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Analytica Chimica Acta (v.531, #2)

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

Contents (pp. iii-iv).

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

A steady-state and flow-through cell for screen-printed eight-electrode arrays by Eva Dock; Andreas Christenson; Svetlana Sapelnikova; Jan Krejci; Jenny Emn�us; Tautgirdas Ruzgas (pp. 165-172).

An electrochemical cell has been developed enabling amperometric steady-state- and flow-injection measurements with screen-printed arrays consisting of eight working electrodes ( �=1mm) arranged radially around a printed Ag/AgCl reference electrode in the centre. The cell contained a rotator, providing similar hydrodynamics over all the working electrodes in the array, which was manually centered under the rotator. The reproducibility of steady-state measurements with eight-electrode platinum or gold arrays in this cell was studied by measuring and comparing currents from ferricyanide reduction at each electrode in the array. It was found that the relative standard deviation (R.S.D.) for the currents at different electrodes on one array was below 5%. Similar R.S.D. was found if measurements were compared between several arrays. This indicates that manual insertion/positioning of the eight-electrode array in the cell and hydrodynamics at the electrodes provided measurement reproducibility similar to the reproducibility of manufacturing eight-electrode platinum or gold arrays by screen-printing. A comparative study was performed between screen-printed and through mask sprayed carbon arrays. It was found that the reproducibility of the sprayed arrays was similar to that of the platinum or gold screen-printed arrays, with R.S.D. values below 6% regarding the variation between electrodes within the same array and the variation between different arrays. To enable flow-injection measurements, a tube (0.4mm inner diameter) was inserted into a hole drilled through the centre of the steady-state cell rotator. This construction made it possible to inject the solution into the cell through the tube (not rotating), while the rotator was spinning over the eight-electrode array. It was found that this combination of flow-injection and mixing by a rotator provided a uniform current response over the array electrodes and that, at optimum conditions, the R.S.D. values between the eight electrodes in the array were nearly the same as in case of the steady-state measurements, i.e., below 5%.

Keywords: Electrode array; Steady-state measurements; Screen-printed electrode; Flow-through cell; Biosensor array

Amperometric immunosensor for detection of antibodies of Salmonella typhi in patient serum by V. Kameswara Rao; G.P. Rai; G.S. Agarwal; S. Suresh (pp. 173-177).

An amperometric sensor for detection of antibodies to Salmonella typhi in the serum of patients was developed. This involved usage of screen-printed electrodes and recombinant flagellin fusion protein. An indirect enzyme-linked immunosorbant assay was used for detection of antibodies to S. typhi in the patient serum. The screen-printed electrodes were made using polystyrene and graphite. These electrodes were tested for their ability to detect 1-naphthol, which is the product formed due to the hydrolysis of the substrate 1-naphthyl phosphate by the enzyme alkaline phosphatase. These electrodes were coated with recombinant flagellin fusion protein made by recombinant DNA technology and blocked with bovine serum albumin (BSA). Further they were incubated with patient serum and goat anti-human alkaline phosphatase conjugate. The immunosensing was performed by using amperometric method. Pooled human serum samples from apparently healthy individuals were used as control. Both the pooled healthy human serum samples and patient sera were subjected to Widal agglutination test and amperometric method. A 100% correlation was found between the Widal test and amperometric method. The time taken for the detection by electrochemical method is 1h and 15min, while the time taken by Widal test is 18h.

Keywords: Immunosensor; Typhoid; Screen-printed electrode; Amperometry; Salmonella typhi; Serum

Lanthanum-selective membrane electrode based on 2,2′-dithiodipyridine by Morteza Akhond; Mohammad Bagher Najafi; Javad Tashkhourian (pp. 179-184).

In this study, a new poly(vinyl chloride) (PVC) membrane sensor for La³⁺ ion based on 2,2′-dithiodipyridine as an ion carrier was prepared. This electrode revealed good selectivity for La³⁺ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of La³⁺ sensor were investigated. The electrode exhibited a Nernstian slope of 20.0±1.0mV per decade of La³⁺ over a concentration range of 7.1×10⁻⁶ to 2.2×10⁻²M of La³⁺ in the pH range 3.3–8.0. The response time was about 7s and the detection limit was 3.1×10⁻⁶M. The electrode can be used for at least 2 months without a considerable divergence in potential. The proposed electrode was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and was applied for determination of F⁻ ion in mouthwash solution.

