Hydrocarbons In Water Samples Research Articles

Characterization and source identification of hydrocarbons in water samples using multiple analytical techniques

This paper describes a case study in which multiple analytical techniques were used to identify and characterize trace petroleum-related hydrocarbons and other volatile organic compounds in groundwater samples collected in a bedrock aquifer exploited for drinking water purposes. The objective of the study was to confirm the presence of gasoline and other petroleum products or other volatile organic pollutants in those samples in order to assess the respective implication of each of the potentially responsible parties to the contamination of the aquifer. In addition, the degree of contamination at different depths in the aquifer was also of interest. The analytical techniques used for analyses of water samples included gas chromatography–mass spectrometry (GC–MS) and capillary GC with flame-ionization detection, solid-phase microextraction and headspace GC–MS techniques. Chemical characterization results revealed the following: (1) The hydrocarbons in sample A (near-surface groundwater, 0–5 m) were clearly of two types, one being gasoline and the other a heavy petroleum product. The significant distribution of five target petroleum-characteristic alkylkated polycyclic aromatic hydrocarbon homologues and biomarkers confirmed the presence of another heavy petroleum product. The concentrations of the TPHs (total petroleum hydrocarbons) and BTEX (collective name of benzene, toluene, ethylbenzene, and p-, m-, and o-xylenes) were determined to be 1070 and 155 μg/kg of water for sample A, respectively. (2) The deepest groundwater (sample B, collected at a depth ranging between 15 and 60 m) was also contaminated, but to a much lesser degree. The concentrations of the TPH and BTEX were determined to be only 130 and 2.6 μg/kg of water for sample B, respectively. (3) The presence of a variety of volatile chlorinated compounds to the groundwater was also clearly identified.

Comparison of Stir Bar Sorptive Extraction and Solid Phase Extraction as Enrichment Techniques in Combination with Column Liquid Chromatography for the Determination of Polycyclic Aromatic Hydrocarbons in Water Samples

The commonly used solid-phase extraction (SPE) was compared with the recently developed stir bar sorptive extraction (SBSE) to determine EPA-PAHs from precipitation water samples. SPE was performed using C18 PAH-filled cartridges; magnetic stirring rods 10 mm long and coated with 0.5 mm (24 µL) polydimethylsiloxane were used for SBSE. Determination was performed by high performance liquid chromatography and fluorescence detection. The investigations were performed at a concentration level of 30 ng/L, adjusted to actual PAH concentration levels of precipitation water. The recoveries ranged between 54% (SBSE) and 20% (SPE) respectively and about 100%, while the standard deviation ( n = 5) varied in the range of 4.7-13.5% (SBSE) and 3.6-16.9% (SPE) except for the more volatile compounds acenaphthene and fluorene. The detection limits calculated were between 0.4 and 5.0 ng/L. Both techniques were applied to study the PAH contents of precipitation water of several polluted sites in the city of Halle (Saxony-Anhalt, Germany). The advantages and disadvantages of the methods used are discussed.

Screening potential of solid-phase extraction and solid surface room temperature fluorimetry for polycyclic aromatic hydrocarbons in water samples

The analytical potential of solid-phase extraction and room temperature fluorimetry for screening polycylic aromatic hydrocarbons in water samples is evaluated. Solid-phase extraction was performed via a syringe procedure previously reported (Talanta 52 (2000) 727). The simplicity of fluorescence measurements on the solid substrate is equivalent to solution measurements. Since oxygen quenching of fluorescence is not significant, placing the extraction membrane in the substrate holder of the spectrometer rapidly performs fluorescence measurements. Limits of detection at the pg ml −1 level were estimated for several pollutants. With a commercial spectrofluorimeter, benzo( a)pyrene was quantitatively determined at the 5 pg ml −1 concentration level. This concentration compared favorably to limits of detection estimated by laser-induced fluorimetry. A unique advantage of this approach was the possibility of adjusting the volume of extracted water to reach concentration levels below instrumental detection levels. Since SPE procedure was rapid and simple the trade-off of including an additional experimental step to lower limits of detection was advantageous. Although the selectivity of this approach was not fully investigated, our studies showed that selective excitation was sufficient to identify benzo( a)pyrene in a seven-component mixture and spiked Red River water of unknown composition.

