Automatic flow system for evaluation of polystyrene-divinylbenzene sorbents applied to preconcentration of phenolic pollutants

In this work, an evaluation of commercially available polystyrene-divinylbenzene sorbents for solid-phase extraction (SPE) of eleven phenolic compounds is intended. Considering the particle size and cross-linking degree, Amberlite XAD-4 (commercial or grounded), Macronet MN-200 and Lichrolut EN were tested. The SPE protocol was performed by an automatic system, providing repeatable experimental conditions for assessment of sorbent capacity, breakthrough volume and enrichment factor (EF). A positive correlation between EF and log?K _ow was found for Amberlite XAD-4 while a negative correlation was observed between EF and molecular weight of analyte for Macronet MN-200 and for Lichrolut EN. This indicates a prevalence of hydrophobic interactions or molecular exclusion depending upon the polymer cross-linking degree. Despite the similar repeatability (RSD?<?4.7%, n?>?6) and recovery values attained (97.6–102.7%, using 50?mL of sample) for all sorbents, Lichrolut EN is the best choice for analytical application as higher EF and lower LOD values (between 18 and 207?ng) were attained for this sorbent.     

Sample and Sorbent Integrity During Combustion Source Sampling

Abstract

A research program was initiated to evaluate the stability of selected organic compounds collected on porous polymer sorbents during combustion source sampling. This type of study is necessary to determine if destruction and removal of hazardous materials waste has occurred during incineration and not as a result of the sampling and analytical approach used. Two compounds, hexachlorobenzene and toluene diisocyanate, were selected for study. Due to difficulties encountered in preliminary work, studies on toluene diisocyanate were discontinued. Hexachlorobenzene sorbed onto XAD-2 resin at the 1 μg level was exposed to the following conditions intended to simulate hazardous waste incineration stack samplin: moist air, moist air in combination with HCl (two concentrations), and warm air. Recoveries following exposure were determined for each of three trials. The results indicate that hexachlorobenzene sorbed onto XAD-2 is stable with respect to the conditions routinely encountered during incineration stack sampling.     

Analyses of Procymidone and Vinclozolin in Greenhouse Air

Abstract

A method for sampling and analysis of procymidone and vinclozolin in greenhouse air was investigated. The behaviour of Chromosorb 102, Porapak R, Supelpak-2, Amberlite XAD-2, Amberlite XAD-4 and polyurethane foam (PUF) as sorbents was studied. Atmospheres containing known concentrations of these pesticides were generated. The desorption process of the analytes, concentration step and behaviour of sorbents in air with different relative humidities were tested. No breakthrough was observed in the range of concentrations studied.

Personal samplers were used with the selected sorbent (PUF), for sampling procymidone and vinclozolin in an experimental greenhouse. GC-ECD analysis and MS confirmation were performed. The dissipation process of the analytes in the 24 h period after application was studied.     

An Investigation on the Concentration Efficiencies of Some Macroreticular and Ambersorb Resins Using Radio-Labelled Organic Contaminants Commonly Encountered in Water

Abstract

The extraction efficiencies of the three commercially available Ambersorb®, carbonaceous, polymeric resins, XE-340, XE-347 and XE-348 were evaluated for their use as sorbents for environmental pollutants using four model, radio-labelled water-borne organic contaminants. Their accumulation behaviour was compared with that of the thoroughly-studied Amberlite®, macroreticular XAD-2 (hydrophobic) and XAD-7 (hydrophilic) resins. These model compounds were desorbed from the resins using known volumes of commonly-used solvents to select the solvent for a particular resin(s). In this preliminary study, at <4 μg/L concentrations of the labelled compounds in aqueous solution (pH 5.78), the order of extraction efficiency of the resins was found to be XAD-2 > XAD-7 > XE-340?-347?-348 for organics. Several inherent impurities originally present in the carbonaceous resins were desorbed by solvents during elution. These resins therefore required exhaustive soxhlet purification prior to use. Most of the impurities were identified by gas chromatography/mass spectrometry.     