Keywords: Lanthanum ion-selective electrode; 2,2′-Dithiodipyridine; PVC membrane; Potentiometry; Fluoride determination

Fluoride determination in some mouth wash preparations by a novel La(III) graphite coated membrane sensor based on amitraz by Mohammad Reza Ganjali; Vahideh Akbar; Maryam Ghorbani; Parviz Norouzi; Abbas Ahmadi (pp. 185-191).

Solution studies on the binding properties of N-2,4-dimethylphenyl- N′-ethylformamidine (amitraz) toward nine lanthanide ions including lanthanum, cerium, neodium, samarium, europium, gadolinium, terbium, dysprosium, ytterbium and some other transition and heavy metal ions such as copper, lead, cobalt, nickel ions, showed a selective 1:1 complexation between amitraz and lanthanum ions. Consequently, amitraz was applied as an ion carrier in construction of a novel poly(vinyl chloride) membrane sensor for La(III). The sensor has a linear dynamic range of 1.0×10⁻¹ to 1.0×10⁻⁷M with a Nernstian slope of 19.8±0.2mV per decade and a detection limit of 8.0×10⁻⁸M. The proposed sensor displays a fast response time (<8s), and can be used for at least 2 months without any considerable divergences in the potentials. The La(III) membrane sensor revealed comparatively good selectivity with respect to most of cations including alkaline, alkaline earth, and some transition and heavy metal ions. It could be used in a pH range of 3.0–9.0. The proposed membrane electrode was used as an indicator electrode in the potentiometric titration of La(III) ions with an EDTA solution, and also in the determination of fluoride concentration in some mouth wash preparations.

Keywords: La(III); Amitraz; Potentiometry; N; -2,4-Dimethylphenyl-; N; ′-ethylformamidine

Duplex RT-PCR and chemiluminometric hybridization assay for combined screening of the mRNAs of prostate-specific antigen and prostate-specific membrane antigen in peripheral blood by Evaggelia Emmanouilidou; Bakhos Tannous; Penelope C. Ioannou; Theodore K. Christopoulos (pp. 193-198).

Combined screening of the mRNAs for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) has been proposed as a more useful test than the separate PSA mRNA or PSMA mRNA assays in the molecular diagnosis and monitoring of prostate cancer. We have developed a simple and highly sensitive method for the simultaneous detection of PSA mRNA and PSMA mRNA using duplex RT-PCR and a chemiluminometric hybridization assay. Total RNA from peripheral blood was reverse-transcribed using oligo(dT)₂₀ primer followed by duplex PCR in the presence of two pairs of primers specific for PSA and PSMA. Heat-denatured biotinylated PCR products were hybridized with PSA- and PSMA-specific oligonucleotide probes immobilized in microtiter wells. The hybrids were determined by using a streptavidin–alkaline phosphatase conjugate and a chemiluminogenic substrate. Using the duplex PCR, 50 copies of PSA DNA and 5 copies of PSMA DNA can be detected with a signal/background ratio of 9.7 and 22, respectively. Analysis of samples containing total RNA corresponding to 0.04–400 LNCaP cells indicated that the detectability of the proposed method is 1 cancer cell equivalent in 10ml of peripheral blood. The overall reproducibility of the duplex assay, including reverse transcription, PCR, and hybridization assay, ranged from 3.6 to 15.5%. The method is very simple, rapid, sensitive and suitable for high-throughput screening analysis as opposed to the commonly used nested RT-PCR assays with electrophoretic detection.

Keywords: Duplex RT-PCR; Prostate-specific antigen; Prostate-specific membrane antigen; Chemiluminescence; Hybridization

Selectivity features of molecularly imprinted polymers recognising the carbamate group by C. Baggiani; L. Anfossi; P. Baravalle; C. Giovannoli; C. Tozzi (pp. 199-207).

