Check out our New Publishers' Select for Free Articles

Analytical and Bioanalytical Chemistry (v.374, #3)

To Professor Dr. Yuri Zolotov on the occasion of his 70th birthday by Boris Spivakov (pp. 359-360).

Polyurethane foams as solid chromogenic reagents for diffuse reflectance spectroscopy by S. Dmitrienko; O. Sviridova; L. Pyatkova; V. Senyavin (pp. 361-368).

The chemical reactions of the functional groups in polyurethane foams (PUF) have been studied by use of diffuse reflectance spectroscopy and infrared spectroscopy. It was found that the functional groups are highly reactive towards diazotization by sodium nitrite, azo coupling with 4-nitrophenyldiazonium tetrafluoroborate, oxidation by active chlorine, and condensation with formaldehyde, resulting in the formation of intensely colored products. Heterogeneous chemical reactions of PUF with these compounds in aqueous solution proceed rapidly at room temperature and at low solute concentrations. PUF do not undergo degradation as a result of chemical interactions. The linear response of the Kubelka–Munk function to analyte concentration makes it possible to recommend PUF as solid chromogenic reagents for the determination of nitrite, nitrate, and 1- and 2-naphthols.

Keywords: Polyurethane foams Nitrite and nitrate determination IR spectroscopy Diffuse reflectance spectroscopy

Identification, characterization and determination of metal-binding proteins by liquid chromatography. A review by M. de la Calle Guntiñas; G. Bordin; A. Rodriguez (pp. 369-378).

The use of liquid chromatography in the separation and determination of metal-binding proteins is reviewed. Advantages and drawbacks of different chromatographic techniques based on various principles: size exclusion, ion exchange (cationic and ionic), reversed phase and affinity, are presented and discussed. The topic "metal-binding proteins" is considered and presented from two different points of view. The first one regards metal speciation in biological samples (serum and blood). In metal speciation studies, the exact identity of the protein to which the metal is bound often remains unknown. The second point of view is that, frequently, the interest of analyzing metal-binding proteins is not related anymore to the metallic fraction of the protein, but to other chemical structures attached to the protein, such as carbohydrates, which indirectly determine how good the function of the protein is. In this review, special attention is paid to studies dealing with the glycosylation of transferrin, and with the glycated isoform of haemoglobin.

Keywords: Metal-binding proteins Glycoproteins Liquid chromatography Biological samples

Determination of the age of highly enriched uranium by M. Wallenius; A. Morgenstern; C. Apostolidis; K. Mayer (pp. 379-384).

This paper describes the analytical methods (thermal ionization mass spectrometry, inductively coupled plasma mass spectrometry, and alpha spectrometry) that have been developed for determination of the age of uranium and discusses their advantages and limitations. With regard to potential application of the methods (e.g. Fissile Material Cut-off Treaty), the discussion focuses on highly enriched uranium, because this seems to be of highest strategic relevance.The different analytical methods were tested and validated by use of uranium reference materials of different ²³⁵U isotope abundance and of known ages. The results show that thermal ionization mass spectrometry and alpha spectrometry are both very accurate and precise techniques for this application. Inductively coupled plasma mass spectrometry, on the other hand, although less precise, because of the different approach to the analytical problem, is still sufficiently accurate to be used as a rapid screening method.

Keywords: Age determination Uranium Mass spectrometry Alpha spectrometry Fissile Material Cut-off Treaty

A simple, low-cost, remote fiber-optic micro volume fluorescence flowcell for capillary flow-injection analysis by Sean J. Hart; Renee D. Jiji (pp. 385-389).

A small volume flowcell for fluorescence detection in capillary flow injection (CFI) analysis has been created by using a low cost, commercially available fluidic device. Fluorescence detection is achieved using an optical fiber to deliver excitation light to the sample flowing through the device and another optical fiber to collect fluorescence emission. The flowcell is a standard fluidic cross with a swept volume of 721 nL. Optical fibers were oriented at right angles using standard sleeves and ferrules to set their position near the cross intersection. Multiple excitation sources were used including a low power UV laser and blue and UV light emitting diodes (LED). The full emission spectrum detection limits, using the laser, for fluorescein and bovine serum albumin (BSA) were 0.30 ppb and 2.1×10^–4% (w/w), respectively. Two fluidic crosses were used in series for multi-wavelength fluorescence excitation using fiber-optically coupled LED.

Keywords: Capillary flow injection analysis flowcell Laser induced fluorescence Fiber optics Blue and UV light emitting diode (LED) Microfluidics BSA fluorescein

Subcellular mass determination by ⁴He⁺ energy-loss micro-spectrometry by Guillaume Devès; Richard Ortega (pp. 390-394).

The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass of human cultured cells. A ⁴He⁺ microbeam of 2.0 MeV energy was chosen to obtain enhanced ion-energy-loss sensitivity through the micron-thick freeze-dried cells. Local sample mass calculation, based on energy-loss conversion by use of appropriate matrix stopping powers, was performed by use of dedicated software. The method was validated with epoxy resin sections and polymer foil as analogues of biological samples in the range of (intra)cellular thickness, 150 to 3000 nm. STIM analysis resulted in less than 5% error in mass determination. ⁴He⁺ energy-loss micro-spectrometry was performed on freeze-dried human ovarian cancer cells, the mean areal mass obtained was 120 µg cm^–2 (200 µg cm^–2 in the nucleus and 250 µg cm^–2 in nucleoli). This method is particularly useful for mass normalization of X-ray fluorescence yields resulting from particle-induced X-ray emission microanalysis (micro-PIXE). When performed successively these two ion-beam micro-analytical methods enable the mapping of true element concentrations within single cells.