Application of stir bar sorptive extraction in combination with column liquid chromatography for the determination of polycyclic aromatic hydrocarbons in water samples

The new technique of stir bar sorptive extraction (SBSE) using stirrers 10 mm long coated with 55 μl polydimethylsiloxane (PDMS) was used to determine polycyclic aromatic hydrocarbons (PAHs) from water samples. The desorption of the extracted analytes was performed with ultrasonic treatment in autosampler vials with glass flat bottom inserts using 150 μl of acetonitrile (ACN) or an ACN–water mixture (4:1) as solvent. The PAHs were determined with column liquid chromatography (LC) and fluorescence detection. The recoveries of the stir bar sorptive extraction for the compounds investigated were between 58% and about 100%, and the detection limits of this method under the given conditions (extraction from a 10 ml sample, 1 h extraction time and 10 min desorption time) were very low (between 0.2 and 2 ng/l). The standard deviations ( n=5) using five different stirrers at a concentration level of 50 ng/l ranged between 4.7 and 13.5%.

On the improvement of solid-phase extraction room-temperature phosphorimetry for the analysis of polycyclic aromatic hydrocarbons in water samples

This article presents considerable improvements in SPE-RTP methodology for the analysis of polycyclic aromatic hydrocarbons in water samples. Bulky glassware and vacuum pump were removed from the previous extraction procedure [E.D. Hagestuen, A.D. Campiglia, Talanta 49 (1998) 547] by processing 10 ml of sample with syringes and stainless steel filter holders. The oven-drying step was substituted by air sample drying, which employed positive pressure to remove water excess from the extraction membrane. As a result, analysis times from 8 to 10 min per sample were obtained. No costs in levels of detection were observed. Limits of detection at the pg ml −1 level were estimated for phenanthrene, pyrene, benzo(k)fluoranthene, benzo(a)pyrene, and chrysene. The feasibility of identifying single components in PAH mixtures was investigated. Binary and tertiary mixtures were resolved by appropriate choice of excitation and emission wavelengths. The advantage of using excitation–emission matrix analysis was demonstrated for a six-component mixture.

Solid-phase microextraction for determining the distribution of sixteen US Environmental Protection Agency polycyclic aromatic hydrocarbons in water samples

A solid-phase microextraction (SPME) procedure has been developed for the determination of 16 US Environmental Protection Agency promulgated polycyclic aromatic hydrocarbons (PAHs). Five kinds of SPME fibers were used and compared in this study. The extracted sample was analyzed by gas chromatography with flame ionization detection or mass spectrometry. Parameters affecting the sorption of analyte into the fibers, including sampling time, thickness of the fiber coating, and the effect of temperature, have been examined. Moreover, the feasibility of headspace SPME with different working temperatures was evaluated. The method was also applied to real samples. The 85-μm polyacrylate (PA) and 100-μm poly(dimethylsiloxane) (PDMS) fibers were shown to have the highest affinities for the selected PAHs. The PA fiber was more suitable than the PDMS fiber for the determination of low-ring PAHs while high sensitivity of high-ring PAHs was observed when a 100-μm PDMS fiber was used. The method showed good linearity between 0.1 and 100 ng/ml with regression coefficients ranging from 0.94 to 0.999. The reproducibility of the measurements between fibers was found to be very good. The precisions of PA and PDMS fibers were from 3 to 24% and from 3 to 14%, respectively. Headspace SPME is a valid alternative for the determination of two- to five-ring PAHs. A working temperature of 60°C provides significant enhancement in sensitivity of two- to five-ring PAHs having low vapor pressures (>10 −6 mmHg at 25°C) (1 mmHg=133.3 Pa) and low Henry’s constants (>10 atm ml/mol) (1 atm=1.01·10 5 Pa).

