Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.562, #2)

Contents (pp. iii-iv).

Outside front cover - Editorial Board (pp. co1).

Obituary by Lutgarde Buydens (pp. 135-136).

Microchip-electrochemistry route for rapid screening of hydroquinone and arbutin from miscellaneous samples: Investigation of the robustness of a simple cross-injector system by Agust�n G. Crevill�n; In�s Barrigas; Antonio Javier Blasco; Mar�a Cristina Gonz�lez; Alberto Escarpa (pp. 137-144).

This work examines in deep the analytical performance of an example of “first-generation�? microdevices: capillary electrophoresis microchip (CE) with end-channel electrochemical detection (ED). A hydroquinone and arbutin separation strategically chosen as route involving pharmaceutical–clinical testing, public safety and food control scenes was carried out. The reproducibility of the unpinched electrokinetic protocol was carefully studied and the technical possibility of working indiscriminately and/or sequentially with both simple cross-injectors was also demonstrated using a real sample (R.S.D.'s less than 7%). The robustness of the injection protocol allowed checking the state of the microchip/detector coupling and following the extraction efficiency of the analyte from real sample. Separation variables such as pH, ionic strength and, separation voltage were also carefully assayed and optimized. Analyte screening was performed using borate buffer (pH 9, 60mM) in less than 180s in the samples studied improving dramatically the analysis times used for the same analytes on a conventional scale (15min), with good precision (R.S.D.'s ranging 5–10%), accuracy (recoveries ranging 90–110%) and acceptable resolution (Rs≥1.0).In addition, the excellent analytical performance of the overall analytical method indicated the quality of the whole analytical microsystem and allowed to introduce the definition of robustness for methodologies developed into the “lab-on-a-chip�? scene.

Keywords: Capillary electrophoresis microchip; Electrochemical detection; Injection protocol; Robustness; Hydroquinone and arbutin

Novel enrofloxacin imprinted polymer applied to the solid-phase extraction of fluorinated quinolones from urine and tissue samples by Ester Caro; Rosa M. Marc�; Peter A.G. Cormack; David C. Sherrington; Francesc Borrull (pp. 145-151).

A new molecularly imprinted polymer, prepared following a non-covalent approach, was synthesised using enrofloxacin as a template molecule. The imprinting effect of the polymer was verified by chromatographic evaluation and, interestingly, this evaluation also revealed that the imprinted polymer showed a high degree of cross-reactivity for ciprofloxacin, the major metabolite of enrofloxacin. The molecularly imprinted polymer was then applied as a selective sorbent in a two-step solid-phase extraction method focussing upon complex biological matrices, specifically human urine and pig liver. This two-step solid-phase extraction protocol, in which a commercial Oasis HLB cartridge and a molecularly imprinted solid-phase extraction cartridge were combined, allowed enrofloxacin and ciprofloxacin to be determined by liquid chromatography coupled to a UV detector at levels below the maximum residue limits established by the European Union. The quantification and detection limits in tissue samples of enrofloxacin and ciprofloxacin were established at 50μgkg⁻¹ and 30μgkg⁻¹, respectively.

Keywords: Molecular imprinting; Solid-phase extraction; Fluorinated Quinolones; Urine sample; Tissue sample

Factorial design optimization of solid phase microextraction conditons for gas chromatography–mass spectrometry (GC–MS) analysis of linear alkylbenzenes (LABs) in detergents by Jos� C. Penteado; Roy E. Bruns; Lilian R. Franco de Carvalho (pp. 152-157).

Linear alkylbenzenes (LABs) are discharged into the environment as sub-products of linear alkylbenzenesulfonate (LAS) detergent. Their association with LAS is attributed to the incomplete sulfonation of the LABs in detergent manufacturing resulting in products having LAB. Recently there has been widespread interest in their use as markers of sewage effluent in the aquatic environment. Although LABs may be potentially useful in assessing the distribution and degradation of domestic wastewater, studies about it are still limited probably due to the analytical difficulties.In this article, a new analytical method for the determination of LABs in detergents using gas chromatography coupled to mass spectrometry (GC–MS) in combination with solid phase microextraction (SPME) is proposed. This alternative sample preparation technology presents several advantages, since it is solvent free, fast, uses the whole sample for analysis, requires only small amounts of sample and the fibers for the extraction procedure are reusable. A factorial experimental design was utilized to obtain the optimum values for the main operational parameters in the analysis of LABs in detergents using direct SPME in the pre-concentration step.

