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Analytica Chimica Acta (v.702, #2)

Mass spectrometry based proteomic studies on viruses and hosts – A review by Jie Zheng; Richard J. Sugrue; Kai Tang (pp. 149-159).

. a) In the background, scanning electron micrograph of RSV infected cells reveals viral filaments budding from the surface of virus infected cells. b) Inserted at the top, MS spectrum represents the characterization of the digested RSV virus particles. c) Inserted at the bottom, RSV infected cells were imaged using immunofluorescence microscopy: red represents virus filaments; green is HSP90; yellow staining represents co-localization of both antigens within the virus filaments.Display Omitted► The current proteomic researches on viruses and hosts are described. ► TAP, IP, SILAC, ICAT, and iTRAQ facilitate sample enrichment and quantification. ► Clinically important viruses are discussed on their interactions with hosts. ► Functional validation is essential to confirm the roles of the identified proteins.In terms of proteomic research in the 21st century, the realm of virology is still regarded as an enormous challenge mainly brought by three aspects, namely, studying on the complex proteome of the virus with unexpected variations, developing more accurate analytical techniques as well as understanding viral pathogenesis and virus–host interaction dynamics. Progresses in these areas will be helpful to vaccine design and antiviral drugs discovery. Mass spectrometry based proteomics have shown exceptional display of capabilities, not only precisely identifying viral and cellular proteins that are functionally, structurally, and dynamically changed upon virus infection, but also enabling us to detect important pathway proteins. In addition, many isolation and purification techniques and quantitative strategies in conjunction with MS can significantly improve the sensitivity of mass spectrometry for detecting low-abundant proteins, replenishing the stock of virus proteome and enlarging the protein–protein interaction maps. Nevertheless, only a small proportion of the infectious viruses in both of animal and plant have been studied using this approach. As more virus and host genomes are being sequenced, MS-based proteomics is becoming an indispensable tool for virology. In this paper, we provide a brief review of the current technologies and their applications in studying selected viruses and hosts.

Keywords: MS-based proteomics; Virus proteome; Virus and host interactions

Models to estimate overall analytical measurements uncertainty: Assumptions, comparisons and applications by E. Rozet; S. Rudaz; R.D. Marini; E. Ziémons; B. Boulanger; Ph. Hubert (pp. 160-171).

Display Omitted► Review of the models used to combine systematic and random influences. ► Highlight of the main pros and cons of these overall uncertainty models. ► Performance evaluation of these models with respect to compliance assessment. ► Review of the main area of applications of these overall uncertainty models.Evaluation of analytical results reliability is of core importance as crucial decisions are taken with them. From the various methodologies to evaluate the fitness of purpose of analytical methods, overall measurement uncertainty estimation is more and more applied. Overall measurement uncertainty allows to combine simultaneously the remaining systematic influences to the random sources of uncertainty and allows assessing the reliability of results generated by analytical methods. However there are various interpretations on how to estimate overall measurement uncertainty, and thus various models for estimating it. Each model together with its assumptions has great impacts on the risks to abusively declare that analytical methods are suitable for their intended purpose. This review paper aims at (i) summarizing the various models used to estimate overall measurement uncertainty, (ii) provide their pros and cons, (iii) review the main areas of application and (iv) as a conclusion provide some recommendations when evaluating overall measurement uncertainty.

Keywords: Measurement uncertainty; Tolerance interval; Results quality; Method validation; Compliance assessment

Blind image analysis for the compositional and structural characterization of plant cell walls by Pradeep N. Perera; Martin Schmidt; P. James Schuck; Paul D. Adams (pp. 172-177).

