Abstracts

Abstract

GREEN CHEMISTRY—CORRELATION BETWEEN CAUSE AND EFFECT: A GUEST EDITORIAL by George‐Emil Baiulescu and Anca‐Iulia Stoica, Department of Analytical Chemistry, Faculty of Chemistry, University of Bucharest, 4‐12 Regina Elisabeta Blvd., 030018, Bucharest‐3, Romania

ABSTRACT: Green chemistry represents an actual tendency to improve the quality of different kinds of technologies used in chemical industries. It represents an improvement of chemical engineering to develop unpolluted systems for producing various kinds of chemicals. The development of this idea is due to the studies on environmental pollution of air, water, and soil, using up‐to‐date analytical techniques. It represents a perfect correlation between chemical technologies (cause) and analytical techniques (which study the pollutants, effects). In these conditions is imposed a perfect cooperation between technologist and system analyst to assure an improvement, step by step, of chemical production.

Analytical Letters, 37(15), 3105–3110, 2004

Abstract

BIOSENSOR BASED ON CHITOSAN BIOPOLYMER AND CRUDE EXTRACT OF GINGER (ZINGIBER OFFICINALES ROSC.) FOR THE DETERMINATION OF HYDROQUINONE IN WASTEWATER OF PHOTOGRAPHIC PROCESS by Inês R. W. Zwirtes de Oliveira, Iolanda Cruz Vieira, Valfredo T. de Fávere, and Mauro C. M. Laranjeira, Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis‐SC, Brazil; and Karina Omuro Lupetti and Orlando Fatibello‐Filho, Departamento de Química, Universidade Federal de São Carlos, São Carlos‐SP, Brazil

ABSTRACT: A new reagentless biosensor for differential pulse voltammetric detection of hydroquinone in the wastewater of the photographic process was developed. Crude extracts of several vegetables, such as arracacha, cassava, corn, ginger, guava, pineapple, swiss chard, and sweetsop were obtained as sources of peroxidase (PER; EC 1.11.1.7). Among them, a ginger crude extract was selected due to the highest specific activity observed after its immobilization by cross‐linking with glutaraldehyde in a prepared chitosan matrix that was incorporated in a carbon paste electrode. In the presence of hydrogen peroxide, this enzyme catalyzes the oxidation of hydroquinone to o‐quinone. The recovery of hydroquinone from the samples ranged from 98.4–105%, and a rectilinear analytical curve for hydroquinone concentration from 2.5 × 10⁻⁴ to 2.4 × 10⁻³ mol L⁻¹ (r = 0.997) was obtained. The detection limit was 2.5 × 10⁻⁶ mol L ⁻¹, and the relative standard deviation was lower than 1.2% for 4.95 × 10⁻⁴ mol L⁻¹ hydroquinone in 0.1 mol L⁻¹ phosphate buffer solution at pH 7.0 (n = 10).

Analytical Letters, 37(15), 3111–3127, 2004

Abstract

CONSTRUCTION AND ANALYTICAL APPLICATION OF A NOVEL ION‐SELECTIVE CAPACITIVE SENSOR FOR DETERMINATION OF CINCHONINE by Fan Yin and Xiaoxing Xu, Department of Chemistry, Changshu Institute of Technology, P.R. China

ABSTRACT: An ion‐selective capacitive sensor was constructed and applied to determine the concentration of cinchonine (CCN). The ion‐pair complex of cinchonine–picrolonate was embedded in electropolymerized o‐phenylenediamine film on gold electrode surface as a specific sensing element for the analysis of CCN. The logarithm of the capacitance change was linear, with the logarithm of CCN concentration in the range of 2.5 × 10⁻⁷ mol dm⁻³ ∼ 1.25 × 10⁻⁵ mol dm⁻³ with a detection limit of 1.0 × 10⁻⁷ mol dm⁻³ at pH = 7. The adsorption model of CCN onto ion‐selective film appears to be of the Langmuir type, and the adsorption equilibrium constant was estimated at 5.73 × 10⁵ dm³ mol⁻¹.

