Helium microwave-induced plasma mass spectrometric detection for reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography (HPLC) is directly coupled to helium microwave-induced plasma mass spectrometry (He MIP-MS) for the element-selective detection of halogenated organic compounds. Absolute detection limits are approximately 50 pg Br for brominated compounds, 1 pg I for iodinated compounds, and 10 ng Cl for chlorinated compounds. The linear dynamic range for Br- and I-containing compounds is 3-4 orders of magnitude. However, the linear range for chlorinated species is severely limited by high background at m/z = 35. The relative standard deviation for repetitive injections is less than 10%. The helium microwave-induced plasma is operated at moderate powers (300-350 W) and with a total helium consumption of 6-8 L/min. The effect of organic solvents on the background mass spectrum is investigated.     

Potential chlorinated and brominated interferences on the polybrominated diphenyl ether determinations by gas chromatography-mass spectrometry

The analysis of polybrominated diphenyl ether (PBDE) congeners by GC-MS was studied in terms of potential interferences. Different MS approaches were normally used for the PBDE analyses: negative ion chemical ionization (NICI-MS) and electron ionization (EI-MS). This paper studied the presence of potential interferences in each instrumental technique approach, principally those corresponding to different chlorinated compounds (PCBs, PCNs, etc.) as well as brominated compounds (PBBs, MeO-PBDEs, TBBPA, etc.). The two ionization modes are subjected to different types of interferences. In general, EI-MS is affected by chlorinated interferences, especially PCBs. NICI-MS eliminated chlorinated interferences but presented different brominated interferences, well resolved with the EI-MS approach.     

Evaluation of the stability and analysis of halogenated furanones in disinfected drinking waters

A refined method for the sub-nanomolar analysis of 13 halogenated furanones in chlorinated drinking water is proposed which uses liquid-liquid extraction, methylation where necessary, gas chromatographic separation, and either micro-electron capture or ion trap mass spectrometric detection. Liquid-liquid extraction with methyl tert-butyl ether was demonstrated to be effective for recovery of halogenated furanones. Confirmation of the halogenated furanones identity and reduction of natural organic matter interference were achieved by ion trap tandem mass spectrometry. Compound stabilities and procedural efficiencies were evaluated to permit optimization of the method for reasonable sample volumes and a 1000:1 pre-concentration factor that would permit feasible sample collection in the field. Both chlorinated and brominated analogues of MX (3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) were included in a suite of compounds targeted in a national occurrence study of disinfection by-products.     

Ultra-trace determination of Persistent Organic Pollutants in Arctic ice using stir bar sorptive extraction and gas chromatography coupled to mass spectrometry

This study presents the optimization and application of an analytical method based on the use of stir bar sorptive extraction (SBSE) gas chromatography coupled to mass spectrometry (GC–MS) for the ultra-trace analysis of POPs (Persistent Organic Pollutants) in Arctic ice. In a first step, the mass-spectrometry conditions were optimized to quantify 48 compounds (polycyclic aromatic hydrocarbons, brominated diphenyl ethers, chlorinated biphenyls, and organochlorinated pesticides) at the low pg/L level. In a second step, the performance of this analytical method was evaluated to determine POPs in Arctic cores collected during an oceanographic campaign. Using a calibration range from 1 to 1800 pg/L and by adjusting acquisition parameters, limits of detection at the 0.1–99 and 102–891 pg/L for organohalogenated compounds and polycyclic aromatic hydrocarbons, respectively, were obtained by extracting 200 mL of unfiltered ice water. α-hexachlorocyclohexane, DDTs, chlorinated biphenyl congeners 28, 101 and 118 and brominated diphenyl ethers congeners 47 and 99 were detected in ice cores at levels between 0.5 to 258 pg/L. We emphasise the advantages and disadvantages of in situ SBSE in comparison with traditional extraction techniques used to analyze POPs in ice.     

NOx formation in the plasma treatment of halomethanes

A nonthermal, atmospheric pressure plasma, made-up of a BaTiO3 packed-bed reactor, has been used to study the formation of NOx and N2O during the plasma destruction of a range of volatile organic compounds (VOCs) and hazardous air pollutants, including chlorinated, brominated, fluorinated, and iodinated methane species, in a carrier gas of air. Using the plasma destruction of pure air as a baseline, it is found that the amount of NOx formed is unaffected by the addition of a few hundred parts per million of a simple hydrocarbon (e.g. methane). In the case of the fluorinated, chlorinated, and brominated methanes, we find enhanced production of NOx and a marked increase in the ratio of NO2 to NO formed, from approximately 1.1 in air and methane to approximately 2.3 in halogenated species. However, iodinated additives (specifically methyl iodide and diiodomethane) have remarkably different results compared to the other halogenated additives; they show enhanced increases in the NO2 to NO ratio ( approximately 6-13) and reduced NOx production. The enhanced conversion of NO to NO2 is attributed to reactions involving halogen oxides, e.g. ClO and IO.     

