A computer program for the optimal ion chromatographic determination of anions in waters

Summary A general form of computer program which can assist in method development for any natural water has been developed. Necessary input data, sequence of main operations, necessary mathematical relationships and the output data are specified. The development of the structure of the computer program was based on experiences with real samples.     

Quality control procedures for chloride and nitrate ions analysis in plant samples by ion chromatography

This paper describes useful procedures to monitor quality of chloride and nitrate ions analysis in plant samples by ion chromatography. The use of certified reference materials (CRMs) provided an efficient way to verify the accuracy of the method. Data generated by the method of analysis for chloride compared favourably with certified values. The quality system included also the systematic analysis of an internal reference sample in each batch of samples routinely analysed. The performance of the method, including extraction and measurement, over a period of 3 years was reported with control charts. The yearly variation coefficients were less than 6.5% for chloride and nitrate ions. Finally, the analytical method was evaluated through the participation of laboratory to an international proficiency testing scheme. Found results were not significantly different from published medians.     

Elaboration and use of a double channel detection ion chromatographic method for determination of ions in aqueous samples

Summary In this paper we report our research in developing a simple and reliable method for determination of various anions in aqueous samples. Among the several methods existing for determining ions in aqueous samples, ion chromatography is becoming more and more important, due to its reliability and ability to determine the concentration of more ions from one sample. Although several detection methods are available, in this work we used conductivity detection, and indirect UV photometric detection. Because in some cases it can be important to gather more detailed information on the composition of a sample, we present a way to meet this demand by using double channel detection. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September, 1–3, 1999     

Preparation and chromatographic performance of polymer-based anion exchangers for ion chromatography: A review

In the last decade the developments in the field of ion chromatography (IC) were aimed at increasing the efficiency, sensitivity and rapidity of analysis, as well as on improving separation selectivity. Since selectivity and efficiency to the large extent depend on the surface chemistry of the stationary phase, the development of novel anion exchangers remains one of the priority tasks in modern IC. The exact chemistry of commercially available resins is not known and not many literature data devoted to the procedures of preparing anion exchangers for IC have become available in the last 10–15 years. However, the knowledge about the surface chemistry of anion exchangers can provide understanding of the trends in selectivity and efficiency changes, as well as help with the choice of the stationary phase type suitable for solving a particular analytical task. The current review is devoted to the methods of preparing anion exchangers based on polystyrene-divinylbenzene (PS-DVB) and ethylvinylbenzene-divinylbenzene (EVB-DVB) for IC of inorganic and small organic anions and is aimed at demonstrating the improvement of their performance over the years, which was brought by the development of the new types of stationary phase architecture.     

Application of ion chromatography to qualitative and quantitative determination of the main inorganic ionic components of samples from a production process of potassium sulphate

This review presents the possibility to use ion chromatography (IC) to analyse solids and brines deriving from treatment procedures of potassium salts. Qualitative and quantitative determination of ions samples has been used to make their chemical reconstruction. By using conventional calibration methods covering the whole concentration interval, analysis were not suitably accurate. During this process, the analysis is considered acceptable when the difference between the sum of the equivalents of cations and anions (ΔE) is ≤2%. For the process, a calibration method has been used employing four reference curves; each defined by three points corresponding to three standards purposely devised in our laboratory. The composition of the standards matched that expected for the samples from the different stages of the process reaction, after their usual sampling, dissolution and dilution. By comparing the conductivity of the analyte in the real sample to the conductivity of the same analyte in a standard, the effects of other analytes present in the medium are practically cancelled and need not be considered. The IC method results are in good agreement with conventional analysis methods (potentiometric titration, atomic absorption, gravimetric analysis).     

A review of quantitative ion exchange,high performance liquid and gas chromatographic analysis of amino acids in physiological fluids

Methodologies for quantitative analysis of amino acids in physiological fluids based on classical ion exchange, high performance liquid chromatography, and gas chromatography are analyzed. As judged by the relative number of reports on these techniques, it appears that classical ion exchange continues to be the main method of choice for amino acid determinations and only limited advantage has been taken of the benefits (e.g. lower capital outlay and running costs and shorter analysis times) offered by other techniques. More importantly, however, there appears to be insufficient quantitative evaluation of the methodologies used. As a result, the validity of many reports based on data from amino acid analysis of physiological samples may be questioned.     