Optimization and evaluation of a procedure for the gas chromatographic-mass spectrometric analysis of the aromas generated by fast acid hydrolysis of flavor precursors extracted from grapes

A procedure has been developed for the GC-MS analysis of the aromas released in fast acid hydrolysis of precursor fractions from grape musts and skins. Different sorbents for the extraction of the precursors were compared. The best results were obtained with LiChrolut EN polymeric resins which displayed two and six-fold more extraction capacity than Amberlite XAD-2 resins and C18 sorbents, respectively. C18 sorbents are more suitable for selective extraction of less polar precursors. The initial version of the method was imprecise and so the imprecision of the different steps was assessed. The maceration of the solid parts and the liquid-liquid extraction of the aromas released in the acid hydrolysis proved to be the critical steps. Greater crushing of the solid parts and solid-phase extraction (SPE) instead of liquid-liquid extraction (LLE) improved reproducibility. In the method finally proposed about 100 aromatic components belonging to four large groups (lipid derivatives, shikimic acid derivatives, norisoprenoids and terpenes) were determined with good reproducibility. Important aroma compounds, such as cis-rose oxide or wine lactone were detected in non-Muscat grapes.     

Application of tryptamine as a derivatizing agent for the determination of airborne isocyanates. Part 5. Investigation of tryptamine-coated XAD-2 personal sampler for airborne isocyanates in workplaces.

The development of an efficient solid sorbent personal sampler with increased convenience for sample collection in workplaces is described. Several solid sorbents were coated with tryptamine, and sampling tubes were prepared with the coated sorbents. These tubes were evaluated for the collection of phenyl isocyanate vapour generated in a commercial test atmosphere generation system that permits the simultaneous collection of up to 12 uniformly loaded samples. Tryptamine-coated XAD-2 resin was shown to be the most efficient solid sorbent for the collection of airborne phenyl isocyanate. The optimum amount of tryptamine needed for coating XAD-2 resin was investigated.     

Comparative Enrichment Capabilities of Some Carbonaceous and Macroreticular Resins Using Selected Radioactive Model Compounds in Fortified Aqueous Samples

Abstract

The concentration efficiency of synthetic macroreticular resins, XAD-2 and XAD-7 and carbonaceous resins, XE-340, XE-347 and XE-348 was evaluated and compared using trace levels of eight radioactive model environmental contaminants present in aqueous medium. Influences of chemical functionalities of the solvents, physical characteristics of the sorbents, and pH of the aqueous medium on sorption of the model compounds were investigated under frontal dynamic chromatographic conditions. The elution behavior of these sorbates and desorption properties of the polymer adsorbents with respect to solvents of different polarities were studied.     

Comparison between DAX-8 and C-18 solid phase extraction of rainwater dissolved organic matter

Rainwater is a very low concentrated matrix and, for dissolved organic matter (DOM) characterization, an efficient extraction procedure is essential. Isolation procedures based on the adsorption onto XAD-8 and C-18 sorbents have been used in the literature for rainwater DOM isolation, but a comparison between these procedures is lacking. In this work, UV-visible and molecular fluorescence spectroscopies highlighted differences between rainwater DOM isolated by DAX-8 (replacement for XAD-8) and by C-18. It was possible to recover higher rainwater DOM percentage by the C-18 based procedure than by the DAX-8 one. Rainwater protein-like compounds were better concentrated by the C-18 procedure than by the DAX-8 one, while humic-like compounds were similarly concentrated by both procedures. Furthermore, rainwater DOM extracted by the C-18 procedure was more representative of the global matrix, while DAX-8 preferentially extracted humic-like compounds.     

Frontal analysis of aqueous phenol solutions in amberlite XAD-4 columns Implications on the operation and design of solid phase extraction systems

Frontal analysis of aqueous phenol solutions in Amberlite XAD-4 columns was carried out at different experimental conditions. Operating variables such as the concentration, pH and ionic strength of the influent, the presence of competitor solutes, the fluid flow-rate and the column length were considered and their effects on the front profile, the phenol breakthrough volume and the equilibrium parameters were determined. The obtained results may explain some contradictory reported data concerning the recovery of hydrophilic compounds in solid phase extraction (SPE) systems using Amberlite XAD-2 or XAD-4 columns. Furthermore, it is demonstrated that the adsorption parameters derived from a frontal analysis in an XAD-4 column are directly transposable to columns of different sizes (at the analytical level). Therefore, the results of this study may also be used for prediction and/or design of a phenol SPE system adapted to a particular problem.     

