Environmental applications of membrane introduction mass spectrometry

The purpose of this review is to highlight the versatility of membrane introduction mass spectrometry (MIMS) in environmental applications, summarize the measurements of environmental volatile organic compounds (VOCs) accomplished using MIMS, present developments in the detection of semi-volatile organic compounds (SVOCs) and forecast possible future directions of MIMS in environmental applications.     

A universal temperature controlled membrane interface for the analysis of volatile and semi-volatile organic compounds

A universal temperature controlled membrane interface (TCMI) has been constructed for hollow-fibre membranes. The membrane temperature is controllable in the range -70 to 250 degrees C using an electric heater and a flow of cooled nitrogen or helium gas. Volatile and semi-volatile organic compounds may be detected either by continuous diffusion across the membrane or by in-membrane pre-concentration followed by thermal desorption into the detector. The TCMI interface is demonstrated in combination with mass spectrometry and GC-MS, for the determination of VOCs and SVOCs in aqueous and air samples and for the on-line monitoring of a bioreactor.     

A coaxially heated membrane introduction mass spectrometry interface for the rapid and sensitive on-line measurement of volatile and semi-volatile organic contaminants in air and water at parts-per-trillion levels

A coaxially heated membrane introduction mass spectrometry (MIMS) sampling interface is presented that demonstrates improved on-line performance for the direct measurement of semi-volatile organic compounds (SVOCs) in air and water samples at parts-per-trillion levels. The device is based on a polydimethylsiloxane (PDMS) capillary hollow fibre membrane (HFM) in a pneumatically assisted "flow-over" configuration that is resistively heated on the membrane interior via a coaxial nichrome wire, establishing a thermal gradient counter to the analyte concentration gradient. This arrangement allows for continuous and/or pulsed heating modes, affording excellent sensitivity for the on-line measurement of SVOCs while retaining sensitivity for volatile organic compounds (VOCs). In addition, the signal response time for SVOCs is reduced substantially over conventional "flow-over" MIMS interfaces. Separation and quantitation of analytes are achieved using quadrupole ion trap tandem mass spectrometry.     

An electrospray membrane probe for the analysis of volatile and semi-volatile organic compounds in water

A new membrane probe incorporating electrospray ionization (ESI) was designed, built and coupled to an ion trap mass spectrometer to detect low levels of semi-volatile organic compounds (SVOCs) in water. Similar to other membrane introduction mass spectrometry (MIMS) systems, the probe contains a capillary polydimethylsiloxane (PDMS) membrane to allow for the preferential permeation of small molecules but, in contrast, the interface uses a liquid/membrane/liquid interface rather than liquid/membrane/gas. The ESI source allows the probe to be operated at atmospheric pressure in positive or negative ionization mode and the lack of fragmentation in ESI allows for the simultaneous screening of many analytes with high sensitivity. The interface allows for the addition of additives to both the external and the internal liquid mobile phases to selectively improve permeation and/or the ionization efficiency of various classes of compounds. Characterization of the probe with methanol as the internal mobile phase showed that the signal for aniline optimized at 60 degrees C and an internal flow rate between 2-5 microL/min. The transfer of analyte through the membrane from water to methanol ensures a strong signal and robust electrospray for both positive and negative ion mode which is not typical when spraying pure water. Detection limits for aniline, pyridine and pentachlorophenol, and for the herbicides alachlor, atrazine, butachlor, metolachlor and simazine, were in the ppb to pptr range.     

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.     