Analytical Letters, 37(15), 3129–3147, 2004

Abstract

LEAD ION‐SELECTIVE MEMBRANE ELECTRODE BASED ON A NOVEL FLUORENE DERIVATIVE by Zhenning Yan, Yanhui Hou, Zhixian Zhou, Chenxia Du, and Yangjie Wu, Department of Chemistry, Zhengzhou University, Zhengzhou, Henan, P.R. China

ABSTRACT: A novel fluorine derivative 4,5‐diaza‐9‐(4‐methylphenyl) imino fluorene has been synthesized and evaluated as a lead (II) ion‐selective ionophore in PVC membrane electrode. The influence of the nature of the plasticizers (o‐NPOE, DBP, and DOS) and of the amount of incorporated ionophore and KTpClPB on the characteristics of the electrode were discussed. The electrode prepared with 5.7 mg ionophore, 187 mg o‐NPOE, 92 mg PVC, and 0.11 mg KTpClPB gave a good Nernstian response of 28.8 mV/decade for lead (II) in the concentration range 1.0 × 10⁻⁶–1.0 × 10⁻² mol dm⁻³. The limit of detection reached 1.0 × 10⁻⁷ mol dm⁻³. The electrode showed high selectivity toward lead over alkali, alkaline earth, and some transition metal ions. The influence of pH has been studied. The electrode exhibited better potential stability and reproducibility. The electrode was used to determine lead levels in polluted water using the developed electrode.

Analytical Letters, 37(15), 3149–3159, 2004

Abstract

TEICOPLANIN‐BASED ENANTIOSELECTIVE, POTENTIOMETRIC MEMBRANE ELECTRODES FOR THE DETERMINATION OF R‐BACLOFEN IN PHARMACEUTICAL FORMULATIONS by Alexander A. Rat'ko and Raluca‐Ioana Stefan, Department of Chemistry, University of Pretoria, Pretoria, South Africa

ABSTRACT: Two enantioselective, potentiometric membrane electrodes were proposed for the assay of R‐baclofen. The electrodes were designed using a macrocyclic glycopeptide antibiotic, teicoplanin. Acetonitrile was added to the teicoplanin to design a modified teicoplanin‐based electrode. The linear concentration ranges for the proposed enantioselective, membrane electrodes were 10⁻⁷–10⁻⁴ mol/L for teicoplanin‐based electrode and 10⁻⁶–10⁻⁴ mol/L for the electrode based on teicoplanin modified with acetonitrile. The slopes of the electrodes were 60.0 mV/pR‐baclofen and 57.2 mV/pR‐baclofen for teicoplanin and teicoplanin modified with acetonitrile‐based electrodes, respectively. The enantioselectivity was determined over S‐baclofen. The proposed electrodes can be employed reliably for the assay of R‐baclofen raw material and from its pharmaceutical formulation, Norton‐Baclofen^® tablets. The surfaces of the electrodes are stable and easily renewable by polishing on alumina paper.

Analytical Letters, 37(15), 3161–3173, 2004

Abstract

LIPOPROTEIN ISOLATION ON CELLULOSE ACETATE MEMBRANE FOR CHOLESTEROL ESTIMATION FROM BLOOD SAMPLES OF CARDIAC PATIENTS by M. Anwar, Department of Chemistry, University of Balochistan, Quetta, Pakistan; and J. Iqbal, Department of Pharmacy, University of Balochistan, Quetta, Pakistan

ABSTRACT: The lipoproteins have been successfully isolated electrophoretically from the blood samples of patients having suffered from type III, hyperlipoproteinemia but survived myocardial infarction. The low‐density lipoprotein (LDL) and high‐density lipoprotein (HDL) fraction from the cellulose acetate membrane is cut, and the total cholesterol and cholesterol of the LDL and HDL are extracted. The cholesterol is determined using an immobilized cholesterol esterase/oxidase column in a flow system.

