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Analytica Chimica Acta (v.532, #2)

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

Calendar of forthcoming meetings (pp. n5-n7).

Contents (pp. iii-iv).

Development of a novel method for screening of estrogenic compounds using nano-sized bacterial magnetic particles displaying estrogen receptor by Tomoko Yoshino; Fukuichi Kato; Haruko Takeyama; Makoto Nakai; Yoshikuni Yakabe; Tadashi Matsunaga (pp. 105-111).

In this study, nano-sized bacterial magnetic particles (BMPs) displaying human estrogen receptor ligand binding domain (ERLBD) on the surface was successfully produced by the magnetic bacterium, Magnetospirillum magneticum AMB-1. Furthermore, a non-isotopic binding assay for estrogenic compounds using the BMPs displaying ERLBD was developed. A BMP membrane-specific protein, Mms16, was used as an anchor molecule to localize ERLBD on the surface of BMPs. ERLBD–BMP complexes were simply extracted by magnetic separation from ruptured AMB-1 transformants and used for the assay based on the competitive binding of alkaline phosphatase conjugated 17β-estradiol (ALP-E2) as a tracer. Dissociation constant of the receptor was 2.3nM. Inhibition curves were evaluated by the decrease in luminescence intensity resulting from the enzymatic reaction of alkaline phosphatase. The overall simplicity of this receptor binding assay results in a method that can be easily adapted to a high throughput format. Moreover, this method can be integrated into a fully-automated ligand screening system using magnetic separation.

Keywords: Abbreviations; BMPs; bacterial magnetic particles; E2; 17β-estradiol; ERLBD; estrogen receptor ligand binding domain; ALP-E2; alkaline phosphatase conjugated 17β-estradiol; RI; radioisotope; ERLBD-BMPs; ERLBD displayed onto BMPs; IC; ₅₀; concentration of 50% inhibition; RBAs; relative binding affinitiesBacterial magnetic particles (BMPs); Estrogen receptor ligand binding domain (ERLBD); Estrogenic compounds; alkaline phosphatase conjugated 17β–estradiol (ALP-E2)

Artifact formation of methyl- and ethyl-mercury compounds from inorganic mercury during derivatization using sodium tetra( n-propyl)borate by Jen-How Huang (pp. 113-120).

Sodium tetra( n-propyl)borate (NaBPr₄) was introduced as derivatization reagent to extend the possibility for determining ethyl-mercury compounds. This study investigated the artifact formation of methyl- and ethyl-mercury compounds during NaBPr₄ derivatization, together with the influence of this artifact on organomercury analysis in environmental samples. The artifact methyl- and ethyl-mercury compounds during NaBPr₄ derivatization were evident and depended strongly on the amount of Hg(II) present in the solution for derivatization. Some unidentified organomercury compounds were found when the amount of Hg(II) in the derivatization solution was over 1μg. The amounts of NaBPr₄ and acetate buffer and the presence of organometallic compounds other than organomercury showed little influence on the artifact effect. The artifact monoethylmercury encompasses 0.99–2.9% of the amount of Hg(II) present and interferes strongly with the monoethylmercury analysis. The formation rate of artifact monomethylmercury is much lower and ca. 0.03–0.28% of the Hg(II) present. The artifact affects remarkably the monomethylmercury analysis for solid samples when these have a low ratio of monomethylmercury-to-total Hg concentrations (≤0.003) and the recovery of Hg from the samples is high. Mathematical correction seems to be difficult due to the low reproducibility of this artifact effect. Formation of artifact organomercury compounds caused during NaBPr₄ derivatization may lead to false Hg speciation and overestimate concentrations of organomercury compounds.

Keywords: Monomethylmercury; Monoethylmercury; Sodium tetra(; n; -propyl)borate; Artifact

Highly selective determination of total mercury(II) sub microgram per liter by β-cyclodextrin polymer solid-phase spectrophotometry using 1,3-di-(4-nitrodiazoamino)-benzene by Yongwen Liu; Xijun Chang; Xiuqin Hu; Yong Guo; Shuangming Meng; Fengying Wang (pp. 121-128).

