Solid Phase Extraction Methodology Research Articles

Optimized Kaempferitrin Isolation from Uncaria guianensis Leaves by Solid-Phase Extraction

A simple and low-cost solid-phase extraction methodology for isolating the bioactive flavonoid kaempferitrin from a defatted fraction of the Uncaria guianensis leaf ethanol extract was developed using the kaempferitrin retention behavior in reversed-phase-high-performance liquid chromatography as well as thin-layer chromatography coupled to ImageJ software (Bethesda, USA) for densitometric analyses. In addition, the method enabled the isolation of less-complex mixtures for the further separation of minor constituents. The target compound was successfully isolated from 1 to 5 mg of the fraction per 500 mg C18 cartridge using 6 mL of 15% acetonitrile at 60% relative recovery and 99% purity.

Facile purification and click labeling with 2-[18F]fluoroethyl azide using solid phase extraction cartridges

A facile method was developed to purify 2-[18F]fluoroethyl azide ([18F]FEA) using a C18 cartridge and an Oasis® HLB cartridge in series, in which [18F]FEA was exclusively trapped on the HLB cartridge. [18F]FEA can be eluted for reactions in solution; alternatively click labeling can be carried out on the HLB cartridge itself by loading an alkyne substrate and copper (I) catalyst dissolved in DMF onto the cartridge. This solid phase extraction methodology for purification and click labeling with [18F]FEA, either in solution or on the cartridge, is safe, simple, reproducible in high yield, and compatible with automated synthesis of 18F-labeled PET tracers.

Newly modified silica-based magnetically driven nanoadsorbent: A sustainable and versatile platform for efficient and selective recovery of cadmium from water and fly-ash ameliorated soil

The interface of magnetically driven nanotechnology with solid phase extraction methodology has been realized to form a novel nanoadsorbent via covalent linkage of amine functionalized silica-coated magnetic nanoparticles with a newly synthesized Schiff’s base. The final nanoadsorbent and parental nanosupport, with each step of successive modifications, were characterized by SEM, TEM, EDS, XRD, VSM and FT-IR. The nanoadsorbent was examined as a versatile, potent, promising and sustainable platform for highly selective determination, separation and recovery of cadmium from the environmental matrix. Further, the sorption equilibrium followed Langmuir isotherm model, and the maximum sorption capacity was found to be 200 mgg−1 at 318K. The adsorption rate agreed well with pseudo second-order kinetics and the evaluated thermodynamic parameters suggested that the sorption process was endothermic, spontaneous and energetically favourable in nature. Desorption of cadmium ions was readily achieved with ultrasonic assisted mild acid treatment. Moreover, the stability and preconcentration efficiency of the recovered magnetic nanoadsorbent was retained over several separation cycles. Under optimal conditions, detection limit, preconcentration factor and relative standard deviation for six replicate extractions are 0.11 ngmL−1, 250 and 2.1% respectively. In addition, the proposed protocol was successfully applied with an excellent reliability and reproducibility for the recovery of Cd2+ ions from water and fly-ash ameliorated soil samples.

Development and validation of a high performance liquid chromatography assay for the determination of temocillin in serum of haemodialysis patients

Therapeutic drug monitoring of β-lactams can be useful for the optimization of therapy, especially when little reference data exist on actual pharmacokinetic profiles such as in patients undergoing haemodialysis. There is no reported validated method for temocillin assay in serum samples, and preliminary studies evidenced potential for interferences by acidic metabolites and co-administered drugs in patients with advanced kidney failure. This paper describes a fully validated method for the determination of temocillin in human serum, and its applicability in haemodialysis patients. Temocillin was extracted from human serum by a solid phase extraction methodology, and then assayed by reversed-phase HPLC with UV-detection. The method was validated according to the accuracy profile methodology, using total error to verify the trueness, precision and overall accuracy. It showed high specificity and precision and was accurate in the concentration range of 5–400mg/L. LOD and LOQ were 1.2 and 5mg/L, respectively. No interference with 30 co-administered drugs was evidenced. The method was successfully applied to clinical samples from haemodialysis patients, showing a high degree of dialysability of temocillin.

