A rapid and sensitive method for methyl tert-butyl ether analysis in water samples by use of solid phase microextraction and gas chromatography-mass spectrometry

This work describes a rapid and sensitive solid-phase microextraction (SPME) method for the isolation and analysis of methyl tert-butyl ether in water samples. Methyl tert-butyl ether was extracted from aqueous solutions using SPME fibre coated with Divinylbenzene/Carboxen/polydimethylsiloxane (30 microm film thickness) and analysed by GC-MS with a Hewlett Packard 6890/5973 system equipped with a capillary column coated with Vocol (30 m x 0.25 mm, 1.5 microm film thickness). Extraction parameters and chromatographic separation conditions were optimised. The developed method showed good analytical performance in terms of precision (RSD between 2% and 8%) and accuracy (mean recovery from 96% to 104%) with a detection limit of 14 ppt. Finally the method was applied to surface, tap and commercial mineral water samples, as well as snow samples collected along a busy road of Bologna town area. The median concentration of methyl tert-butyl ether in all these samples (0.05-0.4 ppb) was well below the maximum aqueous contamination levels in water adopted in the United States (13 ppb).     

Transport and fate of dieldrin in poplar and willow trees analyzed by SPME

Dieldrin is a hydrophobic organochlorine insecticide that is persistent in the environment. The fate and transport of dieldrin in trees is important both in the context of potential remediation, as well as food chain impacts through dieldrin transport to shoots and leaves. Experiments were conducted to measure the degree of dieldrin partitioning to plant tissue and the potential for biodegradation of dieldrin in the microbe rich tree rhizosphere. Dieldrin was analyzed in water and plant tissue using headspace solid-phase microextraction (SPME) coupled with gas chromatography. Poplar and willow saplings planted in soil and watered with 10 microgl(-1) dieldrin for up to 9 months showed no adverse effects due to dieldrin exposure and no dieldrin was observed in plant shoots with a method detection limit (MDL) of 7 ngg(-1). One-week hydroponic tests of poplar saplings exposed to aqueous dieldrin also showed no detection of dieldrin in shoots, with an average of 66% of the dieldrin partitioned to the plant roots and an overall mass balance recovery of 76% in the plant-water system. The root concentration factor (RCF) was found to be 30+/-3 ml water g(-1) root. Biodegradation of dieldrin was not observed in an aqueous batch bioreactor containing 8 microgl(-1) dieldrin, nutrients and bacteria from the root zone of a poplar sapling that had been exposed to dieldrin for 9 months. These results show that planting trees is likely to be safe and potentially useful at sites containing low-levels of dieldrin in groundwater.     

Application of the EPR spin-trapping technique for the investigation of the reactions of carbonate, bicarbonate, and phosphate anions with hydroxyl radicals generated by the photolysis of H2O2

The spin trapping technique with electron paramagnetic resonance (EPR) detection of spin adducts was applied for the investigation of the reaction of hydroxyl radicals, generated by the photolysis of hydrogen peroxide, with bicarbonate and carbonate anions. The results have been compared with those obtained for aqueous solutions of hydrogen peroxide as well as solutions containing phosphate buffers at pH values identical with those of the carbonate, and bicarbonate solutions. Both the carbonate, and bicarbonate anions quenched the hydroxyl radicals more efficiently than phosphate buffers. The effect depended on the anion concentrations, and it was most pronounced in the presence of carbonate. Rate constants for the reaction of OH with the investigated anions have been calculated. They are very close to values reported in the literature, obtained using optical detection of the carbonate and phosphate radicals.     

Evaluation of photolysis and hydrolysis of pyraclostrobin in aqueous solutions and its degradation products in paddy water

This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water.     

Detection of pentachlorophenol and its glucuronide and sulfate conjugates in fish bile and exposure water

The glucuronide and sulfate conjugates of pentachlorophenol (PCP) that were present in the bile and exposure water of goldfish (Carassius auratus) were used to develop methodology to quantify PCP and its metabolites. Reverse phase HPLC with radioactivity detection separated PCP and its metabolites, and was used to verify a method of quantification that used differential extraction and scintillation counting. Extractions of aqueous phase at pH 2 or 8, with butanol, ethyl acetate, or ether indicated that ether at pH 8 best separated PCP from its metabolites. The sulfate conjugate of PCP was the major metabolite produced when goldfish were exposed to 125 micrograms 14C-PCP/l. It was present primarily in the exposure water, but also appeared in the bile.     