Ion-trap tandem mass spectrometry-based analytical methodology for the determination of polychlorinated biphenyls in fish and shellfish. Performance comparison against electron-capture detection and high-resolution mass spectrometry detection

Optimization of the Varian Saturn 2200 ion-trap tandem mass spectrometry (IT-MS/MS) system and comparison of its data quality with two other detection methods [electron-capture detection (ECD) and high-resolution mass spectrometry (HRMS)] was pursued by measuring polychlorinated biphenyls (PCBs) levels in fish and shellfish samples. IT-MS/MS methodology provided limits of detection (LOD) comparable to those obtained by ECD but superior specificity for the detection of a selected number of 39 PCB native congeners and 9 (13)C-labelled PCB standards. The method detection limits (MDLs) established for IT-MS/MS ranged between 1.0 and 5.0 pg/g on a wet weight basis while those obtained by ECD and HRMS were 1.0-4.0 pg/g and 0.1-2.0 pg/g, respectively. Overall, the results obtained in the study demonstrate that gas chromatography (GC) combined with IT-MS/MS provide higher data quality than those achievable by GC-ECD. For this particular set of target analytes the specificity achievable with IT-MS/MS was comparable to that obtained by HRMS and both techniques provided comparable data in terms of accuracy and precision.     

Microwave induced plasma atomic emission spectrometry: a suitable detection system for the determination of volatile halocarbons

Microwave induced plasma atomic emission spectrometry (MIP-AES), a highly sensitive detection system for organometal compounds, was coupled to an automated purge and trap gas chromatographic system for the determination of volatile halogenated hydrocarbons in environmental water samples. Optimisation of the parameters affecting the injection and detection system led to relative detection limits from 1 to 14 ng · L^–1 for chlorine- and bromine-compounds and from 10 to 75 ng · L^–1 for iodine-compounds, on basis of a 10 mL sample volume. A comparison of the analytical characteristics between atomic emission detection (AED) and electron capture detection (ECD) showed a lower sensitivity of the atomic emission detector for halocarbons, but the detection thresholds are low enough to use the method for the determination of volatile halocarbons in trace level concentrations. The ability of the atomic emission detector provides increased selectivity for monitoring individual halogenated compounds under simplified and rapid chromatographic conditions, within a total analysis time of only 30 min. The method was applied with gas chromatographic separation for the analysis of sea water samples. Concentrations for the different elements between 0.05 and 15.28 μg · L^–1 were determined.     

Optimization of congener-specific analysis of 40 polybrominated diphenyl ethers by gas chromatography/mass spectrometry

The analysis by gas chromatography coupled with mass spectrometry (GC/MS) of 40 different congeners of polybrominated diphenyl ethers (PBDEs) containing 1-7 bromine atoms is described. Two different MS approaches were used, negative chemical ionization (NCI-MS) and electron ionization (EI-MS). Operating parameters such as electron energy and source temperature were optimized in order to obtain the maximum sensitivity in the EI-MS study. For NCI-MS analyses, the effects of the moderating gas (methane or ammonia), source temperature and system pressure were studied. The quality parameters of the two approaches tested were compared. NCI-MS gave detection limits between 30 fg and 1.72 pg, whereas EI-MS gave detection limits between 0.53 and 32.09 pg. The main advantage of EI-MS is that it provides better structural information. Moreover, the use of EI-MS allowed the use of an isotope dilution method for quantification, making the analysis more reliable at trace levels.     

Detection of organotin,organomercury, and organolead compounds with a pulsed discharge detector (PDD)

The response of a pulsed discharge detector (PDD) to organometallic compounds in the helium ionization detection (HID) mode was dependant on the number of C atoms in the tested analytes with the limits of detection ranging from 0.7 pg (tetraethyllead (Et(4)Pb)) to 1.2 pg di- n-propyl mercury (Pr(2)Hg)). Response linearity was excellent over three orders of magnitude. Selectivity in the HID mode was enhanced by doping the He discharge gas with argon, although sensitivity dropped threefold. In electron capture detection (ECD) mode, only organolead was detected with a limit of 0.1 pg.     

