Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.635, #1)

Editorial Board (pp. iii).

Stripping voltammetry using sequential standard addition calibration with the analytes themselves acting as internal standards by Richard J.C. Brown; Matthew R. Roberts; Dan J.L. Brett (pp. 1-5).

A novel two-step standard addition calibration procedure for stripping voltammetry, whereby the analytes under investigation act as internal standards for each other, is described. In this way, the benefits of an internal standard for improving precision are obtained, without the requirement to add internal standard solutions. Only the standard solutions used to perform quantification are required. The proposed methodology has been tested against the traditional standard addition method with no internal standardisation, for the measurement of Zn, Cd, Pb and Cu in synthetic and real ambient air sample digests. The new procedure is shown to improve substantially precision and accuracy compared to traditional standard addition without internal standardisation.

Keywords: Stripping voltammetry; Internal standard; Uncertainty; Precision; Accuracy

Role of laser ablation–inductively coupled plasma–mass spectrometry in cultural heritage research: A review by Barbara Giussani; Damiano Monticelli; Laura Rampazzi (pp. 6-21).

Cultural heritage represents a bridge between the contemporary society and the past populations, and a strong collaboration between archaeologists, art historians and analysts may lead to the decryption of the information hidden in an ancient object.Quantitative elemental compositional data play a key role in solving questions concerning dating, provenance, technology, use and the relationship of ancient cultures with the environment. Nevertheless, the scientific investigation of an artifact should be carried out complying with some important constraints: above all the analyses should be as little destructive as possible and performed directly on the object to preserve its integrity.Laser ablation sampling coupled to inductively coupled plasma–mass spectrometry (LA–ICP–MS) fulfils these requirements exhibiting comparably strong analytical performance in trace element determination. This review intends to show through the applications found in the literature how valuable is the contribution of LA–ICP–MS in the investigation of ancient materials such as obsidian, glass, pottery, human remains, written heritage, metal objects and miscellaneous stone materials.The main issues related to cultural heritage investigation are introduced, followed by a brief description of the features of this technique. An overview of the exploitation of LA–ICP–MS is then presented. Finally, advantages and drawbacks of this technique are critically discussed: the fit for purpose and prospects of the use of LA–ICP–MS are presented.

Keywords: Laser ablation–inductively coupled plasma–mass spectrometry; Cultural heritage; Elemental analysis; Archaeology; Archaeometry; Trace elements

Recent development in derivative ultraviolet/visible absorption spectrophotometry: 2004–2008 by F. Sánchez Rojas; C. Bosch Ojeda (pp. 22-44).

Several techniques have been proposed for treatment of spectrophotometric data, with the objective of extracting a largest amount of analytical information from spectra composed of unresolved bands. Undoubtedly, a major success was achieved by derivative treatment of the absorbance curves-plotting of the first or a higher order mathematical derivative of absorbance against wavelength (d A/d λ). Derivative spectrophotometry has been applied to many chemical systems, such as pharmaceuticals, foods, cosmetics, and environmental samples.The instrumental development and analytical applications of derivative UV–vis regions absorption spectrophotometry produced in the last 5 years (since 2004) are reviewed.

Keywords: Derivative UV–vis; Multi-component analysis; Pharmaceutical analysis; Biological compounds; Food analysis; Environmental analysis; Review

Variable selection in visible/near infrared spectra for linear and nonlinear calibrations: A case study to determine soluble solids content of beer by Fei Liu; Yihong Jiang; Yong He (pp. 45-52).

Three effective wavelength (EW) selection methods combined with visible/near infrared (Vis/NIR) spectroscopy were investigated to determine the soluble solids content (SSC) of beer, including successive projections algorithm (SPA), regression coefficient analysis (RCA) and independent component analysis (ICA). A total of 360 samples were prepared for the calibration ( n=180), validation ( n=90) and prediction ( n=90) sets. The performance of different preprocessing was compared. Three calibrations using EWs selected by SPA, RCA and ICA were developed, including linear regression of partial least squares analysis (PLS) and multiple linear regression (MLR), and nonlinear regression of least squares-support vector machine (LS-SVM). Ten EWs selected by SPA achieved the optimal linear SPA-MLR model compared with SPA-PLS, RCA-MLR, RCA-PLS, ICA-MLR and ICA-PLS. The correlation coefficient ( r) and root mean square error of prediction (RMSEP) by SPA-MLR were 0.9762 and 0.1808, respectively. Moreover, the newly proposed SPA-LS-SVM model obtained almost the same excellent performance with RCA-LS-SVM and ICA-LS-SVM models, and the r value and RMSEP were 0.9818 and 0.1628, respectively. The nonlinear model SPA-LS-SVM outperformed SPA-MLR model. The overall results indicated that SPA was a powerful way for the selection of EWs, and Vis/NIR spectroscopy incorporated to SPA-LS-SVM was successful for the accurate determination of SSC of beer.