Determination of the temperature dependence of water solubilities of polycyclic aromatic hydrocarbons by a generator column-on-line solid-phase extraction-liquid chromatographic method

An improved dynamic coupled column liquid chromatographic (DCCLC) technique for determining water solubility data of hydrophobic compounds is presented. The technique is based on pumping water through a thermostated generator column in order to generate emulsion-free, saturated aqueous solutions of the compound under study. Through a switching valve system the solute in the aqueous solution is extracted and concentrated by an on-line solid-phase extraction process and subsequently eluted and analyzed by high performance liquid chromatography (fluorescence detection coupled to photodiode array detection). The improvements carried out to the original DCCLC technique have given rise to savings in time for the experimental work and increased sensitivity during the detection and quantification stage. Applicability of the method for studying highly hydrophobic substances is demonstrated by determining water solubility of anthracene and pyrene in the temperature range of 8.9-49.9 and 8.5-32.2 degrees C, respectively. The measured water solubilities are in good agreement with the best available literature data. The method has also been applied to the determination of water solubility of m-terphenyl, 9, 10-dihydrophenanthrene and guaiazulene, in the temperature range of 4.8-49.9, 4.8-25.0, and 4.5-29.9 degrees C, respectively. The uncertainty in the Sw values determined in this work ranged from 0.7% to 4.6%. The experimental water solubility data, as a function of temperature, are fitted to the equation In Sw = A + B/T; where Sw and T are given in mole fraction and Kelvin, respectively.     

Study on the fluorescence characteristics of bromadiolone in aqueous and organized media and application in analysis

The fluorescence spectroscopic behavior of bromadiolone (anticoagulant rodenticide), a substituted 4-hydroxycoumarin derivative, was investigated in water and in organized media like micelles and cyclodextrins. A detailed study on various photophysical parameters like fluorescence intensity (I_F), quantum yield (), lifetime (τ) and steady state fluorescence anisotropy (r) of bromadiolone in aqueous and in organized media was carried out. Bromadiolone in aqueous solution was observed to be in an aggregated state, thereby showing weak emission due to self-quenching. Marked enhancement of fluorescence intensity was observed in organized media like micelles and β-cyclodextrin. A preliminary investigation has been done to find out whether this enhancement of fluorescence can be used to develop a sensitive analytical method for determination of bromadialone in aqueous media. A linear relationship between the fluorescence intensity and concentration of bromadiolone was observed in the range of 0.15–7.9 μg ml⁻¹ in cetyltrimethylammonium bromide (CTAB) and 0.5–26.4 μg ml⁻¹ in β-cyclodextrin medium. The lower detection limit was found to be 37 ng ml⁻¹ in presence of CTAB and 23 ng ml⁻¹ in β-cyclodextrin. Comparison with 4-hydroxycoumarin, an unsubstituted analogue, was made.     

A new technique for collection,concentration and determination of gaseous tropospheric formaldehyde

This article describes an improved technique for making in situ measurements of gaseous tropospheric formaldehyde (CH₂O). The new technique is based on nebulization/reflux principles that have proved very effective in quantitatively scrubbing water soluble trace gases (e.g. CH₂O) into aqueous mediums, which are subsequently analyzed. Atmospheric formaldehyde extractions and analyses have been performed with the nebulization/reflux concentrator using an acidified dinitrophenylhydrazine solution that indicate that quantitative analysis of CH₂O at global background levels (∼ 0.1 ppbv) is feasible with 20-min extractions. Analysis of CH₂O, once concentrated, is accomplished using high performance liquid chromatography (HPLC) with ultraviolet photometric detection. The CH₂O-hydrazone derivative, produced by the reaction of 2,4-dinitrophenylhydrazine in H₂SO₄ acidified aqueous solution, is detected as CH₂O.     