Low nanogram per liter determination of halogenated nonylphenols,nonylphenol carboxylates,and their non-halogenated precursors in water and sludge by liquid chromatography electrospray tandem mass spectrometry

A new LC-MS-MS method for quantitative analysis of nonylphenol (NP), nonylphenol carboxylates (NPECs), and their halogenated derivatives: brominated and chlorinated nonylphenols (BrNP, ClNP), brominated and chlorinated nonylphenol carboxylates (BrNPE(1)C and ClNPE(1)C) and ethoxycarboxylates (BrNPE(2)C and ClNPE(2)C) in water and sludge has been developed. Electrospray negative ionization MS-MS was applied for the identification of above mentioned compounds. Upon collision-induced dissociation, their deprotonated molecules gave different fragments formed by the cleavage of the alkyl moiety and/or (ethoxy)carboxylic moiety. For halogenated compounds a highly diagnostic characteristic pattern of isotopic doublet signals was obtained and fragmentation yielded, in addition to above mentioned ions, [Br](-) and [Cl](-), respectively. Quantitative analysis was done in the multiple reaction monitoring (MRM) mode, using two specific combinations of a precursor-product ion transitions for each compound. Additionally, for halogenated compounds two specific channels for each transition reaction, corresponding to two isotopes, were monitored and the ratio of their abundances used as an identification criterion. The method has been validated in terms of sensitivity, selectivity, accuracy, and precision and was applied to the analysis of water and sludge samples from drinking water treatment plant (DWTP) of Barcelona (Catalonia, NE Spain). Halogenated NP and NPECs were detected in prechlorinated water in concentrations up to 315 ng/L, BrNPE(2)C being the most abundant compound. In the DWTP effluent non-halogenated compounds were detected at trace levels (85, 12 and 10 ng/L for NP, NPE(1)C, and NPE(2)C, respectively), whereas concentration of halogenated derivatives never exceeded 10 ng/L. Nonylphenol, brominated and chlorinated NPs were found in flocculation sludge in concentrations of 150, 105, and 145 microg/kg, respectively. Acidic polar metabolites were found in lower concentrations up to 20 microg/kg.     

Gas chromatographic determination of pesticide residues in malt, spent grains, wort, and beer with electron capture detection and mass spectrometry

A method for the simultaneous determination of 9 pesticides (dinitroanilines, organophosphorus, triazoles, and pyrimidines) in several products (malt, spent grains, wort, and beer) of the beer industry is reported. Solid samples (malt and spent grains) are extracted by homogenization with a water-hexane mixture, and the pesticides are partitioned with dichloromethane. Liquid samples (wort and beer) are extracted by sonication with a hexane-dichloromethane mixture. Determination of pesticide residues was made by capillary gas chromatography with an electron capture detector (ECD). Confirmation of the compounds was performed by gas chromatography/ion trap mass spectrometry in the selected ion monitoring mode. Detection limits for GC-ECD varied from 0.2 to 5.5 pg for trifluralin and malathion, respectively. Recoveries of the pesticides from spiked samples ranged from 81.2 to 113.7% with a relative standard deviation between 3.4-7.5%. The method presents good linearity over the studied range (0.005-2 microg/mL). The proposed method is rapid and reliable and can be useful for routine monitoring during brewing.     

Interference of Transformer oil Matrices to the Internal Standards on PCB Quantification

Abstract

Polychlorinated biphenyls (PCBs) are toxic, perssstent, global environmental contaminants which were formulated as complex mixtures of congeners. Many methods have been developed in the past to analyze PCB in transformer oil samples for regulatory purposes. The most important consideration in the cleanup procedure is the ability to remove the oil from the sample matrix, since trace amount of oil will interfere with the subsequent GC-MS analysis. Electron capture detection (ECD) has been the most common method for gas chromatographic analysis of PCBs because of its high sensitivity toward halogenated compounds. ECD can also respond to some non-PCB compound resulting in biased concentrations of PCB. In this work, a two-stage cleanup method, using DMSO liquid/liquid extraction and HPLC column chromatography. has been applied to two types of transformer oil. Five internal standards have been selected to show their performance in the presence of different oil matrices. The comparison of the PCB quantification at different conditions for GC-MS and GC-ECD will be demonstrated.     

