Separation Of Organic Acids Research Articles

Dreiphasenextraktion zur Anreicherung bei der Flüssig/Flüssig‐Extraktion von Carbonsäuren

AbstractThree‐Phase Extraction – Enhancing Enrichment in Liquid‐Liquid Extraction of Carboxylic Acids. The three‐phase extraction process, a new variant of reactive extraction, has been investigated for its applicability in the separation of organic acids. It has been compared with reactive extraction, liquid membrane permeation and supercritical fluid extraction. These processes are based on the use of amine extractants, which have to be dissolved in non‐polar solvents, for the extraction of carboxylic acids, hydroxycarboxylic acids and aminocarboxylic acids. This paper compares the above processes and considers their possible use for acid extraction.

Liquid chromatographic determination of acids and anions using liquid membrane ion-selective electrodes in a potentiometric flow-through detector

The sensitive detection of organic acids in liquid chromatographic (LC) systems remains problematic. The behaviour of a potentiometric detector was studied in this type of analysis, using ion-selective PVC-based liquid membranes. One membrane contained a quaternary ammonium salt as a carrier and another contained a lipophilic macrocyclic pentamine. The selectivity and sensitivity of the two membrane types towards 20 ions was determined using flow- injection experiments. The flow-through detector was of the wall-jet type. The response times of the membranes were evaluated and are discussed with respect to their use in LC and flow-injection analysis (FIA). The response times Were compared with these obtained with amperometric wall-jet detectors. The different factors that determine the extent of the response times are discussed. The membranes were used for the sensitive detection of inorganic anions in an LC ion chromatography system. For the separation of organic acids, and Aminex HPX87H ion-exclusion chromatographic column was used. With the potentiometric liquid membrane detector, the detection limits were at least 100 times lower than the values obtained with the low-wavelength UV detector that is normally used in these systems. Typically, a detection limit of 10 ng was measured for acetic acid. The potential and limitations of potentiometric liquid membrane detectors in LC and FIA are discussed.

Optimization of pH for the separation of organic acids in capillary zone electrophoresis

The migration behavior and optimum separation of a set of substituted phenols is presented. A mathematical model that describes mobility in CZE in terms of fundamental constants of each solute (acid dissociation constant Ka, mobility of the dissociated acid microA-) and the pH of the buffer was used to predict the mobility of each solute as a function of pH. The resolution between each peak pair was calculated, and a window diagram of minimum resolution as a function of pH was employed in determining the optimum pH. A comparison of the predicted and actual electropherograms shows the usefulness of this technique.

Extraction Processes for Bioproduct Separation

Abstract The three-phase extraction process, a modification of reactive extraction, has been investigated for its applicability in the separation of organic acids from fermentation broth. It has been compared with reactive extraction, liquid membrane permeation, and supercritical fluid extraction. These processes are based on the use of amine extractants, which have to be dissolved in nonpolar solvents, for the extraction of carboxylic acids, hydroxycarboxylic acids, and aminocarboxylic acids. This paper considers the comparison of the above-mentioned processes. Furthermore, the extractability of acids from synthetic aqueous solutions and fermented broths has been compared. Principal consideration has been paid to the extraction of lactic acid, gluconic acid, citric acid, and L-leucine.

The Selective Separation of Organic Acids through Liquid Membrane Containing Ferrite in the Presence of Alternating Magnetic Field

Abstract The selective separation of phenylglyoxylic acid (PGA) from a mixture of PGA and mandelic acid (MA) was carried out by using a liquid membrane containing ferromagnetic powder (LM-FP) in the presence of an alternating magnetic field (A-MF). Ferromagnetic powder, which exhibits a strong coercive property, was added into a mixture of toluene and chloroform (T–C mixture). Many holes of 0.7 mm in diameter were bored in the bottom wall of a Teflon® cylindrical bottle, in which the total hole area occupied 8%. A T–C mixture containing ferromagnetic powder was filled into the holes to prepare LM-FP. Under an exposure of A-MF (200 Oe, 50 Hz) over a 12 h. Fifty four % PGA and 8% MA in the source phase were found to permeate through the LM-FP-containing Sr-ferrite from the source phase of an equimolar mixture of PGA and MA to the receiving phase. The PGA permeation rate through the LM-FP varied over a region between 0.3 and 7.5 times higher than that through a control liquid membrane not containing any ferromagnetic powder in the presence of a magnetic field.