A new procedure, based on combustion to sulphate and ion chromatography for the analysis of elemental sulphur in sediments

Summary A procedure exploiting the bomb preparation method for the analysis of total sulphur in organic materials has been developed for the determination of zero-valent sulphur (S^o) in sediments. Sediment samples were dried over magnesium oxide and sonicated in the presence of toluene to extract S^o. Toluene solutions were directly oxidized by combustion in a bomb containing sodium carbonate-bicarbonate buffer, which trapped sulphur species generated from S^o as sulphate ions. These were in turn analysed by suppressed anion chromatography with ion-conductivity detection. The method was used to determine the distribution of S^o in saltmarsh sediment cores.     

A polar-copolymerized method to prepare silica-based anion exchanger for ion chromatography

A novel silica-based strong anion exchanger was developed for ion chromatography by copolymerizing methyltrichlorosilane and 3-chloropropyltrichlorosilane. The method allows the column capacity to be easy control simply by adjusting the ratio of silanes. The unwanted residual silanol groups onto the surface of silica gel could also be greatly reduced by this strategy. The effective column capacity of the column used was measured to be 50.8 μequiv/column (2.03 μequiv/cm). The exchanger was characterized by solid state CP/MAS ¹³C NMR and elemental analysis and its separation performance was evaluated for the separation of common inorganic anions. The results showed that the column had good separation efficiency (e.g. the plate number of nitrite is 80,000/m) and the separation mechanism was observed to be dominantly governed by ion exchange mechanism. The utility of the column was demonstrated for the determination of nitrite and nitrate in saliva sample.     

A sensitive high-pressure liquid chromatographic method for the determination of propranolol in microliter serum samples

Summary A high-pressure liquid chromatographic assay capable of quantitating subnanogram per milliliter concentrations of propranolol in microliter volume of serum was developed. Propranolol was extracted from serum with hexane at pH 9.7. Further sample clean up was achieved by back extraction. Separation of propranolol from its metabolites and normal serum constituents was performed on 10 m C₁₈ reversed-phase column packing. High sensitivity was attained with fluorescence detection using a low UV excitation wavelength. This assay is suitable for use in pharmacokinetic studies involving small laboratory animals.     

A novel technique for the sampling and gas chromatographic analysis of vapours

Summary A conventional pyrolysis gas chromatography system has been adapted to the analysis of vapours. A Curie point pyrolysis wire is used as a holder for granular active carbon on which the sample can be adsorbed. Desorption is achieved in the pyrolysis unit, but no pyrolysis occurs. The present study reports on the completeness of adsorption by the sampler and on the degree of release of adsorbate from it.     

On-line liquid backflush—a new technique for GC analysis of samples containing nonvolatile material

Deteriorated performance in capillary GC is often caused by the deposition of nonvolatile components in capillary GC inlets. In many cases this is a limiting factor in trace analysis of complex samples. Volatile solutes of the sample interact with the high boiling material, which leads to broadened and unsymmetrical peaks. This paper describes a novel technique which utilizes independent temperature programs of a retention gap and the column as well as a liquid backflush of the retention gap. Samples that normally contaminate the retention gap after a few injections can be repeatedly injected over extended periods of time, while the chromatographic resolution is retained.     

How to avoid water contamination in the thermodesorption cryofocusing technique. Application to ethane analysis in human breath by means of an ion trap detector (ITD)

The purpose of this study was to modify an automatic pre-concentration system to avoid water contamination and to apply this technique to ethane analysis in breath. The ion trap detector was very useful in monitoring the whole analytical procedure.     

