Direct detection of polyaromatic hydrocarbons, estrogenic compounds and pesticides in water using desorption chemical ionisation membrane inlet mass spectrometry

This paper describes the use of desorption chemical ionisation membrane inlet mass spectrometry (DCI-MIMS) for the detection of a broad range of common contaminants in water. In addition, we discuss the advantages/disadvantages of two different types of chemical ionisation reagent gases, i-butene (a Broensted acid reagent) and argon (a charge exchange reagent). We found that polyaromatic hydrocarbons was detectable at ppt levels, the estrogenic compounds diethyl phthalate and octylphenol at high ppt levels, steroid hormones at ppb levels, hydrophobic pesticides at low ppb levels, whereas hydrophilic pesticides and bisphenol A were not detectable at all. With the exception of the polyaromatic hydrocarbons and pentachlorophenol, none of the reported compounds have to our knowledge been detected previously by other MIMS systems. In most cases the Broensted acid reagent gave characteristic ions at high mass/charge ratio, whereas the charge exchange reagent gave less characteristic ions at low m/z ratio. However, the sensitivity was generally not as good with the Broensted acid reagent as with the charge exchange reagent, since the Broensted acid reagent, i-butene, gave a large chemical background.     

Detection of volatile organic sulfur compounds in water by headspace gas chromatography and membrane inlet mass spectrometry

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in tlie analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethyl-methyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low (μg/1 levels with the two gas chromatographic methods and clearly below μg/1 level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.     

Membrane inlet mass spectrometry of volatile organohalogen compounds in drinking water.

The analysis of organic pollutants in drinking water is a topic of wide interest, reflecting on public health and life quality. Many different methodologies have been developed and are currently employed in this context, but they often require a time-consuming sample pre-treatment. This step affects the recovery of the highly volatile compounds. Trace analysis of volatile organic pollutants in water can be performed 'on-line' by membrane inlet mass spectrometry (MIMS). In MIMS, the sample is separated from the vacuum of the mass spectrometer by a thin polymeric hollow-fibre membrane. Gases and organic volatile compounds diffuse and concentrate from the sample into the hollow-fibre membrane, and from there into the mass spectrometer. The main advantages of the technique are that no pre-treatment of samples before analysis is needed and that it has fast response times and on-line monitoring capabilities. This paper reports the set-up of the analytical conditions for the analysis of volatile organohalogen compounds (chloroform, bromoform, bromodichloromethane, chlorodibromomethane, tetrachloroethylene, trichloroethylene, 1,1,1-trichloroethane, and carbon tetrachloride). Linearity of response, repeatability, detection limits, and spectra quality are evaluated.     

固相萃取-气相色谱-串联质谱法检测水中18种酚类化合物

当前水中酚类化合物种类不清、危害不明,多种酚类化合物的同时检测方法不成熟,因此建立水中多种酚类化合物同时检测的方法具有重要现实意义。该研究建立了固相萃取结合气相色谱-串联质谱同时检测水中18种酚类化合物的分析方法。实验选择超纯水为空白样品,采用固相萃取技术富集、提取水中的酚类化合物,同时对水样初始pH值、洗脱液的种类、洗脱液的用量等条件进行优化,从而确定出最优的前处理方法,最后利用气相色谱-串联质谱法对不同种类的酚类化合物同时进行定量检测。实验结果表明,在初始水样pH值为3.0、不衍生等条件下,使用10 mL乙酸乙酯洗脱,控制洗脱速度为1 mL/min,经固相柱富集净化,氮吹浓缩后,用气相色谱-质谱仪(EI源)测定,选择离子模式监测,外标法定量。结果表明,以3倍信噪比结合浓度外推法确定方法检出限,为0.04～0.6μg/L; 18种酚类化合物的加标回收率为51.7%～117.3%,相对标准偏差为3.1%～7.4%。应用建立的方法分别检测了河流湖泊水、生活用水、生产用水3大类6种不同的水质。检测结果表明,河流湖泊水中酚类化合物所含种类最多,含量最高。研究建立的方法不需要衍生,简化了前处理...     