Determination of Organic Acids in Apple and Cider by Liquid Chromatography with ordinary and narrow-bore columns. A Comparative Study

Abstract Two narrow-bore columns packed with octadecylsilane of various particle sizes were used to compare their efficiency for the separation of organic acids in apple and cider with that of ordinary columns. The best simultaneous resolution of quinic, malic, shikimic, lactic, acetic, citric and succinic acid was accomplished by using a 100 × 2.1 mm ID, 3-μm Spherisorb ODS-2 column and a phosphate buffer as the mobile phase. This chromatographic system provided a separation efficiency comparable to that afforded by an ordinary 250 × 4.6 mm ID, 5-μm Spherisorb ODS-2 column, plus greater rapidity (30%) and economy, all of which allowed the accurate, precise determination (CV=3%) of the above-mentioned compounds. Finally, the performance of an ordinary UV detector and that of a rapid spectral detector in this type of determination were critically compared.

DETERMINATION OF LOW MOLECULAR WEIGHT ORGANIC ACIDS COLLECTED ON SILICA GEL AIR SAMPLING TUBES BY USING ION-EXCLUSION CHROMATOGRAPHY

Ion-exclusion chromatographic separation of organic acids by using tridecafluoroheptanoic acid solution as the eluent and conductivity detection were studied. Air samples were collected on silica gel tubes and desorbed in water. The proposed method was applicable to the separation of formic, acetic, propionic, and butyric acids. The recovery of these four acids was above 95% when air was passed through the spiked tubes at a flow rate of 0.2 L/min for 3 hr. The method was validated for all four compounds at one-half the threshold limit value (TLV), at the TLV, and two times the TLV. No changes in recovery were observed in samples stored for up to 7 days. Desorbed samples were stable for up to 20 days.

STUDIES ON YEAST DIFFERENTIATION USING ORGANIC ACID METABOLITES PART 1. DEVELOPMENT OF METHODOLOGY USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

The separation of organic acids on the column Aminex HPX-87H from Bio-Rad is described. The relationship between column temperature and retention time was studied for both sulphuric and phosphoric acid eluants and an analytical scheme using 0.2% (v/v) phosphoric acid was developed. While the procedure is designed for the commonly occurring non-volatile acid metabolites it was demonstrated that conditions could be established for the analysis of fatty acids to C10. Difficulties in the qualitative and quantitative analysis of organic acids in beer are discussed.

Chromatographic techniques in inborn errors of metabolism

Chromatography has played a pivotal role in the advances made during the last 30 years in our knowledge of inborn errors of metabolism. This review discusses the application of some of these techniques to the analysis of organic acids and acylcarnitines. The separation of organic acids needed a comprehensive approach that would permit all of the many organic acids present in urine or other complex mixtures to be extracted, analysed and identified in a single run. This required analytical methods of great resolving power, wide linear range and universal detectors such as gas chromatography (GC), or GC coupled with mass spectrometry. Sample preparation was another problem that has been tackled by a variety of approaches. Organic solvents have been employed widely for the extraction of organic acids from physiological fluids. Unfortunately, recoveries of the different organic acids by this method are sometimes less than quantitative and variable depending on the compound. Other methods, such as the use of DEAE-Sephadex columns, have the advantage of resulting in close to 100% recoveries, but are more tedious. Liquid partition chromatography on short silicic acid columns has also been recommended as a useful clean-up step prior to GC, permitting both the identification and quantitation of organic acids in urine, plasma or amniotic fluid. Although many derivatization procedure have been used to prepare organic acids for gas chromatography, the most common is trimethylsilylation. Oxo acids are usually reacted with one of several commonly used reagents to form oximes. GC analysis of organic acids was initially done using packed columns with methylsilicone-based, non-polar stationary phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane separation of organic acids from aqueous salt solutions

Membrane technology is finding increasing application for the treatment of aqueous hazardous wastes. Leachates from municipal solid waste and industrial landfills fall into this category. Liquids arise in the interior of fills, due to compression, percolating rainfall, and microbial reactions. The latter include anaerobic acetogenesis, an intermediate pathway to methanogenesis and landfill gas production which yields organic acids. A reverse osmosis (RO) technique for concentrating dilute volatile fatty acids (VFAs) is described. Good separations of VFAs were obtained, without significant flux decline. RO treatment successfully reduced total dissolved solids (TDS) sufficiently to meet common guidelines for direct aqueous discharge. Studies were carried out using a plate-and-frame RO apparatus packed with three different membrane types and operated at a process temperature of 25°C. Permeate and retentate were recycled to the feed tank, simulating an operating mode in which retentate concentration does not change significantly in response to modest changes in feed concentrations. At steady-state, membrane separation of single and binary VFA solutions, exceeded 95% with pH adjustment as a preliminary step.

