Quantification of trovafloxacin in serum by high-performance liquid chromatography with on-line solid-phase extraction

Summary A rapid, simple, accurate and sensitive liquid chromatographic assay with on-line solid-phase extraction is described for determination of trovafloxacin in human serum. Samples were deproteinized with acetonitrile and injected on to an NH₂ extraction column for sample clean-up. Thereafter, an on-line column-switching system was used for quantitative transfer of the drug to a C₁₈ analytical column. Separation was performed by ion-pair chromatography and detection was by ultraviolet absorbance at 275 nm. Recovery was 98.5%. The linear range was from 0.25 to 20μg mL⁻¹, with a correlation coefficient of 0.999. Detection limit was 0.1 μg mL⁻¹ from extraction of 25 μL serum.     

Application of co-electroosmotic capillary electrophoresis for the determination of inorganic anions and carboxylic acids in soil and plant extract with direct UV detection

Summary Indirect UV detection in capillary zone electrophoresis (CZE) is frequently used for the determination of inorganic anions and carboxylic acids. However, there are few reports on direct UV detection of these solutes in real samples. This paper describes the use of direct UV detection of inorganic anions and organic acids in environmental samples using co-electroosmotic capillary zone electrophoresis (co-CZE) at 185 nm. The best separation and detection of the solutes was achieved using a fused silica capillary with an electrolyte containing 25 mM phosphate, 0.5 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile (v/v) at pH 6.0. Four common inorganic anions (Cl⁻, NO₂ ⁻, NO₃ ⁻ and SO₄ ²⁻) and 11 organic acids (oxalic, formic, fumaric, tartaric, malonic, malic, citric, succinic, maleic, acetic, and lactic acid), were determined simultaneously in 15 min. Linear calibration plots for the test solutes were obtained in the range 0.02–0.5 mM with detection limits ranging from 1–9 μM depending on the analyte. The proposed method was successfully used to determine inorganic anions and carboxylic acids in soil and plant tissue extracts with direct injection of the sample.     

Rapid separation of basic drugs by nonaqueous capillary electrophoresis

Summary Nonaqueous capillary electrophoresis (NACE) has been used to achieve rapid separations of basic drugs. A high electric field was obtained by using short capillaries. Baseline separations of basic drugs, including amphetamines, tropane alkaloids and local anesthetics, were achieved in 1 min by selection of the appropriate organic solvent and electrolyte composition. Thus, high-throughput analyses can be performed. Peak efficiency up to 9154 theoretical plates s⁻¹ was achieved in a separation performed at 923V cm⁻¹. No discernible loss in resolution was observed when a conventional capillary (64.5cm) was replaced by a short (32.5 cm) capillary.     

On-line monitoring of gas-phase bioreactors for biogas treatment: hydrogen sulfide and sulfide analysis by automated flow systems

Biogas is produced by biological processes under anaerobic conditions and may contain up to 20,000 ppm_v hydrogen sulfide (H₂S), a corrosive substance that attacks power engines and can affect the health of the industrial staff. H₂S must be removed from the biogas, especially in co-generation facilities where the biogas is burnt for energy production. Nowadays, biofiltration is being studied and considered as an interesting alternative for removing H₂S from the biogas besides classical chemical processes. The novelty of this work is the design and construction of an automated H₂S on-line analyser to assess the composition of the liquid and gas phases of gas-phase bioreactors. The analyser is made of two parallel flow configurations which share the same detection device. The first configuration is a single-channel flow injection analyser (FIA) to detect S²⁻ in the liquid phase. The second configuration is a continuous flow analyser (CFA) with a gaseous diffusion step (GD–CFA) for detecting H₂S in the gas phase. The diffusion step enables separation of the H₂S_(g) from the sample and its conversion into a detectable chemical species (S²⁻). S²⁻ detection was performed with an Ag₂S ion-selective electrode (ISE) selective to . The main response parameters of the FIA system are a linear range between 3 × 10⁻⁵ and 1 × 10⁻¹ mol L⁻¹ S²⁻ (0.61–3,200 mg L⁻¹), with a sensitivity of 27.9 mV decade⁻¹ and a detection limit of 1.93 × 10⁻⁵ mol L⁻¹ S²⁻. The GD–CFA configuration presents a linear range between 400 and 10,000 ppm_v H₂S_(g) with a sensitivity of 26.1 mV decade⁻¹ and a detection limit of 245 ppm_v H₂S. The proposed analyser was used by analysing real gas and liquid samples with optimal results at a full-scale biotrickling filter for biogas treatment at a municipal wastewater treatment plant. Figure The novelty of this work is the design and construction of an automated H₂S on-line analyzer to assess the composition of the liquid and gas phases of gas-phase bioreactors. The analyser is made of two parallel flow configurations which share the same detection device. The first configuration is a single-channel flow injection analyser (FIA) to detect S^2- in the liquid phase. The second configuration is a continuous flow analyser (CFA) with a gaseous diffusion step (GD-CFA) for detecting H₂S in the gas phase.     