Keywords: Chemical imaging Scanning transmission ion microscopy Cellular mass Microanalysis Ion-beam analysis

Determination of proteins at nanogram levels by their quenching effect on the chemiluminscence reaction between luminol and hydrogen peroxide with manganese-tetrasulfonatophthalocyanine as a new catalyst by Yongxin Li; Danhua Zhao; Changqin Zhu; Lun Wang; Jingou Xu (pp. 395-398).

The manganese-tetrasulfonatophthalocyanine (MnTSPc) catalyzed luminol–hydrogen peroxide chemiluminescence (CL) systems can be quenched in the presence of proteins. A highly sensitive CL quenching method has been developed for the determination of proteins. Under optimum conditions, the linear ranges of the calibration curves were 0.1–20 µg/mL for human serum albumin (HSA), 0.2–20 µg/mL for human γ-IgG, and 0.5–50 µg/mL for the bovine serum albumin (BSA) with the corresponding detection limits were 1.9 ng/mL, 2.7 ng/mL, and 3.4 ng/mL. The method has been applied to the analysis of total proteins in human serum samples and the results were in good agreement with clinical data provided.

Keywords: Chemiluminescence Manganese-Tetrasulfonatophthalocyanine Protein Luminol

A chromoreactand for optical sensing of amphetamines by Gerhard J. Mohr; Matthias Wenzel; Frank Lehmann; Peter Czerney (pp. 399-402).

A bisazo dye is presented that undergoes a reversible chemical reaction with amphetamine in thin layers of plasticised PVC and changes its colour from blue to red. The sensitivity of the dye in the polymer layer covers the range from 0.3 to 30 mmol L^–1 amphetamine with a limit of detection of 0.1 mmol L^–1. The maximum signal changes are observed at 630 nm making the dye compatible with cheap light sources and detectors.

Keywords: Optical sensor Reactand Amphetamine

Suitability of hyperbranched polyester for sensoric applications – investigation with reflectometric interference spectroscopy by Georg Belge; Detlev Beyerlein; Carmen Betsch; Klaus-J. Eichhorn; Günter Gauglitz; Karina Grundke; Brigitte Voit (pp. 403-411).

Hyperbranched polyesters (HBP) with different end groups (P-OH, P-COOH, P-OAc) were prepared as thin films. Their surface properties were investigated using zeta potential and contact angle measurements. The differences in surface properties between P-OH and P-COOH, on the one hand, and P-OAc, on the other hand, predicted different behavior in sensoric applications. Therefore, the vapor of the homologous series of alcohols from methanol to pentanol was exposed to the thin films. Changes in thickness were observed with reflectometric interference spectroscopy (RIfS). First investigations in a current analytical problem for the detection and discrimination of refrigerants (freons) using P-OH as sensitive layer have been shown. Polydimethylsiloxane (PDMS) and poly(ether urethane) (PUT) were used as reference sensor materials for the RIfS measurements.

Keywords: Optical sensor Hyperbranched polymers VOC Refrigerants

Determination of hydrogen peroxide based on a metal dispersed sol-gel derived ceramic-graphite composite electrode by D. Ravi Shankaran; N. Uehera; T. Kato (pp. 412-415).

A new copper dispersed ceramic-graphite composite electrode was fabricated by the initial mixing of copper nitrate and (3-mercaptopropyl)trimethoxy silane (MPS) followed by stirring with graphite powder. The combination of the metal catalysis and the advantages of the ceramic composite favored the electrocatalytic reduction of hydrogen peroxide (H₂O₂) at a reduced overpotential of –0.2 V with good sensitivity, stability and reproducibility. The sensor showed a good linear response to H₂O₂ in the range from 8.3 × 10^–6 M to 2.0 × 10^–3 M with a correlation coefficient of 0.9989 and the detection limit was 6.2 × 10^–6 M (S/N =3).

Keywords: Ceramic composite Copper dispersion Sol-gel Electrocatalysis Hydrogen peroxide

Use of a copper electrode in alkaline medium as an amperometric sensor for sulphite in a flow-through configuration by Dennys Corbo; Mauro Bertotti (pp. 416-420).

A flow injection analysis (FIA) method has been developed for the determination of sulphite in beverages. The method is based on the amperometric detection (0.60 V vs Ag/AgCl (sat. NaCl)) of the analyte at a copper surface in an alkaline medium (1 M NaOH solution) with a manifold that incorporates flow extraction of sulphite as SO₂ through a PTFE membrane. Under optimal experimental conditions the peak current response increases linearly with sulphite concentration over the range from 1.0 to 5.0 mM. The repeatability of the electrode response in the FIA configuration was evaluated as 4% (n =20), the limit of detection of the method was 0.04 mM (S/N =3) and the analytical frequency was 50 h^–1. Since ethanol is also electroactive and permeates through the PTFE membrane, a strategy involving in a first step measurements of only ethanol by manipulating the pH of the donor stream was employed for wine samples. Then, both ethanol and sulphite were measured at the copper electrode at 0.40 V vs Ag/AgCl (sat. NaCl) and the sulphite concentration was determined by difference. Results for 3 different beverage samples (alcoholic and non-alcoholic) showed excellent agreement with the ones obtained by using a recommended procedure for sulphite analysis.