Determination of mono- and sesquiterpenes in water samples by membrane inlet mass spectrometry and static headspace gas chromatography

A membrane inlet mass spectrometric (MIMS) method is presented and compared with a static headspace gas chromatographic method (HSGC) for the determination of terpenes in water. The MIMS method provides a very simple and fast analysis of terpenes in water, detection limits being relatively low, from 0.2 mug l(-1) for monoterpenes to 2 mug l(-1) for geraniol. The analysis of terpenes by the HSGC (equipped with flame ionization detector, FID) method is more time-consuming and the detection limits (2 mug l(-1) for monoterpenes to 100 mug l(-1) for geraniol) are higher than with MIMS. However, the HSGC method has the advantage of determining individual mono- and sesquiterpene compounds, whereas MIMS provides only separation of different classes of terpenes. Both methods were applied to the analysis of mono- and sesquiterpenes in several condensation water samples of pulp and paper mills.     

顶空-气相色谱质谱法测定水中10种氯苯类化合物

文文建立了不同水体中10种氯苯类化合物的顶空-气相色谱质谱的检测方法;优化了10种氯苯类化合物的最佳顶空条件,10种氯苯类化合物的最佳顶空条件为水样pH5～6,氯化钠加入量为4.0g,顶空加热平衡温度55℃,加热平衡时间20min,震荡,在此顶空条件下,可以获得满意的10种氯苯类化合物的响应值和回收率.10种氯苯类化合...     

Determination of phthalates in water using fiber introduction mass spectrometry

Fiber introduction mass spectrometry (FIMS)-a direct coupling of SPME and MS-using selective ion monitoring (SIM) was used to detect and quantify dimethylphthalate (DMP), diethylphthalate (DEP) and dipropylphthalate (DPP) in mineral water. In FIMS, a chromatographic silicone septum is the only barrier between ambient and the high-vacuum mass spectrometer, permitting direct introduction of the SPME fiber into the ionization region of the equipment. After their thermal desorption and ionization and dissociation, the extracted phthalates are detected and quantitated by MS. Three types of SPME fibers were screened for best analyte sorption/desorption behaviors: 100 microm polydimethylsiloxane (PDMS), 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 65 microm Carbowax/divinylbenzene (CW/DVB). The PDMS/DVB and CW/DVB fibers were then evaluated for precision, and quantitative figures of merit were assessed for extractions using the PDMS/DVB fiber, which displayed the best overall performance. FIMS with the PDMS/DVB fiber allows simple extraction and MS detection and quantitation of DMP in water with good linearity and precision, and at concentrations as low as 3.6 microg L(-1). The LD and LQ of FIMS are below the maximum phthalate concentration allowed by the USEPA for drinking water (6 microg L(-1)).     

Quantitation of trace phenolic compounds in water by trap‐and‐release membrane introduction mass spectrometry after acetylation

Trap‐and‐release membrane introduction mass spectrometry (T&R‐MIMS) with a removable direct insertion membrane probe (DIMP) is used to quantitate a variety of trace phenolic compounds in water after acetylation. The procedure is simple, rapid and robust, producing linear and reproducible responses for phenolic compounds with varying polarities. Acetylation minimizes the polarity effects of ring substituents; hence, T&R‐MIMS of the acetylated phenols provides lower and more uniform limits of detection (LODs) (2–15 µg L⁻¹) than those obtained by direct T&R‐MIMS analysis of the non‐derivatized phenols. Copyright © 2008 John Wiley & Sons, Ltd.     