High-performance liquid chromatography with conductimetric detection of perfluorocarboxylic acids and perfluorosulfonates

A rapid and simple method for separating and determining various environmentally harmful perfluorocarboxylic acids and perfluorosulfonates was successfully developed using high- performance liquid chromatography with conductimetric detection, for product and waste management of these compounds at manufacturing and processing sites. Compounds having C(3)-C(8) perfluoroalkyl groups were separated using a Tosoh TSKgel Super-ODS column and a mobile phase consisting of a mixture of methanol and aqueous NaH(2)PO(4) at several mixing ratios. The best detection limits for the compounds ranged from 0.12 to 0.66 mg l(-1) (ppm), and linear calibration graphs were obtained up to 87-109 mg l(-1). The combination of this method with concentration of the sample by solid-phase extraction with cartridges based on styrene-divinylbenzene-copolymer enabled the determination of approximately 50 microg l(-1) (ppb) for compounds with C(4)-C(8) perfluoroalkyl groups. This method was successfully used to monitor the artificial decomposition of the perfluorocarboxylic acid n-C(4)F(9)COOH induced by a photocatalyst.     

Description and evaluation of a sampling system for long-time monitoring of PAHs wet deposition

In this paper a new electronically controlled year-round wet-only sampler for wet deposition of trace organic compounds (e.g. airborne PAHs) is described. The sampler provides in situ filtration of the precipitation as well as preconcentration of nonpolar organic compounds by means of a C18-PAH modified silica gel cartridge. The whole assembly is insulated and equipped with heating elements which permit collection of wet deposition as ice or snow and insure correct function of the sampling system even during cold weather. Concurrent chemical analysis of both the particulate and the dissolved phases is performed by high resolution gas chromatography with flame ionization detection or HPLC with fluorescence detection. The reliability of the method was proved by analyzing PAH spiked water (simulated rain) and using NIST SRM 1649 ('urban dust') as certified material for particle-bound PAHs in precipitation. This study proved satisfactorily recoveries of as both particle-bound and unbound aqueous PAH, with only small losses to collector surfaces. It was proved that this new wet-only precipitation sampler can successfully be used for long-time monitoring of PAH in wet depositions in urban areas.     

Environmental photochemistry of fluoroquinolones in soil and in aqueous soil suspensions under solar light

The photodegradation fate of widely used fluoroquinolone (FQ) drugs has been studied both at the water–soil interface and in soil at actual concentrations (500 ng g^?1) under natural solar light. Both human and veterinary drugs have been examined, namely ciprofloxacin, danofloxacin, enrofloxacin, levofloxacin, marbofloxacin and moxifloxacin. After spiking and irradiation, samples were submitted to microwave-assisted extraction and analyzed by high-performance liquid chromatography coupled to fluorescence detection (HPLC–FD). FQs degradation was faster in aqueous soil suspension than in neat soil (but lower than in “clean” water). A number of byproducts were identified by HPLC electrospray ionization tandem mass spectrometry after a post-extraction cleanup based on a molecularly imprinted polymer phase, for a more accurate detection. The distribution in the suspension was intermediate between those observed in soils and in aqueous solutions.     

An important pathway for ozonolysis of alpha-pinene and beta-pinene in aqueous phase and its atmospheric implications

The aqueous ozonolysis of α-pinene and β-pinene was conducted under simulated tropospheric conditions at different pHs and temperatures. Three kinds of products, peroxides, carbonyl compounds, and organic acids, were well characterized, and the detection of these products provides effective evidence for understanding the atmospheric aqueous reaction pathway. We have two interesting findings: (1) the unexpected formation of methacrolein (MACR), with a yield of ～40%, in the α-pinene–O₃ aqueous reaction indicates a potentially new SOA formation pathway, because MACR is one of the important precursors of SOA; and (2) the surprisingly high yields of H₂O₂, ～60% for the α-pinene–O₃ reaction and ～100% for the β-pinene–O₃ reaction, indicates that H₂O₂ can be a significant contributor to the origin and transformation of oxidants in the atmosphere, especially in the humid regions. Moreover, we have determined the rate constant for aqueous reaction between MACR and H₂O₂ in pH 2 to 7 and obtained its upper limit as 0.13 M L^?1 s^?1. A mechanism concerning the formation of the species mentioned above is proposed, and it differs from that in the gas-phase reaction. We suggest that water plays a key role in the mechanism, by participating in the reactions as a direct reactant and by removing the excess energy of intermediates formed in the reactions.     