Keywords: Sulphite Copper electrodes Amperometric detection Flow injection analysis

Development of a laser-induced cell lysis system by Mohit D. Dhawan; Frank Wise; Antje J. Baeumner (pp. 421-426).

A novel cell lysis system was developed that is based on laser-induced disruption of bacterial and yeast cells. It will find application as a rapid, efficient and clean sample preparation step in bioanalytical detection systems. Using E. coli as our model analyte, we optimized cell lysis with respect to optimal laser wavelength, lowest energy input requirements, RNA release from the cells, and potential protein damage. The optimized system was finally applied to the lysis of four additional microorganisms. All experiments were carried out with about 2000 cells per sample or less. Initially, lysis was determined by the detection of cell survival after laser treatment using standard microbiological techniques, (i.e., cells were grown on nutrient agar plates). Then, actual release of mRNA from the cells was proven. Wavelengths investigated ranged from 500 nm to 1550 nm. An average power of 100 mW for the lasers was shown to be sufficient to obtain cell lysis at wavelengths above 1000 nm, with optimal wavelengths between 1250 nm and 1550 nm. Since water absorbs energy at those wavelengths, it is assumed that laser exposure results in an instantaneous increase of the cell temperature, which causes rupture of the cell membrane. Second, damage to protein solutions treated under optimized laser-lysis conditions was also studied. Using a pure solution of horseradish peroxidase as a model protein, no loss in enzyme activity was observed. Thus, it was concluded that damage to intracellular proteins is unlikely. Third, RNA release was tested using an E. coli specific RNA biosensor. Release of RNA was not detected from untreated cells, but laser-treated E. coli cells displayed significant RNA release due to laser-induced cell lysis. Finally, lysis of M. luteus, B. subtilis, B. cereus, and S. cerevisiae were investigated under optimized conditions. In all cases, laser-induced lysis of the cells was confirmed by determination of cell survival. Hence, laser-induced cell lysis is an efficient procedure that can be used for sample preparation, without damage to macromolecules, in bioanalytical detection systems for microorganisms. Miniaturized lasers and miniaturized cell-lysis chambers will create a simple, field-usable cell lysis system and allow the application of laser-induced cell lysis in micro Total Analysis Systems.

Keywords: Laser Cell lysis Biosensor Pathogenic organism E. coli

Determination of 6-oxo-morphinans, as the oximes, by difference circular dichroism spectroscopy by A. Szentesi; A. Gergely; P. Horváth; S. Hosztafi; Gy. Szász (pp. 427-431).

A negative Cotton effect is observed in the circular dichroism (CD) spectra of 6-oxo-morphinans in the wavelength range of n–π* electron transitions. 6-oxo-Morphinans can be transformed into oxime derivatives with hydroxylamine and after oxime formation the CD spectra are significantly different. Oxime formation was monitored by CD and by HPLC. It was established that under the experimental conditions used oxime formation was complete within 90 min. The method suggested for the determination of 6-oxo-morphinans is based on the considerable differences between the ellipticities before and after the oxime formation. The ellipticity difference varies linearly with concentration in the range 2×10^–5–5×10^–4 mol L^–1 for the three 6-oxo-morphinans examined (oxycodone, hydrocodone, and 14-hydroxycodeinone). For hydrocodone the dependence is also linear in a lower concentration range (5×10^–6–10^–4 mol L^–1). The new difference CD spectroscopic method can be applied to the selective determination of 6-oxo-morphinans in bulk and dosage forms.

Keywords: Circular dichroism spectroscopy Oxycodone Hydrocodone 14-Hydroxycodeinone Oxime formation

Determination of antitubercular drugs by micellar electrokinetic capillary chromatography (MEKC) by M. Acedo-Valenzuela; A. Espinosa-Mansilla; A. Muñoz de la Peña; F. Cañada-Cañada (pp. 432-436).

A method for the determination of isoniazid (ISO), pyrazinamide (PYR) and rifampicin (RIF) in pharmaceutical products, by micellar electrokinetic capillary chromatography (MEKC) with ultraviolet detection is described. The influence of pH, concentration of surfactants, buffer and organic solvents, over the separation were studied as experimental variables. The optimal separation was carried out at 30 °C and 20 kV, using a 40 mM borate buffer and 100 mM sodium dodecylsulphate (SDS) adjusted to pH 8.5. Under these conditions, the analysis is accomplished in about 8 min. The method was applied to the determination of these compounds in different pharmaceuticals with good results when compared with a reference liquid chromatographic (LC) method.

Keywords: Antitubercular drugs Micellar electrokinetic capillary chromatography (MEKC) Pharmaceuticals

An international intercomparison exercise for the determination of purified microcystin-LR and microcystins in cyanobacterial field material by Jutta Fastner; Geoffrey A. Codd; James S. Metcalf; Peter Woitke; Claudia Wiedner; Hans Utkilen (pp. 437-444).