A highly selective β-cyclodextrin polymer solid-phase spectrophotometric (β-CDPSPS) method is described for the determination of total mercury(II) sub microgram per liter. The methods are based on the chromogenic reaction of mercury(II) with 1,3-di-(4-nitrodiazoamino)-benzene (DNAAB) loaded on β-cyclodextrin polymer (β-CDP). In pH 10.0 borax buffer, Hg(II)-DNAAB complex on β-CDP gives a positive peak at 445nm and a negative one at 545nm. The absorbance was measured at two peaks and the net absorbance ( A_s) was calculated between the difference of positive and negative peaks. The apparent molar absorptivity is 1.1×10⁷lmol⁻¹cm⁻¹ (82-fold of it in solution) for 100ml sample and the linear range of the determination is 0.062–250μgl⁻¹. The selectivity for coexistent ions was greatly improved, only silver(I) interfered with the mercury determination and the amount of the others was reduced 25–1000 times compared to previous solution method. The interference caused by silver(I) can be eliminated using tri-n-octylmethylammonium bromide as masking agent. The detection limit and the quantification limit were found to be 0.024 and 0.062μgl⁻¹, respectively. The relative standard deviation of ten replicate determinations of 5.0μg mercury(II) in 100ml sample was of 2.4%. The method was validated by analyzing the water and soil reference materials and successfully applied to the determination of mercury(II) in locally collected water and dust samples.

Keywords: Solid-phase spectrophotometry; β-Cyclodextrin; 1,3-Di-(4-nitrodiazoamino)-benzene; Mercury(II); β-CDP-DNAAB; Water; Dust

A novel polymeric membrane electrode for the potentiometric analysis of Cu²⁺ in drinking water by Zs�fia Szigeti; Istv�n Bitter; Kl�ra T�th; Christopher Latkoczy; Daniel J. Fliegel; Detlef G�nther; Ern� Pretsch (pp. 129-136).

Based on a novel ionophore, an ion-selective electrode has been developed for the determination of Cu²⁺ in drinking water. Its selectivity behavior is characterized and its lower detection limit optimized for measurements with different electrolyte backgrounds. The lower detection limit was 2×10⁻⁹M Cu²⁺ for samples with low ionic background and 1×10⁻⁷M Cu²⁺ with ionic background typically found in drinking water.

Keywords: Potentiometric sensor; ICP-MS; Copper determination; Drinking water

A novel biosensing interfacial design based on the assembled multilayers of the oppositely charged polyelectrolytes by Ting Deng; Hua Wang; Ji-Shan Li; Guo-Li Shen; Ru-Qin Yu (pp. 137-144).

A novel biosensing interfacial design strategy has been produced by the alternate adsorption of the oppositely charged polyelectrolytes. A quartz-crystal microbalance (QCM) as a model transducer was modified by use of mercaptoacetic acid (MAA) self-assembled monolayer (SAM) and the adsorption multilayers of the oppositely charged polyelectrolytes. MAA–SAM was first applied to the gold electrode surface of the crystal, and the positively charged chitosan was used as a double-sided linker to attach the negatively charged alginate-HSA antibodies to the negatively charged MAA–SAM layer. The assembly process and conditions were studied using the real-time output device and the surface topologies of the resulting crystals were characterized by atomic force microscopy (AFM) imaging. It is discovered that the optimal pH of immobilizing antibodies was 7.2 and the suited dilution ratio of antibodies was 10:30. The proposed immunosensor in optimal conditions has a linear detection range of 12.3–184.5μg/mL for HSA detection. Comparing with the direct immobilization method of antibodies, the immunosensor with the proposed immobilization procedure shows some advantages, such as improved sensitivity due to the well-retained antibody activity and the significantly extended detection range. In particular, the regeneration of the developed immunosensor was simple and fast. Analytical results indicate that the developed immobilization procedure is a promising alternative for the immobilization of biorecognition element on the electrode surface.

Keywords: Mercaptoacetic acid (MAA); Polyelectrolytes; Immunoassay; Multilayers

A glucose biosensor using methyl viologen redox mediator on carbon film electrodes by Mariana Emilia Ghica; Christopher M.A. Brett (pp. 145-151).

A new methyl viologen-mediated amperometric enzyme electrode sensitive to glucose has been developed using carbon film electrode substrates. Carbon film electrodes from resistors fabricated by pyrolytic deposition of carbon were modified by immobilization of glucose oxidase through cross-linking with glutaraldehyde in the presence of bovine serum albumin. The mediator, methyl viologen, was directly immobilised with the enzyme together with Nafion cation-exchange polymer. The electrochemistry of the glucose oxidase/methyl viologen modified electrode was investigated by cyclic voltammetry and by electrochemical impedance spectroscopy. The biosensor response to glucose was evaluated amperometrically; the detection limit was 20μM, the linear range extended to 1.2mM and the reproducibility of around 3%. When stored in phosphate buffer at 4°C and used every day, the sensor showed good stability over more several weeks.

Keywords: Glucose; Glucose oxidase; Amperometric enzyme electrode; Carbon film electrode; Methyl viologen mediator; Nafion

Zinc(II)-selective sensors based on dibenzo-24-crown-8 in PVC matrix by V.K. Gupta; M. Al Khayat; A.K. Minocha; Pankaj Kumar (pp. 153-158).