Simultaneous Determination of Lidocaine, Proline and Lomefloxacin in Human Urine by CE with Electrochemiluminescence Detection

A new method was developed for the simultaneous determination of lidocaine, proline and lomefloxacin in human urine by capillary electrophoresis-electrochemiluminescence detection with Ru(bpy)₃ ²⁺. Conditions of the separation and detection were investigated and optimized. It was proved that 20 mM phosphate buffer at pH 6.7 could achieve the most favorable resolution, and the high sensitivity of detection was obtained by using the detection potential at 1.15 V and 5 mM Ru(bpy)₃ ²⁺–60 mM phosphate buffer at pH 7.6 in the detection reservoir. The detection limits were 0.02 μg mL⁻¹ for lidocaine, 0.03 μg mL⁻¹ for proline and 0.06 μg mL⁻¹ for lomefloxacin. Relative standard deviations of the ECL intensity and the migration time were 3.5 and 1.1% for 6 μg mL⁻¹ lidocaine, 3.2 and 1.0% for 6 μg mL⁻¹ proline and 3.7 and 1.2% for 6 μg mL⁻¹ lomefloxacin, respectively. A baseline separation for lidocaine, proline and lomefloxacin was achieved within 360 s. The developed method was successfully applied to determine the amounts of lidocaine, proline and lomefloxacin in human urine. The recovery and RSD were in the range of 93.3–97.2 and 3.8–4.9%, respectively.     

Determination of human serum albumin using aurothiomalate as electroactive label

A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I) bound to the anti-HSA was electrodeposited in 0.1 mol L⁻¹ HCl at −1.00 V for 5 min then oxidised in 0.1 mol L⁻¹ H₂SO₄ solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were then performed in aqueous 1.0 mol L⁻¹ NH₃–2.0×10⁻⁴ mol L⁻¹ AgNO₃. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10⁻¹⁰ to 1.0×10⁻⁸ mol L⁻¹ and 1.0×10⁻¹⁰ to 1.0×10⁻⁹ mol L⁻¹ HSA, respectively, with estimated detection limits of 1.5×10⁻¹⁰ mol L⁻¹ (10 ng mL⁻¹) and 1.0×10⁻¹⁰ mol L⁻¹ (7 ng mL⁻¹), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay formats.     

Detection of transferrin isoforms in human serum: comparison of UV and ICP–MS detection after CZE and HPLC separations

Two methods for separation of transferrin (Tf) sialoforms, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) with conventional UV absorbance detection, have been investigated and compared. First, conditions affecting the separation of the Tf isoforms by capillary zone electrophoresis and HPLC were carefully optimized. The use of 15 mmol L⁻¹ borate buffer (pH 8.4) containing 3 mmol L⁻¹ diaminobutane (DAB) as additive enabled good separation of the Tf isoforms by CE (75 cm×50 μm i.d. fused silica capillary) at 25 kV. In HPLC, a gradient of ammonium acetate (from 0 to 250 mmol L⁻¹ in 45 min) buffered at pH 6 (Tris-HCl) proved suitable for separation of Tf isoforms on a Mono-Q HR 5/5 anion-exchange column. On-line specific detection of the iron associated with the different Tf isoforms, after Fe saturation, by inductively coupled plasma mass spectrometry (ICP–MS) was studied in detail to compare its analytical performance with UV detection. For both CE and HPLC an octapole reaction system (ORS) ICP–MS instrument was used to minimize polyatomic interferences on the ⁵⁶Fe major isotope. Limits of detection of the different isoforms were in the range of 0.02–0.04 μmol L⁻¹ Tf for HPLC–ICP (ORS)–MS. This hybrid technique proved more selective and reliable detection of transferrin isoforms with 2, 3, 4, 5, and 6 sialic acid residues (S₂, S₃, S₄, S₅, and S₆) in real serum samples. Interesting results from iron speciation of Tf in serum from healthy individuals and from pregnant women are given.     