Display Omitted► A new image analysis strategy is introduced to determine the composition and the structural characteristics of plant cell walls by combining Raman microspectroscopy and Chemometrics. ► Our approach partitioned the cell walls into many sublayers, based on their composition, thus enabling composition analysis at subcellular levels. ► Pure components spectra were estimated by spectral entropy minimization criteria with simulated annealing optimization. Two pure spectral estimates that represent lignin and carbohydrates were recovered and their spatial distributions were calculated. ► Proposed method overcame the well known problem that native lignin spectra in lignocellulosics have high spectral overlap with contributions from cellulose and hemicelluloses, thus opening up new avenues for microanalyses of each component independently, in situ.A new image analysis strategy is introduced to determine the composition and the structural characteristics of plant cell walls by combining Raman microspectroscopy and unsupervised data mining methods. The proposed method consists of three main steps: spectral preprocessing, spatial clustering of the image and finally estimation of spectral profiles of pure components and their weights. Point spectra of Raman maps of cell walls were preprocessed to remove noise and fluorescence contributions and compressed with PCA. Processed spectra were then subjected to k-means clustering to identify spatial segregations in the images. Cell wall images were reconstructed with cluster identities and each cluster was represented by the average spectrum of all the pixels in the cluster. Pure components spectra were estimated by spectral entropy minimization criteria with simulated annealing optimization. Two pure spectral estimates that represent lignin and carbohydrates were recovered and their spatial distributions were calculated. Our approach partitioned the cell walls into many sublayers, based on their composition, thus enabling composition analysis at subcellular levels. It also overcame the well known problem that native lignin spectra in lignocellulosics have high spectral overlap with contributions from cellulose and hemicelluloses, thus opening up new avenues for microanalyses of monolignol composition of native lignin and carbohydrates without chemical or mechanical extraction of the cell wall materials.

Keywords: Key words; Hyperspectral Raman imaging; Image analysis; Entropy minimization; Lignin; Curve resolution; Biomass

Probing beer aging chemistry by nuclear magnetic resonance and multivariate analysis by J.A. Rodrigues; A.S. Barros; B. Carvalho; T. Brandão; Ana M. Gil (pp. 178-187).

The use of nuclear magnetic resonance (NMR) metabonomics for monitoring the chemical changes occurring in beer exposed to forced aging (at 45°C for up to 18 days) is described. Both principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were applied to the NMR spectra of beer recorded as a function of aging and an aging trend was observed. Inspection of PLS-DA loadings and peak integration revealed the importance of well known markers (e.g. 5-HMF) as well as of other compounds: amino acids, higher alcohols, organic acids, dextrins and some still unassigned spin systems. 2D correlation analysis enabled relevant compound variations to be confirmed and inter-compound correlations to be assessed, thus offering improved insight into the chemical aspects of beer aging.Display Omitted• Use of NMR metabonomics for monitoring the chemical changes occurring in beer exposed to forced aging. • Compositional variations evaluated by principal component analysis and partial least squares-discriminant analysis. • Results reveal importance of known markers and other compounds: amino and organic acids, higher alcohols, dextrins. • 2D correlation analysis reveals inter-compound relationships, offering insight into beer aging chemistry.This paper describes the use of nuclear magnetic resonance (NMR) spectroscopy, in tandem with multivariate analysis (MVA), for monitoring the chemical changes occurring in a lager beer exposed to forced aging (at 45°C for up to 18 days). To evaluate the resulting compositional variations, both principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were applied to the NMR spectra of beer recorded as a function of aging and a clear aging trend was observed. Inspection of PLS-DA loadings and peak integration enabled the changing compounds to be identified, revealing the importance of well known markers such as 5-hydroxymethylfurfural (5-HMF) as well as a range of other relevant compounds: amino acids, higher alcohols, organic acids, dextrins and some still unassigned spin systems. In addition, the multivariate analysis method of 2D correlation analysis was applied to the NMR data enabling the relevant compound variations to be confirmed and inter-compound correlations to be assessed, some reflecting common metabolic/chemical pathways and, therefore, offering improved insight into the chemical aspects of beer aging.

Keywords: Beer; Forced aging; Nuclear magnetic resonance (NMR); Multivariate analysis (MVA); Two-dimensional correlation analysis; Food metabonomics

Using low frequency dielectric absorption to screen full intact wine bottles by S.J. Harley; V. Lim; M.P. Augustine (pp. 188-194).

Display Omitted► Wine dielectric signal depends on subtle solute concentration variations. ► Device built to measure bulk dielectric signal from wine. ► Principal component analysis reduction on data set provides fingerprint. ► Fingerprint is a step towards authentication of full, intact bottles of wine.A ν<25MHz low frequency spectrometer capable of noninvasively and nondestructively screening the dielectric properties of full intact bottles of wine is described, and along with principal component analysis, used to screen rare wine. The sensitivity of this full bottle method to various ionic and molecular wine solutes was established by analyzing standard solutions. Application of the approach to a library of collectible wine and the identification of counterfeit wine are discussed.