New approach for screening polycyclic aromatic hydrocarbons in water samples

For the first time, solid-phase extraction (SPE) has been combined to room-temperature phosphorimetry (RTP) to determine the 16 polycylic aromatic hydrocarbons related as major pollutants by the US Environmental Protection Agency (EPA). These include naphthalene, anthracene, acenaphthylene, acenaphthene, fluorene, fluoranthene, benzo(a)anthracene, benzo(k)fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, pyrene, chrysene, phenanthrene, benzo(g,h,i)perylene and dibenzo(a,h)anthracene. The pre-concentration factor obtained by SPE, combined with the sensitivity of RTP, resulted in calibration curves with linear dynamic ranges at the parts-per-billion level (ng ml −1). The limits of detection were estimated at the parts-per-trillion level (pg ml −1). Several pollutants usually encountered in water samples were tested for interference. These included polychlorinated biphenyls, pesticides, and volatile organic compounds. As a result of the appropriate combination of excitation wavelength (330 nm) and phosphorescence enhancers (0.1 M TlNO 3 and 0.05 M sodium dodecyl sulfate, SDS), no interference was observed. The results demonstrate the potential of SPE-RTP for screening polycyclic aromatic hydrocarbons (PAHs) in environmental waters.

Artificial neural networks (ANNs) in the analysis of polycyclic aromatic hydrocarbons in water samples by synchronous fluorescence

Backpropagation artificial neural networks, principal component regression and partial least squares have been compared in order to establish the best multivariate calibration models for the analysis of mixtures of polycyclic aromatic hydrocarbons containing 10 of these compounds (anthracene, benz[a]anthracene, benzo[a]pyrene, chrysene, fluoranthene, fluorene, naphthalene, perylene, phenanthrene and pyrene). The synchronous fluorescence spectra (recorded at wavelength increments of 50 and 100 nm) of 85 standards, with concentrations ranging from 0 to 20 ng ml −1, have been used for this purpose.

On-line coupling of immunosorbent and liquid chromatographic analysis for the selective extraction and determination of polycyclic aromatic hydrocarbons in water samples at the ng l −1 level

A method employing immunoaffinity chromatography for the selective extraction of polycyclic aromatic hydrocarbons (PAHs) from water was developed. An immunosorbent (IS) based on the immobilization of anti-fluorene antibodies on silica was coupled on-line with LC and applied to the selective extraction of PAHs from water samples. The procedure involves the use of a solubilizer to limit unwanted adsorption on vessels or tubing. Results show that a compromise has to be found between a good solubilization and limitation of the elution from the IS due to the addition of this modifier. The contribution of the selective antigen–antibody interaction to the retention mechanism is demonstrated. The on-line method was optimized for the six more volatile PAHs, and was also applied to the 16 PAHs included in the US Environmental Protection Agency priority list. The sensitivity of the fluorescence detection associated to the selectivity of the extraction sorbent allows one to detect PAHs between 2 and 10 ng l −1 from a sample volume as low as 20 ml. The presence of several PAHs at 20 ng l −1 in surface water was confirmed by spectral identification using diode array detection coupled in series with a fluorescence detector.

Retention model for sorptive extraction–thermal desorption of aqueous samples: application to the automated analysis of pesticides and polyaromatic hydrocarbons in water samples

In this report, an automated method for sorptive enrichment of aqueous samples is presented. It is based on sorption of the analytes of interest into a packed bed containing 100% polydimethylsiloxane (PDMS) particles followed by thermal desorption for complete transfer of the enriched solutes onto the GC column. Compared to other solvent-less sample preparation techniques for water samples, several improvements can be noted of which the most obvious are an enhanced sensitivity and improved blanks. Moreover, degradation products formed from the PDMS material can easily be identified with the use of a mass spectrometric detector. As these products contain silicone, they do not interfere with the target solutes (pesticides, PAHs). In this report a theory model is derived which allows calculation of breakthrough volumes from octanol–water partitioning coefficients ( K O/W). Alternatively, the K O/W value required for complete retention can be calculated using only the sample volume and trap specific parameters. For a sample volume of 10 ml, theory predicts a required log K O/W of 1.77 for the trap used here which was found to be in good agreement with experimental results. For the most apolar solutes, with a log K O/W in excess of seven, poor recoveries were found. This is most likely due to adsorption of these apolar solutes in the system. With the current set-up, detection limits are in the order of 10 ng/l using mass spectrometric detection in the full scan mode.