Keywords: Linear alkylbenzenes; Detergents; Solid phase microextraction; Gas chromatography–mass spectrometry; Factorial experimental design

Enhancing the microdialysis recovery for sampling of Cu and Ni by incorporating humic acid in the perfusion liquid by Kabo Mosetlha; Nelson Torto; Grethe Wibetoe (pp. 158-163).

A strategy to enhance the microdialysis relative recovery for sampling of Cu and Ni ions is presented. Enhanced recovery was achieved by incorporating humic acid, a binding agent, in the microdialysis perfusion liquid during sampling from a Cu and Ni standard solution mixture. All microdialysis sampling experiments were carried out at room temperature under quiescent conditions using a concentric type of microdialysis probe with an adjustable effective dialysis length. For all metal determinations electrothermal atomic absorption spectrometry was employed. Metal recoveries were shown to be dependent on the membrane molecular weight cut-off, perfusion rate, sample solution pH, perfusion liquid composition as well as perfusion liquid pH. Complete recoveries (100%) of Cu and Ni were obtained by microdialysis sampling using a 10kDa molecular weight cut-off polysulfone membrane at a flow-rate of 2μl/min employing a 0.05% (w/v) optimal composition of humic acid incorporated in the perfusion liquid. The optimal sampling pH of humic acid was determined to be 6 where most oxygen containing functional groups are dissociated and available for metal binding. These data have important ramifications for sampling and determination of metal ions in small sample solutions (∼10ml) at very low concentrations in the ppb range.

Keywords: Microdialysis sampling; Metal ions; Humic acid; Enhanced recovery

New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid–molecular solvent mixtures by Y. Fran�ois; K. Zhang; A. Varenne; P. Gareil (pp. 164-170).

The low vapor pressure and the versatility of the physico-chemical properties of ionic liquids make them really attractive as an alternative for conventional molecular solvents. The knowledge of their physico-chemical properties (viscosity, conductivity, miscibility with organic solvents and anion–cation interactions) has appeared mandatory for better targeting their applications, although it is generally still lacking or incomplete.This work promotes capillary electrophoresis instrumentation as an integrated apparatus for measurement of viscosity, conductivity and absorbance of pure ionic liquids and ionic liquid–molecular solvent mixtures. Compared to current conventional techniques, the assets of this instrumentation for this purpose are the combined availability of a pressure delivery system, power supply, diode array absorbance detector and thermoregulation device, allowing unattended, automatic and easy operation, involving minimum sample handling. Most importantly, the required sample volume can be reduced to about 50μL, making this protocol very cost-effective. A protocol was optimized with respect to time, sample consumption and data reliability for the determination of these physico-chemical parameters. Ionic liquids selected for method development and validation differed in the nature of their cation (butyl- and ethyl-methylimidazolium) and anion (trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide). Various molecular solvents were mixed with these ionic liquids (acetonitrile, methanol, dimethylformamide and trifluoroethanol) and the same physico-chemical properties were determined by optimized methods. The knowledge of these data should be of great support in various application areas, including the development of new separation media for capillary electrophoresis and chromatographic techniques.

Keywords: Ionic liquids; Ionic liquid–molecular solvent mixtures; Physico-chemical properties; Viscosity; Conductivity; UV-absorbance; Capillary electrophoresis

Determination of risedronate in rat plasma samples by ion-pair high-performance liquid chromatography with UV detector by Hui-Juan Jia; Wei Li; Kang Zhao (pp. 171-175).

In the present work, an analytical method for determination of risedronate, a member of bisphosphonates, is described for the routine analysis in rat plasma. Sample pre-treatment involves protein precipitation, co-precipitation with calcium at alkaline pH, hydrolysis of possible derivatives of pyrophosphate and reprecipitation. A good separation was obtained by using a reversed-phase column (Hypersil ODS-2 C₁₈, 4.6mm×250mm, 5μm). The mobile phase was an aqueous solution of buffer (contained 1.5mM EDTA-2Na, 1mM sodium etidronate, 11mM sodium phosphate and 5mM tetrabutylammonium bromide as ion-pair reagent) – methanol (88:12, v/v) adjusted to pH 6.75 using 1M NaOH. The flow rate was 1mlmin⁻¹. UV detection ( λ=262nm) was used to quantitate risedronate in the concentration range of 10–500ngml⁻¹. The limit of detection and quantitation for risedronate were 7 and 10ngml⁻¹, respectively. The method was applied successfully to plasma samples from Wistar rats undergoing oral administration of risedronate mini-pills. Precision, extraction recoveries, as well as accuracy results, were satisfactory and no interference was found at the retention time of risedronate. Hence, the method is suitable for monitoring risedronate in rat plasma.

