Ion chromatographic determination of inositol tris- and tetrakisphosphates in rat brain.

Ion chromatography has been applied to the determination of inositol 2,4,5-trisphosphate (Ins 2,4,5-P3), inositol 1,3,4-trisphosphate (Ins 1,3,4-P3), inositol 1,4,5-trisphosphate (Ins 1,4,5-P3), and inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-P4). Other common polyanionic metabolites, including ATP and GTP, do not interfere with the determinations even at concentrations exceeding those normally found in tissue extracts. Assay of rat brain for Ins 1,4,5-P3 and Ins 1,3,4,5-P4 by the method of standard addition gives values which are within 10% of the amount calculated by external calibration. When rat brain homogenates are spiked with Ins 1,4,5-P3, the recoveries are greater than 90%. Treatment of animals with lithium chloride and pilocarpine produces increases in total inositol trisphosphates from 14 to 64 nMol/g wet weight, and increases in Ins 1,3,4,5-P4 from 0.9 to 18 nMol/g wet weight in tissue extracts obtained from the cerebral cortex. Using chemically suppressed conductivity, detection limits in brain are estimated to be 50 pMol/g wet weight for inositol trisphosphates and 22 pMol/g wet weight for inositol tetrakisphosphate.     

Ion chromatographic determination of hydrolysis products of hexafluorophosphate salts in aqueous solution

In this work, hydrolysis of three different hexafluorophosphate salts in purified water was investigated. Aqueous samples of lithium hexafluorophosphate (LiPF₆), sodium hexafluorophosphate (NaPF₆) and potassium hexafluorophosphate (KPF₆) were prepared and stored for different times. Ion chromatography (IC) with UV as well as non-suppressed and suppressed conductivity detection was used for the analysis of the reaction products. For the detection and identification of the formed decomposition products, an IC method using IonPac AS14A 250 mm × 4.0 mm i.d. column and 2.5 mM KHCO₃–2.5 mM K₂CO₃ eluent was established. Besides hexafluorophosphate, four other anionic species were detected in fresh and matured aqueous solutions. The hydrolysis products fluoride (F⁻), monofluorophosphate (HPO₃F⁻), phosphate (HPO₄²⁻) and difluorophosphate (PO₂F₂⁻) were found and were unambiguously identified by means of standards or electrospray ionization mass spectrometry (ESI-MS). It was shown that stability of hexafluorophosphate solutions depends on the nature of the counter ion and decreases in the order potassium > sodium > lithium.     

Ion chromatographic behaviour and determination of perbromates

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

Ion chromatographic determination of platinum in biotic materials

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

Ion chromatographic identification and quantification of glycol degradation products

In water-based heat transfer systems, frequently glycols are added to the water to obtain freeze protection. For this purpose, ethylene glycol (EG) is the most common substance used. When heated, the glycol will slowly degrade and the pH of the glycol-water mixture will decrease, leading to corrosion and foaming problems. Carboxylic acids were identified as the main degradation products. Quantification of the carboxylic acids is of importance to monitor the degradation reactions in order to identify hot spots or overheating, caused by severe heat exchanger scaling, where pH measurements will not be sufficient due to buffer substances added for corrosion protection. In this work, ion chromatographic methods havebeen developed to identify the main degradation products of EG in heat transfer systems and to monitor the degradation process. Possible acidic reaction products of EG are glycolic acid, glyoxylic acid, oxalic acid, acetic acid and formic acid. Separations with a Dionex AS9-HC column with Na2CO3 eluents of differing concentrations showed that only trace amounts of carboxylic acids are present in aged heat transfer media. Oxalic acid can be quantified simultaneously to nitrite or molybdate which are added as corrosion inhibitors. A Dionex AS10 separation column with Na2B4O7 eluent enabled base line separation of glycolic acid, acetic acid and formic acid. Heat transfer media, which are operated in different heat transfer systems under different conditions, were analysed. A system was identified, where severe overheating due to fluid maldistribution in the heat exchanger took place.     