Keywords: Visible/near infrared spectroscopy; Successive projections algorithm; Independent component analysis; Variable selection; Least squares-support vector machine; Beer

Is microwave digestion using TFM vessels a suitable preparation method for Pt determination in biological samples by adsorptive cathodic stripping voltammetry? by Nadine Haus; Tanja Eybe; Sonja Zimmermann; Bernd Sures (pp. 53-57).

The occurrence of Pt in environmental matrices is increasing since the introduction of automobile catalytic converters. Given that Pt is bioavailable and causes biological effects in plants and animals, respective biomonitoring programs are in high demand. But the analytical methods for conducting such programs have not yet been sufficiently established. Therefore, a study was carried out to develop a microwave digestion of biological samples, which allows a rapid determination of Pt by adsorptive cathodic stripping voltammetry.A high pressure microwave system was used and the digestion was performed in HNO₃ and HCl. After digestion the HNO₃ was evaporated with a microwave assisted vacuum concentration set. The study resulted in a procedural detection limit of 37.5ngL⁻¹ and a relative standard deviation of 18%. A recovery study resulted in a Pt loss below 5%. The microwave assisted evaporation of HNO₃ performed satisfactorily and up to 500mL of the sample solution could be used for the voltammetric measurements without any effect on the peak heights. A direct comparison of Pt concentrations conducted after microwave digestion and digestion by high pressure ashing showed similar values. However, these promising results were not persistent throughout the repeated analysis using the same Teflon vessels. The vessels did not endure the harsh conditions and due to aging processes the Pt loss consistently increased until Pt determination in environmental relevant concentrations became impossible. Quartz vessels could not be employed as an alternative to the Teflon vessels, due to a lack of compatibility with the vacuum concentration system. Consequently, the results of this paper show that there is a need for further development of more resistant Teflon materials.

Keywords: Teflon vessel; Aging effect; Platinum group element analysis; High pressure microwave system

Solid-state electrochemiluminescence sensor through the electrodeposition of Ru(bpy)₃²⁺/AuNPs/chitosan composite film onto electrode by Wen Yun; Ying Xu; Ping Dong; Xiongxiong Ma; Pingang He; Yuzhi Fang (pp. 58-62).

Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) has been successfully immobilized onto electrode through the electrodeposition of Ru(bpy)₃²⁺/AuNPs/chitosan composite film. In the experiments, chitosan solution was first mixed with Au nanoparticles (AuNPs) and Ru(bpy)₃²⁺. Then, during chronopotentiometry experiments in this mixed solution, a porous 3D network structured film containing Ru(bpy)₃²⁺, AuNPs and chitosan has been electrodeposited onto cathode due to the deposition of chitosan when pH value is over its p K_a (6.3). The applied current density is crucial to the film thickness and the amount of the entrapped Ru(bpy)₃²⁺. Additionally, these doping Ru(bpy)₃²⁺ in the composite film maintained their intrinsic electrochemical and electrochemiluminescence activities. Consequently, this Ru(bpy)₃²⁺/AuNPs/chitosan modified electrode has been used in ECL to detect tripropylamine, and the detection limit was 5×10⁻¹⁰M.

Keywords: Chitosan; Au nanoparticles; Ru(bpy); ₃; ²⁺; Electrodeposition; Electrochemiluminescence detection

Immobilization of [Cu(bpy)₂]Br₂ complex onto a glassy carbon electrode modified with α-SiMo₁₂O₄₀⁴⁻ and single walled carbon nanotubes: Application to nanomolar detection of hydrogen peroxide and bromate by Abdollah Salimi; Aazam Korani; Rahman Hallaj; Roshan Khoshnavazi; Hasan Hadadzadeh (pp. 63-70).