Flame AAS determination of lead in water with flow-injection preconcentration and speciation using functionalized cellulose sorbent

The on-line solid phase extraction of trace amount of lead in flow-injection system with flame AAS detection was investigated using cellulose sorbents with phosphonic acid and carboxymethyl groups, C(18) sorbent non-modified and modified with Pyrocatechol Violet or 8-quinolinol, commercial chelating sorbents Chelex 100 and Spheron Oxin 1000, non-polar sorbent Amberlite XAD-2 modified with Pyrocatechol Violet and several cation-exchange resins. The best dynamic characteristics of retention were observed for functionalized cellulose sorbents. For Cellex P assumed as optimum sorbent, elution with a separate fractions of nitric acid and ethanol allows the differentiation between tetraalkyllead and sum of inorganic lead and organolead species of smaller number of alkyl groups. The detection limit for the determination of inorganic Pb(II) was estimated as 0.17 microg/l. at preconcentration from 50 ml sample at a flow rate of 7 ml/min.     

Comparative study of breakthrough volumes BTV on various sorbents

Summary Breakthrough volumes on ten sorbents (Chromosorb 102, 104, 105 and 106, Porapak R and S, XAD-2, XAD-7, Tenax GC and Carbosphere) have been determined for vapours of 15 volatile organic compounds (halogenated hydrocarbons, alcohols, etc.). The volumes were determined by an indirect method employing typical chromatographic parameters such as retention volume and peak width.The method seems to be useful for preliminary estimation of adsorption capacity of various sorbents. It is not suitable, however, for the investigation of the effect of various parameters on the breakthrough volume.

---

Vergleichende Untersuchung des Durchbruchsvolumens an verschiedenen Sorbentien

Zusammenfassung An 10 verschiedenen Sorbentien (Chromosorb 102, 104, 105, 106; Porapak R und S; XAD-2; XAD-7; Tenax GC; Carbosphere) wurden für 15 flüchtige organische Verbindungen (halogenierte Kohlenwasserstoffe, Alkohole u. a.) die Durchbruchsvolumina bestimmt. Es wurde dafür ein indirektes Verfahren mit typischen chromatographischen Parametern (Retentionsvolumen, Peakbreite) benutzt. Die Methode erscheint nützlich für die vorläufige Abschätzung der Adsorptionskapazität von Sorbentien, eignet sich jedoch nicht für die Untersuchung des Einflusses verschiedener Parameter auf das Durchbruchsvolumen.

---

---

Part of this research was supported by Institute of Oceanology, Polish Academy of Sciences, Gdask, grant MR. I-15.     

Determination of imidacloprid and its metabolite 6-chloronicotinic acid in greenhouse air by high-performance liquid chromatography with diode-array detection

A method is described for analysing and sampling imidacloprid and its metabolite 6-chloronicotinic acid in greenhouse air by high-performance liquid chromatography (HPLC) with diode-array detection (DAD). The trapping efficiency of two solid sorbents, Amberlite XAD-2 and Amberlite XAD-4 and the use of different desorption procedures have been tested. To validate the methodology, standard atmospheres containing known concentrations of these pesticides and with different relative humidities were generated. No breakthrough was observed in the range of concentrations studied. Dissipation of analytes was investigated in a 24 h period after application by using personal samplers in a field experiment.     