Analytical Letters, 37(15), 3175–3183, 2004

Abstract

CARBON NANOTUBES‐MODIFIED SCREEN‐PRINTED ELECTRODES FOR CHEMICAL SENSORS AND BIOSENSORS by Marek Trojanowicz, Department of Chemistry, Warsaw University, Warsaw, Poland; Ashok Mulchandani, Department of Chemical and Environmental Engineering, University of California, Riverside, USA; and Marco Mascini, Biosensors Laboratory, Department of Chemistry, University of Florence, Florence, Italy

ABSTRACT: Multiwalled carbon nanotubes (MWCNT) have been used for modification of working graphite ink electrode of the three‐electrode screen‐printed sensing stripe. Modification has been made by evaporating on the graphite surface a solution of MWCNT in dimethylformamide. The effect of modification on reversibility of the electrode process of the system hexacyanoferrate(II)/(III) has been shown, along with improvement of the sensitivity of detection of pesticide paraoxon with biosensors containing organophosphorus hydrolase immobilized by adsorption on the nanotubes‐modified graphite ink electrode. The catalytic sensing of methanol was also demonstrated with the use of a screen‐printed sensor modified with MWCNT and Co(II) salt present in the measuring solution.

Analytical Letters, 37(15), 3185–3204, 2004

Abstract

FLOW‐INJECTION CHEMILUMINESCENT DETERMINATION OF THIAMINE IN PHARMACEUTICAL SAMPLES BY ON‐LINE PHOTODEGRADATION by A. Wasielczuk and J. Martínez Calatayud, Department of Analytical Chemistry, University of Valencia, Valencia, Spain; M. Catalá Icardo, Department of Chemistry, Polytechnic University of Valencia, Valencia, Spain; and J. V. García Mateo, Department of Chemistry, Biochemistry and Molecular Biology, University Cardenal Herrera‐CEU, Moncada, Valencia, Spain

ABSTRACT: A simple, sensitive, and precise method for the determination of thiamine hydrochloride in a flow‐injection system is described. The method is based on the UV irradiation of thiamine in acid medium. Then, the photo‐fragments are oxidized by permanganate in acid medium, and the resultant chemiluminescent intensity is measured. The optimum conditions for the photoreaction and for the chemiluminescence emission were investigated. The method allows the determination of thiamine, over the range 0.05(LOD)–84 mg · l⁻¹, with a throughput of 30 h⁻¹, and a RSD (n, 20) at 20 and 0.5 mg · l⁻¹ of the thiamine level of 2.5 and 1.3%, respectively. The method was applied to pharmaceutical preparations.

Analytical Letters, 37(15), 3205–3218, 2004

Abstract

DIFFERENTIAL PULSE STRIPPING VOLTAMMETRIC DETERMINATION OF PARACETAMOL AND PHENOBARBITAL IN PHARMACEUTICALS ASSISTED BY CHEMOMETRICS by Yongnian Ni and Yuerong Wang, Department of Chemistry, Nanchang University, Nanchang, Jiangxi, China; and Serge Kokot, Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technique, Brisbane, Queensland, Australia

ABSTRACT: A voltammetric method, aided by chemometrics, was developed for the simultaneous determination of paracetamol and phenobarbital in pharmaceuticals. Both of these analytes gave well‐defined oxidation peaks in the Britton–Robinson buffer (pH 5.72) when analyzed by differential pulse‐stripping voltammetry (DPSV) at a glassy carbon electrode. The experimental conditions were optimized: 200 mV—deposition potential, 160 sec—deposition time, 4 mV—increment potential, 50 mV—amplitude, and 60 ms—pulse width. Under these selected conditions, the oxidation current had a linear relationship with concentration of paracetamol [ranges: 0.09–0.93 mg l⁻¹ (r ² = 0.999) and 0.9–11.7 mg l⁻¹ (r ² = 0.999)], and phenobarbital [1.0–22.0 mg l⁻¹ (r ² = 0.999)]. Due to the overlapping voltammograms from the two analytes, two chemometrics methods, partial least squares (PLS), and principal component regression (PCR), were used for building calibration models from voltammograms of mixtures. These models were applied for prediction of the analytes from unknown samples. It was found that the two chemometrics methods gave good results for analysis of mixtures of these two compounds. The proposed method was verified by an established HPLC method, and its practical application was demonstrated with the determination of paracetamol and phenobarbital in several commercial tablets with satisfactory results.

