Anion-exchange Separation Research Articles

Interaction of melanoidins, proline, and valine with sorbents of various nature

The isolation of pure amino acids from industrial solutions is one of the important tasks of production. Solutions of amino acids obtained as a result of chemical or microbiological treatment contain a number of impurities, mostly organic ones. The microbiological synthesis of proline is accompanied by the presence of valine, leucine, alanine, and coloured high-molecular components in the culture liquid that belong to the melanoidin group. Melanoidins of proline acid production are high-molecular compounds containing amino acid fragments, heterocyclic structures, and amide bonds. Melanoidins in solutions can exist in cationic, bipolar, and anionic forms. They have different molecular weights, molecular sizes, and isoelectric states. Various ion exchange methods can be used to isolate the target amino acid. It should be noted that the interaction of amino acids with ion-exchange materials is a complex process depending on the electrolytic properties of the sorbate and sorbent and accompanied by multiple side effects. It is necessary to know the specific features of interaction in the “amino acid - sorbent” system and the factors that affect the transport of sorbate ions in the sorbent phase when choosing an isolation method for the target product. The goal of this work was to determine the impact of pH on the sorption process of proline and valine by high-basic ion exchangers, to identify the features of their interactions, and to use the obtained results to optimise the conditions for the separation of amino acids. We studied the process of interaction of bipolar ions and anions of proline (Pro±, Pro-) and valine (Val±, Val-) with anionites AV-17-8 and AV-17-2P. It was established that the mechanism of amino acid ion exchange in granular sorbents depended on the рН value in the “anionite - external solution” system. Based on the studied interactions, we suggested the methods of the anion-exchange separation of proline and valine. The selected conditions of separation of proline and valine were on anionite AV-17-2P in ОН-form (рН of the initial solution was 6.6-6.7; the solution flow rate was 2 cm3/min). The results of separation of proline and valine indicated that even in a one-step sorption process, five to seven fractions with proline contained no valine ions, while the concentration of proline was 2.0-2.7 times higher as compared to the original solution.

Retention time prediction for post-translationally modified peptides: Ser, Thr, Tyr-phosphorylation

The development of a peptide retention prediction model for reversed-phase chromatography applications in proteomics is reported for peptides carrying phosphorylated Ser, Thr and Tyr-residues. The major retention features have been assessed using a collection of over 10,000 phosphorylated/non-phosphorylated peptide pairs identified in a series 1D and 2D LC-MS/MS acquisitions using formic acid as ion pairing modifier. Single modification event on average results in increased peptide retention for phosphorylation of Ser (+ 1.46), Thr (+1.33), Tyr (+0.93% acetonitrile, ACN) on gradient elution scale for Luna C18(2) stationary phase. We established several composition and sequence specific features, which drive deviations from these average values. Thus, single phosphorylation of serine results in retention shifts ranging from -2.4 to 5.5% ACN depending on position of the residue, nature of nearest neighbour residues, peptide length, hydrophobicity and pI value, and its propensity to form amphipathic helical structures. We established that the altered ion-pairing environment upon phosphorylation is detrimental for this variability. Hydrophobicity of ion-pairing modifier directly informs the magnitude of expected shifts: (most hydrophilic) 0.5 % acetic acid (larger positive shift upon phosphorylation) > 0.1 % formic acid (positive) > 0.1 % trifluoroacetic (negative) > 0.1 % heptafluorobutyric acid (larger negative shift). The effect of phosphorylation has been also evaluated for several separation conditions used in the first dimension of 2D LC applications: high pH reversed-phase (RP), hydrophilic interaction liquid chromatography (HILIC), strong cation- and strong anion exchange separations.