Isotachophoretic separation of organic acids in biological fluids

The operating conditions for the isotachophoretic separation of organic acids were evaluated. At pH values ranging from 2.90 to 4.25 both relative step heights and molar flow-rates were determined experimentally for 26 anions. Comparing the observed values with simulated data, highly significant ( p = 0.0001) correlation coefficients of 0.993 and 0.920, respectively, were found at pH 3.50. Whereas the concentration of the leading electrolyte did not affect the relative step heights, it increased the molar flow-rates significantly. The same applied to the detection current. The time of analysis was observed to be a function of the concentration of the leading electrolyte. However, the time elapsed between injection of the analyte and its detection depended solely on the volume and not on the amount of analyte injected. In isotachophoresis, incomplete separation of two compounds is indicated by the occurrence of a mixed zone which can hardly be distinguished from a pure zone. Thus, knowledge of the separation capacity is a prime prerequisite in optimizing the system for the analysis of biological fluids. The separability of nine equimolar pairs of anions was determined at pH values ranging from 2.90 to 4.25. Although two ionogenic constituents would separate only when their migration rates in the mixed state were different, no clear correlation was observed between separation capacity and difference in relative mobility. Separability, however, was found to increase with increasing concentration of the leading electrolyte. While the separation capacity was not influenced by the electric current, it was significantly affected by the volume injected. In subsequent analyses of serum, cerebrospinal fluid, seminal plasma and prostatic fluid, a variety of organic acids could be detected. Calibration graphs for the detected anions revealed a detection limit of 1 nmol and linearity over their biological concentration ranges. Further, the isotachophoretic results correlated well with highperformance liquid chromatographic and enzymatic analyses of citric acid and lactic acid in human seminal plasma and cerebrospinal fluid, respectively.

Selection of optimal pH and solvent composition for the separation of organic acids using three-dimensional diagrams and a computer program

The retention behaviour of different types of organic acids was investigated on an ODS-Hypersil column using eluents of various pH and of various methanol-water ratios. Equations introduced by Horvath and coworkers were fitted onto the experimental data, and the obtained constants were used to calculate the three-dimensional k′-surfaces for the compounds in the investigated pH and solvent composition range. Using the data of the individual surface diagrams the optimal pH and solventg composition was computed for the separation of six selected compounds. To verify the applicability of the above procedure the chromatographic separation of the six compounds was carried out with the predicted conditions, and the chromatogram obtained is presented.

Enzyme-facilitated transport and separation of organic acids through liquid membranes

Enzyme-facilitated transport and separation of organic acids through liquid membranes

Positive-ion thermospray liquid chromatography—mass spectrometry: detection of organic acidurias

Positive-ion thermospray liquid chromatography—mass spectrometry (TSP-LC-MS) is used to detect organic acids via the direct injection of untreated urine from newborns and infants. Two methods are reported for the separation of organic acids. The separation of urinary organic acids is effected in either an acidic, pH 2.5 sulfuric acid, or a non-acidic, 0.05 M ammonium acetate, pH 6.8, mobile phase. Use of pH 2.5 sulfuric acid and an HPX-87H organic acid column produces better separation but has less sensitivity than the use of 0.05 M ammonium acetate, pH 6.8 and a C 18 column. Positive ion TSP-LC-MS has been used to detect methylmalonic aciduria, 3-hydroxy-3-methylglutaric aciduria, propionic aciduria, isovaleric aciduria and argininosuccinic aciduria.