The comparability of current microcystin analysis methods has been evaluated in an international intercomparison exercise. The focus was on the analysis of microcystins by high-performance liquid chromatography coupled with ultraviolet or photodiode-array detection (HPLC–PDA/UV), currently the most widespread method for microcystin analysis, but the exercise was open for other methods such as enzyme-linked immunosorbent assay (ELISA), protein phosphatase inhibition assay (PPA) and high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS).Thirty-one laboratories from 13 countries participated in the study. For a microcystin-LR (MC-LR) standard solution (S1) of undisclosed quantity, and for a field sample (S3) from a natural cyanobacterial bloom, repeatabilities between 4 and 15% and reproducibilities between 24 and 49% were obtained. No significant differences between single methods were found for S1 and S3, except for a significantly higher repeatability value of ELISA for S1. However, the analysis of microcystins in the field sample (S3) by HPLC–PDA/UV was significantly more variable than for the standard solution (S1). Both the extraction and the analysis of the microcystins appeared to contribute to this variability.It is concluded that standard MC-LR (S1) can be measured with adequate precision by all participating laboratories independently of the method used. With respect to the different methods used the results for the field sample can also be regarded as satisfactory, but clearly showed the need for improvement by standardisation between laboratories. Furthermore, quantification with in-house standards compared to quantification using the supplied MC-LR standard indicated that routine microcystin analysis in laboratories may be also influenced by the variability of available standards, emphasising the need for the production of certified reference materials (CRM).

Keywords: Microcystin Intercomparison HPLC Cyanobacteria Analysis

Porphyrin binding to DNA investigated by cyclodextrin supramolecular system by Xiao-ping Wang; Jing-hao Pan; Xiao-dong Yang; Chuan-dong Niu; Yong Zhang; Shao-min Shuang (pp. 445-450).

The interactive mode of meso-tetrakis- (4-N-trimethylaminobenzyl) porphyrin (TAPP) with DNA has been investigated by the cyclodextrin (CD)-porphyrin supramolecular system. The binding of TAPP with DNA is inhibited by the anion CD derivative, sulfurbutyl-β-cyclodextrin (SB-β-CD); however, the neutral CD cannot influence the binding. As for the inclusion procedure of the CDs-TAPP system, the ¹H-NMR data suggests that the hydrophobic segment of TAPP enters into the cavity of CD, which means that the hydrophobic part of TAPP is not the binding site in the TAPP-DNA interaction. Therefore, the binding model cannot be the intercalation and is not related to the grooves of DNA. In addition, experimental data show that the charge attraction, which exists in the inclusion procedure of SB-β-CD and TAPP hampers the binding of TAPP with DNA. The negative groups of SB-β-CD compete with the phosphate groups of the DNA backbone, and have an attraction to the positive groups of TAPP. This competitive attraction supports the theory that the binding mode of TAPP with DNA is "electrostatic binding". Furthermore, there are two binding sites between one TAPP molecule and one DNA standard. We produce a possible binding structure (a suprahelical structure of DNA) for this TAPP-DNA complex. This structure is in good agreement with the literature.

Keywords: Meso-tetrakis- (4-N-trimethylaminobenzyl) porphyrin DNA Cyclodextrin-porphyrin supramolecular system Electrostatic binding Sulfurbutyl-β-cyclodextrin

First- and second-order multivariate calibration applied to biological samples: determination of anti-inflammatories in serum and urine by Juan A. Arancibia; Alejandro C. Olivieri; Graciela M. Escandar (pp. 451-459).

First- and second-order multivariate calibration of fluorescence data have been compared as regards the determination of anti-inflammatories and metabolites in the biological fluids serum and urine. The simultaneous resolution of naproxen–salicylic acid mixtures in serum and naproxen–salicylic acid–salicyluric acid mixtures in urine was accomplished and employed for a discussion of the relative advantages of the applied chemometric tools. The analysis of second-order fluorescence excitation-emission matrices was performed using iteratively reweighted generalized rank annihilation method (IRGRAM), parallel factor analysis (PARAFAC), and self-weighted alternating trilinear decomposition (SWATLD). The results were compared with first-order fluorescence emission data analyzed with partial least-squares regression (PLS). In all cases, the performance of the methods was improved through the formation of inclusion complexes of the analytes with β-cyclodextrin. The concentration ranges in which the analytes could be determined were as follows: naproxen, 0–250 ng mL^–1 in serum and 0–200 ng mL^–1 in urine; salicylic acid, 0–500 ng mL^–1 in serum and 0–300 ng mL^–1 in urine, and salicyluric acid, 0–300 ng mL^–1 in urine.

Keywords: Spectrofluorimetry Chemometrics Naproxen Salicylic acid Salicyluric acid β-Cyclodextrin

Complementary use of partial least-squares and artificial neural networks for the non-linear spectrophotometric analysis of pharmaceutical samples by Héctor C. Goicoechea; María S. Collado; María L. Satuf; Alejandro C. Olivieri (pp. 460-465).

The complementary use of partial least-squares (PLS) multivariate calibration and artificial neural networks (ANNs) for the simultaneous spectrophotometric determination of three active components in a pharmaceutical formulation has been explored. The presence of non-linearities caused by chemical interactions was confirmed by a recently discussed methodology based on Mallows augmented partial residual plots. Ternary mixtures of chlorpheniramine, naphazoline and dexamethasone in a matrix of excipients have been resolved by using PLS for the two major analytes (chlorpheniramine and naphazoline) and ANNs for the minor one (dexamethasone). Notwithstanding the large number of constituents, their high degree of spectral overlap and the occurrence of non-linearities, rapid and simultaneous analysis has been achieved, with reasonably good accuracy and precision. No extraction procedures using non-aqueous solvents are required.

