Determination of anions in landfill leachates by ion chromatography

Ion chromatography has been used to determine inorganic and organic anions within landfill leachates. Two procedures are operated on split samples which have multiple dilutions and vary in sample treatment: gradient ion-exchange chromatography for inorganic anions and isocratic ion-exclusion chromatography for organic anions. Interference between carbonate and organic acid anions using ion-exclusion chromatography is avoided by treatment with octanesulphonic acid eluent. Using ion-exchange chromatography, the presence of valerate, hexanoate and heptanoate is checked (but not quantified) for a subsample which has been treated to remove chloride; these species are then determined by ion-exclusion chromatography. Analysis of certified standards (10 mg/1 certified VFA standard; Supelco, Bellefonte, PA, USA; 20–150 mg/l inorganic anions, ICMIX1-100, Glen Spectra Reference Materials, Middlesex, UK) gives good agreement (within 5% for organic anions except formate, and within 1% for inorganic anions), with R.S.D. values for all anionic species varying from 0.44–2.23.     

Monitoring organochlorine pesticides from landfill leachates by gas chromatography-electron-capture detection after solid-phase microextraction

Landfill leachates contain significant amounts of organic carbon, nitrogen and heavy metals as well as other specific trace organic compounds like organochlorine pesticides. In this study a simple and reliable methodology was improved to detect organochlorine pesticides in leachate samples by using a previous solid-phase microextraction procedure [with a 100 microm poly(dimethylsiloxane) fiber] and chromatographic analysis by GC-electron-capture detection. The extraction time, temperature, ionic strength of the solution and sampling of the headspace were the parameters studied. Reproducibility achieved values below 20% RSD, and standard addition was used for pesticides confirmation.     

Determination of volatile fatty acids in landfill leachates by ion-exclusion chromatography

An ion-exclusion chromatographic method with on-line desalinization for the determination of volatile fatty acids in landfill leachates is described. Highly sensitive conductivity detection of the organic acids was achieved by using dilute p-hydroxybenzoic acid solution as an eluent. Interference with mineral acids was reduced by treatment with barium chloride solution prior to desalinization. A silver-loaded cation-exchange guard column for the desalinization was installed in series with the analytical column to avoid the contamination of organic acids. This method features detection limits of 0.01 mg L(-1) formic acid, 0.02 mg L(-1) acetic acid, 0.05 mg L(-1) propionic acid, and 0.1 mg L(-1) butyric acid, respectively, with an injection of 20 microL sample. Application of the on-line desalinization LC method is illustrated for leachate samples from a Japanese sanitary landfill.     

Direct determination of chlorophenols in landfill leachates by solid-phase micro-extraction-gas chromatography-mass spectrometry

Landfill leachates represent a serious environmental concern with regard to trace priority pollutants introduced into the aquatic environment. From the analytical point of view, they constitute complex matrices because of their high organic matter content and competition with the trace analytes in the extraction procedure. Although the use of SPME to extract chlorophenols in leachates has already been described in several publications, the limited number of chlorophenols restricts this analysis field of application. This paper presents a new analytical methodology to determine 13 chlorophenols and phenol by SPME-GC-MS in landfill leachates. The overall analysis was performed in 90 min and the detection limits range from 0.005 microg/l (pentachlorophenol) to 2.5 microg/l (phenol). Reproducibility, expressed by the coefficient of variation of repeated extractions at different concentration levels of the analytes, was on average inferior to 10%. Recovery, evaluated by standard addition to leachates, was 86.2% on average. Pentachlorophenol, 2,3,4,5-tetrachlorophenol and 2,3,4,6-tetrachlorophenol were the sole analytes detected at nanogram level in the landfill leachates analysed.     