A simple procedure has been used for preparation of modified glassy carbon electrode with carbon nanotubes and copper complex. Copper complex [Cu(bpy)₂]Br₂ was immobilized onto glassy carbon (GC) electrode modified with silicomolybdate, α-SiMo₁₂O₄₀⁴⁻ and single walled carbon nanotubes (SWCNTs)_. Copper complex and silicomolybdate irreversibly and strongly adsorbed onto GC electrode modified with CNTs. Electrostatic interactions between polyoxometalates (POMs) anions and Cu-complex, cations mentioned as an effective method for fabrication of three-dimensional structures. The modified electrode shows three reversible redox couples for polyoxometalate and one redox couple for Cu-complex at wide range of pH values. The electrochemical behavior, stability and electron transfer kinetics of the adsorbed redox couples were investigated using cyclic voltammetry. Due to electrostatic interaction, copper complex immobilized onto GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ electrode shows more stable voltammetric response compared to GC/CNTs/Cu-complex modified electrode. In comparison to GC/CNTs/Cu-complex the GC/CNTs/α-SiMo₁₂O₄₀⁴⁻ modified electrodes shows excellent electrocatalytic activity toward reduction H₂O₂ and BrO₃⁻ at more reduced overpotential. The catalytic rate constants for catalytic reduction hydrogen peroxide and bromate were 4.5(±0.2)×10³M⁻¹s⁻¹ and 3.0(±0.10)×10³M⁻¹s⁻¹, respectively. The hydrodynamic amperommetry technique at 0.08V was used for detection of nanomolar concentration of hydrogen peroxide and bromate. Detection limit, sensitivity and linear concentration range proposed sensor for bromate and hydrogen peroxide detection were 1.1nM and 6.7nAnM⁻¹, 10nM–20μM, 1nM, 5.5nAnM⁻¹ and 10nM–18μM, respectively.

Keywords: Layer by layer assembly; [Cu(bpy); ₂; ]Br; ₂; α-SiMo; ₁₂; O; ₄₀; ⁴⁻; Carbon nanotubes; Bromate; Hydrogen peroxide

Development and characterization of a new conducting carbon composite electrode by Madalina M. Barsan; Edilson M. Pinto; Monica Florescu; Christopher M.A. Brett (pp. 71-78).

A new conducting composite flexible material prepared from cellulose acetate (CA) polymer and graphite has been developed and used for the fabrication of electrodes, which were then characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM) was used to provide information concerning the morphology of the composite electrode surface. The potential window, background currents and capacitance were evaluated by cyclic voltammetry in the pH range from 4.6 to 8.2. The voltammetry of model electroactive species demonstrates a close to reversible electrochemical behaviour, under linear diffusion control. The electroactive area of the composite electrodes increases after appropriate electrode polishing and electrochemical pre-treatment. The electrodes were used as substrate for the electropolymerisation of the phenazine dye neutral red, for future use as redox mediator in electrochemical biosensors. The composite electrodes were also successfully used for the amperometric detection of ascorbate at 0.0V vs. SCE, and applied to the measurement of ascorbate in Vitamin C tablets; the sensor exhibits high sensitivity and a low detection limit of 7.7μM. Perspectives for use as a versatile, mechanically flexible and robust composite electrode of easily adaptable dimensions are indicated.

Keywords: Graphite; Cellulose acetate; Composite electrode; Neutral red; Ascorbate

Methodology for the qualitative screening of parallel arrays of potential Am³⁺ ligands using a photographic film by Henk H. Dam; Tanja Tomasberger; David N. Reinhoudt; Willem Verboom (pp. 79-83).

A screening method for parallel Am³⁺ ligand libraries is presented. The method makes use of α-radiation in combination with a photographic film to detect the complexed Am³⁺. After screening and development of the film spots of varying intensities are obtained. The intensities of the spots correspond with the amount of complexed Am³⁺. This allows a fast discrimination between the Am³⁺ complexation efficiencies of ligands from large libraries. Depending on the exposure time of the film, activities as small as 5Bq²⁴¹Am can be detected. Using internal standards a semi-quantitative assessment can be performed.

Keywords: Actinides; Am; ³⁺; ligand; Combinatorial; Library screening; Photographic film

Determination of gaseous carbonyl compounds by their pentafluorophenyl hydrazones with gas chromatography/mass spectrometry by Jian Li; Yan Li Feng; Chun Juan Xie; Juan Huang; Jian Zhen Yu; Jia Liang Feng; Guo Ying Sheng; Jia Mo Fu; Ming Hong Wu (pp. 84-93).