Parallel factor analysis of partially resolved chromatographic data: Determination of polycyclic aromatic hydrocarbons in water samples

A procedure, based on parallel factor analysis (PARAFAC), has been used for the analysis of polycyclic aromatic hydrocarbons in water samples. The chromatographic system has been set to obtain short-time chromatograms containing several unresolved peaks. The detection system consisted of a fast-scanning fluorescence spectra detector, which allowed three-dimensional data – where retention time, emission wavelengths and fluorescence intensity were represented – to be obtained. The procedure has been applied to spiked tap water samples with good results.

Quantitative multicomponent analysis of polycyclic aromatic hydrocarbons in water samples

A comparative study between three different multivariate calibration methods, classical least squares (CLS), principal component regression (PCR) and partial least squares regression (PLSR) was carried out. The calibration models for all three methods were obtained from a combination of two synchronous fluorescence spectra (recorded at 50 and 100 nm wavelength increments) for each standard of a calibration set of 70 standards, each containing ten polycyclic aromatic hydrocarbons (anthracene, benz[a]anthracene, benzo[a]pyrene, chrysene, fluoranthene, fluorene, naphthalene, perylene, phenanthrene and pyrene). The predictions of the model were compared with the relative root mean squared difference (RRMSD) obtained from the results of an external validation set, formed by 15 independent mixtures. Finally, the PLSR and PCR models were used for the determination of the above mentioned PAHs in spiked natural water samples at concentration levels between 4 and 20 ng ml −1. Recoveries ranged from 80 to 120% in most cases, although fluorene gave significantly lower results.

Multivariate calibration applied to synchronous fluorescence spectrometry. Simultaneous determination of polycyclic aromatic hydrocarbons in water samples

Synchronous fluorescence spectra of mixtures containing ten polycyclic aromatic hydrocarbons (anthracene, benz[a]anthracene, benzo[a]pyrene, chrysene, fluoranthene, fluorene, naphthalene, perylene, phenanthrene and pyrene) have been used for the determination of these compounds by Partial Least Squares Regression (PLSR), using both PLS-1 and PLS-2. Different procedures have been used for the pretreatment of the data in order to obtain better models, and the size of the calibration matrix has also been studied. The best models have been used for the determination of the above mentioned PAHs in spiked natural water samples at concentration levels between 4 and 20 ng ml −1. Recoveries ranged from 80 to 120% in most cases, although fluorene gave significantly lower results.

Three-Way Multivariate Calibration Procedures Applied To High-Performance Liquid Chromatography Coupled with Fast-Scanning Fluorescence Spectrometry Detection. Determination of Polycyclic Aromatic Hydrocarbons in Water Samples

Three-way partial least-squares and n factor parallel factor analysis have been compared for the analysis of polycyclic aromatic hydrocarbons in water samples. Data were obtained with a chromatographic system set to record short-time chromatograms containing several unresolved peaks. The detection system consisted of a fast-scanning fluorescence spectra detector, which allows one to obtain three-dimensional data, where retention time, emission wavelengths, and fluorescence intensity are represented. The combined use of a multivariate calibration method and the three-dimensional data obtained from the HPLC-FSFS system allows resolution of closely eluting compounds, thus making a complete separation unnecessary. The procedure has been applied to tap water samples (spiked at 0.10 and 0.20 μg L(-)(1) levels) with good results, similar to those obtained with a HPLC system with a conventional fluorescence detector.

Development of fast-scanning fluorescence spectra as a detection system for high-performance liquid chromatography Determination of polycyclic aromatic hydrocarbons in water samples

A new detection system based on full-spectrum fast scanning fluorescence has been developed for high-performance liquid chromatography (HPLC-FSFS). Emission spectra were obtained by scanning the effluent from a chromatographic column at 50 nm s −1. The raw chromatograms were corrected by an interpolation method, because the fluorescence intensity measured for each consecutive wavelength corresponded to a different portion of the effluent. Quantification of samples was done by partial least squares (PLS). This procedure has been used for the determination of polycyclic aromatic hydrocarbons in water samples.