Keywords: Partial least-squares Artificial neural networks Chlorpheniramine Dexamethasone Naphazoline

Stability of total selenium and selenium species in lyophilised oysters and in their enzymatic extracts by P. Moreno; M. Quijano; A. Gutiérrez; M. Pérez-Conde; C Cámara (pp. 466-476).

To obtain reliable information on speciation analysis it is necessary to previously evaluate the stability of the species in the sample of interest. Furthermore, in those cases in which sample treatment to extract the species is time-consuming, an evaluation of how to maintain species integrity in the extracts is paramount. Thus, the present paper reports the stability of total Se, SeMet and TMSe⁺ in freeze-dried oyster and in the enzymatic extracts stored in Pyrex and polyethylene containers at different temperatures (–18, 4 and 20 °C). Total selenium determinations and Se speciation were carried out by HG-AAS after acid digestion in a microwave oven and by on-line coupling of cation exchange HPLC-ICP-MS after enzymatic hydrolysis, respectively.The results obtained for the freeze-dried sample showed that total Se and the selenium species evaluated are stable for at least 12 months, under all the conditions tested. However, Se species in the enzymatic extracts are only stable for 10 days if stored at 4 °C in Pyrex containers. These results show that the extracts do not necessarily have to be analysed just after sample treatment.

Keywords: Selenium species Stability HPLC-ICP-MS

Determination of lead in biological samples by use of slurry sampling electrothermal atomic absorption spectrometry by Pérez B. Cid; C. Silva; C. Boia (pp. 477-483).

Slurry-sampling electrothermal atomic absorption spectrometry has been applied to the determination of lead in several biological samples (fish and marine algae). The slurries were prepared both by magnetic shaking and microwave-heating and the effect of instrument operating conditions and slurry preparation conditions on the signal were examined. In addition, results from slurry sampling were compared with those obtained by microwave-assisted acid digestion of the same samples and no significant differences were found between them when the analysis of variance (ANOVA) was applied. The between-batch precision of the slurry techniques employed was similar to that for the microwave-assisted digestion procedure; values were always below 6.7%, except for the Dicentrarchus labrax sample for which the value obtained was 9.5% when using slurry magnetic shaking and 7.6% when using the slurry microwave heating. The accuracy of the slurry methodology employed was also evaluated by analysis of two biological reference materials (NIST-1577b and IAEA-V10); percentage recoveries obtained were between 95.6 and 98.5% of the values certified for lead.

Keywords: Lead Slurry sampling Electrothermal atomic absorption spectrometry Microwave-assisted digestion Biological samples

Spectrophotometric determination of verapamil hydrochloride in drug formulations with chloramine-T as oxidant. by Nafisur Rahman; Md Hoda (pp. 484-489).

A new spectrophotometric method is described for the determination of verapamil hydrochloride, based on its oxidation with chloramine-T in hydrochloric acid medium. It produces a yellow colored compound with maximum absorbance at 425 nm. Beer's law was obeyed in the concentration range 0–340 µg mL^–1 with molar absorptivity 2×10³ L mol^–1 cm^–1 and RSD 0.3–0.82%. All variables were studied to optimize the reaction conditions. No interferences were observed from the common excipients present in the formulations. The method has been applied successfully to the determination of the drug in pharmaceutical preparations. Statistical comparison of the results with those from the reference method reveals excellent agreement and confirms that accuracy and precision are not significantly different.

Keywords: Verapamil hydrochloride Chloramine-T Spectrophotometry Pharmaceutical formulations

Laser-induced fluorescence with an OPO system. Part I. Optimisation of the analytical system by use of experimental design methodology. Application to the direct quantification of traces of benzo[a]pyrene by P. Giamarchi; L. Burel; L. Stephan; Y. Lijour; A. Le Bihan (pp. 490-497).

This study deals with the optimisation and application of a method for direct analysis of trace pollutants in water by laser-induced fluorescence. The arrangement used consisted of an Nd:YAG Laser coupled with an optical parametric oscillator (LYOPO) and connected to a spectrophotometer and a high-sensitivity camera. Optimisation was achieved by developing an experimental design methodology to maximise the signal-to-noise ratio and reduce the limit of detection. The technique was then applied to the detection of benzo[a]pyrene in water. The experimental results were evidence of its high sensitivity and time-resolution potential. The detection limit for benzo[a]pyrene was 0.7 ng L^–1 in drinking water and 4 ng L^–1 in raw water containing 1 mg L^–1 humic acids.

Keywords: Laser-induced fluorescence (LIF) Time-resolved fluorescence Direct determination Optimisation Experimental design Polycyclic aromatic hydrocarbons (PAH) Ultra-trace quantification

Determination of total phenols in environmental wastewater by flow-injection analysis with a biamperometric detector by Chuan Zhao; Jun-feng Song; Jun-cai Zhang (pp. 498-504).