Keywords: Risedronate sodium; High-performance liquid chromatography; Rat plasma; UV detection; Co-precipitation

Liquid chromatography with time-of-flight mass spectrometry for simultaneous determination of chemotherapeutant residues in salmon by M.D. Hernando; M. Mezcua; J.M. Su�rez-Barcena; A.R. Fern�ndez-Alba (pp. 176-184).

Liquid chromatography with time-of-flight mass spectrometry (LC–TOF-MS) method has been developed for simultaneous confirmation by accurate mass measurement and quantitative determination of antibiotics (enrofloxacin, oxolinic acid, flumequine, erythromycin), fungicides (malachite green MG, leucomalachite green LMG) and parasiticide (emamectin benzoate) residues in edible portion of salmon. Confirmation of chemotherapeutant residues has been based on the system of identification points (IPs) established in the Commission Decision 2002/657/EC concerning the use of mass spectrometry (MS) techniques. A validation study on matrix is presented evaluating accuracy in terms of precision ( λ_ppm 0.83–1.15) and trueness (0.22–0.70Da). Limits of detection (LODs) and limits of quantification (LOQs) were in ranges of 1–3 and 3–9μg/kg, below the maximum residue limits (MRLs) established in current EU legislation (100–200μg/kg) for these chemotherapeutants. Considering the EU guidelines, decision limits (CCα) and detection capabilities (CCβ) were determined (ranges of 103–218 and 107–234μg/kg, respectively) for authorised substances. For no authorised compounds (MG and LMG), LODs were 2 and 1μg/kg, respectively, but exceed the MRPL (minimum required performance limit) established in the legislation which corresponds to the sum of MG and LMG (2μg/kg). Acceptable intra-day and inter-day variability, in terms of relative standard deviation (R.S.D.) of the analytical method, were obtained (2–15%). Linearity was demonstrated from the LOQs of the analytes to 600μg/kg ( r>0.9991). The method has involved an extraction procedure based on solid–liquid extraction (SLE) with recoveries higher than 80% for most target chemotherapeutants, with exception of enrofloxacin (40%).

Keywords: Chemotherapeutant residues; Salmon; Liquid chromatography; Time-of-flight mass spectrometry

HPLC-ESI-MS analysis of Vitamin B₁₂ in food products and in multivitamins-multimineral tablets by Xubiao Luo; Bo Chen; Li Ding; Fei Tang; Shouzhuo Yao (pp. 185-189).

Methods for the determination of Vitamin B₁₂ remain limited due to their low sensitivity and poor selectivity. In the present work, a simple and sensitive HPLC-ESI-MS method for determining Vitamin B₁₂ in food products and in multivitamin-multimineral tablets was developed. Vitamin B₁₂ was extracted from food products with 50mM sodium acetate buffer (pH 4.0) in the presence of sodium cyanide. Total Vitamin B₁₂ content in food product can be obtained by efficient enzymatic hydrolysis to release the bound Vitamin B₁₂. Vitamin B₁₂ was quantified with ginsenoside Re as internal standard (I.S.) after their separations on a C₁₈ column with a gradient of mobile phase made of water and acetonitrile. MS with SIR mode at m/ z 930.8 was used for Vitamin B₁₂ quantification. The calibration graphs plotted with five concentrations of Vitamin B₁₂ was linear with a regression coefficient r²=0.9994. The intra-assay R.S.D. and the inter-assay R.S.D. were 2.6% ( n=5) and 3.5% ( n=6), respectively. The recoveries evaluated at spiking three different concentrations on fortified products were above 93%. The method has been applied successfully in the determination of Vitamin B₁₂ in fortified food products and multivitamin-multimineral tablets.

Keywords: Vitamin B; ₁₂; Fortified products; Liquid chromatography-lectrospray ionization-mass spectrometry; Food analysis

A new amperometric method for rapid detection of Escherichia coli density using a self-assembled monolayer-based bienzyme biosensor by Hui Tang; Wen Zhang; Ping Geng; Qingjiang Wang; Litong Jin; Zirong Wu; Min Lou (pp. 190-196).

