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A robust analytical method is required for the determination of low-molecular weight organic acids, which are potential causes of refinery and internal combustion engine corrosion. The ion chromatographic method developed in this study allows the determination of acetic acid and formic acid in diesel oil mixtures with a motor oil volume fraction of up to 10%. The hydrophobic matrix is automatically removed in-line through a matrix elution step with organic solvent and nonaqueous anion-exchange analyte extraction. Acetic acid and formic acid, as the smallest and most acidic aliphatic naphthenic acids, were determined. Gradient anion-exchange chromatography on high-capacity columns in combination with suppressed conductivity detection allowed their selective and sensitive determination. Typical recovery values were from 82 to 107% for each acid in the matrices evaluated with reproducibility less than 5% for acid fortified samples.

The analytical determination of ionic disinfection by-products (DBPs) in many cases is challenged by the usual suspects: the sample matrix, analyte concentration and very often by unfavourable concentration ratios between analytes and other sample components. These challenges can be met by combining highly selective ion chromatography (IC) with specific and sensitive detection schemes. Since its introduction IC has quickly developed into an analytical technique suitable for the determination of trace components in very demanding sample matrices due to its combinability with different detection techniques. Because of the low reporting limits established for various DBPs in water (e.g. bromate, chlorate, haloacetic acids), or emerging needs to analyze low concentrations of DBPs (e.g. perchlorate) not only in water but also in food and beverages, it is this property that facilitates the simplified analysis of DBPs. This work summarizes different ion chromatographic approaches for the determination of anionic DBPs in accordance with ISO-, DIN and US-EPA methods, focussing on suppressed conductivity detection, post-column-derivatisation-techniques for UV-detection, two dimensional IC, and mass selective detection. The benefits of the different detection selectivity as well as the capabilities of each approach are discussed.

To manufacture 300 mm wafers, large quantities of ultra-pure water are required, which makes water the most important chemical used in this process. Therefore, its specification requiring ionic contaminants in the lower pg mL−1-concentration range is very strict. While inductively coupled plasma mass spectrometry (ICP-MS) is widely used for monitoring inorganic cations, ion chromatography (IC) is applied in the determination of ammonium and inorganic anions in the lower pg mL−1 range.

Insbesondere in der Umwelt- und Bioanalytik erschliesen sich der Ionenchromatographie neue Anwendungen. Kopplungstechniken setzen neue Masstabe fur Nachweisgrenzen und Substanzidentifikation.

This report describes a new, automated chromatographic procedure eliminating carbohydrates from amino acid samples prior to their analysis by anion-exchange chromatography and integrated amperometric detection. In the first step, a sample is brought onto a short cation-exchange column (trap column) in hydrogen form. Carbohydrates are passing through this column, while only amino acids are retained. Subsequently, the cation-exchange column, holding the amino acid fraction, is switched in-line with the gradient pump and separator column. The mobile phase used at the beginning of the separation (NaOH; pH 12.7) transfers amino acids from the trap column onto the anion-exchange column and the amino acid separation is completed without any interference by carbohydrates. All common amino acids are recovered following the carbohydrate removal step. The average value of their recovery is 88.1%. The calibration plots were tested between 12.5 and 500 pmol (amounts injected). The mean value of correlation coefficients of calibration plots was calculated as 0.99. The mean value of relative standard deviations from five replicates was 3.9%. The usefulness of the method is illustrated with two chromatograms of a carrot juice sample obtained before and after the in-line removal of carbohydrates.

A method is described for enhancing retention of arginine on a pellicular anion-exchange column. Arginine exhibits adjustable increases of retention time that are dependent on the acidity of standard or sample matrix. This effect is based on interactions of the protonated form of arginine with the residual cation-exchange groups on the core beads of pellicular particles. The relative magnitude of retention time shift of arginine is evaluated for identical concentrations of hydrochloric, sulfuric, and perchloric acids. Although the direct addition of acid is very effective in influencing the retention of arginine, it affects peak shapes and retention of other peaks in the chromatographic separation. The new technique—acid coinjection—achieves a similar retention enhancement for arginine with only a minimal effect on the rest of the separation. Detection limits, reproducibility results, and calibration data are presented for the chromatography of amino acids with acid coinjection. Improved resolution of arginine is demonstrated with chromatograms of soybean hydrolysate and cell culture samples.

