Determination of trimecaine metabolites in blood plasma by capillary isotachophoresis

A method is proposed for the determination of trimecaine (diethylglycylmesidide) and its de-ethylated metabolites (monoethylglycylmesidide and glycylmesidide) in blood plasma by capillary isotachophoresis. The deproteinated plasma is extracted into chloroform after alkalinization and the total solids in the organic layer are dissolved in acidified 25% 2-propanol. Subsequent isotachophoretic analysis is performed in an operational system consisting of potassium acetate buffer (pH 4.75) as the leading and beta-alanine as the terminating electrolyte. The order of the zones corresponds to the molecular weights of the separated compounds. The recovery of all substances of interest is 55% and the limit of determination is 0.05 micrograms of each substance in 1 ml of plasma.     

Analysis of metabolites of glucose pathways in human erythrocytes by analytical isotachophoresis

A method for the quantitative determination of the major anionic constituents of fountain solutions, typically mono-, di- and hydroxycarboxylates, alkylbenzenesulfonates, and inorganic anions, including orthophosphate and polyphosphates, is presented here for the first time. The analytical problems arising from extensive co-elution of many of these analytes on an ion-exchange column have been resolved through a combination of (i) careful selection of the concentration gradient of the sodium hydroxide eluent; (ii) parallel analysis by ion-exclusion chromatography; and (iii) determination of total phosphorus by inductively coupled plasma atomic emission spectrometry.     

Evaluation of diabetic ketoacidosis-related ionic metabolites in human blood serum by capillary electrophoresis.

Three methodologies are presented to contemplate the analysis of sodium, potassium, chloride, bicarbonate, lactate, acetoacetate, and beta-hydroxybutyrate in blood serum samples of diabetic patients using free solution capillary electrophoresis with indirect detection (214 nm for cations and 254 nm for anions). The cations were analyzed in less than 6 min in an electrolyte comprised of 15 mmol x L(-1) imidazole, 5 mmol x L(-1) lactate and 1 mmol x L(-1) 18-crown-6-ether, adjusted to pH 4.5. Chloride and bicarbonate were analyzed in 2 min in a 5 mmol x L(-1) chromate, 0.1 mmol.L(-1) cetyltrimethylammonium bromide (CTAB), pH 9.0 electrolyte solution. Ketoacids and lactate were analyzed in less than 11 min in an electrolyte composed of 15 mmol x L(-1) 3,5-dinitrobenzoate, 0.1 mmol x L(-1) CTAB, at pH 3.5. All methodologies were validated with respect to linearity, selectivity, sensitivity, precision and accuracy performing adequately for clinical purposes.     

Determination of theophylline binding to human serum proteins by isotachophoresis

Free theophylline was isolated from human serum by ultrafiltration and analysed in a leading electrolyte of 7.5 mM morpholinoethanesulphonic acid with ammediol as a counter ion at pH 8.90 and alpha-alanine as a terminator. The UV (280 nm) absorbance of the theophylline spike between serine and bicine as spacers was integrated. Binding percentages to human pool serum, human albumin and alpha 1-acid glycoprotein (orosomucoid) were determined at physiological concentrations, and found to be 55, 44 and 12%, respectively. The calibration lines were straight from 0 to 30 mg/l, with a standard deviation of 0.2 mg/l. The detection limit was 1 mg/l. The time of analysis was 12 min at 40 microA in a 0.2 mm I.D. capillary.     

Determination of heavy metals by isotachophoresis

The suitability of isotachophoresis for the analysis of metals in, e.g., environmental samples was studied. In a cationic operational system the heavy metals Fe, Cu, Ni, Cd, Co, Zn, Pb and Mn were simultaneously determined. The separation was achieved through complex formation with one of the counter ions, hydroxyisobutyric acid. The other counter ion was acetic acid, the leading ion was 0.02 M potassium or sodium (pH 4.1) and the terminator was H+. The analysis time was 15 min at 60 microA in a 0.2 mm I.D. capillary. Aqueous samples containing ppm and ppb amounts were enriched on a cation exchanger with an extremely low affinity for sodium (Chelex 100). Good recovery, linearity, precision and accuracy were obtained even down to the ppb range. Although the sensitivity of the method is not greater than that of some of the more established methods for the individual metals, a great advantage of isotachophoresis is the simultaneous determination of the metals, with equal response factors. An example is given of the determination of metals, including aluminium, in serum.     