Analytical pyrolysis of re-circulated leachates: Towards an improved municipal waste treatment

The harmless removal of municipal solid waste (MSW) requires the biodegradation of organic matter to decrease the risk of gaseous emissions and leaching of contaminants. We studied the re-circulation of leachates from an aerobic treated MSW in a lysimeter and compared these results with a similar laboratory study using small-scale reactors. The reduction of total organic C and biological and chemical oxygen demands provided clear evidence for the biodegradation of organic matter in MSW after 12 months of leachate re-circulation. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that the biodegradation was more efficient in the large-scale lysimeter than in the laboratory reactors. Different from the laboratory experiments, carbohydrates and N-containing compounds were decomposed almost completely after 2 months. Furthermore, temperature-resolved Py-FIMS showed that leachate re-circulation led to a higher thermal stability of the residual, non-decomposed organic matter. In summary, the two analytical pyrolysis methods proved that the re-circulation of leachates through MSW promoted organic matter biodegradation and offers an improved aerobic waste treatment technology.     

External interface for trap-and-release membrane introduction mass spectrometry applied to the detection of inorganic chloramines and chlorobenzenes in water.

Construction and evaluation of an external configuration trap-and-release membrane introduction system for mass spectrometry is described. This novel interface allows independent control of the temperature of the membrane and eliminates the dependence of membrane heating efficiency on its position in the ion source. The external trap-and-release MIMS configuration is successfully applied to detection of inorganic chloramines and chlorobenzenes. The method is shown to give temporal resolution of volatile vs. semi-volatile compounds, which increases its sensitivity for semi-volatiles in the presence of volatiles and provides an additional selectivity parameter. Further selectivity is provided by tandem mass spectrometry.     

A membrane introduction flame ionization/electron capture detection (MIFID/ECD) system for the rapid, real-time screening of volatile disinfection byproducts and hydrocarbon contaminants in water

Described is a system that employs an online membrane introduction (MI) interface coupled with parallel flame ionization and electron capture detectors (FID/ECD). We report the use of a MIFID/ECD system as an online method to detect total volatile organic halides (ΣVOXs) and volatile organic compounds (ΣVOCs) as aggregate parameters in environmental water samples at sub parts-per-billion levels without the need for sample handling or analyte pre-concentration. The instrument provides rapid screening and real-time monitoring capabilities of important classes of water contaminants in a simple system without the vacuum requirements of MS detectors. Furthermore, the MIFID/ECD instrument was successfully employed as a real-time reaction monitor for the photodegradation of toluene by an advanced oxidation process and the formation of volatile disinfection byproducts in the chlorination of natural waters. The results of these experiments compare favorably to those obtained using membrane introduction mass spectrometry (MIMS).     

Separation of technical 4-nonylphenols and their biodegradation products by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry

Comprehensive two-dimensional gas chromatography (GC x GC) coupled to time-of-flight mass spectrometry (TOF-MS) was applied to improve the separation of 4-nonylphenol isomers and their biodegradation products. The structurally similar nonylphenol isomers were separated by combining a 30 m long semi-polar column and a short polar capillary. Both were coupled via a custom-made liquid nitrogen cryogenic modulator. The advanced GC resolution of coeluting isomers, additionally supported by fast scanning TOF-MS, provided clearer, non-interfered mass spectra of individual isomers. Thus, identification of components is facilitated as shown for isomeric 4-nonylphenols and metabolites of their biodegradation by Clavariopsis aquatica, an aquatic fungus. GC x GC-TOF-MS analysis enabled the separation of about 40 alkylphenol isomers included in technical 4-nonylphenol. During biodegradation the variety of emerging compounds increased with longer reaction time. The comprehensive analysis indicated a broad spectrum of hydroxylated, carboxylated nonylphenolisomers and additionally, chlorinated aromatic compounds produced and released from the fungal culture.     

Comparison of different methods for the determination of volatile organic compounds in water samples