Estimating uncertainty in matrix solid phase extraction methodology for the determination of chlorinated compounds in fish

In this study, a detailed process of uncertainty estimation associated with matrix solid phase dispersion method (MSPD) for the extraction of organochlorinated compounds from fish coupled with gas chromatography is given. The evaluation of uncertainty arising from trueness using fully nested experimental designs is presented by estimating proportional bias, in terms of recovery. The uncertainty of measurements associated with the actual chromatographic process was also estimated. The methodology was applied for the determination of selected organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in real fish samples, from selected study locations in Western Greece (Mesologgi lagoon and Trichonida lake), based on chromatographic techniques. The sources of uncertainty are presented along with the calculated combined uncertainty terms derived from the analytical procedure and chromatographic process. The estimation of uncertainty was included in the presentation of final determinations.

Evaluation of SPE as Preparative Technique for the Analysis of Phenolic Metabolites in Human Feces

Solid phase extraction (SPE) methodology has been evaluated as a cleanup strategy prior to the analysis of phenolic metabolites in fecal samples by UPLC–DAD–ESI–TQ MS. Among the sorbents tested, Oasis® HLB led to the higher phenolic standard recoveries. Sample acidification (0.4 M HCl, final concentration) before SPE considerably improved standard recoveries. Values of the process efficiency (CSPE/CWithout SPE) for a standard solution containing gallic acid, protocatechuic acid, caffeic acid, benzoic acid, 3-phenylpropionic acid, (+)-catechin, (−)-epicatechin, procyanidin B2, and 4-hydroxybenzoic 2,3,5,6 d4 acid were acceptable (>90 %) for all compounds, except for procyanidin B2 (26 %). The developed SPE methodology was applied to fecal samples of individuals subjected to a wine intervention study. Phenolic metabolites, including intermediate metabolites (phenyl-γ-valerolactones and phenylvaleric acid derivatives) and end products (simple phenols, hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, and hydroxybenzoic acids) were identified. Most of the compounds (n = 14) exhibited values of process efficiency between 85 and 115 %. Although some compounds (n = 4) showed process efficiency>115 %, there was a group of metabolites (4-O-methylgallic acid, syringic acid, and 4-hydroxy-5-(3′,4′-dihydroxyphenyl)-valeric acid) whose process efficiency was <85 %, which represented a serious limitation and made us to discard SPE as a preparative technique for the analysis of these phenolic metabolites. Finally, the paper reports the concentrations of phenolic metabolites in a randomized set of human fecal samples from healthy volunteers (n = 15) without any previous SPE application. Large inter-individual variability was observed, which was attributed to differences in human gut microbiota composition.

Quechers methodologies as an alternative to solid phase extraction (SPE) for the determination and characterization of residues of cephalosporins in beef muscle using LC–MS/MS

This work was focused on the comparison of two clean-up methods to be used for the simultaneous determination of seven cephalosporins in cow muscle. In particular, the performance of novel dispersive solid phase extraction (d-SPE) procedures based on QuEChERS methodologies was assessed and compared with conventional SPE. The separation and detection of the analytes using both methods was carried out by LC–MS/MS to reach enough sensitivity to be compatible with the detection of the maximum residue limits (MRL) of cephalosporins as regulated by EU directives. The optimization of the clean-up step relied on experimental design in order to find the most suitable conditions with a reduced number of assays. Besides, multi-objective responses were used to reach an overall compromise in the recovery of all analytes simultaneously. The validation of the two methods was done according to the Directive 2002/657/EC. Linearity, decision limit, detection capability, detection and quantification limits (4–50μgkg−1), precision (RSD less than 15% except for PIR) and recoveries were determined and adequate results with comparable values using QuEChERS and SPE methodologies. LOQ were better for SPE method (0.1–10μgkg−1) but both methods show LOQ below MRL values. Precision was slightly better for the QuEChERS method, that also presents better recoveries, higher than 85% except for cephalexin.