Extraction of Organic Compounds from Aqueous Media by Amberlite XAD Resins

Abstract

Three Amberlite polymeric resins, XAD-2, XAD-4 and XAD-7, were evaluated for extraction efficiency from aqueous media of several organic compounds representing pesticides, polyaromatic hydrocarbons, phenols and phthalate esters. The three resins exhibited different extraction characteristics. The extraction efficiency of the resins was found to be dependent on pH conditions and, on the average, was best at pH7. At this pH the XAD-2 and XAD-4 resins yielded quantitative recoveries in the 90–100% range for most compounds at the 20–200ppb level. Recoveries by XAD-7 resins were lower for several compounds. The recovery of aldrin and o, p DDT under all conditions was relatively low (>68%) and showed a higher degree of variability than that obtained for the other compounds. Alkaline pH conditions were generally unfavourable for the extraction of phenolic compounds but acidification to pH2 was not found to be a necessary step for the quantitative extraction of the phenolic compounds. Acidification to pH2 further led to a decrease in the recovery of most compounds for XAD-4 resins. A combined resin column yielded extraction efficiencies comparable to the XAD-2 column at pH 7, but since the three resins possess different extraction characteristics, a mixture comprising all three is recommended for the preconcentration of organic compounds from environmental water samples containing a wide range of compounds.     

Searching for an enhanced predictive tool for mutagenicity

The Multiple Computer Automated Structure Evaluation (MCASE) program was used to evaluate the mutagenic potential of organic compounds. The experimental Ames test mutagenic activities for 2513 chemicals were collected from various literature sources. All chemicals have experimental results in one or more Salmonella tester strains. A general mutagenicity data set and fifteen individual Salmonella test strain data sets were compiled. Analysis of the learning sets by the MCASE program resulted in the derivation of good correlations between chemical structure and mutagenic activity. Significant improvement was obtained as more data was added to the learning databases when compared with the results of our previous reports. Several biophores were identified as being responsible for the mutagenic activity of the majority of active chemicals in each individual mutagenicity module. It was shown that the multiple-database mutagenicity model showed a clear advantage over normally used single-database models. The expertise produced by this analysis can be used to predict the mutagenic potential of new compounds.     

Preparation of phenothiazine bonded silica gel as sorbents of solid phase extraction and their application for determination of nitrobenzene compounds in environmental water by gas chromatography-mass spectrometry

In this paper, two phenothiazine bonded silica (PTZ-Si) sorbents were prepared and used as sorbents of solid-phase extraction (SPE) for the determination of nitrobenzene compounds in environmental water samples by gas chromatography-mass spectrometry (GC-MS). Different synthesis routes were proposed to obtain high bonded amount of PTZ on the surface of silica gel. PTZ molecule was derived to its amino or acyl chloride derivatives for reacting with isocyanate or amino silane coupling agent, which was further reacted with the surface silanol groups of silica gel to obtain the PTZ-Si sorbents. The resultant PTZ-Si sorbents were characterized by nitrogen sorption porosimetry (NSP), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA) to assure the successful bonding of PTZ on the surface of silica gel. Then the PTZ-Si sorbents were served as SPE sorbents for the enrichment of nitrobenzene compounds. Several parameters affecting the extraction performance were investigated. Under the optimized conditions, the proposed method was applied to the analysis of six nitrobenzene compounds in environmental water samples. Good linearities were obtained for all nitrobenzene compounds with R(2) larger than 0.9958. The limits of detection were found to be in the range of 0.06-0.3 ng/mL. The method recoveries of nitrobenzene compounds spiked in water samples were from 71.4% to 124.3%, with relative standard deviations (RSDs) less than 10.1%.     

Analytical potential of fullerene as adsorbent for organic and organometallic compounds from aqueous solutions

In this work, the analytical potential of C60 fullerene as a sorbent for organic and organometallic compounds from aqueous solutions was studied for the first time. Fullerene adsorbs many types of organic substances (e.g., N-methylcarbamates, phenols, polycyclic aromatic hydrocarbons, amines) with efficiencies that depend on the nature of the compound concerned and never exceed 60%. Conventional sorbents such as XAD-2 or polyurethane foam are more efficient than C60 for this purpose. Organometallic compounds (viz. metalocenes and organoleads) are quantitatively adsorbed on C60 via the formation of neutral complexes or chelates; the adsorption constant is dramatically increased by the use of classical reagents such as pyrrolidinedithiocarbamate or diethyldithiocarbamate. A complementary comparative study on the adsorption of organometallic complexes on RP-C18 and silica gel 100, among others, showed C60 to be superior as sorbent. All experiments in this work were carried out by using continuous flow configurations and gas chromatography-atomic absorption spectrometry techniques.     