A new amperometric method was developed for rapid detection of Escherichia coli ( E. coli) density using a bienzyme biosensor. The bienzyme biosensor was fabricated based on the covalent immobilization of laccase and horseradish peroxidase (HRP) at indium tin oxide (ITO) electrode by (3-aminopropyl) triethoxysilane (APTES) monolayer. The bienzyme biosensor showed a high sensitivity in determination of the polyphenolic compounds, which was microbially generated from the salicylic acid (SA) added into the culture medium during the course of E. coli metabolism. Since the amount of polyphenolic compounds depends on E. coli density, the bienzyme biosensor was applied for the rapid and high sensitive detection of E. coli density after the E. coli solution was incubated in culture medium with salicylic acid for 2.5h at 37�C. By chronoamperometry, the amplified response current was obtained at the bienzyme biosensor, due to the substrate recycling of the polyphenolic compounds driven by bienzyme-catalyzed oxidation and electrochemical reduction. The amplified response current at the biosensor was linear with the E. coli density ranging from 1.6�10³ to 1.0�10⁷cells/mL. The bienzyme biosensor could detect the E. coli density with a detection limit of 9.7�10²cells/mL within 3h.

Keywords: Escherichia coli; Amperometric method; Bienzyme biosensor; Self-assembled monolayer

A ratiometric approach for pH optosensing with a single fluorophore indicator by I. S�nchez-Barrag�n; J.M. Costa-Fern�ndez; A. Sanz-Medel; Marta Valledor; Francisco J. Ferrero; Juan Carlos Campo (pp. 197-203).

A new fiber-optic prototype of luminometer has been designed in order to perform ratiometric-based measurements for optical sensing purposes. The coupling of a pH-selective sensing phase to the fiber-optic prototype has been evaluated for robust pH optosensing in drinking water. The pH-sensitive material has been synthesized by entrapping a pH-sensitive luminescent indicator (mercurochrome) in a sol–gel inorganic matrix. The pH optosensing is based on the detection of pH-induced reversible changes in the mercurochrome fluorescent emission and in the light reflected by the sensing phase.The instrument has been constructed using low-cost and simple optoelectronic components. The active phase was excited by means of a visible 470nm high intensity light emitting diode (LED). The radiant power of the LED was modulated using a sinusoidal function so that scattered light due to light sources of different frequency than the modulating signal (e.g. sunlight) can be easily removed by adequate electronic filtering of the emission signal. Both the fluorescence emission from the dye and the sensing phase reflected light were collected in a bifurcated fiber-optic to allow the ratiometric measurement.Two different ratiometric approaches have been evaluated. The analytical performance of the pH optrode using both measurement methods have been compared, between them and with simple fluorescence intensity measurements, in terms of sensitivity, measurement range, response time, repeatability and insensitivity to changes in excitation light intensity.The applicability of the developed pH optrode and methods has been tested for pH analysis in tap and bottled still mineral water samples. The results obtained showed good agreement with the corresponding pH values provided by a commercial glass electrode.In this work, pH was selected as a model analyte to evaluate the performance of the proposed methodology, although other optical sensors for different applications/analytes could benefit of this approach.

Keywords: pH sensing; Ratiometric measurements; Fluorescence; Reflectance; Sol–gel technology

Ion-selective electrode for gallium determination in nickel alloy, fly-ash and biological samples by Sabry K. Mohamed (pp. 204-209).

A poly(vinyl chloride)-based membrane of 2,9-dimethyl-4,11-diphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene (DDTCT) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dibutyl butylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEP) and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Ga(III)-selective electrode. The best performance was observed with the membrane having the ligand–PVC–DBP–STB composition 1:4:1:1, which worked well over a wide concentration range (1.45×10⁻⁶ to 0.1molL⁻¹) with a Nernstian slope of 28.7mV per decade of activity between pH 4.0 and 10.0. This electrode showed a fast response time of 12s and was used over a period of 100 days with good reproducibility ( s=0.3mV). The selectivity coefficients for monovalent, divalent and trivalent cations indicate excellent selectivity for Ga(III) ions over a large number of cations. Anions such as Cl⁻ and SO₄²⁻ do not interfere and the electrode also works satisfactorily in partially water–alcohol medium. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents, i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate and used for the determination of gallium in nickel alloy, fly-ash and biological samples.