The aim of this work was to compare the characteristics of three methods, membrane inlet mass spectrometry (MIMS), purge-and-trap gas chromatography-mass spectrometry (P&T) and static headspace gas chromatography (HSGC), for the determination of volatile organic compounds in water samples as used in routine analysis. The characteristics examined included linear dynamic ranges, detection limits of selected environmentally hazardous volatile organic compounds (e.g. toluene, benzene and trichloroethene) in water, required analysis time and reproducibility of the analytical methods. The MIMS and P&T methods had the lowest detection limits for all the tested compounds, ranging from 0.1 to 5 mug 1(-1). Linear dynamic ranges using the MIMS method were about four orders of magnitude and using the P&T method about two orders of magnitude. Detection limits of the HSGC method were 10-100 times higher than those of the other two methods, but the linear dynamic ranges were larger, even up to six orders of magnitude. The analysis time per sample was shortest for the MIMS method, from 5 to 10 min, and ranged around from 35 to 45 min for the HSGC and P&T methods. The reproducibilities of the methods were of the same order of magnitude, in the range of 1-13%. Agreement between the analytical results obtained for spiked samples and for environmental water samples by the three different methods was very good.     

Novel applications of highly sensitive liquid chromatography/mass spectrometry/mass spectrometry for the direct detection of ultra-trace levels of contaminants in water

Recent advances in the sensitivity of liquid chromatography/mass spectrometry (LC/MS) instrument technology provide the basis for the direct detection, i.e. without sample pre-concentration, of organic contaminants in water in the ng/L range. Novel applications for the analysis of atrazine and some of its desalkylated and hydroxylated degradation products, the pharmaceutical compounds diclofenac and carbamazepine, sulfonylurea herbicides, and iodinated X-ray contrast media have been developed. For each analyte a specific tandem mass spectrometric (MS/MS) transition has been selected and the corresponding mass spectrometric parameters optimised. All analytes could be analysed within three specific analytical runs including different high-performance liquid chromatography (HPLC) conditions. Detection limits were determined to be better than 10 ng/L for the direct analysis of the compounds in water except for X-ray contrast media, for which detection limits were found to be up to one order of magnitude higher. The methods have been successfully utilised for the analysis of natural waters. Matrix effects frequently occurring in LC/MS have shown to be low to moderate in the case of X-ray contrast media. This work demonstrates that for the analysis of a large number of water contaminants, the sample pre-concentration step could possibly be omitted.     

气相色谱-单光子电离飞行时间质谱的联用及在柴油组分表征中的应用

建立了一种气相色谱(GC)与单光子电离-飞行时间质谱(SPI-TOF MS)联用(GC/SPI-TOF MS)的分析方法。首先,设计了一种双层套管的传输管用于连接GC与SPI-TOF MS,实现了GC与单光子电离离子源的无缝连接。在此基础上,以n-十五烷标准品和苯/甲苯/二甲苯的标准气为对象,对电离源的重要电压参数进行了优化,得到了纯净的分子离子峰,实现了对各类有机物的快速和准确定性。最后,将该方法用于分析柴油中的挥发性与半挥发性有机物,获得了柴油组分的二维GC×SPI-TOF MS谱图。不需要复杂的谱图解析和数据处理,根据谱图中离子的质荷比(m/z)归纳了柴油的主要成分,包括脂肪烃、芳香烃和含量很低的苯并吡咯等含氮化合物;根据色谱的保留时间将柴油中的同分异构体区分开来。结果表明GC/SPI-TOF MS法是一种简单、有效的分析方法,非常适于柴油及复杂环境样品等的分析表征。     

Determination of selected natural hormones and endocrine disrupting compounds in domestic wastewater treatment plants by liquid chromatography electrospray ionization tandem mass spectrometry after solid phase extraction

A new analytical method for the simultaneous determination of two natural hormones (progesterone and estrone) and two selected endocrine disrupter compounds (EDCs) (diltiazem and carbamazepine (Cbz)) was developed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) after pre-concentration with solid phase extraction (SPE). Influent and effluent samples taken from five different wastewater treatment plants throughout Turkey namely Hurma/Antalya, Lara/Antalya, Kemer-1 and Kemer-2 and METU/Ankara were analyzed for their EDCs contents under the optimum conditions. All of the parameters in the pre-concentration step were optimized and the best recoveries for all compounds of interest were achieved at pH 7 (about 100%). Progesterone was not detected in any of the treatment plants while diltiazem was found in all samples with the exception of Lara effluent.     