Integration of structure-activity relationship and artificial intelligence systems to improve in silico prediction of ames test mutagenicity

The Ames mutagenicity test in Salmonella typhimurium is a bacterial short-term in vitro assay aimed at detecting the mutagenicity caused by chemicals. Mutagenicity is considered as an early alert for carcinogenicity. After a number of decades, several (Q)SAR studies on this endpoint yielded enough evidence to make feasible the construction of reliable computational models for prediction of mutagenicity from the molecular structure of chemicals. In this study, we propose a combination of a fragment-based SAR model and an inductive database. The hybrid system was developed using a collection of 4337 chemicals (2401 mutagens and 1936 nonmutagens) and tested using 753 independent compounds (437 mutagens and 316 nonmutagens). The overall error of this system on the external test set compounds is 15% (sensitivity = 15%, specificity = 15%), which is quantitatively similar to the experimental error of Ames test data (average interlaboratory reproducibility determined by the National Toxicology Program). Moreover, each single prediction is provided with a specific confidence level. The results obtained give confidence that this system can be applied to support early and rapid evaluation of the level of mutagenicity concern.     

Gas-chromatographic identification of fluorine-containing organic compounds

The gas-chromatographic retention of a series of fluoroalkylarenes on the standard nonpolar polydimethylsiloxane stationary phase OV-101 was characterized, and the retention indices of these compounds were determined. It was found that large negative values of the homological increments of these constants can serve as a sign of fluorine derivatives that contain no less than three fluorine atoms per molecule. The retention indices on polar inorganic sorbents, the silica gels Silipor 75 and Silipor 600, were chosen as the second chromatographic parameter. On these sorbents (unlike partition separation), the nonadditivity effect of the retention indices of polyfunctional organic compounds with respect to their simpler structural analogs was found for the first time. It was found that a mutual correlation between indices for this combination of a phase and a sorbent was lower than that for the combinations of phases with different polarities; this fact is responsible for the higher information content of this combination for the identification of compounds from this class.     

Batch and column study: sorption of perfluorinated surfactants from water and cosolvent systems by Amberlite XAD resins

Amberlite XAD resins have been employed to a great extent as the sorbent for removing or concentrating organic compounds from different matrices. We present for the first time a systematic study on the sorption of perfluorochemical (PFC) surfactants, an emerging class of environmental contaminants, by XAD-7HP (moderately polar) and XAD-2 (nonpolar). The results show that XAD-7HP can strongly sorb PFCs at circumneutral pH; the isotherm-determined linear sorption coefficient can reach 10(6)L/kg. On the other hand, the sorption coefficient for XAD-2 was two orders of magnitude lower than that for XAD-7HP. PFC sorption on XAD-7HP increased with an increase of the perfluorocarbon chain length of PFC and a decrease of the solution pH, indicating the importance of hydrophobic and electrostatic effects. The sorption coefficient for XAD-7HP reduced markedly with increasing fraction of the organic cosolvent (methanol) in the water-cosolvent mixture; however, the trend could not be predicted by a log-linear cosolvency model. Furthermore, the statistical analysis of column test results showed that after regeneration XAD-7HP can be used at least eight times without significant loss of performance. Finally, the experimental results imply that XAD-7HP sorption of shorter-chained PFCs (≤5 perfluorinated carbons) from water can be thermodynamically favorable.     

The application of solid sorbents for the purification of aluminum contaminated chemicals used as modifiers in electrothermal atomic absorption spectrometry

Various microcolumns with solid sorbents (ion exchange resins, functionalised cellulose sorbents, chelating resins) have been tested with respect to their ability for the purification of aluminum contaminated chemicals used as modifiers in electrothermal atomic absorption spectrometry. The purification of NaNO(3), Mg(NO(3))(2), K(2)SO(4) and (NH(4))(2)HPO(4) has been the most effective with an almost 100% efficiency, when Spheron-Oxine was used as chelating resin. The sorption of aluminum from KOH solution has been found to be very high (around 90%) for all investigated sorbents. However, the best results have been obtained with anion-exchange resins. It has been difficult to purify concentrated mineral acids (HCl, H(2)SO(4)). A retention of aluminum above 80% has been achieved only when Cellex P, Chelex 100 or Amberlite XAD-2 have been used.