT and RSD < 15% was also obtained. The method was efficiently applied to a real sample sediment from Sado River estuary in Portugal, revealing the existence of BTs pollution, as the TBT level of 189 ± 15 ng g^− 1 was much higher than the maximum established as provisional ecotoxicological assessment criteria.