A flow injection (FI) method with a biamperometric detector, based on the biamperometry for an irreversible redox couple, is described for the determination of phenols in environmental wastewater. The method relies on coupling of the oxidation of phenols at one platinum-wire electrode with the reduction of MnO₄ ^– at another platinum wire electrode to enable biamperometric detection with an applied potential difference of 0 V. The linear dynamic range for the dependence of current on phenol concentration was from 1.0×10^–6 to 1.0×10^–4 mol L^–1, with a detection limit of 4.0×10^–7 mol L^–1 (signal-to-noise ratio, S/N=3). In comparison with the 4-aminoantipyrine (4-AAP) standard method and the 3-methyl-2-benzothiazoline hydrazone (MBTH) method the proposed method can be used to detect many para-substituted phenols that do not react with 4-AAP and MBTH, and response factors are higher for most of the phenols tested. The method, which is simple, economic, and rapid (180 samples h^–1), has been applied to the analysis of four wastewater samples. The results obtained were compared with those from 4-AAP method. The recoveries obtained by adding phenol standards to samples ranged from 94.3 to 105.2% with a standard deviation of 3.6%.

Keywords: Phenols Flow-injection analysis Biamperometry Irreversible redox couple Environmental analysis

Interlaboratory assessment of measurement precision and bias in the coulometric Karl Fischer determination of water by Sam A. Margolis; Jacob B. Angelo (pp. 505-512).

The precision and bias of the coulometric Karl Fischer ASTM method D1533–00 have been assessed in a collaborative ASTM round robin program for a group of 34 laboratories. The test materials used in this study included water saturated 1-octanol (WSO), water saturated 1-butanol (WSB), and a series of new and used transformer oil samples. Fundamental systematic biases have been demonstrated in the accuracy of the measurement of water in the WSO, WSB, and transformer oil samples. The systematic bias in the measurement of the WSO and WSB standards indicates that for some laboratories either the instruments were not accurate or the quantity of the standard was not measured accurately. A second type of systematic bias consisted of measurement errors associated with the selection of the Karl Fischer solvent that was used with each instrument, and this was superimposed upon the error in the measurement of the water in the standards. Using the statistical calculation method ASTM D 6300 the repeatability and reproducibility for water in transformer oil were found to be 7 mg/kg and 14 mg/kg respectively. The method detection limit of water was 8 mg/kg oil. The method bias was estimated based on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2890, WSO, since no suitable reference material for water in transformer oil was available for this study.

Keywords: Karl Fischer method Coulometry Transformer oil Measurement error Precision Bias

Stability study of As(III), As(V), MMA and DMA by anion exchange chromatography and HG-AFS in wastewater samples by Marta Segura; Juan Muñoz; Yolanda Madrid; Carmen Cámara (pp. 513-519).

The stability of arsenic species {arsenate [As(V)], monomethylarsonate [MMA], dimethylarsinate [DMA] and arsenite [As(III)]} in two types of urban wastewater samples (raw and treated) was evaluated. Water samples containing a mixture of the different arsenic species were stored in the absence of light at three different temperatures: +4 °C, +20 °C and +40 °C. At regular time intervals, arsenic species were determined by high performance liquid chromatography (HPLC)-hydride generation (HG)-atomic fluorescence spectrometry (AFS). The experimental conditions for the separation of arsenic species by HPLC and their determination by AFS were directly optimised from wastewater samples. As(III), As(V), MMA and DMA were separated on an anion exchange column using phosphate buffer (pH 6.0) as the mobile phase. Under these conditions the four arsenic species were separated in less than 10 min. The detection limits were 0.6, 0.9, 0.9 and 1.8 µg L^–1 for As(III), DMA, MMA and As(V), respectively. As(V), MMA and DMA were found stable in the two types of urban wastewater samples over the 4-month period at the three different temperatures tested, while the concentration of As(III) in raw wastewater sample decreased after 2 weeks of storage. A greater stability of As(III) was found in the treated urban wastewater sample. As(III) remained unaltered in this matrix at pH 7.27 over the period studied, while at lower pH (1.6) losses of As(III) were detected after 1 month of storage. The results show that the decrease in As(III) concentration with time was accompanied by an increase in As(V) concentration.

Keywords: Arsenic Speciation Wastewater Atomic fluorescence spectrometry Stability

On-column complexation and simultaneous separation of vanadium(IV) and vanadium(V) by capillary electrophoresis with direct UV detection by ZuLiang Chen; Ravendra Naidu (pp. 520-525).

An on-column complexation method has been developed for the simultaneous determination of V(IV) and V(V). Vanadium species were chelated with aminopolycarboxylic acids to form anionic complexes which were separated by capillary zone electrophoresis (CZE) with direct UV detection. Ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentacetric acid (DTPA), nitrilotriacetic acid (NTA), and N-2-hydroxyethylethlendiaminetriacetric acid (HEDTA) were investigated as both ligand and running electrolyte. Of the ligands studied the complexes of EDTA with V(IV) and V(V) resulted in the highest selectivity and UV response.The conditions used for on-column complexation and separation, including pH, and electrolyte ligand concentration, were examined to achieve reasonable separation selectivity and detection sensitivity. The optimum separation of the anionic forms of V(IV) and V(V) was obtained by use of CZE with UV detection at 185 nm and an electrolyte containing 5 mmol L^–1 EDTA at pH 4.0. Linear calibration plots were obtained in the concentration range10–300 µmol L^–1; detection limits were 3 µmol L^–1 for V(IV) and 1 µmol L^–1 for V(V). The proposed method was demonstrated for the determination of vanadium in groundwater spiked with V(IV) and V(V).