Polar herbicides,pharmaceutical products,perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and nonylphenol and its carboxylates and ethoxylates in surface and tap waters around Lake Maggiore in Northern Italy

A survey of contamination of surface and drinking waters around Lake Maggiore in Northern Italy with polar anthropogenic environmental pollutants has been conducted. The target analytes were polar herbicides, pharmaceuticals (including antibiotics), steroid estrogens, perfluorooctanesulfonate (PFOS), perfluoroalkyl carboxylates (including perfluorooctanoate PFOA), nonylphenol and its carboxylates and ethoxylates (NPEO surfactants), and triclosan, a bactericide used in personal-care products. Analysis of water samples was performed by solid-phase extraction (SPE) then liquid chromatography–triple-quadrupole (tandem) mass spectrometry (LC–MS–MS). By extraction of 1-L water samples and concentration of the extract to 100 μL, method detection limits (MDLs) as low as 0.05–0.1 ng L⁻¹ were achieved for most compounds. Lake-water samples from seven different locations in the Southern part of Lake Maggiore and eleven samples from different tributary rivers and creeks were investigated. Rain water was also analyzed to investigate atmospheric input of the contaminants. Compounds regularly detected at very low concentrations in the lake water included: caffeine (max. concentration 124 ng L⁻¹), the herbicides terbutylazine (7 ng L⁻¹), atrazine (5 ng L⁻¹), simazine (16 ng L⁻¹), diuron (11 ng L⁻¹), and atrazine-desethyl (11 ng L⁻¹), the pharmaceuticals carbamazepine (9 ng L⁻¹), sulfamethoxazole (10 ng L⁻¹), gemfibrozil (1.7 ng L⁻¹), and benzafibrate (1.2 ng L⁻¹), the surfactant metabolite nonylphenol (15 ng L⁻¹), its carboxylates (NPE₁C 120 ng L⁻¹, NPE₂C 7 ng L⁻¹, NPE₃C 15 ng L⁻¹) and ethoxylates (NPE _n Os, n = 3-17; 300 ng L⁻¹), perfluorinated surfactants (PFOS 9 ng L⁻¹, PFOA 3 ng L⁻¹), and estrone (0.4 ng L⁻¹). Levels of these compounds in drinking water produced from Lake Maggiore were almost identical with those found in the lake itself, revealing the poor performance of sand filtration and chlorination applied by the local waterworks.     

A microfluidic system for evaluation of antioxidant capacity based on a peroxyoxalate chemiluminescence assay

A microfluidic system incorporating chemiluminescence detection is reported as a new tool for measuring antioxidant capacity. The detection is based on a peroxyoxalate chemiluminescence (PO-CL) assay with 9,10-bis-(phenylethynyl)anthracene (BPEA) as the fluorescent probe and hydrogen peroxide as the oxidant. Antioxidant plugs injected into the hydrogen peroxide stream result in inhibition of the CL emission which can be quantified and correlated with antioxidant capacity. The PO-CL assay is performed in 800-μm-wide and 800-μm-deep microchannels on a poly(dimethylsiloxane) (PDMS) microchip. Controlled injection of the antioxidant plugs is performed through an injection valve. Of the plant-food based antioxidants tested, β-carotene was found to be the most efficient hydrogen peroxide scavenger (SA _HP of 3.27 × 10⁻³ μmol⁻¹ L), followed by α-tocopherol (SA _HP of 2.36 × 10⁻³ μmol⁻¹ L) and quercetin (SA _HP of 0.31 × 10⁻³ μmol⁻¹ L). Although the method is inherently simple and rapid, excellent analytical performance is afforded in terms of sensitivity, dynamic range, and precision, with RSD values typically below 1.5%. We expect our microfluidic devices to be used for in-the-field antioxidant capacity screening of plant-sourced food and pharmaceutical supplements. Figure Assembled PDMS microchip sandwiched between two glass plates with the top plate containing capillary reservoirs     

Multisyringe flow injection analysis hyphenated with liquid core waveguides for the development of cleaner spectroscopic analytical methods: improved determination of chloride in waters