Synthesis and structure of Americium(III) diglycolate oxalate Trihydrate, Am(ODA)(C2O4)(H2O)3

Improving f-element separations is important for actinide(III) (An3+) and lanthanide(III) (Ln3+) based technologies. Unfortunately, An3+ and Ln3+ ions are difficult to separate from one another because they have similar chemical characteristics. One successful separation method utilizes anion exchange chromatography. This approach exploits differences in An3+ and Ln3+ Lewis acidities and their varying abilities to attract anionic complexing agents, like oxalates (C2O42–) and diglycolates (ODA2–). The resulting negatively charged complexes are then separated using an anion exchange resin. To better understand how this anion exchange separation works, we reacted Am3+(aq) (aq designates Am3+ dissolved in water) with the anion exchange complexing agents (H2C2O4 and H2ODA). The resulting Am(ODA)(C2O4)(H2O)3 product was characterized using single crystal X-ray diffraction and UV-Vis-NIR spectroscopy. The Am(ODA)(C2O4)(H2O)3 structure was similar to that established previously for Ln3+ analogues, namely Ln(ODA)(C2O4)(H2O)x. These compounds were all isomorphous, had bridging C2O42– and ODA2– ligands, and crystallized as 2-dimensional extended solids. In addition, the Am3+–O bond distances could be predicted based on relative differences in Am3+ and Ln3+ 9-coordinate metal ionic radii. Overall, isolation of Am(ODA)(C2O4)(H2O)3 showcased similarities in complexation and crystallization chemistry for Am3+ and Ln3+.

The Efficiency Improvement of Electrodeposition of High-Purity Zn by a Proper Electrolyte Solution Preparation from Spent Pickling Liquor by Anion-Exchange Separation

A better procedure for recovering high-purity Zn from the SPL solution has been devised. To provide a suitable electrolyte for the efficient cathodic deposition of high-purity Zn, complete anion-exchange purification had been done by chromatographic technique. The process was then continued by galvanostatic electrodeposition to determine the efficiencies. As the SPL needs to be neutralized before any attempts of Zn electrodeposition, NaCl may provide the required source of Cl- ions for complex formation. The equilibrium studies of the anion-exchange distribution in such solutions showed similar tendencies to those already known in HCl media. The anion-exchange chromatographic separation was devised – with the finer tuning of the parameters – according to the equilibrium result, but other physical parameters were also examined for improving the efficiency of separation and the recovery of Zn. The devised anion-exchange separation in chloride media can purify the SPL, containing Zn as the valuable component and higher concentrations of Fe as the main impurity. The most important impurities (Fe, Mn, Ni, Al and Co) can be efficiently separated in a dissolved state. At the same time, Zn is sorbed in the strongly basic anion[1]exchange resin at a moderate Cl- ion concentration (~ 2 M). Stirring with Fe chips provides a reduction of iron to the Fe(II) state. The remaining problem is minor copper contamination in the same effluent fraction as Zn, which however can be eliminated by a simple additional step of cementation or directly by pre-electrolysis.

Identifying structure-function relationships to modulate crossover in nonaqueous redox flow batteries.

Nonaqueous redox flow batteries (NARFBs) offer a promising solution for large-scale storage of renewable energy. However, crossover of redox active molecules between the two sides of the cell is a major factor limiting their development, as most selective separators are designed for deployment in water, rather than organic solvents. This report describes a systematic investigation of the crossover rates of redox active organic molecules through an anion exchange separator under RFB-relevant non-aqueous conditions (in acetonitrile/KPF6) using a combination of experimental and computational methods. A structurally diverse set of neutral and cationic molecules was selected, and their rates of crossover were determined experimentally with the organic solvent-compatible anion exchange separator Fumasep FAP-375-PP. The resulting data were then fit to various descriptors of molecular size, charge, and hydrophobicity (overall charge, solution diffusion coefficient, globularity, dynamic volume, dynamic surface area, clogP). This analysis resulted in multiple statistical models of crossover rates for this separator. These models were then used to predict tether groups that dramatically slow the crossover of small organic molecules in this system.

A single-stage anion exchange separation method for Cd isotopic analysis in geological and environmental samples by MC-ICP-MS

A single-stage column separation method based on an anion exchange resin column is developed to purify Cd from geological and environmental materials for high-precision determination of Cd isotopes by double spike MC-ICP-MS.

Rapid determination of plutonium isotopes in small samples using single anion exchange separation and ICP-MS/MS measurement in NH3-He mode for sediment dating.

To accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH3-He mode, and investigated mechanism of 238U interference removal and measurement sensitivity improvement for plutonium isotopes. The interference of uranium and uranium hydrides was effectively eliminated using 0.4mL/min NH3 as reaction gas by shifting them to U(NHm)n+ and UH(NHm)n+. The overall interference of uranium was reduced to <2.4×10-7, while remaining excellent 239Pu sensitivity (13,900 Mcps/(mg/L)) mainly due to ion focusing effect of Pu by helium gas. On this basis, the purification of plutonium using a single AG1-×4 column was proved to be sufficient for accurate determination of plutonium isotopes by the developed detection method, and the detection limits for the method were estimated to be 0.16fg (0.4 μBq) for 239Pu, 0.046fg (0.4 μBq) for 240Pu and 0.039fg (0.15mBq) for 241Pu. The method was validated by analyzing plutonium isotopes in certificated reference materials and reported environmental samples of only 1-2g. The analytical results of ultra-trace Pu isotopes in small amounts (∼1g) of lake sediments obtained by the developed method were successfully applied to sediment dating.

Size Exclusion and Ion Exchange Chromatographic Hardware Modified with a Hydrophilic Hybrid Surface.

Certain biomolecules have proven to be difficult to analyze by liquid chromatography (LC), especially under certain chromatographic conditions. The separation of proteins in aqueous mobile phases is one such example because there is the potential for both hydrophobic and ionic secondary interactions to occur with chromatographic hardware to the detriment of peak recovery, peak shape, and the overall sensitivity of the LC analysis. To decrease non-specific adsorption and undesired secondary interactions between column hardware and biomolecules, we have developed and applied a new hydrophilically modified hybrid surface (h-HST) for size exclusion chromatography (SEC) and anion exchange (AEX) separations of proteins and nucleic acids. This surface incorporates additional oxygen and carbon atoms onto an ethylene bridge hybrid siloxane polymer. As a result, it exhibits reduced electrostatic properties and hydrophilicity that facilitates challenging aqueous separations. Flow injection tests with a phosphate buffer showed superior protein recovery from an h-HST frit when compared to unmodified ethylene-bridged hybrid HST, titanium, stainless steel, and PEEK frits. When applied to SEC of rituximab, ramucirumab, and trastuzumab emtansine with a 50 mM ammonium acetate buffer, this new hydrophilic chromatographic hardware yielded improved monomer and aggregate recovery, higher plate numbers, and more symmetrical peaks. AEX columns also benefited from h-HST hardware. An acidic mAb (eculizumab) showed improved recovery, more stable retention, and a sharper peak when eluted from an h-HST versus SS column. Moreover, AEX separations of intact mRNA samples (Cas9 and EPO mRNA) were improved, where it was seen that h-HST column hardware provided higher sensitivity and more repeatable peak areas from injection to injection. As such, there is significant potential in the use of h-HST chromatographic hardware to facilitate more robust and more sensitive analyses for a multitude of challenging separations and analytes.

Anion exchange separations to produce a suitable electrolyte for the electrodeposition of pure zinc

Anion exchange separations have been devised to purify model solutions of the usual pickling liquor (SPL) obtained from hot dip galvanization to produce a suitable ZnCl2 electrolyte for electrodepositing pure Zn. The method was based on the established anion-exchange distribution functions in chloride media. Both the simple batch and the more accurate chromatographic methods of separation were examined. The loaded solutions contained Zn, Fe, Mn, Ni and Pb of different concentrations with 1.8 - 2 M NaCl or HCl as the background. The resin bed primarily retained Zn while divalent Fe, Mn and Ni were removed in the loading and the continued rinsing steps with the mobile phase at the initial level of Cl- ion concentration. The elution of Zn was carried out by a significantly reduced Cl- ion concentration. The preliminary reduction of the iron to its divalent state was found of utmost importance. The only difficulty arises from the separation of Pb, which has an equilibrium distribution function comparable to the anion exchange of Zn, however in Europe this minor impurity should not be present at disturbing levels. Kinetic examination of the batch process revealed that Zn sorption is virtually complete within 20 minutes, however despite the low distribution coefficients, some 10 % of iron is also sorbed. Almost 90 % of the retained iron could be in the Fe(III) state caused by aerial oxidation. It was also found that the elution of Zn in the batch technique was not possible by just lowering the Cl- ion concentration. Therefore, the chromatographic method is the only possible way if only chloride media are to be applied.