Analytical Letters, 37(15), 3219–3235, 2004

Abstract

FLOW INJECTION POTENTIOMETRIC DETERMINATION OF DOTHIEPIN HYDROCHLORIDE by N. T. Abdel Ghani, R. M. El‐Nashar, and A. A. Bioumy, Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt

ABSTRACT: New plastic membrane electrodes for dothiepin hydrochloride (DpCl) based on dothiepin phosphotungstate (Dp‐PTA), dothiepin phosphomolybdate (Dp‐PMA), and a mixture of both (Dp‐PTA/PMA) were prepared. The electrodes were fully characterized in terms of their composition, life span, pH, and temperature, and then were applied to the potentiometric determination of the dothiepinium ion in its pure state and pharmaceutical preparations in batch and flow injection conditions. The selectivity of the electrodes toward many inorganic cations, sugars, and amino acids was also tested.

Analytical Letters, 37(15), 3237–3254, 2004

Abstract

POLISHED SILVER SOLID AMALGAM ELECTRODE: FURTHER CHARACTERIZATION AND APPLICATIONS IN VOLTAMMETRIC MEASUREMENTS by R. Fadrná, J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Czech Republic

ABSTRACT: Polished silver solid amalgam electrode (p‐AgSAE) appears to be a good alternative to hanging mercury drop electrode (HMDE). The present work focuses on analysis of the electrode material and of the working electrode surface. It has been demonstrated that this electrode can be successfully used in inorganic electrochemical measurements for determination of metal cations, nitrates, and thiocyanates, etc.

Analytical Letters, 37(15), 3255–3270, 2004

Abstract

ANODIC ADSORPTIVE STRIPPING VOLTAMMETRIC DETERMINATION OF ATRAZINE IN SPIKED SOIL SAMPLES WITH A GOLD MICROELECTRODE by Simone Morais, Oriza Tavares, Paula C. Baptista‐Paíga, and Cristina Delerue‐Matos, Requimte/Instituto Superior de Engenharia do Instituto Politécnico do Porto, Departamento de Engenharia Química, Rua S. Tomé, Porto, Portugal

ABSTRACT: Microwave‐assisted solvent extraction was combined with anodic adsorptive stripping voltammetry at a gold microelectrode to extract and quantify the herbicide atrazine in spiked soil samples. A systematic study of the experimental parameters affecting the stripping response was carried out by square‐wave voltammetry. The voltammetric procedure is based on controlled adsorptive accumulation of atrazine at the potential of 0.35 V (versus Ag/AgCl) in the presence of Britton–Robinson buffer pH (2.0). The limit of detection obtained for a 30 sec collection time was 4.3 × 10⁻⁷ mol L⁻¹. Recovery experiments, at the 1 µg g⁻¹ level of spiking, gave good results for the global procedure, and the values found were comparable to those obtained by HPLC.

Analytical Letters, 37(15), 3271–3286, 2004

Abstract

DETERMINATION OF RUTIN, QUERCETIN, AND CHLOROGENIC ACID IN MULBERRY LEAVES BY CAPILLARY ZONE ELECTROPHORESIS by Jianwei Yan, Zhejiang University, Department of Chinese Medicine Science and Engineering, Hangzhou, P.R. China; and Miao Wang and Jiande Lü, Zhejiang University, Department of Chemistry, Hangzhou, P.R. China

ABSTRACT: A simple, rapid, and accurate capillary zone electrophoresis (CZE) technique has been developed for the separation and determination of rutin, quercetin, and chlorogenic acid in mulberry leaves collected in different periods. The effects of various parameters, such as buffer concentration, pH value, and proportion of methanol on electrophoresis behaviors of the analytes, rutin, quercetin, and chlorogenic acid, were investigated. After a series of optimization, the separation of the three compounds in mulberry leaves was achieved successfully within 12 min in the buffer solution of 40 mmol · L⁻¹ borax (pH 9.3). The linearity, limit of quantification, reproducibility, and recovery for all were satisfactory. The optimized CZE method proposed here has been satisfactorily employed to analyze real samples of mulberry leaves.