Ion chromatographic separations of phosphorus species: a review

The aim of this paper is to review recent literature regarding the determination of phosphorus species by ion chromatography (IC), and describe the implementation of new developments in sample treatment and ion chromatography methodology for the analysis of these compounds. Ion-exchange methods using both carbonate/hydrogencarbonate and hydroxide selective columns in combination with self-regenerating membrane and solid-phase-based suppressors enable determination of phosphate down to ppb levels. New technology, particularly on-line electrolytic hydroxide generators and electrolytic self-regenerating suppressor devices, has allowed the use of elution gradients in both carbonate/hydrogencarbonate and hydroxide selective systems, improving sensitivity and reducing total analysis time for samples containing phosphate together with other inorganic anions. In addition to a review of these developments, optimization and application of chromatographic methods using reversed stationary phases and cationic and/or zwitterionic surfactants is also discussed.The objective of most of the IC methods developed for phosphorus species is the determination of phosphate and total phosphorus. Therefore, sample treatment and separation conditions specifically developed for this purpose are also described. In addition, application of IC to the analysis of other inorganic (reduced and condensed) and organic (phytates, alkyl phosphate, and phosphonates) phosphorus species is discussed along with methodology and relevant applications in water analysis and other miscellaneous fields.     

Modeling adsorption rate of organic micropollutants present in landfill leachates onto granular activated carbon

The overall adsorption rate of single micropollutants present in landfill leachates such as phthalic acid (PA), bisphenol A (BPA), diphenolic acid (DPA), 2,4-dichlorophenoxy-acetic acid (2,4-D), and 4-chloro-2-methylphenoxyacetic acid (MCPA) on two commercial activated carbons was studied. The experimental data obtained were interpreted by using a diffusional model (PVSDM) that considers external mass transport, intraparticle diffusion, and adsorption on an active site. Furthermore, the concentration decay data were interpreted by using kinetics models. Results revealed that PVSDM model satisfactorily fitted the experimental data of adsorption rate on activated carbon. The tortuosity factor of the activated carbons used ranged from 2 to 4. The contribution of pore volume diffusion represented more than 92% of intraparticle diffusion confirming that pore volume diffusion is the controlling mechanism of the overall rate of adsorption and surface diffusion can be neglected. The experimental data were satisfactorily fitted the kinetic models. The second-order kinetic model was better fitted the experimental adsorption data than the first-order model.     

Ion chromatographic system with a novel switching suppression device

Ion chromatography (IC) has been a powerful tool for measuring ionic species in environmental samples such as tap, river and drain waters. Suppressor modules (membrane and disposable column types) have been used for reducing the background of a baseline. A new type of suppressor device, which has a suppressor resin and switching valve was developed. Fresh ionic resin is introduced into a groove for each analysis to perform the suppression of the working eluent. The eluent composition for obtaining higher sensitivity and better resolutions among ionic species and carbonate ion was also investigated. Although carbonate buffers are used for ion separation in general, the separation of carbonate ion from other ions was not achieved. A borate eluent resulted in good resolutions and higher sensitivity. A new column was also developed for obtaining higher column efficiency and resolution. The optimization of anion separation using a new IC system (IC-2001) that consists of a new suppressor device, an anion-exchange column (TSKgel SuperIC-Anion, 150x4.6 mm), an autosampler, a conductivity cell and a pump in a compact module is described.     

Determination of semi-volatile priority pollutants in landfill leachates and sediments using microwave-assisted headspace solid-phase microextraction

The present work was focused on the development of a simple method aimed at the determination of 12 polycyclic aromatic hydrocarbons (PAHs) and 15 polychlorinated biphenyls (PCBs) in landfill leachates and sediments by adapting a domestic microwave oven to perform microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatographic separation and tandem mass spectrometric detection. Good linearity was observed within the concentration range studied; detection limits ranged from 0.1 ng/l to 7 ng/l for PCBs and from 5 ng/l to 926 ng/l for PAHs. Concerning precision, the relative standard deviations obtained were, on average for the leachate and sediment samples analysed, 18% for PCBs and 20% for PAHs. Average recovery values were 37% and 76% for PCBs, and 58% and 48% for PAHs, respectively, for the leachate and reference sediment studied. The method allows the determination of PAHs and PCBs in landfill leachates and sediments, avoiding clean-up steps and the consumption of organic solvents.     