Headspace analysis of chlorinated organic solvents in aerosol cans by gas chromatography

Summary A gas chromatographic (GC) method for the analysis of chlorinated solvents in chemical products in aerosol cans is described. Conditions for the sampling of chemical products from aerosol cans were optimized, so that the recovery of the solvents was better than 90%. Chlorinated solvents were identified by headspace GC—electron capture detection (ECD) as well as by GC — mass spectrometry. Headspace analysis employing the standard additions method and GC-ECD was used for the quantitation of chlorinated solvents. Analysis of 159 acrosol products, for various uses, revealed that 9% of these did not comply with the Danish Aerosol Regulations. The results of the study further indicated that aerosol products for haircare, paints and paint removers, and many others, can be formulated without chlorinated solvents.     

Biogenic volatile organoiodine and organobromine hydrocarbons in the Atlantic Ocean from 42°N to 72°S

During the cruise ANT X/1 and 2 of the research vessel Polarstern from November 1991 to March 1992, 39 surface water samples of the Atlantic Ocean from 42°N to 72.5°S were collected and analysed for their concentration of volatile iodinated and brominated hydrocarbons. The concentration of chlorophyll-a was used as an indicator for phytoplankton, which is one of the main producers of iodinated and brominated compounds in the ocean. For determination of chlorophyll-a, fluorescence spectroscopy was applied, whereas the measurement of halogenated volatile hydrocarbons was carried out by a purge and trap system with subsequent gas chromatographic separation and detection by an electron capture detector. With this technique the brominated substances CHBr₃, CH₂Br₂, CHBr₂Cl and CHBrCl₂ have been detected in the range of <0.03?ng/L to 15?ng/L. For these volatile bromomethanes a distinct concentration profile was found. CHBr₃ was always found to be the substance with the highest concentration followed by CH₂Br₂, CHBr₂Cl and CHBrCl₂. It could also be shown that in addition to CH₃I, which for a long time was believed to be the only volatile iodinated substance in the marine environment, other iodinated substances like CH₂ClI, CH₂I₂ and CH₃CH₂CH₂I exist in the range of <0.01?ng/L to 2.2?ng/L in surface water of the Atlantic Ocean. Although it is improbable that chlorophyll-a is directly involved in the marine production of halogenated hydrocarbons, it was found that it could be used as an indicator for the biogenic formation of brominated compounds, whereas the correlation between chlorophyll-a and the iodinated substances was not of the same quality. The positive correlation between bromoform and dibromomethane proves the same biogenic origin and mechanism of formation, which could not be found for the different iodinated compounds.     

Development of a solid-phase microextraction method for the analysis of phenolic flame retardants in water samples

A solid-phase microextraction (SPME) method for the ultra-trace determination of brominated phenols in aqueous samples has been developed and is reported for the first time to the best of our knowledge. 3,5,3',5'-tetrabromobisphenol A (TBBPA), the most widely used brominated flame retardant, and other phenolic flame retardants in commercial use, such as 2,4-dibromophenol (2,4-DBP), 2,4,6-tribromophenol (TBP) and pentabromophenol (PBP) have been included as target analytes. The analytical procedure involves the in situ acetylation-SPME and gas chromatography-mass spectrometry (GC-MS) determination of the target analytes. A multi-factor categorical experimental design was created to study the main parameters affecting the extraction efficiency, allowing also the evaluation of interaction effects between factors. The factors studied were type of fiber, extraction mode, exposing the fiber directly into the sample (DSPME) or into the headspace over the sample (HSSPME), and extraction temperature. Carboxen-polydimethylsiloxane (CAR-PDMS) fiber appeared to be the most suitable of the five fibers tested for the extraction of most compounds, excluding PBP and TBBPA for which polydimethylsiloxane (PDMS) was the most efficient coating. The highest response was achieved for both fibers sampling in headspace mode at 100 degrees C. In order to test the linearity of the method, calibration studies were performed with both CAR-PDMS and PDMS coatings. For both fibers, the method was linear in a range of 2 orders of magnitude, giving relative standard deviation (RSD%) below 10% for most compounds and detection limits at the low pg/mL level. In addition, the feasibility of the method for simultaneous determination of chlorinated and brominated phenols was studied. Finally, the method was applied to several real samples including tap water and effluent and influent waste water samples from an urban treatment plant, in which several phenolic compounds, such as phenol, methylphenols and chlorophenols, could be detected and quantified.     