In this work, the hyphenation of the multisyringe flow injection analysis technique with a 100-cm-long pathlength liquid core waveguide has been accomplished. The Cl⁻/Hg(SCN)₂/Fe³⁺ reaction system for the spectrophotometric determination of chloride (Cl⁻) in waters was used as chemical model. As a result, this classic analytical methodology has been improved, minimizing dramatically the consumption of reagents, in particular, that of the highly biotoxic chemical Hg(SCN)₂. The proposed method features a linear dynamic range composed of two steps between (1) 0.2–2 and (2) 2–8 mg Cl⁻ L⁻¹, thus extended applicability due to on-line sample dilution (up to 400 mg Cl⁻ L⁻¹). It also presents improved limits of detection and quantification of 0.06 and 0.20 mg Cl⁻ L⁻¹, respectively. The coefficient of variation and the injection throughput were 1.3% (n = 10, 2 mg Cl⁻ L⁻¹) and 21 h⁻¹. Furthermore, a very low consumption of reagents per Cl⁻ determination of 0.2 μg Hg(II) and 28 μg Fe³⁺ has been achieved. The method was successfully applied to the determination of Cl⁻ in different types of water samples. Finally, the proposed system is critically compared from a green analytical chemistry point of view against other flow systems for the same purpose.     

Preconcentration technique for manganese by adsorption onto a tantalum wire for tungsten tube atomizer electrothermal atomization atomic absorption spectrometry

A multi-pumping flow system for the spectrophotometric determination of nitrite and nitrate is described. The determination of nitrite is based on the Griess-Ilosvay reaction. Nitrate can be determined after its on-line reduction to nitrite using hydrazine sulphate in alkaline medium. Calibration was linear up to 3 mg NO₂ ⁻ L⁻¹ with a limit of detection (3s_b/S) of 0.013 mg NO₂ ⁻ L⁻¹ an injection throughput of 55 injections h⁻¹ and a repeatability (RSD) of 0.5% for the direct determination of nitrite. Two calibration graphs within the ranges 0.039–7 mg NO₃ ⁻ L⁻¹ and 0.026–5 mg NO₂ ⁻ L⁻¹ were run for the determination of nitrate and nitrite under reducing conditions, respectively. A limit of detection of 0.039 mg NO₃ ⁻ L⁻¹ was obtained. An injection throughput of 27 injections h⁻¹ and an RSD lower than 1.5% were achieved. The method was successfully applied to the determination of nitrite and nitrate in water samples. Correspondence: Víctor Cerdà, Department of Chemistry, University of the Balearic Islands, Carretera de Valldemossa Km7.5, 07122 Palma de Mallorca, Spain     

Simultaneous Determination of Baicalin, Baicalein, Wogonin, Oxysophocarpine, Oxymatrine and Matrine in the Chinese Herbal Preparation of Sanwu-Huangqin-Tang by Ion-Paired HPLC

A sensitive and reliable ion-paired high-performance liquid chromatographic method has been established for the simultaneous quantification of six major active ingredients, namely baicalin, baicalein, wogonin, oxysophocarpine, oxymatrine and matrine in the Chinese herbal preparation, Sanwu-Huangqin-Tang. HPLC analyses were performed on a Phenomenex luna C₁₈ column with mobile phase of methanol–acetonitrile–aqueous phosphoric acid at a flow rate of 0.9 mL min⁻¹. The complete separation was achieved within 35 min for the six target constituents. A good linear regression relationship between peak-areas and concentrations was obtained over the range of 12.10–242.0 μg*mL⁻¹ for baicalin, 5.05–101.0 μg*mL⁻¹ for baicalein, 0.95–19.0 μg*mL⁻¹ for wogonin, 2.75–55.0 μg*mL⁻¹ for oxysophocarpin, 2.75–55.0 μg*mL⁻¹ for oxymatrine and 4.90–98.0 μg*mL⁻¹ for matrine, respectively. The repeatability was evaluated by intra- and inter-day assays with relative standard deviation (RSD) being less than 5.1%. The recoveries, measured at three concentration levels, varied from 93.8 to 102.1%. The assay was successfully applied for determination of six bioactive compounds in Sanwu-Huangqin-Tang. The interaction of chemical constituents was observed when the herbs were used in compatibility. The results indicated that the developed assay method was rapid, accurate and could be readily utilized as a quality control method for Sanwu-Huangqin-Tang.     