Ion chromatographic determination of sugar phosphates in physiological samples

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

High-performance liquid chromatographic determination of tocopherols in infant formulas

A method for the simultaneous determination of alpha-tocopherol acetate and alpha-, delta-, and gamma-tocopherols by normal-phase high-performance liquid chromatography (HPLC) with a fluorescent detector in infant formula is proposed. The values obtained in the determination of the analytical parameters: linearity, precision, limit of detection and accuracy (analysis of a standard reference material, SRM 1846), confirm the quality of the method. The proposed method is useful for the determination of alpha-, delta-, and gamma-tocopherols and alpha-tocopherol acetate in infant formulas at a low cost and in a total time of 2 h.     

Ion chromatographic determination of selected ions in antarctic ice

Ion chromatography is used to measure the concentrations of chloride, nitrate, sulphate, ammonium and sodium ions at the μg l^?1 level in Antarctic ice and to investigate the occurrence of methanesulphonate, fluoride, formate, acetate and nitrite. Of the latter group of ions, only methanesulphonate was found in measurable concentrations.     

Ion chromatographic determination of trace level phosphorus in purified quartz

Trace levels of phosphorus in purified quartz are determined by ion chromatography. In situ reagent purification, matrix digestion and oxidation of phosphorus to orthophosphate ion are carried out simultaneously in a vapour phase digestion (VPD) assembly using a mixture of HF, HNO3 and H2O2. A drastic reduction (475 times) in phosphate blank from reagents (HF/H2O2) was achieved in the VPD through in situ purification of the reagent. The residues remaining after volatilisation (solvent/matrix), mostly consisting of insoluble phosphate/fluoride salts of divalent and trivalent cations, were solubilised by ion-exchange dissolution. Phosphate was analysed on the IonPac AS17 column with suppressed conductivity detection. The results of the ion chromatography (IC) method were compared with a spectrophotometric method. Accuracy was evaluated by analysing a certified reference material (silicon, NIST 57a). The method detection limit was 0.05 microg g(-1).     

Ion chromatographic methods for the detection of starch hydrolysis products in ruminal digesta.

Dionex high-performance ion chromatographic methods were evaluated for separation and quantitation of plant sugars and starch digestion products in the ruminal digesta of cattle. Mono- and disaccharides were eluted from a Dionex CarboPac PA1 column with sodium hydroxide used isocratically or as a pH gradient. Maltooligosaccharides which had a degree of polymerization (DP) less than 30 glucose residues were eluted in 60 min by a sodium hydroxide eluent containing a sodium acetate gradient. Carbohydrates were detected amperometrically. Responses were linear (r2 greater than 0.99) for glucose, disaccharides and maltooligosaccharides (DP less than 8). Precipitation and solid-phase extraction methods were evaluated for clean-up of samples of feedstuffs, ruminal contents, and bacterial culture fluids. Perchloric acid precipitation hydrolyzed sucrose but did not affect recoveries of cellobiose, isomaltose or maltose. Ethanol in concentrations of 79 and 86% precipitated maltooligosaccharides having chain lengths larger than 14 and 9 glucose residues, respectively. Maltooligosaccharide recoveries from solid-phase extraction columns varied with maltooligosaccharide size and column packing. Recoveries were greater than 94% for short chains (DP less than 6) eluted from phenyl-substituted columns and variable for all oligosaccharides eluted from C18 columns. Applications of these methods are presented and include: (1) detection of sugars in ruminant feed, (2) monitoring changes in ruminal sugars after feeding and (3) monitoring changes in extracellular sugars and oligosaccharides in the culture fluids of the ruminal bacterium, Bacteroides ruminicola.     

Simultaneous liquid chromatographic determination of ezetimibe and simvastatin in pharmaceutical products

A reversed-phase liquid chromatographic (LC) method was developed and validated for the simultaneous determination of ezetimibe and simvastatin in pharmaceutical dosage forms. The LC method was carried out on a Synergi fusion C18 column (150 mm x 4.6 mm id) maintained at 45 degrees C. The mobile phase consisted of phosphate buffer 0.03 M, pH 4.5-acetonitrile (35 + 65, v/v) run at a flow rate of 0.6 mL/min, and detection was made using a photodiode array detector at 234 nm. The chromatographic separation was obtained within 15.0 min, and calibration graphs were linear in the concentration range of 0.5-200 microg/mL. Validation parameters such as specificity, linearity, precision, accuracy, and robustness were evaluated, giving results within the acceptable range for both compounds. Moreover, the proposed method was successfully applied for the routine quality control analysis of pharmaceutical products.     