Determination of potassium in sea-water by capillary isotachophoresis

Summary A new analytical procedure for the determination of potassium in sea-water was developed using capillary isotachophoresis and ion-exchange. After the sea-water sample was passed through the column packed with an ammonium form cation-exchange resin, sodium ion was removed with 2×10^–2 mol/l ammonium chloride solution and then potassium ion was eluted with 3×10^–1 mol/l ammonium chloride solution. Simultaneous determination of potassium and sodium ions was performed with a newly developed electrolyte system; the leading electrolyte was 5 mmol/l cesium hydroxide containing 2 mmol/l 18-crown-6, 0.01% hydroxypropyl methylcellulose (HPMC) and 70% methanol; the terminating electrolyte was 5 mmol/l tetrabutylammonium bromide containing 0.01% HPMC and 70% methanol. A large amount of ammonium in the eluate did not interfere with the isotachophoretic measurement of potassium and sodium ions. A linear working curve was obtained for artificial sea-water samples containing up to 700 mg/l potassium ion. The proposed method was applied to the determination of potassium in surface and bottom sea-water samples.

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Kaliumbestimmung in Meereswasser durch Capillar-Isotachophorese

     

Fluorescence behavior and specific interactions of an ionic liquid in ethylene glycol derivatives

The excitation-wavelength- and concentration-dependent fluorescence response of an ionic liquid (IL), 1-octyl-3-methylimidazolium tetrafluoroborate [Omim][BF(4)], in the ethylene glycol derivatives, [CH(3)(OCH(2)CH(2))n-OH, n = 1-3], has been critically examined in the entire composition range. The pure IL exhibited a large red shift beyond an excitation wavelength of 390 nm, showing the heterogeneous nature of the liquid. Concentration dependence of the fluorescence spectra in the organic solvent-rich region favors the association of IL molecules into the aggregated structures. The maximum of the fluorescence spectra shifted toward blue with the increase of organic component concentration in all of the mixtures, reflecting an appreciable solute-solvent interaction. Very high concentrations of the organic liquid in the mixtures resulted in the inversion of the spectral shift toward red, indicating the dominance of pi-pi* transitions over the n-pi* transitions as a consequence of imidazolium ring stacking. (1)H NMR and FT-IR investigations over the whole composition range of the mixtures showed multiple hydrogen-bonded interactions of varying strengths between the unlike molecules and the existence of associated species of the IL in the dilute region. Both the specific interactions between unlike molecules and the tendency of aggregation of IL molecules in the dilute region reduced with the introduction of the -OC(2)H(4) group in the glycol derivative. A comparison of specific interactions with the volumetric properties of the similar mixtures shows that the packing efficiency depending on differences in the shape and size of the molecules mainly decides the overall magnitude of deviations from ideality.     

Determination of metoprolol tartrate by capillary isotachophoresis

This paper describes two isotachophoretic methods of metoprolol tartrate (MT) determination in pure and dosage forms. The first method was used for direct analysis where the following electrolyte system was applied: 10 mmol dm⁻³ 3-morpholino-2-hydroxypropanesulfonic acid, 10 mmol dm⁻³ NaCl, 2 % hydroxyethylocelulose as leading (LE) and 10 mmol dm⁻³ glycyl-glycine as terminating (TE) electrolytes. The second method was used for indirect analysis of MT as tartrate ions. In this case, the leading electrolyte consisted of 10 mmol dm⁻³ HCl, β-alanine (BALA), pH 4-5, and the terminating one of 5 mmol dm⁻³ glutamic acid, 10 mmol dm⁻³ β-alanine. Calibration curves were calculated as follows: for system A: y = (0.52 ± 0.05)x − (0.9 ± 0.2) (LOD = 13.0 mg dm⁻³, LOQ = 31.7 mg dm⁻³); and for system B: y = (0.240 +- 0.001)x + (0.18 ± 0.06) (LOD = 1.8 mg dm⁻³, LOQ = 4.4 mg dm⁻³). The isotachophoretic method was compared with the pharmacopoeial one by statistical tests.     

Determination of some antirheumatics by capillary isotachophoresis

Isotachophoresis (ITP) was applied for the determination of some antirheumatic drugs (fenoprofen, naproxen, ibuprofen, and ketoprofen) in human serum. The leading electrolyte contained hydrochloric acid (10 mmol x L(-1)), creatinine (pH 4.5) and methylhydroxyethyl cellulose (0.1%). The terminating electrolyte was 2-(N-morpholino)ethanesulfonic acid (10 mmol x L(-1)) adjusted with tris(hydroxymethyl)aminomethane to pH 6.9. The ITP separations were carried out in column-coupling configuration of the separation unit provided with a preseparation column of 160 x 0.8 mm inner diameter (ID) and analytical column of 160 x 0.3 mm ID. The limit of detection for ibuprofen, fenoprofen, and naproxen in serum by direct sampling was 0.008, 0.005 and 0.004 mmol x L(-1). The limit of detection for ketoprofen in serum after ethanol precipitation was 0.001 mmol x L(-1).     