A sensitive and reliable method has been developed for the simultaneous determination of 20 airborne carbonyl compounds in the C₁–C₁₀ range. The carbonyls were collected onto solid sorbent coated with pentafluorophenyl hydrazine (PFPH), followed by solvent extraction and gas chromatographic (GC)/mass spectrometric (MS) analysis of the PFPH derivatives. The sorbent is packed into two separate sections in a glass sampling tube. The two-section design allows convenient checking of collection efficiency and breakthrough. The sampling tube, with a coating amount of 971nmol PFPH per 100mg Tenax TA and operated at a sampling flow rate of 80mLmin⁻¹, collects the 20 carbonyls with efficiencies above 95%. Hexane extracts the collected carbonyls in their PFPH derivatives in the sampling tube with better than 95% extraction efficiency. It is necessary to let the sampling tube sit at ambient temperature for 3 days before solvent extraction to ensure complete derivatization of the carbonyls. The limits of detection (LODs) of the tested carbonyls are in the range of 3.7–11.6ng per sample. The method has been field-tested both in ambient environment and in an indoor environment from burning mosquito-repellent incense. Eighteen carbonyls were detected in the ambient air samples with the exception of o-tolualdehyde and m-tolualdehyde, while all the 20 target carbonyls were found in the incense smoke. Compare field test with classical DNPH–HPLC/UV method, good agreement exited between the two methods for lower molecular carbonyls but PFPH method is found to be a better analytical method for determination of high molecular weight carbonyls.

Keywords: Carbonyl compounds; Pentafluorophenyl hydrazine; Gas chromatography/mass spectrometry; Solvent extraction

Comparison of homoleptic and heteroleptic 2,2′-bipyridine and 1,10-phenanthroline ruthenium complexes as chemiluminescence and electrochemiluminescence reagents in aqueous solution by Michaela M. Cooke; Egan H. Doeven; Conor F. Hogan; Jacqui L. Adcock; Geoffrey P. McDermott; Xavier A. Conlan; Neil W. Barnett; Frederick M. Pfeffer; Paul S. Francis (pp. 94-101).

We have conducted a comprehensive comparative study of Ru(bipy)₃²⁺, Ru(bipy)₂(phen)²⁺, Ru(bipy)(phen)₂²⁺, and Ru(phen)₃²⁺ as chemiluminescence and electrochemiluminescence (ECL) reagents, to address several previous conflicting observations and gain a greater insight into their potential for chemical analysis. Clear trends were observed in many of their spectroscopic and electrochemical properties, but the relative chemiluminescence or ECL intensity with a range of analytes/co-reactants is complicated by the contribution of numerous (sometimes opposing) factors. Significantly, the reversibility of cyclic voltammetric responses for the complexes decreased as the number of phenanthroline ligands was increased, due to the lower stability of their ruthenium(III) form in the aqueous solvent. This trend was also evident over a longer timescale when the ruthenium(III) form was spectrophotometrically monitored after chemical oxidation of the ruthenium(II) complexes. In general, the greater stability of Ru(bipy)₃³⁺ resulted in lower blank signals, although this effect was less pronounced with ECL, where the reagent is oxidised in the presence of the co-reactants. Nevertheless, this shows the need to compare signal-to-blank ratios or detection limits, rather than the more common comparisons of overall signal intensity for different ruthenium complexes. Furthermore, our results support previous observations that, compared to Ru(bipy)₃²⁺, Ru(phen)₃²⁺ provides greater ECL and chemiluminescence intensities with oxalate, which in some circumstances translates to superior detection limits, but they do not support the subsequent generalised notion that Ru(phen)₃²⁺ is a more sensitive reagent than Ru(bipy)₃²⁺ for all analytes.

Keywords: Chemiluminescence; Electrochemiluminescence; Electrogenerated chemiluminescence; Heteroleptic ruthenium complexes

On-line molecularly imprinted solid-phase extraction for the selective spectrophotometric determination of nicotine in the urine of smokers by Eduardo Costa Figueiredo; Daniela Mayra de Oliveira; Maria Elisa Pereira Bastos de Siqueira; Marco Aurélio Zezzi Arruda (pp. 102-107).