Determination of phenolic compounds in modern and old varieties of durum wheat using liquid chromatography coupled with time-of-flight mass spectrometry

An evaluation of the grain functional components of Italian durum wheat cultivars was conducted. The raw material was obtained from the field trial performed in 2006–2007 at the Experimental Farm of the University of Bologna, (Bologna, Italy). The aim of this study was to define the phytochemical profile of ten varieties, comprised of old and modern durum wheat genotypes, including quantitative and qualitative phenolic and flavonoid content (free and bound forms). The results showed that mean values of total phenolic compound and total flavonoid content in old wheat varieties (878.2 ± 19.0 μmol gallic acid equivalent/100 g of grain and 122.6 ± 25.4 μmol catechin equivalent/100 g of grain, respectively) did not differ significantly from those detected in modern genotypes (865.9 ± 128.9 μmol gallic acid equivalent/100 g and 123.5 ± 20.6 μmol catechin equivalent/100 g, respectively). However, the HPLC–ESI-TOF-MS analysis highlighted remarkable differences between modern and old cultivars. The interpretation of the mass spectra allowed the identification of 70 phenolic compounds, including coumarins, phenolic acids, anthocyanins, flavones, isoflavones, proanthocyanidins, stilbenes and lignans. The free extracts of ancient wheat varieties showed the presence of a mean number of phenolic compounds and isomer forms (8.7 ± 2.5 and 7.7 ± 4.7 respectively) significantly higher than in modern genotypes (4.4 ± 2.9 and 2.0 ± 2.4, respectively). A similar trend was observed also for the bound phenolic fraction. Moreover, the phytochemical profiles showed the presence of unique phenolic compounds in both free and bound fractions of some of the investigated wheat genotypes. Results highlighted that investigated old wheat cultivars may offer unique nutraceutical values for their peculiar contents in bioactive phytochemicals, suggesting their uses into a wide range of regular and specialty products naturally enriched with health-promoting compounds.     

Analysis of phenolic compounds in rhubarbs using liquid chromatography coupled with electrospray ionization mass spectrometry

Rhubarb is an important herbal medicine for the treatment of constipation, inflammation, and cancer. In this study, a facile method based on liquid chromatography coupled with electrospray ionization tandem mass spectrometry has been established for the analysis of bioactive phenolic compounds in rhubarbs. From six rhubarb species, official (Rheum officinale, R. palmatum, and R. tanguticum) and unofficial (R. franzenbachii, R. hotaoense, and R. emodi), a total of 107 phenolic compounds were identified or tentatively characterized based on their mass spectra. These compounds include sennosides, anthraquinones, stilbenes, glucose gallates, naphthalenes, and catechins. Ion chromatograms for the identified compounds of different rhubarbs were then compared. Consistent with previous reports, sennosides and rhein were only detected in official rhubarbs. Unexpectedly, we found that R. officinale contained very different phenolic compounds from the other two official species. Sennoside A, which has been considered as the major purgative component of rhubarb, was only detected in R. officinale, while its close isomers were observed in R. palmatum and R. tanguticum. In addition, the predominant anthraquinone glycosides in R. officinale were found to be rhein 8-O-glucoside and emodin 1-O-glucoside, whereas those in R. palmatum and R. tanguticum were rhein 1-O-glucoside and emodin 8-O-glucoside. Stilbenes, which are the major constituents of unofficial rhubarbs, were also different among the species. Our results clarify the chemical composition of rhubarbs comprehensively for the first time. Due to the significant differences in chemical components of rhubarbs, we suggest that different Rheum species be used separately in clinical practice.     

高效液相色谱-紫外/质谱检测法联合测定新鲜烟叶中的25种酚类物质

建立了烟叶中25种酚类物质的高效液相色谱-紫外/质谱(HPLC-UV/MS)测定方法,其中11种主要酚类物质采用HPLC-UV法进行绝对定量分析,其余采用HPLC-MS法进行半定量分析。方法验证结果表明：11种酚类标准物质在0.90~99.00 mg/L(绿原酸及芸香苷为0.95~380.00 mg/L)范围内呈现很好的线性关系,相关系数为0.9993~0.9999。在22.5~24.8、45.0~49.5、67.5~74.3 mg/L 3个水平的加标回收率为91.0%~112.4%。方法重复性的相对标准偏差(RSD)为1.48%~13.40%,日内日间精密度的RSD为0.35%~15.54%。采用本方法对云南、河南、贵州的成熟期新鲜烟叶样品进行了分析,主要酚类物质总量为贵州>云南>河南,贵州与河南两地间存在显著性差异;芸香苷含量为云南>贵州>河南,且相互间有显著性差异。本方法预处理简单,酚类物质的分析覆盖面广,可用于批量烟叶样品的检测。     