The molecular recognition properties of molecular imprinted polymers which bind the carbamate function were studied. Functional monomers potentially able to form non-covalent interactions with the model molecule N, O-dibenzylcarbamate were selected on the basis of a computational approach describing possible interactions between the template and a small library of vinylic monomers. These results were in accordance with N, O-dibenzylcarbamate batch-rebinding measurements performed on several miniMIPs prepared with the same library. From these preliminary results, four polymers were prepared by thermoinduced radical polymerization, using ethylene dimethacrylate as a cross-linker, chloroform (MIP1, MIP3) or acetonitrile (MIP2, MIP4) as porogens and methacrylic acid (MIP1, MIP2) or acrylamide (MIP3, MIP4) as functional monomers. Molecular recognition features of these materials were studied by high-performance liquid chromatography. In this manner selectivity was evaluated by considering the column retention of a library of sixteen structural analogues of dibenzylcarbamate, characterized by the transformation of the carbamate into a related function, or by the alteration of the molecular structure.The experimental results show that methacrylic acid is more efficient than acrylamide as a functional monomer (imprinting factors: MIP1=24.1, MIP2=25.6, MIP3=13.3, MIP4=2.44), and that chloroform enhances polymer selectivity. As regards structural motifs which conditionate the selectivity, the carbamate function strictly controls the presence/absence of molecular recognition, while shape and dimension of the substituents modulate the recognition itself. In particular, a marked recognition for analogs which were slightly bigger than the template was observed ( N-benzyl- O-phenethylcarbamate: MIP1 α=1.13, MIP2 α=1.41, MIP3 α=0.97; N-phenethyl- N-benzylcarbamate: MIP1 α=1.61, MIP2 α=1.17, MIP3 α=0.81; N, O-diphenethylcarbamate: MIP1 α=0.89, MIP2 α=1.20, MIP3 α=0.55).

Keywords: Carbamates; Liquid chromatography; MiniMIPs; Molecular imprinting; Molecular recognition; Selectivity

Analysis of lipoproteins using 2D diffusion-edited NMR spectroscopy and multi-way chemometrics by Marianne Dyrby; Martin Petersen; Andrew K. Whittaker; Lynette Lambert; Lars N�rgaard; Rasmus Bro; S�ren Balling Engelsen (pp. 209-216).

This study represents the first application of multi-way calibration by N-PLS and multi-way curve resolution by PARAFAC to 2D diffusion-edited¹H NMR spectra. The aim of the analysis was to evaluate the potential for quantification of lipoprotein main- and subfractions in human plasma samples. Multi-way N-PLS calibrations relating the methyl and methylene peaks of lipoprotein lipids to concentrations of the four main lipoprotein fractions as well as 11 subfractions were developed with high correlations ( R=0.75–0.98). Furthermore, a PARAFAC model with four chemically meaningful components was calculated from the 2D diffusion-edited spectra of the methylene peak of lipids. Although the four extracted PARAFAC components represent molecules of sizes that correspond to the four main fractions of lipoproteins, the corresponding concentrations of the four PARAFAC components proved not to be correlated to the reference concentrations of these four fractions in the plasma samples as determined by ultracentrifugation. These results indicate that NMR provides complementary information on the classification of lipoprotein fractions compared to ultracentrifugation.

Keywords: Lipoproteins; Subfractions; Diffusion-edited; ¹; H NMR; DOSY; PARAFAC; N-PLS

Adduct formation in LC–ESI–MS of nonylphenol ethoxylates: mass spectrometrical, theoretical and quantitative analytical aspects by Niels Jonkers; Harrie Govers; Pim De Voogt (pp. 217-228).

The analysis of nonylphenol ethoxylate (A₉PEO_n) surfactants with LC–ESI–MS was investigated in a detailed study of the formation of different types of adducts. Part of the observations was explained by calculating their relative stabilities using molecular dynamics techniques.Strong differences in adduct formation behaviour were found for different oligomers.Beside the common sodium adducts, surfactant dimer adducts [2×A₉PEO_1,2+Na]⁺, adducts including a solvent molecule [A₉PEO_1,2+MeOH+Na]⁺ and doubly charged adducts [A₉PEO_>11+2×Na]²⁺ were found.Molecular dynamics calculations showed that the A₉PEO_n molecule wraps itself around the complexing sodium ion in a way that negative electronic charges on oxygen have optimum electrostatic interaction with this ion. van der Waals interactions between alkyl chains are of less importance for the stability of these adducts. Both [2×A₉PEO_2,5+Na]⁺ dimer and [A₉PEO_2,5+Na]⁺ monomer adducts turned out to be stable from an energetic point of view with adducts of A₉PEO₅ being more stable than adducts of A₉PEO₂. Only for the monomer adduct the latter is in accordance with experimental observations.Consequences of the formation of several adducts per A₉PEO_n oligomer for the quantitative analysis of environmental samples were evaluated. In clean samples, it was found that the presence of short-chain A₉PEO_1,2 can cause an overestimation of long-chain A₉PEO_>2. In real environmental extracts, other processes like matrix effects have a stronger influence on the quantitative result, and therefore no significant influence of adduct formation processes could be observed. However, inclusion of [A₉PEO_1,2+MeOH+Na]⁺ adduct signals does improve the detection limits of the two short-chain oligomers.Correct quantitative results are obtained when A₉PEO₁ and A₉PEO₂ are quantified separately, and longer oligomers with a molar calibration followed by correction of the average molar weight of the A₉PEO_>2 in the sample.