Semicontinuous Detection of 1,2-Dichloroethane in Water Samples Using Xanthobacter autotrophicus GJ 10 Encapsulated in Chitosan Beads

A semicontinuous microbial assay for the determination of halogenated short-chain hydrocarbons in water samples was developed. The bacterium Xanthobacter autotrophicus GJ 10 forms dehalogenating enzymes, which liberate the halides in 1,2-dichloroethane as halogen ions. Cells of the organism were immobilized in chitosan beads and placed into a tube reactor, whose outlet was connected to a flow-through cell with chloride-selective potentiometric electrodes. Water samples were delivered continuously to the system, and the EMF was recorded. Both the difference in EMF between blank and sample and the velocity of the EMF change were used for calibration. The detection limit for 1,2-dichloroethane was below 0.5 mg/L; the relative standard deviation was <10%. The effects of several parameters like flow rate and cell density were studied in detail.

Use of cloud point extraction methodology for the determination of PAHs priority pollutants in water samples by high-performance liquid chromatography with fluorescence detection and wavelength programming

The cloud point extraction methodology has been used to develop a new procedure for the preconcentration of polycyclic aromatic hydrocarbons in water samples (bottled and network supply). Triton X-114 was used as extractant agent. The procedure, consisting of three steps (preconcentration into the surfactant, clean-up and concentration of the eluate), allows good detection limits to be reached (from nanograms per liter to even sub-nanograms per liter in some cases). Determination was carried out by HPLC, with fluorimetric detection and wavelength programming.

Development of a Room-Temperature Phosphorescence Fiber-Optic Sensor

The design of a new fiber-optic sensor based on solid-surface room-temperature phosphorimetry is presented for the analyses of polycyclic aromatic hydrocarbons in water samples. Analytical figures of merit are given for several compounds of environmental importance. Limits of detection at the nanograms per milliliter level were estimated for pyrene, benzo[e]pyrene, benzo[ghi]perylene, 1,2:3,4-dibenzanthracene, coronene, and 2,3-benzofluorene. The linearity of response of the phosphorescence sensor was evaluated, showing a fairly linear behavior for quantitative analysis. Finally, the feasibility of monitoring polycyclic aromatic hydrocarbons in aqueous media was illustrated by identifying pyrene in a contaminated groundwater sample.

Determination of polycyclic aromatic hydrocarbons in water samples using high-performance liquid chromatography with amperometric detection

The determination of polycyclic aromatic hydrocarbons (PAHs) using high-performance liquid chromatography (HPLC) with UV and fluorescence detection has been well established. Although most of the PAHs can be detected by these methods, some environmentally important polyaromatic compounds, such as acenaphthylene, do not show fluorescence and can only be determined by UV detection at higher concentrations. A sensitive and selective determination of acenaphthylene, acenaphthene and the six PAHs listed in the TVO, the German drinking water standard, is also possible by amperometric detection following HPLC separation. The method was applied to the determination of PAHs in different water samples after solid-phase extraction (SPE). The efficiency of the amperometric determination was found to be superior to UV detection (λ = 300 nm).

Detection of halogenated hydrocarbons by a microbial sensorsystem using a stop-flow-technique

To improve the applicability and efficiency of the microbial assay developed by W. Hutter, J. Peter, H. Swoboda, W. Hampel, E. Rosenberg, D. Kramer, and R. Kellner (1995) a stop-flow-technique was developed for the determination of halogenated hydrocarbons in water samples. Cells of Rhodococcus sp. DSM 6344 were immobilized in alginate beads and placed in a stirred flow-through reactor. The time of incubation, the bacterial cell density and the amount of alginate beads in the reactor on the response of the system as determined by the drop in EMF was investigated. Optimal conditions were achieved with 2 g beads containing a bacterial cell concentration of 0,1 g cells wet wt/g matrix and an incubation time of 20 min. Calibrations with chlorinated and brominated substrates like ethyl bromide, 1,2-dibromopropane, isobutyl bromide, 1-chlorobutane and 1,5-dichloropentane showed a non-linear dependence at low substrate concentrations. The detection limits for ethyl bromide and 1-chlorobutane were estimated as 0.02 mg/l and 0.45 mg/l, respectively, the relative standard deviation was below 10 %. The great advantage of the stop-flow-technique compared to discontinuous measurements can be seen in a simplified handling and an increase of sample capacity.