Analysis of haloacetic acid mixtures by HPLC using an electrochemical detector coated with a surfactant-nafion film

High pressure liquid chromatography (HPLC) using an electrochemical (EC) detector electrode of pyrolytic graphite coated with a film of ionomer Nafion and the water-insoluble surfactant didodecyldimethylammonium bromide (DDAB) was used to achieve separation and detection of all six bromo- and chloro-acetic acids. The Nafion-DDAB film preconcentrates the acid anions facilitating their electrochemical detection by direct reduction at -1.2 V versus SCE. Detection limits were poorer than the EPA-approved GC-ECD method, but HPLC-EC avoids the derivatization necessary for GC. The HPLC-EC method also detected tribromoacetic acid, which has not been determined simultaneously with other halogenated acids by reported chromatographic methods. The HPLC-EC method using a Nafion-DDAB-coated detector electrode gave comparable results to GC-ECD for the determination of TCA in drinking water.     

A micro electron capture detector for temperature programmed analysis with capillary columns for a wide range of applications

Summary The electron capture detector (ECD) has become a indispensable and widely used tool for the detection of halogenated compounds in gas chromatography. The ECD is successfully used for routine analysis particularly in the field of environmental survey, residue determination in the food and agriculture chemistry and even more so in clinical chemistry. However, its application with high resolution glass capillary columns revealed a substantial drawback of existing ECD's, primarily the relatively large internal detector volume. The micro ECD described, with its very small cell volume (140 mm³), particularly designed for use with high resolution capillary columns, minimizes drastically the loss of separation efficiency since diffusion effects are negligible. The micro ECD permits the use of splitless or split injection techniques, as well as temperature programmed analysis to optimize sample separation. Very stable baseline and low noise conditions lower the detection limits considerably (2 pg Lindane full scale). The micro ECD can be operated either with direct current, pulsed frequency or constant current modes. Examples demonstrating the capabilities of this detector include the detection of halogenated organic volatiles in water at subnanogram levels, the determination of PCB's and pesticide residues in food as well as selected analysis in clinical chemistry, such as bile acids and amino acids in body fluids.     

Comparison of three types of mass spectrometers for HPLC/MS analysis of perfluoroalkylated substances and fluorotelomer alcohols

The performance of three different types of mass spectrometers (MS) coupled to high performance liquid chromatography (HPLC) was compared for trace analysis of perfluoroalkylated substances (PFAS) and fluorotelomer alcohols (FTOHs). Ion trap MS in the full scan and product ion MS2 mode, time-of-flight (TOF) high resolution MS and quadrupole MS in the selected ion mode as well as triple quadrupole tandem MS were tested. Electrospray ionisation in the negative ion mode [ESI-] was best suited for all instruments and compounds. PFAS could only be separated by a buffered mobile phase, but the presence of buffer suppressed the ionisation of FTOHs. Therefore, two independent chromatographic methods were developed for the two compound classes. Mass spectra and product ion spectra obtained by in-source and collision induced dissociation fragmentation are discussed including ion adduct formation. Product ion yields of PFAS were only in the range of 0.3 to 12%, independent from the applied MS instrument. Ion trap MS2 gave product ion yields of 20 to 62% for FTOHs, whereas only 4.1 to 5.8% were obtained by triple quadrupole tandem MS. Ion trap MS was best suited for qualitative analysis and structure elucidation of branched isomeric structures of PFAS. Providing typical detection limits of 5 ng injected in MS2 mode, it was not sensitive enough for selective trace amount quantification. TOF high resolution MS was the only technique combining high selectivity and excellent sensitivity for PFAS analysis (detection limits of 2 to 10 pg), but lacked the possibility of MS-MS. Triple quadrupole tandem MS was the method of choice for quantification of FTOHs with detection limits in the low pg range. It is also well suited for the determination of PFAS, though its detection limits of 10 to 100 pg in tandem MS mode are about one order of magnitude higher than for TOF MS.     

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.     

Determination of trace-level haloacetic acids in drinking water by ion chromatography-inductively coupled plasma mass spectrometry

A new method for the determination of nine haloacetic acids (HAAs) with ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was developed. With the very hydrophilic anion-exchange column and steep gradient of sodium hydroxide, the nine HAAs could be well separated in 15 min. After suppression with an ASRS suppressor that was introduced in between IC and ICP-MS, the background was much decreased, the interference caused by sodium ion present in eluent was removed, and the sensitivities of HAAs were greatly improved. The chlorinated and brominated HAAs could be detected as 35ClO and 79Br without interference of the matrix due to the elemental selective ICP-MS. The detection limits for mono-, di-, trichloroacetic acids were between 15.6 and 23.6 microg/l. For the other six bromine-containing HAAs, the detection limits were between 0.34 and 0.99 microg/l. With the pretreatment of OnGuard Ag cartridge to remove high concentration of chloride in sample, the developed method could be applied to the determination of HAAs in many drinking water matrices.