Development of membrane inlet mass spectrometry for examination of fermentation processes

Membrane inlet mass spectrometry (MIMS) is useful for on-line monitoring of fermentation processes. However, readings are affected by the complex and dynamic matrix in which biological processes occur, making MIMS calibration a challenge. In this work, two calibration strategies were evaluated for measurement of typical products of acidogenic fermentation, i.e., ethanol, H₂, and CO₂ in the liquid phase, and H₂ and CO₂ in the gas phase: (1) “standard calibration”, which was performed independent of fermentation experiments with sterile standards in water with a N₂ headspace, and (2) “in-process calibration” whereby fermentation was monitored concurrent with off-line analysis. Fermentation was operated in batch and continuous modes. In-process calibration was shown to be most effective for measurements of H₂ and CO₂ in both gas and liquid phases; standard calibration gave erroneous results. In the gas phase, this was due to a lower sensitivity during experiments compared to the independent standard calibration, believed to be caused by formation of a liquid film on the surface of the probe. In the liquid phase, moving from the standard calibration environment to the fermentation caused the linear relationship between the H₂ concentration and MIMS signal to change in intercept, and the relationship for CO₂ to change in slope, possibly due to dissolved ions, and related non-ideality. For ethanol, standard calibration results were fairly consistent with in-process calibration results. The main limitation with in-process calibration is the potential for a lack of variability in target concentration. This could be addressed by spiking the targeted compound at the end of the experiment. Regardless, MIMS is an ideal instrument for analysing fermentation experiments, due to its ability to measure targeted compounds semi-continuously, and due to a lack of drift over long periods.     

Fast and direct screening of solid materials for their potential liberation of hydrophobic organic compounds using hot cell membrane inlet mass spectrometry

We demonstrate that solid materials can be screened directly and without any pretreatment for their potential liberation of chemicals into the surroundings using a hot (150-250 degrees C) sample cell membrane inlet mass spectrometer with electron ionization. Three very different types of solids were tested: polymers (in this context regarded as a solid), tea leaves and pesticide-contaminated soil. From the polymers phthalates and other additives were liberated; from the tea leaves flavor additives and caffeine were liberated; and from the contaminated soil degradation products of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were liberated. In all cases we detected characteristic compounds directly from the untreated sample with an analytical turnover of 8-10 samples per hour. Improved selectivity of compounds penetrating the membrane was achieved either by operating the hot cell at different temperatures or by using variations in the time trend of individual ions following insertion of a piece of the solid material into the hot cell.     

Analysis of phenolic compounds in Epimedium plants using liquid chromatography coupled with electrospray ionization mass spectrometry

A new method based on HPLC coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) has been established for the analysis of phenolic compounds in Epimedium plants. The characteristic fragmentation pathways of 29 phenolic compounds were studied, and 126 compounds were identified or tentatively characterized based on their mass spectra from fourteen samples including the aerial samples and the underground parts of the seven species. Furthermore, the differences in phenolic compound profiles between different Epimedium plants and two parts of the seven species were reported for the first time. Due to their significant chemical differences, these Epimedium species should be used separately in clinical practice.     

Direct detection of large fat-soluble biomolecules in solution using membrane inlet mass spectrometry and desorption chemical ionization

This paper presents the first membrane inlet mass spectrometry system capable of detecting large biomolecules, such as testosterone (M(r) 288), testosterone acetate (M(r) 330) and alpha-tocopherol (M(r) 430, vitamin E). The result was obtained using a home-made chemical ionization ion source with a thermostated tubular silicone membrane mounted right in the centre of a methane CI plasma. The liquid sample was flushed through the inside of the membrane for a period of 20-25 min, where the analyte diffused into the membrane. Following this trapping period the analyte was released from the membrane into the mass spectrometer by the combined action of heat radiation from the filament and charge transfer from the chemical ionization plasma. As a result of this stimulated desorption a good desorption peak was obtained as the analyte vaporized out of the membrane. Retinol (M(r) 286, vitamin A), cholecalciferol (M(r) 384, vitamin D3) and cholesterol (M(r) 386) were also detected. However, these compounds (all containing a long hydrocarbon chain and being aliphatic alcohols) did not give a protonated molecule. They gave a series of cluster ions with the dominant located 20 mass units below the molecular ion. The detection limits of the new desorption chemical ionization MIMS technique were at low or sub-micromolar concentrations (high ppb levels) and the reproducibility was within 20%, when the area of the desorption peak was used for quantitation.     