Crystal structures of ethylene glycol and ethylene glycol monohydrate

We have carried out a neutron powder diffraction study of deuterated ethylene glycol (1,2-ethanediol), and deuterated ethylene glycol monohydrate with the D2B high-resolution diffractometer at the Institut Laue-Langevin. Using these data, we have refined the complete structure, including all hydrogen atoms, of the anhydrous phase at 220 K. In addition, we have determined the structure of ethylene glycol monohydrate at 210 K using direct space methods. Anhydrous ethylene glycol crystallizes in space-group P2(1)2(1)2(1) with four formula units in a unit-cell of dimensions a = 5.0553(1) ?, b = 6.9627(1) ?, c = 9.2709(2) ?, and V = 326.319(8) ?(3) [ρ(calc)(deuterated) = 1386.26(3) kg m(-3)] at 220 K. Ethylene glycol monohydrate crystallizes in space-group P2(1)/c with four formula units in a unit-cell of dimensions a = 7.6858(3) ?, b = 7.2201(3) ?, c = 7.7356(4) ?, β = 92.868(3)°, and V = 428.73(2) ?(3) [ρ(calc)(deuterated) = 1365.40(7) kg m(-3)] at 210 K. Both the structures are characterized by the gauche conformation of the ethylene glycol molecule; however, the anhydrous phase contains the tGg' rotamer (or its mirror, g'Gt), whereas the monohydrate contains the gGg' rotamer. In the monohydrate, each water molecule is tetrahedrally coordinated, donating two hydrogen bonds to, and accepting two hydrogen bonds from the hydroxyl groups of neighboring ethylene glycol molecules. There are substantial differences in the degree of weak C-D···O hydrogen bonding between the two crystals, which calls into question the role of these interactions in determining the conformation of the ethylene glycol molecule.     

Thermodynamic and spectroscopic studies on binary mixtures of imidazolium ionic liquids in ethylene glycol

The thermodynamic behaviour of imidazolium based ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride [C₄mim][Cl]; 1-octyl-3-methylimidazolium chloride [C₈mim][Cl], and 1-butyl-3-methylimidazolium methylsulfate [C₄mim][C₁OSO₃] in ethylene glycol [HOCH₂CH₂OH] (EG) have been investigated over the whole composition range at T = (298.15 to 318.15) K to probe the interactions in bulk. For the purpose, volumetric properties such as excess molar volume, $V_m^E$, apparent molar volume, V_?,i, and its limiting values at infinite dilution, $V_{?\text{,}i}^{\infty }$, have been calculated from the experimental density measurements. The molecular scale interactions between ionic liquids and EG have been investigated through Fourier transform infrared (FTIR) and ¹H NMR spectroscopy. The shift in the vibrational frequency for C–H stretch of aromatic ring protons of ILs and O–H stretch of EG molecules has been analysed. The NMR chemical shifts for various protons of RTILS or EG molecules and their deviations show multiple hydrogen bonding interactions of varying strengths between RTILs and EG in their binary mixtures.     

Determination of organic acids in tobacco by capillary isotachophoresis

Nine organic acids and phosphate have been separated and quantified in tobacco by capillary isotachophoresis. Two operating systems for the separation were found: hydrochloric acid (10 mmol l(-1)) adjusted with beta-alanine to pH 2.9 plus 0.1% poly(vinylpyrrolidone) was used as the leading electrolyte and 10 mmol l(-1) nicotinic acid as the terminating electrolyte and hydrochloric acid (10 mmol l(-1)) including 5.5 mmol l(-1) 1,3-bis[tris(hydroxymethyl)methylamino]propane plus 0.1% poly(vinylpyrrolidone) was used as the leading electrolyte and 5 mmol l(-1) 2-morpholinoethanesulfonic acid as the terminating electrolyte. Linearity was observed from 0.008 to 0.100 mmol l(-1) with a coefficient of determination (r2) of 0.999. The separation of anions was achieved in less than 16 min. The minimal sample pretreatment and relatively low running cost make isotachophoresis a good alternative to existing methods.     

Determination of phenol in industrial waste water by isotachophoresis

Summary The present work deals with the isotachophoretic analysis of phenol in industrial waste water. By variation of pH, temperature, leading and terminating electrolytes an optimal system for the determination of phenol in waste water was found. All samples were examined without preliminary chemical or physical treatment and therefore a direct analysis of waste water containing phenol is possible. The limit of the sensitivity for phenol is 0.1 ppm. The second part of this work concerns the separation of phenolic compounds, such as phenol, p-cresol and vanillin using the method described.