Keywords: Vanadium species On-line complexation CZE Ligands

Hydride generation for the direct determination of trace and ultra-trace level of arsenic and antimony in waters using derivative atomic absorption spectrometry by Han-Wen Sun; Jing Ha; Jian-Min Sun; De-Qiang Zhang; Li-Li Yang (pp. 526-529).

A new method is developed for the direct determination of trace and ultra-trace level of arsenic and antimony in waters by hydride generation derivative atomic absorption spectrometry (DHGAAS). The signal model and fundamentals of DHGAAS are described. The effects of atomization temperature, argon flow rate, acidity and concentration of KBH₄and KI were investigated and analytical conditions were optimized. The sensitivities for arsenic and antimony were increased 36.4 and 27.6 times better than those of conventional hydride generation atomic absorption spectrometry (HGAAS). For a 2 mV min^–1 sensitivity range setting, the characteristic concentration was 0.003 µg L^–1 for arsenic and 0.004 µg L^–1for antimony, and the detection limits (3σ) were 0.015 µg L^–1 for arsenic and 0.020 µg L^–1 for antimony. The proposed method was applied to the determination of arsenic and antimony in several water samples with satisfactory results.

Keywords: Derivative signal model Fundamental HGAAS Arsenic Antimony Water

Field preconcentration of cadmium from seawater by using a minicolumn packed with Amberlite XAD-4/4-(2-pyridylazo) resorcinol and its flow-injection-flame atomic absorption spectrometric determination at the ng L^–1 Level by M. Yebra; J. Salgado; L. Puig; A. Moreno-Cid (pp. 530-534).

A flow injection analysis-flame atomic absorption spectrometric method for the determination of cadmium in seawater was developed with the aim of yielding a sensitive assay with a low detection limit. The method employs a field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 4-(2-pyridylazo) resorcinol. A Plackett-Burman 2⁷×3/32 design for seven factors (sample pH, sample flow rate, eluent volume, eluent concentration, eluent flow rate, ethanol percentage in the eluent and minicolumn diameter) was carried out in order to find the significant variables affecting the field continuous preconcentration system (FCPS) and the flow injection elution manifold for cadmium determination in seawater samples by flame atomic absorption spectrometry. Cadmium can be preconcentrated with an enrichment factor of 1053 for a sample volume of 200 mL and a preconcentration time of 57 min. In these experimental conditions, the method provides a linear relationship between absorbance and cadmium concentration in the range from 22–1900 ng L^–1, with a detection limit (3SD) of 6 ng L^–1. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 8.9–0.8% in cadmium solutions of 50–700 ng L^–1. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified value. This procedure was applied to the determination of cadmium in seawater from Galicia (Spain).

Keywords: Field sample preconcentration Chelating minicolumns Flow–injection Cadmium Seawater

A high–efficiency annular diffusion scrubber for the collection of water-soluble trace atmospheric gases by In-Hyoung Chang; Sung-Bong Chun; Dong Lee (pp. 535-539).

The design and construction details of an annular diffusion scrubber to be used as a quantitative gas sampler are described. A large-diameter inner tube (12 mm o.d.) wrapped with liquid channel interior of thin membrane (70 µm thickness) provided high collection efficiency. With SO₂ as the test gas, the performance data for a high-efficiency annular diffusion scrubber, coupled to an ion chromatograph, are presented. Quantitative collection and excellent reproducibility are observed at air sampling rates up to 2 L/min. The estimated detection limit is 4 pptv for a 20-L air sampling volume.

Keywords: Annular diffusion scrubber Hydrophilic inner tube Porous membrane Atmospheric analysis

Removal of trivalent chromium from tannery waste waters using bone charcoal by S. Dahbi; M. Azzi; N. Saib; M. de la Guardia; R. Faure; R. Durand (pp. 540-546).

The ability of bone charcoal to remove Cr(III) from aqueous solutions by adsorption has been investigated. The adsorbent used was first characterised and then the adsorption was studied as a function of time and amount of charcoal. Tests were carried out with synthetic solutions whose Cr concentrations (500 mg L^–1) were similar to those found in some effluents of Moroccan tannery industries. Cr removal efficiencies higher than 90% were obtained at pH 3.5 using 3 g of bone charcoal and a stirring time of about 30 min. Results of Cr removal by all sieved fractions of bone charcoal had shown the same interesting capabilities for Cr(III) retention. The cross interference with other elements was also investigated. Pre-treatment of bone charcoal by nitric acid led to an increase in its specific surface area but induced a drastic reduction in its Cr elimination abilities. Adsorption tests were also carried out using calcinated bone charcoal. The results obtained showed a similar percentage of Cr retention to those found with untreated bone charcoal. On the other hand, a double treatment of bone charcoal with HCl and NaOH provided an enhancement of Cr(III) retention. The role played by the mineral fraction of the solid phase of bone was thus evidenced.

Keywords: Tannery wastewaters Chromium Bone charcoal Chemical treatment Thermal treatment

Microwave-assisted extraction and mild saponification for determination of organochlorine pesticides in oyster samples by N. Carro; I. García; M.-C. Ignacio; M. Llompart; M.-C. Yebra; A. Mouteira (pp. 547-553).