Identification and structural characterization of biodegradation products of atenolol and glibenclamide by liquid chromatography coupled to hybrid quadrupole time-of-flight and quadrupole ion trap mass spectrometry

In this paper we report about the biodegradation of the beta-blocker atenolol and the hypoglycaemic agent glibenclamide. The biodegradation tests were performed in batch reactors under aerobic conditions, using as inocculums sewage sludge from a conventional activated sludge treatment and a laboratory-scale membrane bioreactor. Pharmaceuticals were used as sole carbon sources, spiked at 50ng/L and 10mg/L concentrations. Quadrupole time-of-flight mass spectrometry coupled to ultra-high-pressure liquid chromatograph was used for the screening and the structural elucidation of biodegradation products. A microbial metabolite of atenolol with [M+H](+) at 268 was detected in the positive electrospray ionization mode. This new compound was determined to be a product of microbial hydrolysis of the amide of the parent compound. Biodegradation of glibenclamide by activated sludge proceeded via bacterial hydroxylation of the cyclohexyl ring, which resulted in formation of metabolite with a protonated molecule, [M+H](+)=510. MS(3) experiments performed by hybrid quadrupole linear ion trap (QqLIT) mass spectrometry coupled to high-performance liquid chromatography enabled further structural elucidation of the identified metabolites. Moreover, the highly sensitive QqLIT instrument in the MRM mode enabled the detection of parent compounds and one of the microbial metabolites identified in real wastewater samples. The methodology used in this study permitted for the first time the identification and detection of biodegradation product of beta-blocker atenolol in real wastewater samples.     

Multi-residue contaminants and pollutants analysis in saffron spice by stir bar sorptive extraction and gas chromatography-ion trap tandem mass spectrometry

A method for the simultaneous determination of 46 semi-volatile organic contaminants and pollutants in saffron has been developed for the first time using a stir bar sorptive extraction technique and thermal desorption in combination with gas chromatography-ion trap tandem mass spectrometry. The analytical method proposed was easy, rapid and sensitive and showed good linearity, accuracy, repeatability and reproducibility over the concentration range tested. Moreover, the correlation coefficients were higher than 0.98 for all target compounds and detection limits were lower than 1 microg/kg except for simazine. The present method was also applied for the analysis of trace contaminants in saffron samples.     

Gas chromatography with mass spectrometry for the determination of phthalates preconcentrated by microextraction based on an ionic liquid

A new procedure is proposed for the analysis of migration test solutions obtained from plastic bottles used in the packaging of edible oils. Ultrasound‐assisted emulsification microextraction with ionic liquids was applied for the preconcentration of six phthalate esters: dimethylphthalate, diethylphthalate, di‐n‐butylphthalate, n‐butylbenzylphthalate, di‐2‐ethylhexylphthalate, and di‐n‐octylphthalate. The enriched ionic liquid was directly analyzed by gas chromatography and mass spectrometry using direct insert microvial thermal desorption. The different factors affecting the microextraction efficiency, such as volume of the extracting phase (30 μL of the ionic liquid) and ultrasound application time (25 s), and the thermal desorption step, such as desorption temperature and time, and gas flow rate, were studied. Under the selected conditions, detection limits for the analytes were in the 0.012–0.18 μg/L range, while recovery assays provided values ranging from 80 to 112%. The use of butyl benzoate as internal standard increased the reproducibility of the analytical procedure. When the release of the six phthalate esters from the tested plastic bottles to liquid simulants was monitored using the optimized procedure, analyte concentrations of between 1.0 and 273 μg/L were detected.     