This work describes an on-line molecularly imprinted solid-phase extraction (MISPE) method for spectrophotometric determination of nicotine in urine samples of smokers. This method is based on manganese (VII) to manganese (VI) reduction in an alkaline medium, promoted by nicotine. Two wash solutions (1:4 (v/v) acetonitrile:sodium hydroxide – pH 11.4, and nitric acid – pH 2.5) were employed to circumvent interferences. Aqueous solutions containing nicotine plus different possible concomitants (cotinine, anabasine, norcotinine and caffeine) were tested individually. The analytical calibration curve was prepared in urine samples collected from non-smokers and spiked with nicotine standard from 1.1 to 60μmolL⁻¹ ( r²>0.998). The limit of quantification and the analytical frequency were 1.1μmolL⁻¹ and 11h⁻¹, respectively. The precision, evaluated using 3, 10 and 30μmolL⁻¹ nicotine in urine, was 10, 10 and 4% (intra-day precision) and 12, 13 and 5% (inter-day precision), respectively. Accuracy was checked through high performance liquid chromatography and the results did not present significant differences at the 95% confidence level according to the Student's t-test.

Keywords: Molecularly imprinted polymers; Spectrophotometry; Solid-phase extraction; Nicotine; Urine

Comparison of total fluorine, extractable organic fluorine and perfluorinated compounds in the blood of wild and pefluorooctanoate (PFOA)-exposed rats: Evidence for the presence of other organofluorine compounds by Leo W.Y. Yeung; Yuichi Miyake; Peng Li; Sachi Taniyasu; Kurunthachalam Kannan; Keerthi S. Guruge; Paul K.S. Lam; Nobuyoshi Yamashita (pp. 108-114).

The widespread occurrence and environmental persistence of perfluorinated compounds (PFCs) received worldwide attention recently. Exhaustive analysis of all fluorinated compounds in an environmental sample can be daunting because of the constraints in the availability of analytical standards and extraction methods. Combustion ion chromatographic technique for trace fluorine analysis was used to assess the concentrations of known PFCs (e.g., PFOS, PFOA) and total fluorine (TF) in the blood of wild rats collected from Japan. The technique was further validated using tissues from PFOA-exposed rats. Six PFCs (PFOS, PFOSA, PFUnDA, PFDA, PFNA, and PFOA) were detected in all of the wild rat blood samples. Concentrations of extractable organic fluorine (EOF) in fraction 1 (Fr1; MTBE extraction) of wild rats ranged 60.9–134ngFmL⁻¹, while those in fraction 2 (Fr2; hexane) were below LOQ (32ngFmL⁻¹); TF concentrations in the blood of wild rats ranged from 59.9–192ngFmL⁻¹. The contribution of known PFCs in EOF-Fr1 (MTBE) varied from 9% to 89% (56% on average), and known PFC concentrations in TF content were less than 25%. In contrast, TF concentrations in the blood of PFOA-exposed rats ranged from 46900 to 111000ngFmL⁻¹, with PFOA contributing over 90% of TF. A comparison of results from the samples analyzed in this study and the literature revealed three distinct groups with PFOA/known PFC and TF levels (i.e., wild rats and general population, occupationally exposed workers, and PFOA-exposed laboratory rats). The mass balance analysis of the different forms of fluorine in blood suggested the presence of other forms of organic fluorine in addition to known PFCs.

Keywords: Combustion ion chromatography; Perfluorinated chemicals; Organofluorine; Mass balance analysis; Perfluorooctanesulfonate (PFOS); Perfluorooctanoate (PFOA)

Dynamics of reepithelialisation and penetration rate of a bee propolis formulation during cutaneous wounds healing by E. Sehn; L. Hernandes; S.L. Franco; C.C.M. Gonçalves; M.L. Baesso (pp. 115-120).

The aim of this work is to investigate the dynamics of reepithelialisation and the penetration rate of a propolis ointment formulation during cutaneous wounds healing. The experiments were performed as a function of the treatment time in a well controlled group of rats. We observed that the propolis ointment influenced the healing process stimulating keratinocytes cell proliferation as compared to the control group. It was shown that the propagation of the bee propolis was dependent on the wound healing stages. In addition, the photoacoustic spectroscopy showed that the applied substances reached the deep wound region, highlighting once again the particular characteristic of this technique to evaluate the penetration rate of substances through the skin.

Keywords: Photoacoustic spectroscopy; Percutaneous penetration; Propolis ointment; Wound healing; Reepithelialisation

Sections

Personal tools

Analytica Chimica Acta (v.635, #1)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.635, #1)