Study of bond Elut® Plexa™ PCX cation exchange resin in flow injection column preconcentration system for metal determination by flame atomic absorption spectrometry

A simple and sensitive on-line solid-phase extraction methodology for preconcentration and determination of trace amounts of Cd(II), Pd(II) and Cu(II) in natural water samples has been developed using the strong cation exchange capability of Bond Elut® Plexa™ PCX polymer resin. Plexa PCX is a mixed-mode sorbent, commercially available in a cartridge format and as far as we know, there is no application into the field of metal determination. The analytes were retained on the resin, eluted with 1molL−1 hydrochloric acid and subsequently directed to FAAS for quantification. The influence of chemical and flow variables which affect the performance of the system have been studied, providing the appropriate conditions for the analysis of real samples. For preconcentration time of 90s, an enrichment factor of 90, 95 and 95 and a detection limit (3s) of 0.1, 1.8 and 0.5μgL−1 for Cd(II), Pb(II) and Cu(II), respectively were obtained along with a sampling frequency of 30h−1. The accuracy of the proposed method was evaluated by analyzing certified reference materials. This procedure was successfully applied for metal determination in environmental and biological samples.

Determination of quinolones of veterinary use in bee products by ultra-high performance liquid chromatography–tandem mass spectrometry using a QuEChERS extraction procedure

A reliable and rapid ultra high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method has been developed for the determination of the eight quinolones of veterinary use regulated by European Union (marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, flumequine and oxolinic acid). Chromatographic conditions were optimized in order to increase sample throughput and sensitivity. The antibiotics were detected by electrospray ionization in positive ion mode with multiple reaction monitoring (MRM) and MS/MS conditions were optimized in order to increase selectivity, selecting the corresponding product ions for quantification and identification. The separation was achieved in 3min, using a Zorbax Eclipse Plus C18 column (50mm×2.1mm, 1.8μm), with a mobile phase of 0.02% aqueous formic acid solution and acetonitrile. A dispersive solid phase extraction methodology, often referred to as the “QuEChERS” (quick, easy, cheap, effective, rugged, and safe) method, was optimized for extraction of the quinolones from honey and also it was evaluated for other bee products such as royal jelly and propolis. The method was validated for each matrix in terms of linearity, trueness, precision, limits of detection (LODs) and quantification (LOQ). LODs ranged between 0.2 and 4.1μgkg−1 with precision lower than 12% and satisfactory recoveries in most cases. The method was also applied for studying the occurrence of these antibiotics in several market samples.

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, Río Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MA(V)) and dimethylarsinic acid (DMA(V)). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San José de Jáchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 to 357μgl(-1) As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 to 1326μgl(-1) As. The pH range for the provinces of San Juan (7.2-9.7) and La Pampa (7.0-9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (>2,600 μS cm(-1)) and TDS (>1,400mgl(-1)). Reverse osmosis (RO) treatment of well waters in La Pampa for domestic drinking water in EC and LU significantly reduced total arsenic concentrations from a range of 216-224μgl(-1) As to 0.3-0.8μgl(-1) As. Arsenic species for both provinces were predominantly As(III) and As(V). As(III) and As(V) concentrations in San Juan ranged from 4-138μgl(-1) to <0.02-22μgl(-1) for surface waters (in the San José de Jáchal region) and 23-346μgl(-1) and 0.04-76μgl(-1) for groundwater, respectively. This translates to a relative As(III) abundance of 69-100% of the total arsenic in surface waters and 32-100% in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is As(V). However, data from the SPE methodology suggests that As(III) is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had As(III) and As(V) concentrations of 5-1,332μgl(-1) and 0.09-592μgl(-1) for EC and 32-242μgl(-1) and 30-277μgl(-1) As for LU, respectively. Detectable levels of MA(V) were reported in both provinces up to a concentration of 79μgl(-1) (equating to up to 33% of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in situ arsenic speciation in water supplies is discussed.