Simultaneous separation of nitrate, nitrite and ammonium by capillary electrophoresis

Summary A capillary electrophoretic method for the simultaneous separation of nitrate, nitrite and ammonium has been developed. Direct (NO₃ ⁻, NO₂ ⁻) and indirect (NH₄ ⁺) UV detection at 214 nm in conjunction with electromigration sampling from both ends of the capillary was used. Two electrolyte systems based on imidazole-sulfate (pH 3.8) and copper(II)-ethylenediamine-chloride (pH 8.0) were investigated. Optimisation of the experimental parameters such as electrolyte concentration, pH, nature of the counter-ion, was studied. The method permits excellent separation of three nitrogen species in only 4 min. The analytical performance of both electrolyte systems is compared in terms of migration time and peak area repeatability and detectability. Alkaline electrolyte shows a better overall analytical performance.     

Capillary electrophoretic speciation of Cu(II) and Co(III) in the electroless copper plating baths

Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.) filled with an ethylenediamine sulfate electrolyte (20 mol L⁻¹ ethylendiamine, pH7.0 with H₂SO₄; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s hydrodynamic injection were 5×10⁻⁶ mol L⁻¹ for Cu(II) and 1×10⁻⁶ mol L⁻¹ for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively, with five consecutive injections of standard solution containing 5×10⁻⁵ mol L⁻¹ of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples is also demonstrated.     

Determination of magnesium,calcium, sodium,and potassium in blood plasma samples by capillary zone electrophoresis

A capillary zone electrophoretic assay has been developed and validated for analysis of magnesium, calcium, sodium, and potassium in blood plasma samples. Optimum results were obtained with 20 mmol L⁻¹ imidazole (pH 2.8) and 0.5 mmol L⁻¹ oxalic acid containing 5% methanol, capillary temperature 25°C, applied voltage 30 kV, hydrodynamic injection time 3 s, and a poly(vinyl alcohol)-coated capillary (i.d. 50 μm, total length 64.5 cm and effective length 56 cm). Indirect detection was performed at 214 nm. Cadmium was used as internal standard. The migration times of magnesium, calcium, sodium, and potassium were 4.25, 3.79, 3.96, and 2.79 min, respectively. The method was applied to the determination of magnesium, calcium, sodium, and potassium in blood plasma samples. The results were compared with those from atomic absorption spectrophotometry and no statistically significant difference was found (P>0.05). This study was supported by the Turkish Republic, Prime Ministry State Planning Organization (Project Number: 98K121730)     

Flow injection on-line hydrophobic sorbent extraction for flame atomic absorption spectrometric determination of cadmium in water samples

A flow injection system was developed for on-line sorbent extraction preconcentration and flame atomic absorption spectrometric determination of cadmium in natural water samples. The non-charged cadmium complex with diethyl-dithiophosphate (DDPA) was formed on-line in 0.1 mol L⁻¹ HNO₃ and retained on the hydrophobic poly-chlorotrifluoroethylene (PCTFE) sorbent material. The adsorbed complex was eluted with isobutyl methylketone (IBMK) and injected directly into the nebulizer via a flow compensation unit. All major chemical and flow parameters affecting the complex formation adsorption and elution as well as interference were studied and optimized. By processing 2.4 mL of sample, the enhancement factor was 39 and the sampling frequency was 50 h⁻¹. For 30 s preconcentration time the detection limit was 0.3 μg L⁻¹ and the relative standard deviation at 5.0 μg L⁻¹ Cd concentration level was 2.9%. The calibration curve was linear in the range 0.8–40.0 μg L⁻¹. The accuracy of the method was estimated by analyzing a certified reference material NIST-CRM 1643d (Trace elements in water). Good recoveries were obtained for spiked natural-water and waste-water samples. Correspondence: Aristidis N. Anthemidis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, GR-Thessaloniki 54124, Greece     

Determination of ibuprofen and tetrazepam in human urine by micellar electrokinetic capillary chromatography

A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm × 75 μm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 °C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction–preconcentration step with a preconditioned C₁₈ cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 μg L⁻¹ for ibuprofen and 300 μg L⁻¹ for tetrazepam were obtained. These analytes were then determined in real urine using the technique.     