Gas chromatographic and mass spectrometric investigations of organic residues from Roman glass unguentaria

A combination of gas chromatographic (GC) and mass spectrometric (MS) techniques, including direct exposure-MS (DE-MS), high-temperature GC-MS (HTGC-MS) and GC-MS of neutral and acid fractions, was employed to study the composition and recognise origin of the organic materials used to manufacture balm residues surviving in a series of glass unguentaria recovered from excavations of a Roman villa (Villa B) in the ancient town of Oplontis (Naples, Italy). DE-MS provided comprehensive 'fingerprint' information on the solvent soluble components of the contents of the unguentaria, while GC-MS analyses provided detailed molecular compositions, highlighting the presence of a wide range of compound classes including mid- and long-chain fatty acids, long-chain hydroxy-acids, n-alkanols, alkandiols, n-alkanes, long-chain monoesters, phytosterols and diterpenoid acids. Characteristic biomarkers and their distributions indicate the presence of beeswax, Pinaceae resin and another wax, as the main organic constituents of all of the preparations examined. In particular, the occurrence of phytosterols and long-chain monoesters, in which the acyl moiety was not exclusively palmitic acid, suggested the presence of a second waxy-lipid constituent of plant origin. The results are consistent with beeswax being used in the preparation of the cosmetics preserved in the unguentaria, while the other lipids are most likely the residue of some as yet unidentified plant extract(s), possibly deriving from the cuticular waxes of flowers and/or leaves. The composition of the extracts are consistent with the ancient practices of maceration and/or "enfleurage", in which lipid-based materials, such as beeswax, animal fat or vegetables oils, were used to extract aromatic and fragrant substances from resin, flowers, spices and scented wood, in order to produce unguents and balms.     

Ion chromatographic determination of N-nitrosoglyphosate in a glyphosate matrix

The use of high-performance ion chromatography (HPIC) for the determination of N-nitrosoglyphosate [N-nitroso-N-(phosphonomethyl)glycine] is reported. NMR, spectrophotometric and electroanalytical measurements showed that two conformers of N-nitrosoglyphosate in slow equilibrium are always present. Separation of these conformers is achieved by using appropriate chromatographic conditions. The conductimetric detection of N-nitrosoglyphosate and glyphosate and application to the determination of traces of N-nitrosoglyphosate in complex matrices are also reported.     

Ion chromatographic behaviour and determination of perbromates

Ion chromatographic behaviour of perbromates in aqueous solutions was studied, using ion suppressed conductimetric detection (Dionex DX-100 ion chromatograph with ASRS-I suppressor). Various eluents (sodium hydroxide, carbonate and phenate solutions) were examined using the AS-14  mm anion-exchange column and an optimization study concerning pH and total eluate concentration of mobile phase was carried out. Phenate buffer (20.0 mM, pH 11.0) at 1.18 ml/min flow rate, gave the best results. Calibration curve was linear in the range of 1.5-200 ppm, with a limit of detection of 0.46 ppm and R.S.D. 1.8% (100 ppm standard). Perbromates were separated with good resolution from potentially interfering anions (bromides, bromates, iodides, perchlorates). Selectivity coefficients were determined for perbromates, perchlorates and iodides, from linear plots of retention volume versus the reciprocal of eluent concentration. The new method was used to monitor the perbromate reactions with lactic acid, iodide and citric acid in the absence and presence of Fe(II) acting as an inducer. Furthermore, it was confirmed the inability of various common strong oxidative media to oxidize bromate to perbromate.     

A chromatographic method for hydrophobicity investigations of sorbents

Summary The energy of interaction (₀) between the methylene group and the surface of a sorbent is proposed for use in the quantitative evaluation of the hydrophobicity of a sorbent. A method was developed to determine the ₀ parameter from chromatographic measurements using the investigated sorbent as the stationary phase and linear methylene-containing homologous series, e.g., alkanols, amino-alkanes, etc., as the test compounds. The effectiveness of this method is demonstrated by using, as examples, a series of bonded stationary phases and a series of cross-linked copolymeric sorbents differing in the concentration of the hydrophobic groups. The proposed method is compared with the Martin rule used extensively in the chromatography of oligomers.     