Screening anti‐tumor compounds from Ligusticum wallichii using cell membrane chromatography combined with high‐performance liquid chromatography and mass spectrometry

Tyrosine 367 Cysteine‐fibroblast growth factor receptor 4 cell membrane chromatography combined with high‐performance liquid chromatography and mass spectrometry was developed. Tyrosine 367 Cysteine‐HEK293 cells were used as the cell membrane stationary phase. The specificity and reproducibility of the cell membrane chromatography was evaluated using 1‐tert‐butyl‐3‐{2‐[4‐(diethylamino)butylamino]‐6‐(3,5‐dimethoxyphenyl)pyrido[2,3‐d]pyrimidin‐7‐yl}urea, nimodipine and dexamethasone acetate. Then, anti‐tumor components acting on Tyrosine 367 Cysteine‐fibroblast growth factor receptor 4 were screened and identified from extracts of Ligusticum wallichii. Components from the extract were retained on the cell membrane chromatographic column. The retained fraction was directly eluted into high‐performance liquid chromatography with mass spectrometry system for separation and identification. Finally, Levistolide A was identified as an active component from Ligusticum wallichii extracts. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐tetrazolium bromide‐formazan colorimetric assay revealed that Levistolide A inhibits proliferation of overexpressing the mutated receptor cells with dose‐dependent manner. Phosphorylation of fibroblast growth factor receptor 4 was also decrease under Levistolide A treatment. Flex dock simulation verified that Levistolide A could bind with the tyrosine kinase domain of fibroblast growth factor receptor 4. Therefore, Levistolide A screened by the cell membrane chromatography combined with high‐performance liquid chromatography and mass spectrometry can arrest cell growth. In conclusion, the two‐dimensional high‐performance liquid chromatography method can screen and identify potential anti‐tumor ingredients that specifically act on the tyrosine kinase domain of the mutated fibroblast growth factor receptor 4.     

Fast characterization of intact proteins using a high-throughput eight-channel parallel liquid chromatography/mass spectrometry system

The preparation of protein substrates requires that a large number of chromatographic fractions be analyzed for the presence of reactants, products and by-products. Analyses using linear matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) or single column liquid chromatography/mass spectrometry (LC/MS) have been inadequate because of mass resolution or throughput. Therefore, a high-throughput method employing an eight-channel parallel reverse-phase LC/MS system was developed. This system is capable of screening fractions from preparative ion-exchange chromatography with the required mass accuracy and throughput so that the protein purification process can be monitored in a relatively short period of time. As an example, the purification and analysis of an acylated protein with a molecular weight of 8.9 kDa is described and the detection of a contaminating by-product that differs in size by less than 20 Da is demonstrated. Using the current instrumentation and approach, it is practical to analyze 50 protein-containing fractions from column chromatography in less than 1 hour using parallel LC/MS.     

Liquid chromatography/negative ion atmospheric pressure photoionization mass spectrometry: a highly sensitive method for the analysis of organic explosives

Gas chromatography/mass spectrometry (GC/MS) is applied to the analysis of volatile and thermally stable compounds, while liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI‐MS) and liquid chromatography/electrospray ionization mass spectrometry (LC/ESI‐MS) are preferred for the analysis of compounds with solution acid‐base chemistry. Because organic explosives are compounds with low polarity and some of them are thermally labile, they have not been very well analyzed by GC/MS, LC/APCI‐MS and LC/ESI‐MS. Herein, we demonstrate liquid chromatography/negative ion atmospheric pressure photoionization mass spectrometry (LC/NI‐APPI‐MS) as a novel and highly sensitive method for their analysis. Using LC/NI‐APPI‐MS, limits of quantification (LOQs) of nitroaromatics and nitramines down to the middle pg range have been achieved in full MS scan mode, which are approximately one order to two orders magnitude lower than those previously reported using GC/MS or LC/APCI‐MS. The calibration dynamic ranges achieved by LC/NI‐APPI‐MS are also wider than those using GC/MS and LC/APCI‐MS. The reproducibility of LC/NI‐APPI‐MS is also very reliable, with the intraday and interday variabilities by coefficient of variation (CV) of 0.2–3.4% and 0.6–1.9% for 2,4,6‐trinitrotoluene (2,4,6‐TNT). Copyright © 2008 John Wiley & Sons, Ltd.