Use of 1-(2-pyridylazo)-2-naphthol as the post column reagent for ion exchange chromatography of heavy metals in environmental samples

Ion exchange chromatography (IEC) using a bi-functional column (quaternary ammonium and sulfonate groups), followed by post-column reaction (PCR) with 1-(2-pyridylazo)-2-naphthol (PAN), was used to separate and quantitate Cu(II), Ni(II), Zn(II), Co(II), Cd(II), Mn(II) and Hg(II) at low concentration levels. IEC-PCR separation was achieved within 14 min using the mobile phase containing 3 mmol L^− 1 2,6-pyridinedicarboxylic acid (PDCA) and 3 mmol L^− 1 oxalate at pH 12.5. Effects of pH as well as PAN, detergent and chloride ion concentrations during post-column reaction on detector response were examined. Detection limits were less than 4.5 μg L^− 1 for all metals except Hg(II) (19 μg L^− 1) using spectrophotometric measurements at 550 nm. Analytical validations showed good linearity for detection up to 6.0 mg L^− 1, with R² higher than 0.99. Precisions based on retention time evaluation for intra-day and inter-day measurements with the relative standard deviation (RSD) were less than 2.9% and 3.6%, respectively. The method gave good accuracy with the recoveries ranged from 80.5 to 105% for all metal ions studied. The proposed method was applied to the analysis of metal ions in environmental samples (leachate, soil and sediment) in Northeastern Thailand. The results were in good agreement with atomic spectroscopic measurements on the same samples.     

A new tool for inorganic nitrogen speciation study: simultaneous determination of ammonium ion, nitrite and nitrate by ion chromatography with post-column ammonium derivatization by Nessler reagent and diode-array detection in rain water samples

The paper presents a new method for a simultaneous determination of inorganic nitrogen species in the oxidized (NO₂⁻, NO₃⁻) and reduced (NH₄⁺) form in rain water samples. The method is based on a system of nitrogen species separation employing ion exchange and diode-array detection. The ions are separated in a strong ion-exchanger, nitrites and nitrates are determined directly at 208 and 205 nm, respectively, while the ammonium ions are determined in the column hold-up time after a post-column derivatization by the Nessler reagent, at 425 nm. The use of a diode-array detector permits a simultaneous identification of the inorganic nitrogen species in 8 min. The detection limits obtained are: NO₂⁻, 0.1 mg L⁻¹; NO₃⁻, 0.05 mg L⁻¹; NH₄⁺, 1 mg L⁻¹. The method proposed has been successfully used for speciation analysis of inorganic nitrogen in precipitation.     

Gas chromatographic technique for determination of Irgafos 168 in polyolefin samples after conversion to the related phenolic compound by saponification

A gas chromatographic technique is reported for the determination of a secondary antioxidant, Irgafos 168, in polymeric samples. Irgafos 168 [tris(2,4-di-tert-butyl phenyl)phosphite] is extracted by dissolution/precipitation, saponified to 2,4-di-tert-butyl phenol by refluxing in the presence of methanolic potassium hydroxide, and determined by gas chromatography-flame ionization detection. The method’s repeatability is good, and the relative standard deviation is 7.5% (between runs) and 15.5% (between days). This method was applied to the determination of Irgafos 168 in commercial polymers, and the obtained results were in relatively good agreement with those obtained by the previously reported spectrophotometric method. Correspondence: Mir Ali Farajzadeh, Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran     

A simplified version of the total kjeldahl nitrogen method using an ammonia extraction ultrasound-assisted purge-and-trap system and ion chromatography for analyses of geological samples

The total Kjeldahl nitrogen (TKN) method was simplified by using a manifold connected to a purge-and-trap system immersed into an ultrasonic (US) bath for simultaneous ammonia (NH₃) extraction from many previously digested samples. Then, ammonia was collected in an acidic solution, converted to ammonium (NH₄⁺), and finally determined by ion chromatography method. Some variables were optimized, such as ultrasonic irradiation power and frequency, ultrasound-assisted NH₃ extraction time, NH₄⁺ mass and sulfuric acid concentration added to the NH₃ collector flask. Recovery tests revealed no changes in the pH values and no conversion of NH₄⁺ into other nitrogen species during the irradiation of NH₄Cl solutions with 25 or 40 kHz ultrasonic waves for up to 20 min. Sediment and oil free sandstone samples and soil certified reference materials (NCS DC 73319, NCS DC 73321 and NCS DC 73326) with different total nitrogen concentrations were analysed. The proposed method is faster, simpler and more sensitive than the classical Kjeldahl steam distillation method. The time for NH₃ extraction by the US-assisted purge-and-trap system (20 min) was half of that by the Kjeldahl steam distillation (40 min) for 10 previously digested samples. The detection limit was 9 μg g⁻¹ N, while for the Kjeldahl classical/indophenol method was 58 μg g⁻¹ N. Precision was always better than 13%. In the proposed method, carcinogenic reagents are not used, contrarily to the indophenol method. Furthermore, the proposed method can be adapted for fixed-NH₄⁺ determination.     