In ion chromatography, samples of very different ammonium-to-sodium concentration ratios are difficult to quantify since these two cations have similar selectivities for stationary phases containing commonly used sulfonate or carboxylate cation-exchange functional groups. The IonPac CS15 cation-exchange column, with carboxylate and phosphonate functional groups as well as a crown ether group, was developed to address this limitation. Selectivity for the common inorganic cations on this column is different from that of conventional cation-exchange columns in that the separation between sodium and ammonium ions has been greatly increased, allowing for determinations of low levels of one in the presence of high levels of the other with an isocratic eluent. For larger than 4000:1 sodium-to-ammonium concentration ratios, an eluent step change or gradient elution is needed. For moderate ratios, combinations of this column with a carboxylate column, containing no crown ether group, can be used at room temperature with an isocratic eluent containing no organic solvent.

Hydrogen peroxide plays an important role in the semiconductor industry and needs to be analyzed for anionic impurities. In the past, the sample was pretreated with Pt to avoid reactions of H 2 O 2 with the resin material of the respective anion exchanger. However, this pretreatment with Pt is time-consuming, may cause contaminations and leads to degradation of stabilizers because of the heat generated during the treatment. An ion chromatographic technique has been developed allowing the direct injection of the sample. Within this paper chromatograms of different types of H 2 O 2 were analyzed, the observed method detection limits and the reproducibility of this method are shown.

Mixing of S2Cl2 and Se2Cl2 at 21°C results in the formation of SeSCl2 as shown by 77Se NMR, mass, and Raman spectroscopy. The enthalpy of this reaction has been determined as + 13 kJ mol−1 (S2Cl2), and the equilibrium constant Kc = 0.066 at 294 K. In addition, the formation of other Se—S—Cl molecules and of SeCl2 is observed. An Se2Cl2-S2Cl2-SeSCl2 mixture (Se:S = 1:1) reacts with titanocene pentasulphide to give mainly S7, SeS6 and 1,2-Se2S5 but small concentrations of six-, eight-,nine- and 12-membered Se—S ring molecules have also been observed. The reaction of Se2Cl2-S2Cl2 mixtures (Se:S = 1:2) with potassium iodide affords 1,2,5-Se3S5 as the major product followed by 1,2-Se2S6, 1,4-Se2S6 and 1,3-Se2S6. HPLC analysis of this reaction shows, however, that selenium sulphide ring molecules of ring sizes 6–8 are formed. Mixing of SCl2 and Se2Cl2 at 21°C results in precipitation of SeCl4 and formation of S2Cl2, which reacts with Se2Cl2 to give SeSCl2.

The HPLC retention times of 25 cyclic compounds of type SexSy, (x = 0 · · · 8; y = 0 · · · 12) have been measured under identical conditions and are used to evaluate the factors which determine the retention. Linear relationships are derived for the dependence of retention (Ink'; k′ = capacity factor) on ring size, number of Se atoms, and number of SeS bonds per molecule for six-, seven-, eight-, and twelve-membered SexSy rings. These relationships allow the prediction of retention times for all SexSy heterocycles of these ring sizes (ca. 100 compounds). The results are applied to the qualitative analysis of mixed sulfur-selenium melts of two compositions: at a molar ratio of S : Se = 8.7 twenty-one HPLC signals have been observed for the CS2 extract of the quenched melt and assigned to SexSy rings of sizes 6··· 12. At S : Se = 0.33 mainly six-, seven-, and eight-membered species with cumulated Se atoms have been found.

Selenium dibromide prepared from Se and SeBr 4 in acetonitrile shows a singlet at 1496 ppm in the 77 Se-NMR spectrum and Raman lines at 291, 265, and 105 cim −1 . Selenium dibromide which is in equilibrium with Se 2 Br 2 and Br 2 reacts with titanocene-pentasulphide at 20°C in CS 2 to give SeS 5 which partly dimerizes to give 1,2-Se 2 S 10 and 1,7-Se 2 S 10 . Raman spectra of Se 2 S 10 and Se 2 S 1O ·CS 2 are reported and their formation from SeS 5 is discussed. Other products of the SeBr 2 -titanocenepentasulphide reaction are 1,2-Se 2 S 5 (from Se 2 Br 2 ), S 1O (from Br 2 ), 1,2-Se 2 S 6 , 1,5-Se 2 S 6 , and 1,2,5,6-Se 4 S 4 .