Simultaneous analysis of free and sulfo-conjugated steroid estrogens in artificial urine solution and agricultural soils by high-performance liquid chromatography

A simple and robust analytical method was developed to simultaneously detect and quantify 17β-estradiol (E2), estrone (E1), 17β-estradiol-3-sulphate (E2-3S), and estrone-3-sulphate (E1-3S) in aqueous solutions (calcium chloride and artificial urine solutions) and agricultural soils using high performance liquid chromatography and UV detection. The standards for all four compounds were linear in the range of 0.01 to 1.0 μg mL(-1) (n = 6) and 1.0 to 20 μg mL(-1) (n = 6), respectively, with correlation coefficients > 0.999. The on-column limits of detection at an injection volume of 50 μL and S/N (signal: noise) ratio of 3 were: 9.0 ng mL(-1), 10 ng mL(-1), 5.0 ng mL(-1), and 7.0 ng mL(-1) for E2-3S, E1-3S, E2 and E1, respectively. The limit of detection and quantification in artificial urine solution and CaCl(2) solution was 1.0 ng mL(-1) for all four compounds. Method detection limits for the compounds in the 3 soils ranged from 2 to 2.4 ng g(-1) (E2-3S and E1-3S), and 1.0 to 2.9 ng g(-1) (E2 and E1), respectively.     

Collection and analysis of organic acids in exhaust gas. Comparison of different methods

This paper reports the development of a specific method to identify organic acids in exhaust gases. The organic acids are collected in two impingers containing liquids (pure water or Na₂CO₃ 1% aqueous solution) and four cartridges containing solids (silica, fluorisil, alumina B and alumina N). Once collected, the acids are eluted of the solids by a hot water stream. These traps performances, in terms of organic acids collection and elution efficiency, are evaluated and compared. Two sources are used to produce the gas flow containing organic acids: one generates a flow whose concentration is known and stable, the other produces organic acids among other combustion products. For eluted solutions analysis, two methods are used: isocratic ionic chromatography/conductivity detection and GC/FID. Their efficiency in separating 10 aliphatic acids are compared. Their characteristics such as detection limits, detection linearity, repeatability and possible interferences with other components found in exhaust gases are determined. The stability of the organic acids solutions is also studied. Lastly, the use of these methods is illustrated by the analysis of the gas-phase organic acids exhausted by a spark ignition and by a diesel engine.     

Effects of organic matter on the distribution of uranium in soil and plant matrices

This work studied interactions of uranium with pure organic compounds, such as glutathione, and more complex mixtures, such as humic acid and aqueous plant extracts. High performance liquid chromatography with UV absorption interfaced to inductively coupled plasma mass spectrometry sequential detection was used to detect organouranium complexes in a variety of soils and plant materials, indicating that nearly 100% of the uranium extracted from certain plant tissues was bound to organic ligands. In addition, soil sorption experiments indicated that humic acid generally decreased uranium sorption to soils and promoted subsequent desorption of uranium because of uranium partitioning to the organic phase. These experiments demonstrate that organic compounds influence the mobility and chemistry of uranium in the environment.     

Sorption of chlorpyrifos and fonofos on four soils and turfgrass thatch using membrane filters

Abstract

Chemical transport in soil is a major factor influencing soil and water contamination. Four soils and turfgrass thatch, representing a wide range of organic carbon OC content were studied to determine sorption K_d and K_f parameters for the insecticides chlorpyrifos and fonofos. The batch equilibrium method was used. The concentration of insecticide was measured in the solution as well as in the solid phase to determine the most accurate sorption data. Four soils and thatch were equilibrated for 24 h at 22 ± 1^OC with aqueous insecticide solutions. Four concentrations of the insecticides, each <50% of their respective water solubilities, were selected for the experiments. After extraction with an organic solvent, the concentration of insecticides in the aqueous solution was determined by gas liquid chromatography using electron capture detection for chlorpyrifos, and nitrogen/phosphorus detection for fonofos. Data obtained were fitted to the log and simple linear form of the Freundlich equation. Mass balance Freundlich isotherm exponents n ranged between 0.82 and 0.93 for chlorpyrifos. 0.82 and 1.21 for fonofos, with r² ≥ 0.97. K_oc (percent of organic carbon %OC normalized Sorption coefficient) values were calculated by using experimentally developed K_d and K_f coefficients in relation to OC levels from 0.29 to 34.85%. K_d and K_f coefficients of both insecticides were positively correlated with OC (r² ≥ 0.96). organic matter OM (r² ≥ 0.96), and cation exchange capacity CEC (r² ≥ 0.90).     