The use of polymeric solid phase extraction and HPLC analysis for the determination of ranitidine in routine plasma samples obtained from paediatric patients.

A sensitive HPLC method for the determination of ranitidine in small-volume (0.5 mL) paediatric plasma samples is described. Plasma samples were extracted using a simple, rapid solid phase extraction (SPE) technique developed using disposable copolymer packed SPE cartridges. Chromatographic separation was achieved by reverse-phase HPLC with isocratic elution using a microBondapak C18 column and a phosphate buffer (10 mM, pH 3.75)-acetonitrile (87:13 v/v) mobile phase with UV detection at 313 nm. The HPLC system exhibited linearity in the range 8-800 ng mL(-1). Intraday % CV and % bias values were in the range 1.28-8.09% (% bias -4.33 to -0.87) and interday % CV and % bias values were in the range 0.73-15.28% (% bias -1.80 to + 1.65). The limits of detection and quantitation obtained were 2 ng mL(-1) and 8 ng mL(-1), respectively, and ranitidine extraction recoveries from plasma ranged from 92.30 to 103.88%. In this study, the developed HPLC and SPE methodologies have been successfully applied to the determination of ranitidine concentrations in 68 paediatric plasma samples. The sampled population was drawn from patients already receiving the study drug therapeutically. Patients recruited had received ranitidine by two main routes - oral and intravenous. The plasma concentrations of ranitidine encountered in paediatric samples following oral or intravenous administration of a range of prescribed doses are presented graphically. These profiles are based on analysis of the first 68 plasma samples obtained from the first 35 patients recruited to the study receiving ranitidine by the oral or intravenous route.

New HPLC assay for urinary salbutamol concentrations in samples collected post-inhalation

A new reversed phase high performance liquid chromatography (HPLC) method with florescence detection and two solid phase extraction (SPE) methods have been developed, optimised and validated for determining salbutamol in human urine after an inhalation. SPE methodology for unchanged salbutamol (USAL) and salbutamol plus its metabolites (USALMET) concentrations in urine has been developed using terbutaline as the internal standard. Confirm HCX cartridges were used for USAL and Oasis HLB for USALMET. Calibration lines of salbutamol urine standards were linear over the range 25–300 μg/L with mean (RSD) r 2 values of 0.9983 (0.06%) for USAL and 0.9976 (0.202%) for USALMET. The HPLC method was accurate (mean bias −0.40% for USAL and 0.46% for USALMET) and precise (mean RSD 5.0% for USAL and 2.90% for USALMET). The calculated LOD and LOQ for salbutamol using a 1 mL urine sample were 4.0 and 12.12 μg/L for USAL, and 4.80 and 14.56 μg/L for USALMET, respectively. The mean (RSD) SPE recoveries of salbutamol were 90.82% (2.32%) for USAL and 91.54% (2.96%) for USALMET. Both HPLC and SPE methods were applied to quantify unchanged and metabolised salbutamol excreted in urine after the inhalation of 200 μg salbutamol from metered dose inhalers (MDIs) by 14 healthy volunteers. Charcoal slurries were also ingested to prevent gastro-intestinal absorption. Urine samples were collected at 30 min post-inhalation and then pooled for the next 24 h. All urine concentrations were within the sensitive portion of the assay. The volunteer study revealed that following inhalation from an MDI about 20% of the nominal dose is deposited into the lungs and 46% is delivered to the systemic circulation. The results confirm the application, sensitivity, reliability and robustness of the HPLC and SPE methods for urinary pharmacokinetic studies after salbutamol inhalations using therapeutic doses.