Keywords: Susceptibility; Principal component analysis; Wine; Counterfeit; Noninvasive

A solid-contact Pb²⁺-selective electrode using poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) as ion-to-electron transducer by Shunyang Yu; Fuhai Li; Tanji Yin; Yongming Liu; Dawei Pan; Wei Qin (pp. 195-198).

Display Omitted► All reagents used for the electrodes preparation were commercially available. ► The lower detection limit of the proposed electrode reached subnanomolar levels. ► No water film was observed with conventional commercially available PVC ion-sensing membranes. ► This research provides an excellent strategy for fabrication of robust polymeric ion sensors.In this work, a novel all-solid-state polymeric membrane Pb²⁺-selective electrode was developed by using for the first time poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) as solid contact. To demonstrate the ion-to-electron transducing ability of MEH-PPV, chronopotentiometry and electrochemical impedance spectroscopy measurements were carried out. The proposed electrodes showed a Nernstian response of 29.1mVdecade⁻¹ and a lower detection limit of subnanomolar level. No water film was observed with the conventional plasticized PVC membrane. This work demonstrates a new strategy for the fabrication of robust potentiometric ion sensors.

Keywords: Ion-selective electrodes; Solid contact; Low detection limit; Conducting polymer

Determination of 2,4,6-tricholoroanisole in water and wine samples by ionic liquid-based single-drop microextraction and ion mobility spectrometry by Isabel Márquez-Sillero; Eva Aguilera-Herrador; Soledad Cárdenas; Miguel Valcárcel (pp. 199-204).

Display Omitted► Ionic liquid-based single drop microextraction is proposed for the determination of 2,4,6-trichloroanisol. ► The imidazolium-based ionic liquid presents high affinity for the analyte and negligible response in the detector. ► The use of ion mobility spectrometry working under the negative ionization mode confers an adequate selectivity. ► It has been applied to the analysis of water and wine samples.This article presents for the first time the joint use of ionic liquid-based single drop microextraction (IL-SDME) and ion mobility spectrometry (IMS) for the determination of 2,4,6-trichloroanisol (2,4,6-TCA) in water and wine samples. An imidazolium-based IL was used as extractant taking into account both, its affinity for the analyte and its negligible response in the detector. Water samples were directly analyzed by IL-SDME while wines required a previous solid phase extraction step to remove the interference of ethanol in the ion mobility spectra. All the parameters affecting the extraction were optimized in order to achieve the highest sensitivity, taking into account the lower concentrations reported for this compound in the matrices selected. Moreover, the use of ion mobility working under the negative ionization mode confers an adequate selectivity. The limits of detection and quantification were 0.2 and 0.66ngL⁻¹, respectively. The precision of the method calculated at 10ngL⁻¹ was 1.4% (repeatability, n=5) and 2.2% (reproducibility, n=5, 3 days). The analysis of water and wine samples reported the presence of 2,4,6-TCA in wine samples commercialized in bottles with cork stoppers.

Keywords: 2,4,6-Trichloroanisole; Ion mobility spectrometry; Ionic liquids; Headspace single-drop microextraction; Wine; Water

Method development for the determination of wood preservatives in commercially treated wood using gas chromatography–mass spectrometry by Jana Šťávová; Carl A. Sedgeman; Zachary T. Smith; Lillian A. Frink; Jessica A. Hart; Vadoud H. Niri; Alena Kubátová (pp. 205-212).

Display Omitted► The method developed for the analysis of species used for wood treatment was designed. ► The 80–100% recoveries were achieved for the species of differing chemical nature. ► The recovery standards enabled accurate quantification during the sample preparation. ► The method revealed gradient distribution of analytes in commercially treated wood.Fungicides and insecticides are commonly used preservatives to protect wood products against microbiological degradations. Currently, there is a lack of analytical methods addressing the quantitative determination of a wide range of wood preserving species in wood matrices. In this study, a reliable method was developed for the determination of a mixture of wood preserving agents with differing chemical structures (i.e., properties), including tebuconazole (TAZ), propiconazole (PAZ), 3-iodo-2-propynyl butylcarbamate (IPBC), and permethrin (PER), in pine wood. The analyte recoveries obtained by Soxhlet and multiple-stage sonication extractions were compared. While both extraction methods yielded similar results (80–100%), Soxhlet extraction was found to be less labor-intensive and thus preferred providing also lower RSDs of 1–6%. In comparison to methanol, commonly used as an extraction solvent for triazoles, acetone yielded similar extraction efficiencies for all analytes while reducing the time of sample concentration. The solid phase extraction method for triazoles was adapted to allow for a separation of IPBC and PER from the wood matrix. As opposed to previous studies, three recovery standards were employed, which enabled the correction of individual analyte losses during the sample preparation. The matrix-affected limits of detection (LODs) using gas chromatography with mass spectrometric detection were nearly the same for triazoles 0.07 and 0.21ngg⁻¹ for PAZ and TAZ in sapwood and 0.18 and 0.21ngg⁻¹ in heartwood, respectively. Higher LODs were observed for IPBC and PER: 3.9 and 1.7ngg⁻¹ in sapwood, and 2.0 and 6.0ngg⁻¹ in heartwood, respectively. The recoveries in the wood submitted to commercial sample treatment showed gradient distribution of analytes depending on the penetration of the treatment.