New ionic liquid for inorganic cations analysis by capillary electrophoresis: 2-hydroxy- N , N , N -trimethyl-1-phenylethanaminium bis(trifluoromethylsulfonyl)imide (phenylcholine NTf2)

The potentialities of new ionic liquids (ILs) based on choline were evaluated as an electrophoretic medium in capillary electrophoresis for the analysis of alkaline and alkaline earth cations (Li⁺, K⁺, Na⁺, Cs⁺, Mg²⁺, Ba²⁺, Ca²⁺, and Sr²⁺) with indirect UV detection. Two types of capillaries were tested: an untreated fused silica and fused silica coated with a film of polyvinylalcohol. The coated capillary proved to be the best adapted for the metal ions studied. Moreover, it appeared that the nature of the ionic liquid anion influenced the baseline stability, and the bis(trifluoromethylsulfonyl) imide (NTf₂ ⁻) anion seemed to be the most efficient. These preliminary studies led us to synthesize a new ionic liquid, 2-hydroxy-N,N,N-trimethyl-1-phenylethanaminium NTf₂ (phenylcholine NTf₂). This liquid was able to act as the running electrolyte and probe, generating the background signal in indirect UV light and consequently simplifying the electrophoretic medium. Excellent baseline stability, good reproducibility, as well as good sensitivity of detection were obtained with this new ionic liquid. Thus, 510,000 plates/meter for Li⁺ with 40 mM IL were successfully obtained. The optimal concentration of IL was 20 mM with a detection limit ranging from 28 μg L⁻¹ for Li⁺ to 1,000 μg L⁻¹ for Cs⁺. This method (phenylcholine NTf₂ with polyvinylalcohol capillary) was applied to analyze different commercial source and mineral waters. Finally, the potentiality of this ionic liquid in nonaqueous capillary electrophoresis was explored. The use of phenylcholine NTf₂ with a fused silica capillary, in pure methanol medium and in the presence of acetic acid, made it possible to obtain separation selectivity different from that obtained in aqueous medium.     

Direct GC determination of methylmercury chloride on HBr-methanol-treated capillary columns

Summary Gas chromatography with electron capture detection (GC-ECD) for the analysis of methylmercury choloride (MMC) using a packed column and a capillary column has been investigated. The columns were 2% silicone OV-227 Uniport HP glass column and a DB-17 capillary column, each pretreated by about ten injections of HBr-methanol solution. MMC was separated as a sharp peak by the HBr-teated column and determined directly by ECD without derivatisation. The mass spectrum of MMC indicated that halide exchange from chloride to bromide proceeded during separation. The minimum detectable concentrations were approximately 5 ng mL⁻¹ on the packed column, and 2 ng mL⁻¹ on the capillary. Calibration curves showed good linearity between 5–200 ng mL⁻¹ for the packed column, and between 2–200 ng mL⁻¹ for the capillary. Relative standard deviations of peak areas were 0.95% for the packed column and 0.43% for the capillary at the level of 100 ng mL⁻¹ in both cases. The column treatment technique was applicable to determination of methylmercury in fish samples.     

Kinetic, spectral and redox properties of the transients formed on one-electron reduction of 3, 3, 6, 6-tetramethyl-3, 4, 6, 7, 9-pentahydro-10-phenyl (1, 8) (2H, 5H) acridinedione in aqueous-organic mixed solvent system: A pulse radiolysis study

The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH₃)₂*COH radicals with a bimolecular rate constant of 0.6 × 10⁸ dm³ mol⁻¹ s⁻¹ in acidic aqueous-organic mixed solvent system. The transient optical absorption band (λ_max = 465 nm, ɛ = 6.8 × 10² dm³ mol⁻¹ cm⁻¹) is assigned to ADH* formed on protonation of the radical anion. In basic solutions, (CH₃)₂*COH radicals react with a bimolecular rate constant of 4.6 × 10⁸ dm³ mol⁻¹ s⁻¹ and the transient optical absorption band (λ_max = 490 nm, ɛ = 10.4 × 10³ dm³ mol⁻¹ cm⁻¹) is assigned to radical anion, AD*⁻, which has a pK_a value of 8.0. The reduction potential value of the AD/AD*⁻ couple is estimated to be between −0.99 and −1.15 V vs NHE by pulse radiolysis studies. The cyclic voltammetric studies showed the peak potential close to −1.2 V vs Ag/AgCl.