Membranes of dibenzo-24-crown-8 (I) as an ion active material in poly(vinylchloride) (PVC) based matrix have been tried for zinc(II)-selective sensors. The effect of anion excluder, sodium tetraphenylborate (NaTPB) and plasticizers, tris(2-ethylhexyl)phosphate (TEP), tributylphosphate (TBP), dibutylphthalate (DBP), dibutyl(butyl)phosphonate (DBBP), 1-chloronaphthalene (CN) and dioctylphthalate (DOP) on the performance of the membrane electrodes has also been studied. It was observed that the membrane having the composition (I): PVC:NaTPB:DOP in the ratio 10:200:2:100 gave the best results with a wide working concentration range of 9.2×10⁻⁵ to 1.0×10⁻¹M, Nernstian slope of 29.0±0. 5mV/decade of activity, fast response time of 12s and good selectivity over a number of mono-, bi-, and trivalent cations. The sensor works well in a pH range 4.8–6.2 and can be employed for the estimation of zinc ions in partially non-aqueous medium having up to 10% (v/v) methanol, ethanol or acetone content. The practical utility of the sensor has been demonstrated by using it successfully as an indicator electrode in the potentiometric titration of Zn²⁺ with EDTA and also for the determination of Zn²⁺ in a real sample analysis of wastewater.

Keywords: Crown ether; Potentiometric sensor; Waste analysis; Zinc sensor

Terbium-sensitized luminescence optosensor for the determination of norfloxacin in biological fluids by E.J. Llorent Mart�nez; J.F. Garc�a Reyes; P. Ortega Barrales; A. Molina D�az (pp. 159-164).

The use of a flow through solid phase terbium-sensitized luminescence system is described for the determination of the widely used fluoroquinolone norfloxacin. A chelate between the terbium ion and the analyte is formed online previously to the sample injection into the carrier stream. Then the chelate is transported towards the flow-through cell, where it is retained on a cationic Sephadex resin packed in the cell, developing the corresponding luminescence signal. Afterwards, an ethylenediaminetetraacetic acid solution was used as eluting agent, in order to regenerate the sensing zone. The system has been satisfactorily applied to the determination of norfloxacin in human urine and serum, without the need of a pre-treatment. The response was linear in the range 10–150ngml⁻¹. The detection and quantification limits were 1.5 and 5ngml⁻¹, respectively and the R.S.D. 1.82%.

Keywords: Norfloxacin; Lanthanide-sensitized luminescence; Terbium; Urine; Serum

Study of 17β-estradiol-3-benzoate, 17α-methyltestosterone and medroxyprogesterone acetate fixation in bovine hair by Lauriane Rambaud; Emmanuelle Bichon; Nora Cesbron; Fran�ois Andr�; Bruno Le Bizec (pp. 165-176).

The detection of steroid residues in hair is a powerful strategy to demonstrate long-term administration of these growth promoters in meat production animals. A fast and reliable method was developed for monitoring anabolic steroids and their esters in hair. A 100mg hair sample was converted into powder and extracted at 50°C with methanol (sebum fraction). The remaining hair was digested with 1M NaOH for further extraction of bound steroids. The two fractions were separately purified onto an aminopropyle solid-phase extraction column and onto a silica SPE cartridge. Steroids were detected either by gas chromatography–tandem mass spectrometry after silylation using N-methyl-N-(trimethylsilyl)-trifluoroacetamide/trimethyliodosilane/dithiothreitol or liquid chromatography–tandem mass spectrometry. This method was applied to hair samples collected over a three months period after treatment of three cows respectively with 17α-methyltestosterone, medroxyprogesterone acetate and 17β-estradiol-3-benzoate. The fixation kinetic into hair of the three steroids have been deeply examined and discussed; relation in-between concentration and distance from the injection site, influence of hair colour and sample treatment consequences have been discussed.

Keywords: Anabolic; Steroid; Esters; Hair; GC–MS/MS; LC–MS/MS

FT-Raman spectroscopic studies of guarana and some extracts by Howell G.M. Edwards; Dennis W. Farwell; Luiz F.C. de Oliveira; Jose-Maria Alia; Mireille Le Hyaric; Mauro V. de Ameida (pp. 177-186).

The Raman spectrum of guarana, an important product of the Amazonian rain forest, has been investigated; the therapeutic properties of guarana and it's extracts have been realised for some time and have been attributed to guaranine, which could be a complex of caffeine and tannins or to a new xanthine natural product. The purpose of this study is two-fold: firstly, to provide molecular structural information about guarana seeds and their extracts and, secondly, to test the viability of using the technique as a method of verification of genuine guarana extracts from synthetic composites. Raman spectroscopy shows that the composition of the guarana is very similar for the whole seed and for the outer and inner portions of the dissected seed, which are closely similar also to the ground commercial powders produced in the Amazon for the distributors. The results indicate that Fourier-transform Raman spectroscopy could be used for the monitoring of quality control of guarana products in the phytopharmaceutical industry.