Peptide retention time prediction for peptides with post-translational modifications: N-terminal (α-amine) and lysine (ε-amine) acetylation

Development of a peptide retention prediction model in reversed-phase chromatography is reported for acetylated peptides – both N-terminal (α-) and side chain of Lys (ε-amine) residues. Large-scale proteomic 2D LC-MS analyses of acetylated/non-acetylated tryptic digest of whole human cell lysate have been used to assemble representative retention data sets of 25,000+ modified/non-modified pairs. This allowed elucidating chromatographic behaviour of modified peptides in three different separation modes: high pH reversed-phase, HILIC separation on amide phase (first dimension of 2D) and reversed-phase separation with formic acid as ion-pairing modifier in the second dimension. On average, N-terminal acetylation increases peptide RP retention at acidic pH by 5 Hydrophobicity Index units (% acetonitrile). Acetylation of first lysine adds another 4.1%. The magnitude of the retention shift varies greatly depending on the number of modified amines, peptide length, and N-terminal peptide sequence. Large retention shifts have been observed for peptides with hydrophobic N-termini and specifically peptides carrying sequences characteristic for amphipathic helical structures – all in complete agreement with major sequence-specific features of RP retention mechanism. The utility of the modified Sequence Specific Retention Calculator model has been verified for the in-vivo N-terminally acetylated peptides detected by 2D LC-MS/MS analysis of a yeast tryptic digest. The effect of N-terminal acetylation was also evaluated for six different HILIC columns, strong cation- and strong anion exchange separations using previously acquired 2D LC-MS/MS data.

A novel high-throughput liquid chromatography assay for Carbohydrate-Deficient transferrin (CDT) based on flow-modulated isocratic elution and terbium-induced fluorescence

Transferrin is a glycoprotein containing two bi- or tri-antennary carbohydrate chains ending with sialic acid. Its glycosylation is reduced in chronic alcohol abuse and in inborn glycosylation pathologies, where the carbohydrate-deficient fraction of the protein (CDT) increases significantly. The current methods require a gradient chromatographic separation and time-consuming sample preparation. In comparison, the proposed approach uses a novel flow-modulated liquid chromatography technique (fmLC) and a highly selective and sensitive fluorescence derivatization reaction with terbium ion.A fmLC-FLD method using isocratic anion exchange separation was optimized and validated to resolve disialo-transferrin and trisialo-transferrin from other transferrin glycoforms. Detection took place by recording fluorescence at 550 nm wavelength (excitation at 298 nm). The chromatographic separation needed 5 min, allowing seriate injection every 7.5 min.The method was validated according to the current guidelines of analytical chemistry showing adequate accuracy and precision for the quantitative determination of CDT. The proposed method proved also to be suitable to analyse haemolyzed sera which, because of interference by haemoglobin, fail the standard HPLC-Vis analysis. The method was tested in parallel with HPLC-Vis on 131 sera showing an excellent correlation of results proved by a correlation coefficient of 0.995 (Pearson’s r).The proposed approach proved much simpler than the current methods and cheaper in terms of instrumental costs offering a ground-breaking analytical tool that could likely make available the characterization of CDT outside specialized laboratories, such as in occupational medicine centres, doctor’s offices, small laboratories, alcohol rehabilitation centres, and in developing countries.