Utilization of a multimembrane inlet and a cyclic sudden sampling introduction mode in membrane inlet mass spectrometry

Sudden sampling introduction into a membrane inlet mass spectrometer (MIMS) considerably improves the selectivity of the membrane inlet and is therefore applicable even for compounds with low permeabilities through a silicone membrane. In this study the basics of cyclic non-steady-state sudden increase sample injection were studied using a three-membrane inlet and a portable sector double-focusing mass spectrometer. The operational parameters of the inlet system providing the most efficient enrichment of volatile organic compounds (VOCs) in air were defined. Simulation of the diffusion process following sudden sample introduction into the three-membrane inlet was also carried out. Experimental testing of the three-membrane inlet system with the cyclic sudden sample injection mode for benzene, toluene, styrene, and xylene in air was performed. The simulation and the experimental results demonstrated that, when this mode is used, the VOCs/nitrogen relative enrichment factor of samples introduced into the mass spectrometer equipped with a three-membrane inlet is increased by a factor of approximately 10(5) compared with a direct introduction method. This effect may be used to decrease detection limits of compounds obtained with mass spectrometry to decrease matrix flow through the inlet at the same detection limits.     

Determination of phenolic compounds in wines by novel matrix solid-phase dispersion extraction and gas chromatography/mass spectrometry

A novel matrix solid-phase dispersion (MSPD) extraction method was developed to extract simultaneously 23 phenolic compounds from wine samples prior to determination by gas chromatography with mass spectrometric detection in the selected ion monitoring mode. Different parameters of the MSPD technique such as dispersant solid-phase, eluting solvent, and sample ionic strength and pH were optimized. The optimized MSPD procedure requires a small volume of wine (1 mL), commercial silica gel (1.5 g) as dispersant solid-phase and a small volume of ethyl acetate (5 mL) as eluting solvent. Under these conditions, the extraction of the studied compounds was almost complete (mean values of recoveries between 87 and 109%) in a short time (15 min). Moreover, satisfactory standard deviations of repeatability (RSD<9% in most cases), linear regression coefficients (r(2)>0.993) and detection limits (<8 microg/L) confirm the usefulness of the methodology for routine monitoring of the concentration of individual phenolic antioxidants in wines. Application was illustrated by analysis of different wine samples.     

Dynamic calibration and dissolved gas analysis using membrane inlet mass spectrometry for the quantification of cell respiration

A membrane inlet mass spectrometer connected to a miniaturized reactor was applied for dynamic dissolved gas analysis. Cell samples were taken from 7 mL shake flask cultures of Corynebacterium glutamicum ATCC 13032, and transferred to the 12 mL miniaturized reactor. There, oxygen uptake and carbon dioxide and its mass isotopomer production rates were determined using a new experimental procedure and applying nonlinear model equations. A novel dynamic method for the calibration of the membrane inlet mass spectrometer using first-order dynamics was developed. To derive total dissolved concentration of all carbon dioxide species (C(T)) from dissolved carbon dioxide concentration ([CO(2)](aq)), the ratio of C(T) to [CO(2)](aq) was determined by nonlinear parameter estimation, whereas the mass transfer coefficient of CO(2) was determined by the Wilke-Chang correlation. Subsequently, the suitability of the model equations for respiration measurements was examined using residual analysis and the Jarque-Bera hypothesis test. The resulting residuals were found to be random with normal distribution, which proved the adequacy of the application of the model for cell respiration analysis. Hence, dynamic changes in respiration activities could be accurately analyzed using membrane inlet mass spectrometry with the novel calibration method.