Keywords: Surfactants; Nonylphenol ethoxylates; Adduct formation; Liquid chromatography–mass spectrometry; Molecular dynamics; Quantification

Determination of isoflavones and coumestrol in river water and domestic wastewater sewage treatment plants by Alessandro Bacaloni; Chiara Cavaliere; Angelo Faberi; Patrizia Foglia; Roberto Samperi; Aldo Lagan� (pp. 229-237).

Phytoestrogens activate a biological response in vertebrata where they can mime or modulate the action of endogenous estrogens. For this reason they have been subjected to several studies about their physiological effects on humans and many analytical methodologies for their determination in food matrices and physiological fluids have been developed. On the contrary, little information can be found in literature about the presence of isoflavones and coumestrol in the environment, even if it is known that this may have significance. In the present study we investigated the presence of nine selected free and conjugated phytoestrogens in environmental water. A liquid chromatography–mass spectrometry (LC–MS/MS) based analytical methodology was developed and employed for detection of target compounds in surface water and wastewater.The methodology uses solid-phase extraction, followed by high performance liquid chromatography coupled to tandem mass spectrometry using an electrospray (ESI) interface operating in positive ion mode (LC–ESI–MS/MS). The extraction was made with 200mg, 6mL OASIS HLB^® cartridges. Recoveries for the selected compounds were in the 67–97% range for all the considered analytes. The method was employed for environmental monitoring. Samples of river water and wastewater collected over a 4-month period were analyzed with the developed procedure. Results showed the presence of isoflavones in most of the samples analyzed. Average concentration of target analytes found in wastewater sewage treatment plant influent ranged from 454 to 12ng/L. In effluent water and river water the analytes were present at lower concentration.

Keywords: Phytoestrogens; Isoflavones; Coumetrol; Water analysis; EDCs

Detection and quantification of honey adulteration via direct incorporation of sugar syrups or bee-feeding: preliminary study using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and chemometrics by Christophe Cordella; Julio S.L.T. Milit�o; Marie-Claude Cl�ment; Patrick Drajnudel; Daniel Cabrol-Bass (pp. 239-248).

Honey adulteration is a complex problem which currently has a significant economic impact and undeniable nutritional and organoleptic consequences. This paper describes the development of an effective anionic chromatographic method (HPAEC-PAD) for honey analysis and adulteration detection. The method relies on the use of chemometric methods to process chromatograms in order to achieve a better discrimination between authentic and adulterated honeys by linear discriminant analysis and to quantify adulteration levels by partial least squares analysis. This approach was investigated using honey samples adulterated from 10 to 40% with various industrial bee-feeding sugar syrups. Good results were obtained in the characterization of authentic and adulterated samples (96.5% of good classification) using linear discriminant analysis followed by a canonical analysis. The application of the partial least squares modeling method provided a corresponding linear regression model allowing the percentage of adulteration of new samples to be estimated directly from sample chromatograms.Additionally, a bee-feeding experiment on a small apiary was conducted in order to evaluate the effect of supplying hives with bee-feeding syrups. This practice is specific to the apicultural area. It has been demonstrated that bee-feeding can modify the sugar composition of the produced honey if it is conducted without safeguards.

Keywords: Honey; Anionic chromatography; Chemometrics; Adulteration; Bee-feeding; Sugar syrups

Determination of hydroxy-PCBs in urine by gas chromatography/mass spectrometry with solid-phase extraction and derivatization by Jee Eun Hong; Heesoo Pyo; Song-Ja Park; Won Lee (pp. 249-256).