A sample-preparation procedure (extraction and saponification) using microwave energy is proposed for determination of organochlorine pesticides in oyster samples. A Plackett–Burman factorial design has been used to optimize the microwave-assisted extraction and mild saponification on a freeze dried sample spiked with a mixture of aldrin, endrin, dieldrin, heptachlor, heptachorepoxide, isodrin, transnonachlor, p,p′-DDE, and p,p′-DDD. Six variables: solvent volume, extraction time, extraction temperature, amount of acetone (%) in the extractant solvent, amount of sample, and volume of NaOH solution were considered in the optimization process. The results show that the amount of sample is statistically significant for dieldrin, aldrin, p,p′-DDE, heptachlor, and transnonachlor and solvent volume for dieldrin, aldrin, and p,p′-DDE. The volume of NaOH solution is statistically significant for aldrin and p,p′-DDE only. Extraction temperature and extraction time seem to be the main factors determining the efficiency of extraction process for isodrin and p,p′-DDE, respectively. The optimized procedure was compared with conventional Soxhlet extraction.

Keywords: Microwave-assisted extraction (MAE) Microwave-assisted mild saponification (MAMS) Organochlorine pesticides Oyster sample Gas chromatography–mass spectrometry

Enrichment of iron(III), cobalt(II), nickel(II), and copper(II) by solid-phase extraction with 1,8-dihydroxyanthraquinone anchored to silica gel before their determination by flame atomic absorption spectrometry by Anupama Goswami; Ajai K. Singh (pp. 554-560).

A chelating matrix prepared by immobilizing 1,8-dihydroxyanthraquinone on silica gel modified with 3-aminopropyltriethoxysilane has been characterized by use of cross-polarization magic angle spinning (CPMAS) NMR, diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy, and thermogravimetric analysis and used to preconcentrate Fe(III), Co(II), Ni(II), and Cu(II) before their determination by flame atomic absorption spectrometry. The optimum pH ranges for quantitative sorption are 6.5–8.0, 6.0–7.0, 6.0–8.0, and 7.0–8.5 for Cu, Fe, Co, and Ni, respectively. All the metal ions can be desorbed with 2 mol L^–1 HCl or HNO₃. The sorption capacity (µmol g^–1 matrix) and preconcentration factor were 226.6, 250; 365.6, 300; 101.8, 150; and 109.0, 250 for Cu, Fe, Co, and Ni, respectively. The lowest concentration for quantitative recovery was 4.0, 3.3, 6.6, and 4.0 ng mL^–1, respectively for the four metal ions. The limits up to which electrolytes NaNO₃, NaCl, NaBr, Na₂SO₄, and Na₃PO₄ and cations Ca(II) and Mg(II) can coexist with the four metal ions during their sorption without adverse effect are reported. The simultaneous enrichment and determination of all the four metals is possible if the total load of metal ions is less than the sorption capacity. Flame AAS was used to determine the metal ions in underground, tap, and river water samples (RSD≤7.1%) after their enrichment with the matrix. The cobalt content of pharmaceutical samples (multivitamin tablet) preconcentrated by use of this silica gel matrix and determined by FAAS was found to be 2.00 µg g^–1, with RSD˜1.7% (reported concentration level, 1.99 µg g^–1).

Keywords: Silica gel 1,8-Dihydroxyanthraquinone Metal ion Flame atomic absorption spectrometry Solid-phase extraction

Determination of caffeine in tea samples by Fourier transform infrared spectrometry by Janina Ohnsmann; Guillermo Quintás; Salvador Garrigues; Miguel de la Guardia (pp. 561-565).

A sustainable and environmentally friendly procedure has been developed for the FTIR determination of caffeine in tea leaf samples. The method is based on the extraction with ammonia and CHCl₃ and direct determination of caffeine on the chloroform extracts using peak height absorbance measurements at 1658.5 cm^–1 and external calibration. The method provides a sensitivity of 0.2142 absorbance units mg^–1 mL and a limit of detection of 1 mg L^–1, corresponding to 0.002% m/m caffeine in tea leaves. As compared with a reference procedure, based on UV absorbance measurement at 276 nm after low pressure column chromatography, the developed procedure reduces the consume of CHCl₃ by a factor of 10, that of NH₄OH by a factor of 20 and avoids the use of diethyl ether and Celite. The time required to do the analysis of a sample is 15 minutes as compared with the 6 hours for the reference one.

Keywords: Caffeine Tea FTIR Solvent extraction

Comparative analysis of ancient ceramics by neutron activation analysis, inductively coupled plasma–optical-emission spectrometry, inductively coupled plasma–mass spectrometry, and X-ray fluorescence by Alexandra Tsolakidou; Vassilis Kilikoglou (pp. 566-572).

The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma–optical-emission spectrometry (ICP–OES) and inductively coupled plasma–mass spectrometry (ICP–MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics.

Keywords: Ceramics Neutron activation analysis X-ray fluorescence Inductively coupled plasma–optical-emission spectrometry Inductively coupled plasma–mass spectrometry

The rapid identification of organic colorants by UV/vis spectroscopy by Heinz Langhals (pp. 573-578).

A rapid UV/vis spectroscopic method for the identification of organic colorants by the use of Gaussian analysis is presented. Sets of parameters are obtained for the screening with a low number of data. An optical distance using line positions and intensities is defined as a measure for the similarity of UV/vis spectra.

Keywords: UV/vis spectroscopy Analysis of dyes Azo dyes Line-type analysis Identification of dyes

Sections

Personal tools

Analytical and Bioanalytical Chemistry (v.374, #3)

Sections

Personal tools

Local resources

Analytical and Bioanalytical Chemistry (v.374, #3)