Analytical Letters, 37(15), 3287–3297, 2004

Abstract

DERIVATIZATION OF ACIDIC HERBICIDES WITH SELECTED TETRAALKYL AMMONIUM AND TRIMETHYL SULFHONIUM HYDROXIDES FOR THEIR GC ANALYSIS by M. Rompa, E. Kremer, and B. Zygmunt, Department of Analytical Chemistry, Chemical Faculty, Gdansk University of Technology, Gdansk, Poland

ABSTRACT: This work presents studies on acidic MCPP—2‐(4‐chloro‐2‐methylphenoxy)propanoic acid; MCPA—(4‐chloro‐2‐methylphenoxy)acetic acid; 2,4‐D‐2,4‐dichlorophenoxyacetic acid; (2,4,5‐T‐2,4,5‐trichlorophenoxy) acetic acid and phenolic (PCP—pentachlorophenol, dinoterb‐2‐(1,1‐dimethylethyl)‐4,6‐dinitrophenol, dinoseb‐2‐(1‐methylpropyl)‐4,6‐dinitrophenol) herbicides with derivatization aimed at their gas chromatographic determination. The derivatization was performed in an injection port of a gas chromatograph with trimethylphenylammonium hydroxide (TMPH), trimethylsulfonium hydroxide (TMSH), and tetramethylammonium hydroxide (TMAH). The effects of temperature of the injection port, reaction medium (solvent), and reagent excess on derivatization yield were investigated. TMPH in 20‐fold excess in methanol was selected for analysis. Dichloromethane was also found to be an appropriate solvent. Repeatability of the results was poor when tert‐butyl methyl ether (MTBE) was used as reaction medium.

Analytical Letters, 37(15), 3299–3312, 2004

Abstract

OPTIMIZATION OF A THERMAL DESORPTION METHOD FOR A MIXTURE OF VOLATILE ORGANIC COMPOUNDS (C₁–C₁₀): COMPARISON OF TWO TYPES OF COLD‐TRAPS by V. Fernández‐Villarrenaga, P. López‐Mahía, S. Muniategui‐Lorenzo, D. Prada‐Rodríguez, and E. Fernández‐Fernández, Department of Analytical Chemistry, University of A Coruña, Campus da Zapateria, A Coruña, Spain; and X. Tomàs, Department of Applied Statistics, Institut Químic de Sarrià, Ramón Llull University, Barcelona, Spain

ABSTRACT: This study concerns the optimization of the desorption of 42 volatile organic compounds (nonhalogenated and halogenated aliphatic hydrocarbons, alkylated and chlorinated monoaromatic compounds, and terpenes) from a sorbent trap that contains 140 mg of Tenax‐GR and 60 mg of Chromosorb‐106. Gaseous standards were used for this purpose and were prepared using the packed column injector method. Generation conditions were optimized by means of a centered factorial experimental design and fixed at 125°C of injector temperature, 50 mL/min of carrier gas flow rate, and 40 sec of injection time. After tube desorption, analytes were focused on a cold‐trap. The type of cold‐trap determines the load of analytes on the system and, therefore, the method sensitivity. The influence of some variables (times, flows, and temperatures of desorption for tube and cold‐trap) on the whole desorption process was studied using two types of traps: a standard packed cold‐trap, and a low‐flow one. In the case of the standard cold‐trap, no variables have a significant effect on the process, and therefore, tube desorption was carried out at 190°C for 4 min with a helium flow of 100 mL/min. For cold‐trap desorption, values were 275°C, 3 min, and 3.9 mL/min. But in the case of the low‐flow trap, the flow that desorbs adsorption tube and cold‐trap was significant and was classically optimized. The final values were 190°C, 4 min, and 60 mL/min of desorb flow for tube desorption and 275°C, 3 min, and 1 mL/min of outlet split flow for cold‐trap desorption. An important improvement (ca 50%) on method detection limits was observed using the low‐flow cold‐trap.

Analytical Letters, 37(15), 3313–3330, 2004