The paper is part of a research project to examine the use of intelligent technologies like fuzzy controllers, artificial neural networks, genetic algorithms or evolutionary strategies in the resource management of high speed networks. It deals with an investigation on adaptive flow-control mechanism based on fuzzy controllers integrated in ATM networks. In addition to a new overall concept, a new method for fair flow control of services or connections is presented. The results are verified by means of extensive simulations.

An ion chromatography method was developed to determine trace anionic contamination in matrices that have a high concentration of nitrate ion. Contaminant anions of interest were separated on an IonPac AS15 high-capacity anion-exchange column and detected by suppressed conductivity detection. An EG40 eluent generator was used to prepare high-purity and carbonate-free potassium hydroxide. Using the EG40, performance at trace levels was enhanced because background conductivity decreased and retention time reproducibility improved. Trace anionic contamination from the mobile phase was minimized when using the eluent generator compared to using conventionally prepared sodium hydroxide eluents. The signal-to-noise ratio was also improved with the use of a temperature controlled conductivity cell and chromatography hardware in the microbore (2-mm) format. The eluent concentration was optimized to separate the contaminant anions from the excess of the nitrate matrix ions. The procedure was demonstrated for a solution of reagent-grade sodium nitrate and high-purity 0.7% nitric acid. Method detection limits for chloride, sulfate and phosphate of 150 microg/l and lower were achieved.

For the detailed analysis of energy metabolism, a HPLC method is described allowing the single-run separation and quantification of most metabolites from glycolysis and the Krebs cycle including the high energy phosphates. With a detection limit in the picomolar range this method is even applicable when only small sample sizes of tissue are obtained.

Anfang des Jahres trafen sich in der Universitat Trier mehr als 150 Teilnehmer zur 3. Fachtagung „Ionenanalyse mit modernen Trenntechniken”, die vom Fach „Analytische und Okologische Chemie” der Universitat Trier und Dionex, Idstein, gemeinsam veranstaltet wurde.

Sulfur vapor has been investigated by Raman spectroscopy in a wide temperature and pressure range (300 to 900°C, 0.05 to 0.5 MPa for overheated vapor and 0.007 to 1.65 MPa for saturated vapor). At least eight different species have been observed through their characteristic Raman lines. Well separated Raman lines have been selected for the observation of the change in vapor composition with temperature: symmetrical bending modes for the cyclic species S8, S7, and S6 and stretching modes for the chain-like species S3 and S2. There are indications for the presence of two conformational isomers of S4, and in addition a new species has been discovered by its resonance Raman line at 635 cm−1 which is tentatively assigned to chain-like molecules Sn (n > 4) of helical conformation. Several relationships between the thermodynamic properties of the vapor and the Raman measurements are proposed, e.g., the determination of the temperature at which the molar fraction xi is maximum for the overheated vapor at constant pressure; estimation of the xi/x8 ratios using solution measurements of the Raman cross section for the molecules S8, S7, S6. A careful comparison of these results with the values deduced from Rau's model results in good agreement for the behavior of most of the species apart from S7 which is underestimated in Rau's model. S7 is the dominating species in saturated sulfur vapor above 600 K until S2 takes over at ca. 1000 K.

The Raman spectrum of commercial "sulfur dichloride" shows strong lines due to SCl2 and S2Cl2 and weak Cl2 lines at 25 °C, but strong SCl2 and SCl4 signals at -100 °C (the latter are superimposed on the S2Cl2 lines). Thus, the intense Raman effect of SCl4 can be used to detect small amounts of chlorine in SCl2 . Mixtures of SCl2 and Cl2 (1:15) yield the Raman spectrum of SCl4 at -140 °C, while at 25 °C not trace of this compound can be detected. The spectra of SCl4 and α-SeCl4 are quite different, indicating different molecular and/or crystal structures, although ECl3 + ions (E = S, Se) are present in both cases. While Se2Cl2 dimerizes reversibly below -50 °C, S2Cl2 neither dimerizes nor isomerizes on cooling. The S2Cl2 dimer is characterized by a Raman line at 215 cm-1 the intensity of which was used to calculate an enthalpy of dimerization as of -17 kJ/mol.