Ion chromatographic determination of alkali and alkaline earth metals in mineral waters

Summary The rapid, simultaneous, suppressed ion chromatographic determination of alkali, alkaline earth metals and ammonium in highly mineralized waters has been examined using the novel cation exchange IonPac CS12 column. General ability for the determination of lithium, sodium, ammounium, potassium, magnesium, calcium and strontium in concentrations from a few g to several mg per liter was studied. The relative standard deviations of retention times of all seven cations were below 0.7% and the relative standard deviations of the measurements of peak areas and peak heights were mostly below 5%. Six natural mineral waters of different types were selected for evaluation of the method. It was not possible to determine lithium in the one run and ammonium usually partially coelutes with sodium precluding quantitative determination. Strontium was undetectable because of the necessary dilutions. All the reltionships between peak areas and concentrations or peak height and concentrations were linear and there was also no evidence of the effect of different matrices on the slope of regression lines.     

Thin-layer chromatographic method for separation and determination of papaverine and its oxidation products

A method is presented for the separation of papaverine, papaverinol and papaveraldine by TLC on silica gel with chloroform saturated with ammonia as the solvent system. The spots are extracted with absolute methanol and each compound determined spectrophotometrically in 1 M hydrochloric acid. Papaveraldine is also determined polarographically in Britton-Robinson buffer, pH 4.1, after its separation and elution. The method is rapid and sensitive and permits the determination of papaverine, after its extraction from drugs, without interference by papaverinol and papaveraldine.     

Ion chromatographic determination of cyanate in saline gold processing samples.

An ion chromatographic method was developed for the determination of cyanate (CNO-) in saline gold processing samples. The method is based on the use of a very weak-eluting buffer (5 mM sodium borate) and a Dionex AS4A-SC anion-exchange column. This weak-eluting buffer facilitates the wide chromatographic separation of chloride (Cl-) from CNO-. After CNO- has been eluted, the switch to 1.8 mM Na2CO3-1.7 mM NaHCO3 buffer allows the fast elution of other major inorganic and organic anions. Validation of this method, including identification of interferences, has shown that this method is reliable, accurate, sensitive (detection limit, 0.1 mg/l CNO-) and reproducible.     

Ion chromatographic determination of alkaline earth metals and some heavy metals

The method is described for ion chromatographic determination of Ba, Ca, Cd, Cu, Mn, Ni, Sr, Pb and Zn. Ethylenediammonium chloride or tartrate solutions are used as eluents with a suppressor column. The detection limits for the listed elements are (in μg l^?1): Ba 1.4, Ca 0.045, Cd 0.6, Cu 0.3, Mn 0.8, Ni 0.5, Pb 6.3, Sr 0.3, Zn 1.2. Relative standard deviations are 0.015–0.050 ar the 20 mg l^?1 level (n = 5, p = 0.95). Interferences are considered.     

Development of gas chromatographic method for determination of cholesterol oxides in meat products

Summary A method of extraction, purification and gas chromatographic analysis of five cholesterol oxidation products (COPs) (7β-hydroxycholesterol, 5α, 6α-epoxycholesterol, 25-hydroxycholesterol, 7-ketocholesterol and cholestane-3β, 5α, 6β-triol) has been developed. The method is aimed at the determination of COPs in meat and meat products, in particular dry sausages, where large differences in the content of cholesterol and its oxidation derivatives may occur. Linearity of response of trimethylsilyl ethers was defined. The minimum concentration tested was 2.5 μg g⁻¹ in the injected solution. The main feature of the present work is the addition of a purification step of unsaponifiables by SPE on silica cartridges. Extraction recoveries of COP standard mixtures, performed with or without the SPE step, are evaluated. The introduction of the clean-up step results in high purity samples without further losses in the entire process.