Keywords: A chelating complex; Ion-selective electrode; Gallium determination; Various samples analysis

5,10,15-Tris(pentafluorophenyl)corrole as highly selective neutral carrier for a silver ion-sensitive electrode by Xiao-Bing Zhang; Zhi-Xiang Han; Zheng-Hui Fang; Guo-Li Shen; Ru-Qin Yu (pp. 210-215).

A new highly selective silver(I) electrode was prepared with a PVC membrane using 5,10,15-tris(pentafluorophenyl)corrole as an electroactive material, 2-nitrophenyl octyl ether ( o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:3:62:32 (corrole:NaTPB: o-NPOE:PVC, w:w). The electrode exhibited linear response with a near Nernstian slope of 54.8mV/decade within the concentration range of 5.1×10⁻⁶ to 1.0×10⁻¹M silver ions, with a working pH range from 4.0 to 8.0, and a fast response time of <30s. Selectivity coefficients for Ag(I) relative to a number of interfering ions were investigated. The electrode is highly selective for Ag(I) ions over a large number of mono-, bi-, and tri-valent cations. Common interferents like Hg²⁺ and Cd²⁺ show very low interfering effect on the silver assay, which is valuable property of the proposed electrode. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The sensor was applied to the determination of silver in real ore samples with satisfied results.

Keywords: Potentiometric sensor; Silver(I) ion; Corrole; Neutral carrier

Sulfate-selective electrode and its application for sulfate determination in aqueous solutions by S.V. Lomako; R.I. Astapovich; O.V. Nozdrin-Plotnitskaya; T.E. Pavlova; Shi Lei; V.A. Nazarov; E.B. Okaev; E.M. Rakhman’ko; V.V. Egorov (pp. 216-222).

A sulfate-selective electrode based on the composition of a neutral carrier – n-hexyl 4-trifluoroacetylbenzoate – and a quaternary ammonium salt with improved steric accessibility of the exchange center – (2,3,4-tris-dodecyloxy)benzyltrimethylammonium chloride – has been proposed. The effect of plasticizer nature on the main electrode parameters has been studied, approaches for correct sulfate determination in natural objects have been formulated. Determination of sulfate in sea water, mineral water and urine by the methods of direct potentiometry and potentiometric titration has been performed. Relative error of sulfate determination in the samples investigated, did not exceed 7%.

Keywords: Ionometry; Sulfate-selective electrode; Quaternary ammonium salts; Sulfate determination

Impedimetric sensing of uranyl ion based on phosphate functionalized cysteamine self-assembled monolayers by Reza Karimi Shervedani; Seyed Ahmad Mozaffari (pp. 223-228).

A phosphate functionalized cysteamine self-assembled monolayer based on gold electrode is designed for uranyl ion (UO₂²⁺) detection. The response of the modified electrode is studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The EIS data are approximated using constant phase element (CPE) model from which kinetic and analytical parameters are evaluated. Uranyl ion is recognized based on blocking effect against charge transfer between p-benzoquinone as a probe and the modified electrode. This effect is detected from linear variation of charge transfer resistance ( R_ct) as a function of UO₂²⁺ concentration. From the analysis of the EIS data and approximated parameters, a method is developed for UO₂²⁺ determination based on impedimetric measurements.

Keywords: Self-assembled monolayer; Electrochemical impedance spectroscopy; CPE model; Modified gold electrode; Uranyl ion; Impedimetric sensor

Determination of hexavalent chromium in exhaled breath condensate and environmental air among chrome plating workers by Matteo Goldoni; Andrea Caglieri; Diana Poli; Maria Vittoria Vettori; Massimo Corradi; Pietro Apostoli; Antonio Mutti (pp. 229-235).

Chromium speciation has attracted attention because of the different toxicity of Cr(III), which is considered relatively non-toxic, and Cr(VI), which can cross cell membranes mainly as a chromate anion and has been classified as a class I human carcinogen. The aims of the present study were to measure soluble Cr(VI) levels in environmental samples, to develop a simple method of quantifying Cr(VI) in exhaled breath condensate (EBC), and to follow the kinetics of EBC Cr(VI) in chrome plating workers.Personal air samples were collected from 10 chrome platers; EBC was collected from the same workers immediately after the work shift on Tuesday and before the work shift on the following Wednesday. Environmental and EBC Cr(VI) levels were determined by means of colorimetry and electrothermal absorption atomic spectrometry, respectively.The method of detecting Cr(VI) in environmental air was based on the extraction of the Cr(VI)-diphenylcarbazide (Cr(VI)–DPC) complex in 1-butanol, whereas EBC Cr(VI) was determined using a solvent extraction of Cr(VI) as an ion pair with tetrabutylammonium ion, and subsequent direct determination of the complex (Cr(VI)–DPC) in EBC.Kinetic data showed that airborne Cr(VI) was reduced by 50% in airway lining fluid sampled at the end of exposure and that there was a further 50% reduction after about 15h. The persistence of Cr(VI) in EBC supports the use of EBC in assessing target tissue levels of Cr(VI).