Simultaneous Determination of Low Molecular Weight Organic Acids in Soil Solution by Ion Chromatography

AbstractA simple and precise ion chromatographic (IC) method for determination of citric, malonic, succinic, formic, acetic and propionic acids in soil solution was developed. It requires a prior cleanup to the soil solution samples by anion exchange resin (AG1‐X8) and determination of organic acids using a Dionex Model 2010i IC. Separation of organic acids by IC permitted their quantitation by conductivity measurements, following suppression of background conductivity by a fiber suppressor. A high degree of precision was achieved in the quantitation of organic acids studied. With the IC method, citric, malonic, succinic, formic, acetic and propionic acids can be determined simultaneously in 16 min. A single operator can analyze about 30 samples in a single working day.

Gas‐chromatographic Separation of Organic Acids and Electrophoretic Determination of Phosphatases from VA Mycorrhizal Roots

AbstractA report is given on methods for separation and identification of organic acids, including phenolic acids, and on the determination of phosphatases from VA mycorrhizal (VAM) roots.For gas‐chromatographic preparation of the samples containing the organic acids silylation and methylation were tested, as well as various solvents and silylating reagents. Columns of different polarity were examined for their separation properties. Gas‐ chromatographic separation of the acids was incomplete on the packed column OV 7. With the capillary column PVMS 54 separation was much better, but improvements are still needed.Mycorrhiza‐specific phosphatases (MSP) appearing as three bands were found by electrophoresis with porosity‐gradient gels in mycorrhizal roots of Allium, Sorghum and Eupatorium plants. In these three species each MSP was located at the same position. Inoculated onion roots enzymatically digested with cellulase and pectinase showed no root‐specific phosphatases, but still revealed MSP. Further improvements in electrophoresis techniques are being investigated.

Liquid chromatographic separation and indirect detection of organic acids using iron(II) 1,10-phenanthroline as a mobile-phase additive.

Iron(II) 1,10-phenanthroline (Fe(phen)/sub 3//sup 2 +/ salts are used as mobile-phase additives for the liquid chromatographic separation of organic acids as anionic analytes on a reverse stationary phase. Major elution variables that affect selectivity and resolution are Fe(phen)/sub 3//sup 2 +/ concentration and its retention on the stationary phase, type and concentration of counter-anions, pH, buffer components and concentration, ionic strength, organic modifier, and analyte anion selectivity. Indirect detection is used to detect nonabsorbing organic analyte anions by monitoring the effluent at 510 nm where Fe-(phen)/sub 3//sup 2 +/ exhibits maximum absorbance. Separations of multicomponent mixtures of alkylsulfonic, mono- and diprotic alkyl carboxylic, and and aromatic carboxylic acids are shown. Detection limits, depending on analyte and conditions, approach 20 ng. A linear detector response was found for analyte anion (propionate and lactate) concentrations from 20 ng to over 10,000 ng of injected analyte.

Anion Exchange-Adsorption on Low Capacity Anion Exchangers: Separation of Organic Acids, Amino Acids, Small Chain Peptides

Abstract The variables that influence the retention of organic analyte anions on a macroporous, high surface area polystyrenedivinyl-benzene copolymer that is chemically modified by attaching tetraalkylammonium groups to the copolymer surface are identified and studied as a function of anion exchange capacity. A combined adsorption-anion exchange retention of the organic analyte anion is possible providing the analyte has both a hydrophophic center and an anionic charge site. As the column anion exchange capacity (0 to 173 μeq of anion exchange sites/column was studied) increases, analyte retention due to adsorption decreases and retention due to anion exchange increases. The factors influencing organic analyte anion retention by adsorption are low anion exchange capacity and mobile phase solvent composition, type of organic modifier, and pH for analytes that are weak organic acids. For anion exchange the major factors are a high anion exchange

Ion-exclusion Chromatography of Weak Acids Using a Carbonic Acid Solution as Eluent

Abstract Ion-exclusion chromatographic separation of organic acids using a carbonic acid solution as eluent is presented. This permits conductivity detection of ionic species without a suppressor as a post-column reactor. It was found that the proposed method was applicable to the separation of organic acids having pKa over ca 3.5. This technique was applied to the determination of acetic acid in pharmaceuticals without tedious sample preparation.

Isotachophoresis of organic acids after oxidation of hydrolytic products of some monosaccharides

One of the basic components of cultivation media for microorganisms at biotechnological processes are organic compounds as the source of organic acids. Optimal conditions were found for separation of organic acids by isotachophoresis. The products of the alkaline degradation of glucose and their oxidation products after successive glucose oxidation were tested.