Determination of dimethylamine and nitrite in pharmaceuticals by ion chromatography to assess the likelihood of nitrosamine formation

Since July 2018 several drugs have been recalled due to contamination with N-nitrosodimethylamine (NDMA), a probable human carcinogen. Dimethylamine (DMA) and nitrite are precursors in the formation of NDMA. In this study, ion chromatography (IC) methods were developed for the determination of these two precursors in drug substances and drug products. Two methods were developed to determine DMA in two drug products using a cation exchange separation coupled to suppressed conductivity detection. The limit of detection of DMA is < 1 μg/g of active pharmaceutical ingredient (API) for both methods. Nitrite was determined using an anion exchange separation coupled with UV absorbance detection. The limit of detection of nitrite was 0.918 μg/g API. The developed methods were successfully applied to DMA and nitrite determinations in five drug products including metformin, losartan, ranitidine, Nytol, and Benadyrl, and two drug substances (APIs), losartan potassium and metformin hydrochloride. Some samples contained nitrite and DMA at detectable levels. Dimethylamine and nitrite recovery from pharmaceutical samples ranged from 96.0-104 %. The developed methods should be useful for the rapid screening and quantification of nitrite and DMA in pharmaceuticals and in-process samples to assess the likelihood of NDMA formation. The methods for DMA should be applicable to other amines to assess the likelihood of the formation of other nitrosamines in pharmaceutical products.

Sensitive and Reproducible Mass Spectrometry-Compatible RP-UHPLC Analysis of Tricarboxylic Acid Cycle and Related Metabolites in Biological Fluids: Application to Human Urine

We describe a method for the analysis of organic acids, including those of the tricarboxylic acid cycle (TCA cycle), by mixed-mode reversed-phase chromatography, on a CSH Phenyl-Hexyl column, to accomplish mixed-mode anion-exchange separations, which results in increased retention for acids without the need for ion-pairing reagents or other mobile phase additives. The developed method exhibited good retention time reproducibility for over 650 injections or more than 5 days of continuous operation. Additionally, it showed excellent resolution of the critical pairs, isocitric acid and citric acid as well as malic acid and fumaric acid, among others. The use of hybrid organic-inorganic surface technology incorporated into the hardware of the column not only improved the mass spectral quality and subsequent database match scoring but also increased the recovery of the analytes, showing particular benefit for low concentrations of phosphorylated species. The method was applied to the comparative metabolomic analysis of urine samples from healthy controls and breast cancer positive subjects. Unsupervised PCA analysis showed distinct grouping of samples from healthy and diseased subjects, with excellent reproducibility of respective injection clusters. Finally, abundance plots of selected analytes from the tricarboxylic acid cycle revealed differences between healthy control and disease groups.

Accurate measurement of 55Fe in radioactive waste

A radiochemical method was developed for the accurate 55Fe determination in various radioactive waste, in particular samples contaminated with 241Pu. It consisted of three purification steps based on first ammonium hydroxide precipitation, and then anion exchange separation followed by TRU®-based extraction chromatography. It was characterized by an iron recovery yield of about 80% for all the studied samples and a 60Co decontamination factor of 106. In comparison to a standard protocol based on iron cupferrate extraction in chloroform, an improvement of a 30-fold factor was achieved towards plutonium. The developed TRU®-based procedure was validated by participating in interlaboratory exercises.

Regulation of groundwater arsenic concentrations in the Ravi, Beas, and Sutlej floodplains of Punjab, India

Recent testing has shown that shallow aquifers of the Ravi River floodplain are more frequently affected by groundwater arsenic (As) contamination than other floodplains of the upper Indus River basin. In this study, we explore the geochemical origin of this contrast by comparing groundwater and aquifer sand composition in the 10–30 m depth range in 11 villages along the Ravi and adjacent Beas and Sutlej rivers. The drilling was preceded by testing wells in the same villages with field kits not only for As but also for nitrate (NO3–), iron (Fe), and sulfate (SO42−). Concentrations of NO3– were ≥ 20 mg/L in a third of the wells throughout the study area, although conditions were also sufficiently reducing to maintain > 1 mg/L dissolved Fe in half of all the wells. The grey to grey-brown color of sand cuttings quantified with reflectance measurements confirms extensive reduction of Fe oxides in aquifers of the affected villages. Remarkably high levels of leachable As in the sand cuttings determined with the field kit and As concentration up to 40 mg/kg measured by X-ray fluorescence correspond to depth intervals of high As in groundwater. Anion-exchange separation in the field and synchrotron-based X-ray spectroscopy of sand cuttings preserved in glycerol indicate speciation in both groundwater and aquifer sands that is dominated by As(V) in the most enriched depth intervals. These findings and SO42− concentrations ≥ 20 mg/L in three-quarters of the sampled wells suggest that high levels of NO3–, presumably from extensive fertilizer application, may have triggered the release of As by oxidizing sulfide-bound As supplied by erosion of black shale and slate in the Himalayas. Radiocarbon dating of sub-surface clay cuttings indicates that multiple episodes of inferred As-sulfide input reached the Ravi floodplain over the past 30 kyr. Why the other river basins apparently did not receive similar inputs of As-sulfide remains unclear. High NO3– in groundwater may at the same time limit concentrations of As in groundwater to levels lower than they could have been by oxidizing both Fe(II) and As(III). In this particular setting, a kit can be used to analyze sand cuttings for As while drilling in order to target As-safe depths for installing domestic wells by avoiding intervals with high concentrations of As in aquifer sands with the well screen.