Keywords: Raman spectroscopy; Guarana; Caffeine; Natural plant extracts

Black crusts and patinas on Pentelic marble from the Parthenon and Erechtheum (Acropolis, Athens): characterization and origin by P. Maravelaki-Kalaitzaki (pp. 187-198).

This study describes an analytical approach for the characterization and origin of the encrustation formed on the surface of monuments from the Acropolis in Athens. The morphology of encrustation was investigated by optical and scanning electronic microscopy. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray fluorescence (EDXRF) and scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDS) identify and quantify the key elements and compounds associated with the genesis of encrustation. Black crusts (>200μm thick), consisting of gypsum, calcite and elements such as Si, Al, Fe, Pb, Ti, Zn and Mn, were being formed from interaction between the marble surface and atmospheric pollutants. Orange-brown accretions on the Parthenon, called patinas (∼150μm thick), comprise calcite, calcium oxalates, low amount of S, and both in the inner and outer parts significant and almost constant amounts of Si, P and Fe; P and Fe identified as hydroxyapatite and hematite, respectively. In the Parthenon patinas, the EDS distribution maps of Si, Fe and P indicate an origin that may be attributed to the residue and transformation of ancient treatments rich in these elements. Patinas from the Erechtheum (∼100μm thick) resemble plasters consisting of calcite, siliceous sand, hydroxyapatite, calcium oxalates and hematite. EDXRF highlighted the presence of Pb in the patinas from the Erechtheum; FTIR revealed that Pb is in the form of cerussite most probably from the use of attic ochre. The patinas from the Parthenon and Erechtheum, as opposed to black crusts, are associated with the best-preserved surfaces and should remain intact during conservation interventions.

Keywords: Parthenon; Crusts; Patina; Oxalates; Silicon; Erechtheum; Lead

Radium measurement in water samples by α-liquid scintillation counting with α/β discrimination by J. Aupiais (pp. 199-207).

A fast and inexpensive sample preparation method for quantitative determination of radium in water involving α-liquid scintillation with α/β discrimination has been assessed. The optimal extraction of²²⁶Ra by the extractive-scintillator cocktail RADAEX^® requires pH above 10, which leads to salt precipitation in samples of high salinity. Salt precipitation can be prevented by addition of α-hydroxyisobutyric acid (HIBA). This methodology, including sample preparation and peak treatment, has been successfully tested with 13 natural and synthetic certified samples furnished by the International Atomic Energy Agency (IAEA). Furthermore, two natural waters collected in France during a Round Robin exercise have been used to evaluate the repeatability. For 5ml sample aliquot and 240000s counting-time, the detection limit is estimated to be 0.04Bql⁻¹. The sample preparation requires less than 1h per sample. The precision ranges from about 50% at the detection limit to a maximal theoretical uncertainty of 4% due to the combined uncertainties of the pipettes, the balance and the chemical yield. The repeatability has been estimated to about 7%.

Keywords: α-Liquid scintillation; Extractive-scintillator cocktail; Radium

Measurement of diffusion and partition coefficients of ferrocyanide in protein-immobilized membranes by Hsien-Chang Chang; Ching-Chou Wu; Shinn-Jyh Ding; I-Shiun Lin; I-Wen Sun (pp. 209-214).

True diffusion ( D_m) and partition ( α) coefficients for the transport of potassium ferrocyanide through diaphorase (Dp)– and bovine serum albumin (BSA)–glutaraldehyde (GA) membranes with different cross-linking degrees of 1–8% GA concentrations immobilized on gold electrodes are investigated by using potential-step method and rotating-disk-electrode method. The thickness of dry and hydrated immobilized membranes is accurately measured by the focus-difference method with a reflection microscope. The thickness of hydrated Dp–GA and BSA–GA membranes are about 1.4 and 2.4 times that of dry membranes, respectively. In addition, the actual area of electrode surface is calculated by the charge amount of chemisorbed oxygen on gold electrode. Owing to the increase of swelling degree and net negative charge of the immobilized membranes, the values of D_m and α for both of Dp–GA and BSA–GA membranes enlarge and decrease with increase of GA concentration, respectively. Furthermore, BSA–GA membranes possess greater D_m and α than those of Dp–GA membranes due to the thinner thickness and the greater swelling degree of BSA–GA membranes.

Keywords: Diffusion coefficient; Partition coefficient; Glutaraldehyde; Protein membrane; Potential step method

Author Index (pp. 215-216).

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Analytica Chimica Acta (v.532, #2)