The dinuclear titanocene complexes Cp4Ti2S6, Cp4Ti2S4 and Cp4Ti2Se4 have been reacted with SCl2, S2Cl2, and Se2Cl2, respectively. The reaction products are rings of type Sn (n = 6…20) and six-, seven- and eight-membered rings of type Sex Sy, respectively, which have been characterized by HPLC, Raman and Se-NMR spectroscopy, as well as X-ray diffraction on single crystals.

The optical absorption spectra of the sulfur homocycles Sn (n = 6–10,12, 15, 20) in methanol or methylcyclohexane solution have been recorded in the region 200–360 nm using a conventional spectrophotometer as well as a diode-array spectrophotometer. Each compound shows a characteristic absorption curve. The extinction coefficients at 254 nm increase with increasing ring size, and the lowest-energy absorption maximum shifts to the red with increasing number of atoms in the molecule. The data are used to re-interprete the published absorption spectra of liquid and irradiated sulfur.

The 77Se NMR spectrum of 1,2-Se2S5 exhibits one singlet at 1077.3 ppm indicating pseudorotation in solution; the same conclusion is reached from the solution Raman spectrum of S7 showing characteristic line broadening compared to the solid state spectrum

Sulfur vapor has been investigated by Raman spectroscopy in a wide temperature and pressure range (300 to 900°C, 0.05 to 0.5 MPa for overheated vapor and 0.007 to 1.65 MPa for saturated vapor). At least eight different species have been observed through their characteristic Raman lines. Well separated Raman lines have been selected for the observation of the change in vapor composition with temperature: symmetrical bending modes for the cyclic species S8, S7, and S6 and stretching modes for the chain-like species S3 and S2. There are indications for the presence of two conformational isomers of S4, and in addition a new species has been discovered by its resonance Raman line at 635 cm−1 which is tentatively assigned to chain-like molecules Sn (n > 4) of helical conformation. Several relationships between the thermodynamic properties of the vapor and the Raman measurements are proposed, e.g., the determination of the temperature at which the molar fraction xi is maximum for the overheated vapor at constant pressure; estimation of the xi/x8 ratios using solution measurements of the Raman cross section for the molecules S8, S7, S6. A careful comparison of these results with the values deduced from Rau's model results in good agreement for the behavior of most of the species apart from S7 which is underestimated in Rau's model. S7 is the dominating species in saturated sulfur vapor above 600 K until S2 takes over at ca. 1000 K.

Background Perchlorate salts are relatively stable, soluble in water, and migrate into groundwater sources. Groundwater is an essential source for drinking water suppliers. Perchlorate bears health risks as it is identified to impair normal thyroid function by interfering with iodine uptake by the thyroid gland. The development of a sensitive analytical method for the determination of perchlorate is therefore of the highest interest or public health. Ion chromatography is a sensitive method suitable for perchlorate determinations. This manuscript describes the validation of an ion chromatographic method. Perchlorate is determined by ion chromatography (IC) with conductivity detection after suppression (CD) applying isocratic elution. Results In this study, the suitability of IC-CD was tested for synthetic samples, selected environmental water, drinking water, and swimming pool water in order to evaluate potential matrix effects on the perchlorate signal even after sample preparation. A sample injection volume of 750 μL was applied to the selected 2-mm-IC column. In untreated samples, the perchlorate peak can be interfered by neighbouring signals from matrix ions like chloride, nitrate, carbonate, and sulphate. Depending on the concentration of the matrix ions, the perchlorate peak can show asymmetric shape in particular when the perchlorate concentration is low. Recovery is reduced with increasing matrix ion concentrations. Dedicated matrix elimination was applied to minimize such effects. A reporting limit of 1.5 μg/L perchlorate and an expanded measurement uncertainty of 13.2 % were achieved. Conclusion The extended method validation proves the applicability of IC based on the EPA 314.0 method for the determination of trace amounts of perchlorate in water samples of different origin. The results support the development of a respective international standard pursued by ISO. The approach evidenced its working robustness and ease of use in terms of eluent preparation, chromatographic resolution, column life time and sample preparation. Due to the simplified analytical workflow of the analytical procedure the application’s integration into the collection of methods of interested laboratories should be facilitated.