Thorium-229 Generator Production of Actinium-225 at Oak Ridge National Laboratory

Oak Ridge National Laboratory (ORNL) is a major producer of 225Ac and supplies research and clinical trials for the treatment of various forms of cancer with this promising radioisotope. Actinium-225 (t1/2 = 10 days) has nuclear properties well suited for use in targeted alpha therapy, emitting four α-particles in a decay cascade via short half-life daughters. It can also be used as a generator for 213Bi (t1/2 = 45.6 min.). ORNL has been producing and shipping 225Ac for research and clinical applications since 1997. During the first year of production, a total of 135 mCi was shipped. Since then, production levels have steadily increased, and in 2018, ORNL produced ∼800 mCi of 225Ac in 13 processing campaigns. From 1997 through the end of calendar year 2018, ORNL conducted 145 production campaigns and provided 11.2 Ci in over 1,200 shipments. ORNL’s objective is to continually improve quality and quantity of product to meet the increasing demand for 225Ac using the limited amount of high-purity 229Th currently available. The chemical separation process consists of anion exchange separation using hydrochloric and nitric acids followed by cation exchange separation for the final purification. Gamma spectroscopy is used for quality control analysis of the final product before shipping, and mass spectroscopy data is used to evaluate chemical purity. Various processing schedules have been used for the production of the 225Ac, depending on the needs of the scientific community, staffing, and funding. This presentation will review various production sequences and present ways to optimize production from ORNL’s current 229Th cow. ORNL’s goal is to continue to produce high-quality 225Ac for use in research and clinical trials. Research supported by the U.S. Department of Energy (DOE) Office of Science, Office of Nuclear Physics, under contract DE-AC05-00R22725 with UT-Battelle, LLC.

Analytical Techniques in Pharmaceutical Analysis for Samples Separation, Characterization, Determination and its Handling

Separations are key aspects of many modern analytical methods. Real world samples contain many analytes. Many analytical methods do not offer sufficient selectivity to be able to speciate all the analytes that might be present. Separation isolates analytes. Most separation methods involve separation of the analytes into distinct chemical species, followed by detection. Instrumental methods may be used to separate samples using chromatography, electrophoresis or field flow fractionation. The development of the pharmaceuticals brought a revolution in human health. These pharmaceutical would serve their intended only if they are free from impurities and administered in appropriate amount. To make drugs serve their purpose various chemical and instrumentation method were developed at regular intervals which are involved in the estimation of drugs. For this analytical instrumentation and methods plays an important role. This review highlights the role of the analytical instrumentation and analytical method in assessing the quality of the drug. The review highlights variety of analytical techniques such as chromatographic, spectroscopic, electrophoretic, titrimetric, microscopic and electrochemical and their corresponding methods that has been applied in the analysis of pharmaceuticals. Quality of pharmaceutical product largely depends upon the environment controls during its storage and handling. Each pharmaceutical product should be handled and stored under specified storage condition labelled on product information data sheet or product pack. Ion chromatography was based on the use of a low-capacity anion exchange separator column used with a basic eluent and a suppressor column. IC is a part of high-performance liquid chromatography used to separate and determine anions and cations. Keywords: Analytical techniques, Sample separation, Chromatography, Spectroscopy, Electrochemical method, Microscopically method, Sample handling, Sample determination Electrophoresis.