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Bestimmung von Phenol im Industrieabwasser mittels Isotachophorese

Zusammenfassung Die vorliegende Arbeit beschäftigt sich mit der isotachophoretischen Analyse von Phenol im Abwasser von Industriebetrieben. Durch Variation von pH, Temperatur sowie der leading und terminating Elektrolytlösungen wurde ein optimales System zur Analyse von Phenol im Abwasser erstellt. Alle Proben wurden ohne chemische oder physikalische Vorbehandlung untersucht, somit kann eine direkte Analyse zur Bestimmung von Phenol durchgeführt werden. Die Bestimmungsgrenze für Phenol in diesem System liegt bei 0,1 ppm. Ein zweiter Teil dieser Arbeit beschäftigt sich mit der Trennung von Phenol, p-Kresol und Vanillin unter den beschriebenen Analysenbedingungen.

     

Determination of ammonium ion in sea-water by capillary isotachophoresis

A new procedure for determination of ammonium ion in sea-water by means of capillary isotachophoresis and a gas-liquid separator with a tubular microporous polytetrafluoroethylene membrane for preliminary enrichment has been developed. Ammonia generated by adding sodium hydroxide solution to the sea-water samples is allowed to permeate through the membrane and then dissolve in sulphuric acid. A linear calibration graph has been obtained with artificial sea-water samples containing up to 300 mug/1. ammonium ion. The method has been applied to the determination of ammonium ion in surface and bottom sea-water samples.     

Determination of inorganic anions in saliva by capillary isotachophoresis

Nitrite, nitrate, iodide and thiocyanate have been quantified in non-smoker and smoker saliva by capillary isotachophoresis (CITP). Hydrochloric acid (10 mmol l⁻¹) adjusted with histidine to pH 6.0 plus 6% poly(vinylpyrrolidone) was used as the leading electrolyte (LE) and 5 mmol l⁻¹ acetic acid as the terminating electrolyte (TE). Linearity was observed from 0.005 to 0.500 mmol l⁻¹ with a coefficient of determination (r²) of 0.999. The separation of anions was achieved in less than 19 min. The minimal sample pretreatment and relatively low running cost make isotachophoresis good alternative to existing methods.     

Determination of ethyl glucuronide in human serum by hyphenation of capillary isotachophoresis and zone electrophoresis

The determination of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in human serum by hyphenation of capillary ITP (CITP) and CZE is reported. For CITP step, 1 x 10(-2) M hydrochloric acid adjusted with epsilon-aminocaproic acid (EACA) to pH 4.4 was used as the leading electrolyte, and 1 x 10(-2) M nicotinic acid with EACA, pH 4.4, was used as the terminating electrolyte (TE). All electrolytes contained 0.2% hydroxypropylcellulose to suppress electroosmosis. In CITP, EtG was separated from fast serum macrocomponents chloride, phosphate, lactate, and acetate. Zones of microcomponents including EtG that migrated between acetate and nicotinate were forwarded to the second capillary filled with a BGE identical with the TE. Conductivity detection was used in the CITP step. Sensitive detection in the CZE step was performed using indirect spectrophotometric detection at 254 nm. The assay is based on a 1:5 dilution of serum with deionized water and has a concentration LOD for EtG in diluted sample of 9.8 x 10(-9) M. The method was used for the determination of EtG in sera of volunteers consuming alcohol.     

Determination of fluoride in feed mixtures by capillary isotachophoresis

An isotachophoretic (ITP) method for the determination of fluoride in feed mixtures was developed. A sample of feed mixture, after extraction with 1 M HCl, was analysed using a ZKI 02 column-coupling isotachopherograph. Leading electrolytes for presentation and analytical capillaries consisted of 0.008 M HCl-0.022 M -aminocaproic acid (EACA)-0.001 M CaCl₂-0.05% hydroxypropylmethyl cellulose (HPMC) and 0.002 M HCl-0.005 M EACA-0.05% HPMC, respectively. The terminating electrolyte was 0.01 M tartaric acid. The fluoride released from samples by microdiffusion in 25% perchloric acid was determined using an Ionosep 900.1 single capillary isotachopherograph with 0.002 M HCl-0.005 M EACA-0.05% HPMC as the leading electrolyte and 0.002 M tartaric acid as the terminating electrolyte. The detection limit, depending on the sample treatment, was as low as 4 μg/g as fluoride. A comparison of the developed ITP method with ion- selective electrode method was carried out.