Keywords: Fungicide; Gas chromatography–mass spectrometry; Wood preservation; Triazole; IPBC; Permethrin

Simple flow injection method for simultaneous spectrophotometric determination of Fe(II) and Fe(III) by J. Kozak; N. Jodłowska; M. Kozak; P. Kościelniak (pp. 213-217).

Display Omitted• Simultaneous reversed-flow injection determination of Fe(II) and Fe(III) is proposed. • Phenanthroline and sulfosalicylic acid added to sample form complexes with analytes. • EDTA injected, replaces sulfosalicylic acid forming more stable complex with Fe(III). • Area of a registered peak corresponds to Fe(III) concentration. • Absorbance measured in the peak minimum corresponds to Fe(II) concentration.The method is based on spectrophotometric determination of Fe(II) and Fe(III) at a single wavelength (530nm) with the use of a dedicated reversed-flow injection system. In the system, EDTA solution is injected into a carrier stream (HNO₃) and then merged with a sample stream containing a mixture of sulfosalicylic acid and 1,10-phenanthroline as indicators. In an acid environment (pH≅3) the indicators form complexes with both Fe(III) and Fe(II), but EDTA replaces sulfosalicylic acid, forming a more stable colourless complex with Fe(III), whereas Fe(II) remains in a complex with 1,10-phenenthroline. As a result, the area and minimum of the characteristic peak can be exploited as measures corresponding to the Fe(III) and Fe(II) concentrations, respectively. The analytes were not found to affect each other's signals, hence two analytical curves were constructed with the use of a set of standard solutions, each containing Fe(II) and Fe(III). Both analytes were determined in synthetic samples within the concentration ranges of 0.05–4.0 and 0.09–6.0mgL⁻¹, respectively, with precision less than 1.5 and 2.6% (RSD) and with accuracy less than 4.3 and 5.6% (RE). The method was applied to determination of the analytes in water samples collected from artesian wells and the results of the determination were consistent with those obtained using the ICP-OES technique.

Keywords: Flow injection analysis; Two-component analysis; Simultaneous determination of Fe(II) and Fe(III)

Analysis of carcinogenic polycyclic aromatic hydrocarbons in complex environmental mixtures by LC-APPI-MS/MS by Christoph Hutzler; Andreas Luch; Johannes G. Filser (pp. 218-224).

.Display Omitted► Here we developed an improved LC-APPI-MS/MS method for analysis of high molecular-weight and carcinogenic PAHs and nitro-PAHs. ► Validation of the method was performed through analysis of certified Standard Reference Materials. ► Regulatory needs usually prompt laboratories to perform PAH analysis based on LC-UV/FLD or GC–MS methodology. ► Due to its easiness, specificity and reduced sample preparation time, the new LC-APPI-MS/MS approach is now being suggested as reference method for PAH analysis in complex mixtures.Here we developed a highly sensitive, fast and reliable liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the detection and analysis of 16 different polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs that have been identified as carcinogens and classified according to their biological potency. Comparison to standard analysis procedures based on gas chromatography–mass spectrometry (GC–MS) instrumentation demonstrated an improved easiness of sample preparation and sensitivity of detection achieved with the new LC-MS/MS method employing an atmospheric pressure photoionization (APPI) source attached to an API 4000 mass spectrometer (LC-APPI-MS/MS). The favorable outcome could be confirmed by analyzing complex mixtures such as certain Standard Reference Materials (SRMs) obtained from the National Institute of Standards & Technology (NIST), i.e., SRM 1975 and SRM 2975, and several diesel exhaust soots provided by the German automobile industry. Certified concentrations of individual analytes provided by NIST not only could be confirmed, but additional extremely potent carcinogens such as several isomeric hexacyclic dibenzopyrenes (DBPs), 5-methylchrysene (5-MC), and others have been detected in these crude samples in a concentration range down to below 1ngg⁻¹ raw material.