Anion exchange separation of antimony and the integrated ion exchange process for decontamination of used zircaloy pressure tubes from Indian pressurized heavy water reactors

ABSTRACT A two-step ion exchange process has been developed for decontamination of used pressure tube zircaloy, from pressurized heavy water reactors, with respect to 125Sb and 60Co. The steps are: anion exchange separation of Sb (III) and cation exchange separation of Co (II); from Zr (IV). Our earlier results on distribution coefficients, isotherms and kinetic separation of Co were the erecting pillars of the present integrated separation process. Oxidation state of Sb in the feed solution, need for reduction of Sb (V) to Sb (III), the nature and amount of reagents required were investigated. Effect of Zr concentration on uptake of Sb and Co, resin capacity, requirement, column dimensions, and flow rate was evaluated.

Electroactive sugars, organic acids and sugar alcohol analysis in wine using anion-exchange chromatography with electrochemical detection

The present work describes an easy, rapid and sensitive alternative methodology for simultaneous detection of sugars (glucose, fructose and arabinose), organic acids (gluconic, glucuronic and glucaric acids) and sugar alcohol (arabitol) in wine samples. The method is based on high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) at gold electrode under detection potential of 0.26 V vs Pd|PdO. The optimized chromatographic anion-exchange separation indicates good separation and detection using a binary gradient with 0.28 mol L−1 CH3COONa containing 0.10 mol L−1 NaOH and ultrapure water as mobile phase with a flow rate at 1.0 mL min−1. Analytical curves presented linear relationship from 1.0 × 10−7 and 1.0 × 10−3 mol L−1 with detection limits (S/N = 3) from 3.0 × 10−8 (glucose) to 9.0 × 10−7 mol L−1 (gluconic acid). The present method was successfully applied in the determination of sugars, organic acids and sugar alcohols in wine, without time consuming pre-treatment of the sample, no need for organic solvent, fast relative execution time, satisfactory separation, high sensitivity and accuracy.

Development of an online-coupled MARGA upgrade for the 2 h interval quantification of low-molecular-weight organic acids in the gas and particle phases

Abstract. A method is presented to quantify the low-molecular-weight organic acids such as formic, acetic, propionic, butyric, pyruvic, glycolic, oxalic, malonic, succinic, malic, glutaric, and methanesulfonic acid in the atmospheric gas and particle phases, based on a combination of the Monitor for AeRosols and Gases in ambient Air (MARGA) and an additional ion chromatography (Compact IC) instrument. Therefore, every second hourly integrated MARGA gas and particle samples were collected and analyzed by the Compact IC, resulting in 12 values per day for each phase. A proper separation of the organic target acids was initially tackled by a laboratory IC optimization study, testing different separation columns, eluent compositions and eluent flow rates for both isocratic and gradient elution. Satisfactory resolution of all compounds was achieved using a gradient system with two coupled anion-exchange separation columns. Online pre-concentration with an enrichment factor of approximately 400 was achieved by solid-phase extraction consisting of a methacrylate-polymer-based sorbent with quaternary ammonium groups. The limits of detection of the method range between 0.5 ng m−3 for malonate and 17.4 ng m−3 for glutarate. Precisions are below 1.0 %, except for glycolate (2.9 %) and succinate (1.0 %). Comparisons of inorganic anions measured at the TROPOS research site in Melpitz, Germany, by the original MARGA and the additional Compact IC are in agreement with each other (R2 = 0.95–0.99). Organic acid concentrations from May 2017 as an example period are presented. Monocarboxylic acids were dominant in the gas phase with mean concentrations of 306 ng m−3 for acetic acid, followed by formic (199 ng m−3), propionic (83 ng m−3), pyruvic (76 ng m−3), butyric (34 ng m−3) and glycolic acid (32 ng m−3). Particulate glycolate, oxalate and methanesulfonate were quantified with mean concentrations of 26, 31 and 30 ng m−3, respectively. Elevated concentrations of gas-phase formic acid and particulate oxalate in the late afternoon indicate photochemical formation as a source.