Keywords: Cr(VI); Speciation; Exhaled breath condensate; ETAAS; Chrome plating

Continuous chemiluminescence determination of formaldehyde in air based on Trautz–Schorigin reaction by Kamil Motyka; Pavel Mikuška; Zbyněk Ve�?eřa (pp. 236-244).

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5Lmin⁻¹ (absorption liquid flow rate of 336μLmin⁻¹). The limit of detection (S/N=3) is 0.60μgm⁻³ HCHO (0.49ppb). The calibration graph is linear up to 300μgm⁻³ HCHO (244ppb). The relative standard deviations of chemiluminescence method for 1×10⁻⁶ and 5×10⁻⁶M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.

Keywords: Formaldehyde; Wet effluent diffusion denuder; Chemiluminescence; Air

Detection of volatile organic compounds by temperature-programmed desorption combined with mass spectrometry and Fourier transform infrared spectroscopy by Raimo A. Ketola; Jari T. Kiuru; Virpi Tarkiainen; Juha T. Kokkonen; Jaakko R�s�nen; Tapio Kotiaho (pp. 245-251).

A temperature-programmed desorption (TPD) device connected to a mass spectrometer was used to detect volatile organic compounds from air samples. The main aim was to develop an analytical method, by which both non-polar and polar organic components can be detected in the same run. In TPD, the adsorbed compounds are desorbed from the resin more slowly than in the conventional trapping techniques, such as purge-and-trap technique, in which the resin is flash-heated and the compounds are desorbed at the same time to a cryogenic trap or an analytical column. In TPD, the adsorbent resin acts also as an analytical column. In this way it is possible to obtain more rapid analysis, and also a more simple instrumentation, which can be used on-line and on-site. In this work, a new version of TPD device, which uses a resistor for heating and a Peltier element for rapid cooling, was designed and constructed. Various adsorbent resins were tested for their adsorption and desorption properties of both polar and non-polar compounds. When using a mixture of adsorbent resins, Tenax TA and HayeSep D, it was possible to analyze both polar, low-molecular weight compounds, such as methanol and ethanol, and non-polar volatile organic compounds, such as benzene and toluene, in the same run within 15min including sampling. The same TPD principle was also tested using a Fourier transform infrared spectrometer as an analytical instrument, and the results showed that it was possible to obtain a separation of similar compounds, such as hexane and heptane, and still retaining the same sensitivity as the original on-line FTIR instrument.

Keywords: Volatile organic compound; Temperature-programmed desorption; Mass spectrometry; Air analysis; Fourier transform infrared spectroscopy

Total reflection X-ray fluorescence mercury analysis after immobilization on quartz surfaces by I.N. Aretaki; P. Koulouridakis; N. Kallithrakas-Kontos (pp. 252-257).

Quartz reflectors are a common substrate for total reflection X-ray fluorescence (TXRF) analysis. Especially low masses of trace elements can be determined on these surfaces. In the present work, various complexing reagents were immobilized on the surface of quartz reflectors. The reflectors were immersed in mercury solutions and selective mercury collection took place. The effect of immersion time was examined and a few minutes were found adequate. The reflectors were analysed for mercury by TXRF. Different complexing reagents showed different collection capabilities; 4-(2-pyridazo-resorcinol) gave the best among them. The effect of various experimental parameters was examined like pH, interferences from other ions, etc. Mercury speciation was successfully tested by comparing inorganic mercury results with the methyl mercury ones. A very good selectivity for inorganic mercury was found. It was achieved very good linearity in the 1–500ngmL⁻¹ mercury concentration range and the minimum detection limit was equal to 2.5ngmL⁻¹.

Keywords: Mercury; Total reflection X-ray fluorescence (TXRF); Reflectors; Immobilization; Water analysis

Author Index (pp. 258-260).

Sections

Personal tools

Analytica Chimica Acta (v.562, #2)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.562, #2)