Simultaneous analysis of free and sulfo-conjugated steroid estrogens in artificial urine solution and agricultural soils by high-performance liquid chromatography

A simple and robust analytical method was developed to simultaneously detect and quantify 17β-estradiol (E2), estrone (E1), 17β-estradiol-3-sulphate (E2-3S), and estrone-3-sulphate (E1-3S) in aqueous solutions (calcium chloride and artificial urine solutions) and agricultural soils using high performance liquid chromatography and UV detection. The standards for all four compounds were linear in the range of 0.01 to 1.0 μg mL^?1 (n = 6) and 1.0 to 20 μg mL^?1 (n = 6), respectively, with correlation coefficients > 0.999. The on-column limits of detection at an injection volume of 50 μL and S/N (signal: noise) ratio of 3 were: 9.0 ng mL^?1, 10 ng mL^?1, 5.0 ng mL^?1, and 7.0 ng mL^?1 for E2-3S, E1-3S, E2 and E1, respectively. The limit of detection and quantification in artificial urine solution and CaCl₂ solution was 1.0 ng mL^?1 for all four compounds. Method detection limits for the compounds in the 3 soils ranged from 2 to 2.4 ng g^?1 (E2-3S and E1-3S), and 1.0 to 2.9 ng g^?1 (E2 and E1), respectively.     

Membrane introduction/laser photoionization time-of-flight mass spectrometry

Two-photon resonance enhanced multiphoton ionization (REMPI) has been shown to be a unique ionization method for mass spectrometry, exhibiting both high sensitivity and chemical selectivity. Because REMPI is a gas-phase method, its applications have been limited either to direct analysis of vapor phase samples, or in conjunction with an initial laser desorption or other vaporization step. We describe here for the first time a combination of membrane introduction mass spectrometry (MIMS) and REMPI with time-of-flight mass spectrometry (TOF-MS), which allows for the direct analysis of trace amounts of organic compounds in water samples. The objective of our research was the detection of very low levels of aromatic contaminants, particularly benzene, toluene, and xylene (BTX), in aqueous solutions without interference due to the water. We have measured limits of detection (LOD) for selected aromatics in water below 1 part-per-trillion with an averaging time of less than 10 s using a continuous sample flow.     

The leachability of carbon-14-labelled 3,4-benzopyrene from coal ash into aqueous systems

The leachability of polycyclic aromatic hydrocarbons from coal ash into aqueous systems was studied. Carbon-14-labeled 3,4-Benzopyrene (BaP) was deposited on coal fly ash by adsorption from the liquid phase in quantities of about 10 μg/g ash. After a thermal treatment in air at 120 °C for 2 hours the desorption of BaP was measured using aqueous solutions of acetone and methanol as extractants and liquid scintillation counting as detection method. In all cases the ¹⁴C-recovery was incomplete. Using water as extractant, ¹⁴C-recoveries of about 1 % were found. In the presence of a non-ionic surface active agent (Tween 80) the ¹⁴C-recovery was enhanced significantly. For these reasons further experiments under realistic waste disposal conditions are necessary.     

Comparison of methods for determination of volatile organic compounds in drinking water

Comparison of four methods including liquid-liquid extraction (LLE), direct aqueous injection (DAI), purge and trap (PAT) and head space (HS) were carried out in this work for determination of volatile organic compounds (VOCs) including trihalomethanes (THMs) in drinking water. This comparison is made especially to show the advantages and disadvantages and specifically the different detection limits (DL) that can be obtained for a given type of analysis. LLE is applicable only for determination of the THMs concentrations, while DAI, PAT, HS methods with different DL each of them are applicable for all VOCs, with PAT to be the most sensitive. Sampling apparatus and procedure for all these methods except of PAT are very simple and easy, but possible disadvantages for LLE and DAI are the low sensitivity and especially the detection only of THMs with LLE.