Quantification of penicillin G during labor and delivery by capillary electrophoresis

In this study, a capillary electrophoresis (CE) method was developed as a means to measure levels of penicillin G (PCN G) in Group B Streptococcus (GBS) positive pregnant women during labor and delivery. Volunteers for this developmental study were administered five million units of PCN G at the onset of labor. Urine, blood, and amniotic fluid samples were collected during labor and post delivery. Samples were semi-purified by solid-phase extraction (SPE) using Waters tC18 SepPak 3 cc cartridges with a sodium phosphate/methanol step gradient for elution. Capillary electrophoresis or reversed-phase high-performance liquid chromatography (RP-HPLC) with diode-array absorbance detection were used to separate the samples in less than 30 min. Quantification was accomplished by establishing a calibration curve with a linear dynamic range. The tC18 SPE methodology provided substantial sample clean-up with high recovery yields of PCN G (∼ 90%). It was found that SPE was critical for maintaining the integrity of the separation column when using RP-HPLC, but was not necessary for sample analysis by CE where no stationary phase is present. Quantification results ranged from millimolar concentrations of PCN G in maternal urine to micromolar concentrations in amniotic fluid. Serum and cord blood levels of PCN G were below quantification limits, which is likely due to the prolonged delay in sample collection after antibiotic administration. These results show that CE can serve as a simple and effective means to characterize the pharmacokinetic distribution of PCN G from mother to unborn fetus during labor and delivery. It is anticipated that similar methodologies have the potential to provide a quick, simple, and cost-effective means of monitoring the clinical efficacy of PCN G and other drugs during pregnancy.

Poly(methyltetradecylsiloxane) immobilized onto silica for extraction of multiclass pesticides from surface waters

A new material based on poly(methyltetradecylsiloxane) (PMTDS) thermally immobilized onto a silica support has been tested as a sorbent for the solid-phase extraction (SPE) from water of several pesticides used in soybean cultivation. The SPE methodology was developed and validated for six of these pesticides (imazethapyr, imazaquin, metsulfuron-methyl, bentazone, chlorimuron-ethyl and tebuconazole) according to the International Conference on Harmonization directives and the results were compared with those obtained with a commercial C18 SPE cartridge. The PMTDS-based sorbent gives results similar to the commercial sorbent with recoveries and precisions in agreement with directives for residue analysis. The quantification limits, after concentration, of all the pesticides evaluated were 1.0 μg L −1, below the levels imposed by the principal regulatory agencies. The PMTDS-based sorbent preparation is fast, easy and reproducible and the cartridges are less expensive than similar commercial SPE materials.

Quantitative plasma determination of a novel antiretroviral derivative of zidovudine by solid-phase extraction and high-performance liquid chromatography

A solid-phase extraction methodology, followed by high-performance liquid chromatography (HPLC) quantification with UV absorbance detection (lambda = 267 nm), was developed in order to study the stability of 3'-azido-3'-deoxy-5'-O-isonicotinoylthymidine (AZT-Iso), a novel derivative of the antiretroviral AZT, in different matrixes. The half-lives (t1/2) for AZT-Iso were 1.19, 1.13 and 0.30 h for human, rat and rabbit plasma, respectively, and 14.91 and 25.49 h for potassium phosphate buffer (pH 7.4) and human serum albumin solution, respectively. The HPLC method proved to be selective, sensitive and accurate. Good recovery, linearity and precision were achieved using p-fluorophenol as an internal standard. The validity of this method was tested using synthetic mixtures of the intact drug with its decomposition products. In conclusion, the method presented is applicable to in vivo pharmacokinetics studies of AZT-Iso in rats.