A sensitive derivatization and extraction method is proposed for the determination of hydroxy-PCBs in urine. Phenolic hydroxyl groups of PCBs were allowed to react with five different reagents such as iodomethane, iodoethane, iodopropane, BSTFA and MTBSTFA. Propylated products at 100°C for 30min showed the best sensitivity with mass selective detector. Extraction recoveries and relative standard deviations of hydroxy-PCBs by SPE using C2 column were in the range of 78.0–112.3% and 2.5–9.6%, respectively. Instrumental detection limits for derivatized hydroxy-PCBs were in the range of 1–2pg and were 10–1000 times more sensitive than those of non-derivatized hydroxy-PCBs. The correlation coefficients of the linear regression curves exceed 0.99, and the intra- and inter-day precisions were evaluated by RSDs within 10% at the concentrations of 0.4 and 4.0ng/mL.

Keywords: Hydroxy-PCBs; GC/MS; Derivatization; SPE; Urine

Photoinduced spectrofluorimetric determination of fluoroquinolones in human urine by using three- and two-way spectroscopic data and multivariate calibration by A. Espinosa-Mansilla; A. Mu�oz de la Pe�a; D. Gonz�lez G�mez; F. Salinas (pp. 257-266).

Multivariate methods comprise of a group of chemometric tools allowing the analysis of different analytical data, i.e., spectroscopic, chromatographic obtained from multichannel detector systems. Second-way data are widely used in analytical applications in combination with multivariate calibration methods, but three- and higher-way data are yet not as widely applied. In complex biological samples, the employment of the three-way data is of special interest, as they may be combined with methods that exploit the second-order advantage allowing calculating individual concentrations of the analytes of interest in the presence of unknown interferences in untreated samples. A very sensitive and selective method is proposed, by coupling photoinduced fluorescence and multivariate analysis of the three-way data excitation-emission fluorescence matrices (EEMs), of the photoproducts obtained from UV irradiation of three fluoroquinolones: enoxacin (ENO), norfloxacin (NOR) and ofloxacin (OFLO). The application of a previous photoirrradiation process allows the determination of mixtures of ENO, NOR and OFLO, in urine samples at biological levels without sample pretreatments. The resolution ability of N-way partial least squares ( N-PLS), parallel factor analysis (PARAFAC) and self weighted alternating trilinear decomposition (SWATLD), is compared with partial least squares (PLS) and unfolded-PLS (U-PLS), in the analysis of ENO, NOR and OFLO in human urine samples.

Keywords: Photoinduced spectrofluorimetry; Urine; PLS; PARAFAC; SWATLD

Ultraviolet photolytic vapor generation from particulate ensembles for detection of malathion residues in aerosols by Roderick R. Kunz; Frank L. Leibowitz; Deanna K. Downs (pp. 267-277).

A method to selectively generate vapor signatures from malathion entrained within matrices of surface-impacted aerosol particles has been demonstrated. The method uses ultraviolet radiation (172 or 222nm) from a continuous wave discharge lamp to photodissociate malathion molecules collected within and on surface-impacted particles, followed by detection via ion mobility spectrometry (IMS). Since surface heating does not occur, only those molecules whose photofragments exhibit high vapor pressure are introduced into the IMS instrument and then only those exhibiting high proton affinity are subsequently detected. This process produces less signal clutter than in pyrolysis-IMS, where the background aerosol is pyrolyzed along with the sample. Quantities of malathion as small as 50ng could be detected when the malathion was entrained on a clean surface, and as small as 100ng when co-entrained on a surface with much larger quantities of background aerosols such as diesel soot, road dust, Bacillus globigii, albumin, and cotton lint. This sensitivity indicates that, when combined with a particle collector as an effective pre-concentrator, detection of malathion aerosol concentrations of <0.01mg/m³ will be possible. Since malathion can be viewed as a model compound, this technique is also extendable to the detection of organophosphate war chemicals.

Keywords: Vacuum ultraviolet; Photolysis; Ion mobility spectrometry; Malathion; Organophosphates; Aerosol

An improved sampling approach in multi-pumping flow systems applied to the spectrophotometric determination of glucose and fructose in syrups by Josiane M. Toloti Carneiro; Ana Cristi B. Dias; Elias A.G. Zagatto; Jo�o L.M. Santos; Jos� L.F.C. Lima (pp. 279-284).