A new method for the routine analysis of LAS and PAH in sewage sludge by simultaneous sonication-assisted extraction prior to liquid chromatographic determination

Linear alkylbenzene sulphonates (LAS) and polycyclic aromatics hydrocarbons (PAH) are organic pollutants in sewage sludge which will have to be monitored in the European Union according to the third draft of a future sludge directive. In the present work, an analytical method for the simultaneous extraction of 4 LAS homologues and 16 PAH congeners in sludge from wastewater treatment plants is proposed to improve the routine analysis of these compounds in sludge samples. The method involves sonication assisted extraction, clean-up and preconcentration by solid phase extraction, and determination by high-performance liquid chromatography with ultraviolet diode array (UV-DAD) and fluorescence (FLD) detectors. Average recoveries were 87% for LAS and 76% for PAH, with relative standard deviations below 13%. Limits of quantification of LAS and PAH were in the range from 13 to 56 mg kg⁻¹ and from 80 to 650 μg kg⁻¹, respectively, when using UV-DAD. Limits of quantification of LAS and PAH were in the range 5-18 mg kg⁻¹ and from 1 to 150 μg kg⁻¹, respectively, when using FLD. The applicability of the proposed method was evaluated by the determination of these compounds in sludge from wastewater treatment plants in Seville (South Spain).     

A novel multiwalled carbon nanotubes bonded fused-silica fiber for solid phase microextraction-gas chromatographic analysis of phenols in water samples

The present work reports on the synthesis of chemically bonded multiwalled carbon nanotubes (MWCNTs)/fused-silica fibers and their use in solid phase microextraction of seven phenols from water samples coupled with gas chromatography (GC). The synthetic strategy was verified by infrared (IR) spectroscopy and field emission scanning electron microscopy. Adsorption factors (pH, ionic strength, stirring rate, adsorption time and temperature) and desorption factors (time and temperature) of the fibers were systematically investigated. Detection limits to seven phenols were less than 0.05 μg L⁻¹, and their calibration curves were all linear (R² ≥ 0.9984) in the range from 0.05 to 5000 μg L⁻¹. This method was then utilized to analyze two real water samples from Yellow River and sanitary wastewater, resulting in satisfactory results. Compared with normal solid phase materials, this MWCNTs-bonded fused-silica fibers showed a number of advantages: wide linear range and low detection limit for extracting phenols couple with GC, and good stability in acid, alkali, organic solvents and at high temperature.     

Comparison of pulse glow discharge‐ion mobility spectrometry and liquid chromatography with tandem mass spectrometry based on multiplug filtration cleanup for the analysis of tricaine mesylate residues in fish and water

Analytical methods based on multiplug filtration cleanup coupled with pulse glow discharge‐ion mobility spectrometry and liquid chromatography tandem mass spectrometry were developed for the analysis of tricaine mesylate residue in fish and fish‐raising water samples. A silica fiber holder and an appropriate new interface were designed to make the direct introduction of the fiber into the pulse glow discharge‐ion mobility spectrometry introduction mechanism. The multiplug filtration cleanup method with adsorption mixtures was optimized for the determination of tricaine mesylate in fish samples. Good linear relationships were obtained by the two methods. For fish samples, limits of detection were 6 and 0.6 μg/kg by ion mobility spectrometry and liquid chromatography with tandem mass spectrometry, respectively. The matrix effect of the established liquid chromatography tandem mass spectrometry method was negligible for fish samples but that of the ion mobility spectrometry method was not. The two methods were compared. The ion mobility spectrometry system could be used a rapid screening tool on site with the advantage of rapidity, simplicity, and portability, and the liquid chromatography tandem mass spectrometry system could be used for validation in laboratory conditions with the advantage of lower limit of detection, stability, and precision.