Roquefortine/Oxaline Biosynthesis Pathway Metabolites in Penicillium ser. Corymbifera: In Planta Production and Implications for Competitive Fitness

Three strains of each of the seven taxa comprising the Penicillium series Corymbifera were surveyed by direct injection mass spectrometry (MS) and liquid chromatography-MS for the production of terrestric acid and roquefortine/oxaline biosynthesis pathway metabolites when cultured upon macerated tissue agars prepared from Allium cepa, Zingiber officinale, and Tulipa gesneriana, and on the defined medium Czapek yeast autolysate agar (CYA). A novel solid-phase extraction methodology was applied for the rapid purification of roquefortine metabolites from a complex matrix. Penicillium hordei and P. venetum produced roquefortine D and C, whereas P. hirsutum produced roquefortine D and C and glandicolines A and B. P. albocoremium, P. allii, and P. radicicola carried the pathway through to meleagrin, producing roquefortine D and C, glandicolines A and B, and meleagrin. P. tulipae produced all previously mentioned metabolites yet carried the pathway through to an end product recognized as epi-neoxaline, prompting the proposal of a roquefortine/epi-neoxaline biogenesis pathway. Terrestric acid production was stimulated by all Corymbifera strains on plant-derived media compared to CYA controls. In planta, production of terrestric acid, roquefortine C, glandicolines A and B, meleagrin, epi-neoxaline, and several other species-related secondary metabolites were confirmed from A. cepa bulbs infected with Corymbifera strains. The deposition of roquefortine/oxaline pathway metabolites as an extracellular nitrogen reserve for uptake and metabolism into growing mycelia and the synergistic role of terrestric acid and other Corymbifera secondary metabolites in enhancing the competitive fitness of Corymbifera species in planta are proposed.

Selective Quantification of Trace Palladium in Road Dusts and Roadside Soils by Displacement Solid-Phase Extraction Online Coupled with Electrothermal Atomic Absorption Spectrometry

There is a growing concern about the effect of palladium on human health because of the toxicity and increasing occurrence of palladium as a result of its extensive use in automotive catalytic converters. Development of reliable analytical methodologies for the determination of palladium in environmental materials is of great importance for critical evaluation of the possible risks for human health. In this work, a displacement solid-phase extraction technique was developed and online coupled to electrothermal atomic absorption spectrometry (ETAAS) for selective and sensitive determination of trace palladium in environmental samples without need of any special selective complexing agents, selective sorbents, and masking agents. The developed methodology involved the online formation of copper pyrrolidine dithiocarbamate (Cu-PDC), and the resultant Cu-PDC was extracted onto a microcolumn packed with the sorbent from a cigarette filter. Trace Pd(II) was selectively preconcentrated through loading the sample solution onto the microcolumn by online displacement reaction between Pd(II) and the extracted Cu-PDC on the microcolumn. The retained analyte was subsequently eluted with 40 microL of ethanol for online ETAAS determination. Interferences from coexisting heavy metal ions with lower stability of their PDC complexes relative to Cu-PDC were minimized. The tolerable concentrations of Cd-(II), Fe(III), Co(II), Mn(II), Cr(III), and Zn(II) were up to 2, 6, 40, 2, 1.5, and at least 100 mg L(-1), respectively. Compared with conventional solid-phase extraction methodology, the developed displacement solid-phase extraction protocol gave 2-4 orders of magnitude improvement in the maximum tolerable concentrations of coexisting heavy metal ions. With the consumption of only 2.8 mL of sample solution, an enhancement factor of 52 and a detection limit (3sigma) of 18 ng L(-1) were achieved at a sample throughput of 30 samples h(-1). The precision (RSD, n = 13) was 2.5% at the 1 microg L(-1) level. The present methodology was successfully applied to selective determination of trace palladium in local road dusts and roadside soils.