A novel sampling approach in flow analysis exploiting the multi-pumping concept is proposed and applied to the spectrophotometric determination of glucose and fructose in invert sugar syrups. The samples are collected in gelatin capsules and brought to the laboratory. The capsules are placed directly into the dissolution chamber of a flow-batch system, therefore, the manual sample dissolution step is not required. All the involved analytical steps, including the capsule dissolution under acidic conditions, are efficiently controlled by using discretely actuated solenoid micro-pumps. Glucose and fructose determinations involve sugar oxidation by periodate and evaluation of the remaining periodate by monitoring the tri-iodide complex formed after addition of potassium iodide.The proposed system is very stable, handles about 50 samples per hour and requires 28.8μg NaIO₄ and 2.5mg KI per determination. Precise results (R.S.D.<2%) in agreement with HPLC are obtained.

Keywords: Sampling; Flow analysis; Spectrophotometry; Multi-pumping; Syrup analysis

Wavelet neural network-based QSPR for prediction of critical micelle concentration of Gemini surfactants by Z. Kardanpour; B. Hemmateenejad; T. Khayamian (pp. 285-291).

A QSPR study is performed to develop a model, relating the structure of 94 Gemini surfactants to their critical micelle concentrations for the first time. A whole number of descriptors were calculated with Dragon software and a subset of calculated descriptors was selected from 18 classes of Dragon descriptors with a forward stepwise MLR method. The data set was randomly divided into three data sets: calibration (69 molecules), prediction (15 molecules) and test set (10 molecules). The selected descriptors were used as input neurons in a wavelet neural network (WNN) model. The WNN architecture and its parameters were optimized simultaneously. The performance of the model was investigated by the test set and the average absolute error was 0.105 for the test set. The capability of the WNN model was compared with the MLR model. It was demonstrated that the WNN is superior to the MLR model.

Keywords: Gemini surfactants; QSPR; cmc; WNN; MLR

Simultaneous kinetic determination of Fe(II) and Fe(III) based on their reactions with NQT4S in micellar media by using PLS and PCR methods by G. Absalan; M. Nekoeinia (pp. 293-298).

Simultaneous determination of Fe(II) and Fe(III) was studied using partial least squares regression (PLS) and principal component regression (PCR) methods. The models were based on the difference observed in the rates of the complex formation of iron in its two oxidation states with 1,2-naphthaquinone-2-thiosemicarbazone-4-sulphonic acid (NQT4S) at pH 4.0 in cetyltrimethylammoniumbromide (CTAB) as micellar media. The results showed that simultaneous determination of Fe(II) and Fe(III) could be performed in their concentration ranges of 0.10–2.10 and 0.25–2.25μg/ml, respectively. The models used can proceed the data with low percent relative error of prediction (i.e. <5.5%). The procedure was successfully applied for the simultaneous determination of Fe(II) and Fe(III) in some environmental samples. The method would allow the transformation of the two oxidation states of iron to be monitored overtime in a water sample.

Keywords: Simultaneous determination; Speciation; Partial least squares; Micellar media

Influence of several experimental parameters on As and Se leaching from coal fly ash samples by Jos� R. Otero-Rey; Mar�a J. Mato-Fern�ndez; Jorge Moreda-Pi�eiro; Elia Alonso-Rodr�guez; Soledad Muniategui-Lorenzo; Purificaci�n L�pez-Mah�a; Dar�o Prada-Rodr�guez (pp. 299-305).

Coal fly ash leaching process for As and Se is studied. Environmental parameters such as pH, temperature, solid–liquid ratio, particle size and leaching time are taken into account in order to simulate As and Se leaching process for disposal coal fly ash. Analysis of reference materials was carried out by using of hydride generation coupled to atomic fluorescence spectrometry. Plackett–Burman experimental design is used to know the significative parameters, and Box–Behnken experimental design is used to refine the results obtained for these significative parameters. pH and temperature shown a hardly influence in leaching process. Furthermore, leaching time was also significative. According our results, it may be assumed that percentage of As and Se leaching in experimental conditions tested is relatively low for acidic fly ashes.

Keywords: Coal fly ash; Arsenic and selenium leaching; Experimental design; Atomic fluorescence spectroscopy

Author Index (pp. 307-309).

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Analytica Chimica Acta (v.531, #2)