Arsenic and heavy metals in leachate from a real landfill and a laboratory landfill

A preliminary study, based particularly on Arsenic and some heavy metals determination (Cd, Cr, Hg and Pb) in three leachate tipologies produced from municipal waste landfill plant, lab-scale aerobic landfill, lab-scale anerobic landfill was undertaken. Leachate was collected and analysed monthly; samples were homogenized and then, all heavy metals were determined after mineralization, except for Hg, determined before mineralization, due to his high volatility. In all samples pH was measured. In general we can say that low concentrations of the elements analyzed were found in all kinds of landfills considered; in particular, in the lab-scale anaerobic reactors, where low pH values have been found, we have a more considerable mobilization of As and the others heavy metals, moreover due to the behaviour of these elements.     

Theoretical investigations of the chromatographic separation of interacting enantiomers

Separation of a pair of enantiomers by liquid chromatography is modeled using the equilibrium dispersive (ED) model of chromatography. It is assumed that the chiral stationary phase used for the separation consists of two types of adsorption sites, including chiral selectors linked to the surface and nonselective centers belonging to the achiral matrix. Additionally, intermolecular interactions between adsorbed enantiomers are taken into account. The corresponding equilibrium adsorption isotherms of the enantiomers are derived by means of the mean field approximation (MFA) and used as input data for the ED model. Special attention is paid to the influence of the lateral interactions on the effectiveness of the enantiomer separation. In particular, we examine the effect of the interactions on the shape and relative position of the chromatographic peaks associated with the enantiomers. Furthermore, the influence of the spacer length, which modifies screening of the lateral interactions, on the adsorption process is studied. The obtained results suggest that the lateral interactions combined with the screening effect may cause serious changes in the separation, depending on the nature (attraction or repulsion) and strength of the interactions as well as on the spacer length.     

亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子（英文）

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.     

Ion chromatographic determination of platinum in biotic materials

A method for the determination of platinum is presented. The procedure consists of a high-pressure digestion of the sample followed by an ion Chromatographic separation. Then the platinum chloro complex is detected by UV-absorption.     

Adsorption/bioadsorption of phthalic acid, an organic micropollutant present in landfill leachates, on activated carbons

This study investigated the adsorption of phthalic acid (PA) in aqueous phase on two activated carbons with different chemical natures, analyzing the influence of: solution pH, ionic strength, water matrix (ultrapure water, ground water, surface water, and wastewater), the presence of microorganisms in the medium, and the type of regime (static and dynamic). The activated carbons used had a high adsorption capacity (242.9 mg/g and 274.5 mg/g), which is enhanced with their phenolic groups content. The solution pH had a major effect on PA adsorption on activated carbon; this process is favored at acidic pHs. PA adsorption was not affected by the presence of electrolytes (ionic strength) in solution, but was enhanced by the presence of microorganisms (bacteria) due to their adsorption on the carbon, which led up to an increase in the activated carbon surface hydrophobicity. PA removal varies as a function of the water type, increasing in the order: ground water相似文献   

Ion chromatographic separation of alkylsulphonic acids with conductivity detection

Summary An ion chromatographic (IC) method has been developed for the separation of alkylsulphonic acid. Two different stationary phases, silica-based and polymer-based ion-exchange resins, were studied using pure ion exchange and/or hydrophobic interaction mechanisms. Correlations between analyte hydrophobicity and eluent polarity were made in order to investigate the possibility of changing the dominant separation mechanism by varying the eluent composition. The alkyl chain lengths of the sulphonic acids analysed ranged from C₁ to C₉. Detection limits in the submicromolar range were obtained by suppressed conductivity detection.     

Ion chromatographic determination of sugar phosphates in physiological samples

Ion chromatography is shown to be capable of simultaneous determination of biologically important anions. Application of this technique is illustrated for the separation and quantification of the major anions present in rat brain and liver tissues. Sugar phosphates and carboxylic acids are separated on high-performance anion-exchange columns and are detected using chemically suppressed conductivity. Detection limits range from 20 to 100 pmol for the anions tested, including inositol phosphates, lactate, pyruvate, glucuronic acid-1-phosphate, fructose-6-phosphate and glucose-6-phosphate. The coefficient of variation for the determination of most anions was in the range 5-10%. Many of these anions are either difficult to separate with other methods, or require expensive radiochemical techniques for detection. This method should be applicable to other biological studies, from the flow of carbons in photosynthesis to the study of synaptic transmission.