Miniaturized method for separation and quantification of nitrogen species in petroleum distillates ☆

The properties of nitrogen compounds are a subject of interest to petroleum refiners due to the detrimental role, these compounds play in catalyst deactivation and product stability. It is thought that basic nitrogen is a major contributor to these phenomena, and therefore identification and quantification of nitrogen species by type would be of great importance. A practical miniaturized method for quantitative separation of nitrogen compounds by type in petroleum distillates is described. Solid phase extraction methodology was used to concentrate the nitrogen compounds and to separate them further into neutral and basic types. The basic nitrogen compounds could not be fully recovered, while full recovery was achieved for the neutral nitrogen types. The amount of basic nitrogen was calculated by difference, and boiling point distribution profiles were produced. For identification of nitrogen compounds in separated fractions, a combined GC–MS/AED method with retention time locking was used. Carbazole and its substituted derivatives methyl, dimethyl, and trimethylcarbazoles were identified in the product from fluid catalytic cracking.

Determination of linear alkylbenzensulfonates in aqueous matrices by ion-pair solid-phase microextraction–in-port derivatization–gas chromatography–mass spectrometry

Trace determination (low ng/ml) of linear alkylbenzensulfonates (LASs) in water was achieved by solid-phase microextraction (SPME) of ion-pairs formed with tetrabutylammonium. This ion-pairing reagent served two purposes. First, it allowed the extraction of LAS with the polydimethylsiloxane fiber by counterion association and second, the derivatization of the formed LAS ion pairs in the GC injection port at 300 °C to form the corresponding sulfonated butyl esters. The methodology developed allows the isomer specific determination of LAS at low detection limits (0.16–0.8 ng/ml), depending on the alkyl chain lengths of LASs with RSDs of 10–12%. Furthermore, the developed methodology was applied to urban wastewater and sea water and compared with a solid-phase extraction (SPE) method (e.g. C 18 and strong anion-exchange sorbent) to obtain concordant values for urban wastewater. Moreover, the developed SPME methodology overcame the procedural blank and matrix-dependent recoveries found in the SPE methodologies at low LAS concentrations.

Porous organoclay composite for the sorption of polycyclic aromatic hydrocarbons and pentachlorophenol from groundwater

Complex mixtures of hazardous chemicals such as polycyclic aromatic hydrocarbons (PAHs) in contaminated soil and groundwater can have severe and long-lasting effects on health. The evidence that these contaminants can cause adverse health effects in animals and humans is rapidly expanding. The frequent and wide-spread occurrence of PAHs in groundwater makes appropriate intervention strategies for their remediation highly desirable. The core objective of this research was to assess the ability of a clay-based composite to sorb and remove toxic contaminants from groundwater at a wood-preserving chemical waste site. Treatment efficiencies were evaluated using either effluent from an oil–water separator (OWS) or a bioreactor (B2). The effluent water from these units was passed through fixed bed columns containing either an organoclay composite or granular activated carbon. The sorbent columns were placed in-line using existing sampling ports at the effluent of the OWS or B2. Individual one-liter samples of treated and untreated effluent were collected in Kimax bottles over the course of 78 h (total of 50 samples). Subsequently each sample was extracted by solid phase extraction methodology, and pentachlorophenol (PCP) and PAH concentrations were quantitated via GC/MS. Columns containing porous organoclay composite, i.e. sand-immobilized cetylpyridinium–exchanged low-pH montmorillonite clay (CP/LPHM), were shown to reduce the contaminant load from the OWS effluent stream by 97%. The concentrations of benzo[a]pyrene (BaP) and PCP were considerably reduced (i.e. >99%). An effluent stream from the bioreactor was also filtered through columns packed with composite or an equivalent amount of GAC. Although the composite reduced the majority of contaminants (including BaP and PCP), it was less effective in diminishing the levels of lower ring versus higher ring PAHs. Conversely, GAC was more effective in removing the lower ring PAHs, except for naphthalene and PCP. The effectiveness of sorption of PCP from the OWS effluent by the composite was confirmed using a PCP-sensitive adult hydra bioassay previously described in our laboratory. The findings of this initial study have delineated differences between CP/LPHM and GAC for groundwater remediation, and suggest that GAC (instead of sand) as the solid support for organoclay may be more effective for the treatment of contaminated groundwater under field conditions than GAC or CP/LPHM alone. Further work is ongoing to confirm this conclusion.