Keywords: PAHs; Dibenzopyrenes; Dinitropyrenes; LC-APPI-MS/MS; Benzo[; a; ]pyrene; Dibenzo[; a; ,l]pyrene

Simple derivatization of aldehydes withd-cysteine and their determination in beverages by liquid chromatography–tandem mass spectrometry by Hyun-Ji Kim; Ho-Sang Shin (pp. 225-232).

Display Omitted► This study describes a new derivatization method of aldehydes in water matrix withd-cysteine. ► The optimum derivatization conditions were 10min at 50°C and pH 7.0. ► The formed alkyl thiazolidine-4-carboxylic acid derivatives were directly injected in LC–MS/MS. ► The LOD and LOQ of the eight aldehydes in beverages were in range of 0.2–1.9μgL⁻¹ and 0.7–6.0μgL⁻¹, and RSD was less than 2.0%. ► All the beverage samples had detectable levels of almost all aldehydes.We describe a simple derivatization method to determine aldehydes. This method is based on derivatization withd-cysteine and consecutive liquid chromatography–tandem mass spectrometry (LC–MS/MS). The optimum derivatization conditions of aldehydes withd-cysteine were 10min at 50°C and pH 7.0. The formed alkyl thiazolidine-4-carboxylic acid derivatives were directly injected in LC–MS/MS. In the established condition, the method was used to detect eight aldehydes in beverages. The limit of detection (LOD) and limit of quantification (LOQ) of the aldehydes were 0.2–1.9μgL⁻¹ and 0.7–6.0μgL⁻¹ and the relative standard deviation was less than 2.0% at concentrations of 0.1mgL⁻¹ and 1.0mgL⁻¹ with the exception of octanal. All the beverage samples had detectable levels of methanal (0.033–0.145mgL⁻¹), ethanal (0.085–2.12mgL⁻¹), propanal (ND to 0.250mgL⁻¹), butanal (ND to 0.003mgL⁻¹), pentanal (ND to 0.471mgL⁻¹), hexanal (ND to 0.805mgL⁻¹), heptanal (0.019–3.91mgL⁻¹) and octanal (0.029–0.118mgL⁻¹).

Keywords: Aldehydes; Derivatization; d; -Cysteine; Beverage; Liquid chromatography-tandem mass spectrometry

Separation and detection of bacteria using rupture event scanning by Matthew A. Cooper; Fedor N. Dultsev; Victor P. Ostanin; David Klenerman (pp. 233-238).

Display Omitted► Highly sensitive QCM-based method is proposed for direct detection of bacteria. ► Detection is made on the basis of measuring the binding force. ► This approach allows one to separate bacteria due to specific bonding. ► The method is quantitative over 6 orders of magnitude. ► Sensitivity allows detection of as few as 10 bacteria.We have developed a sensitive and economical method to directly detect bacteria, based on the interaction between the bacteria and specific antibodies attached to an oscillating surface. By monotonously increasing the amplitude of oscillation of a quartz crystal microbalance (QCM) coated with the antibody, the QCM can be used to sensitively detect the acoustic noise produced when the interactions between the bacteria and the surface were broken. We term this process rupture event scanning (REVS). The method is quantitative over at least 6 orders of magnitude and can detect as few as 10 bacteria. We demonstrate here that this approach allows one to arrange separation of bacteria and follow the process completion on the basis of the acoustic signal. Detection is not significantly affected by non-specific binding of sample contaminants and thus can be achieved both in buffer and in serum.

Keywords: Biosensor; Bond-rupture event; Separation; Quartz crystal microbalance

Molecularly imprinted polypyrrole nanonecklaces for detection of herbicide through molecular recognition-amplifying current response by Guijian Guan; Shuangshuang Wang; Haibo Zhou; Kui Zhang; Renyong Liu; Qingsong Mei; Suhua Wang; Zhongping Zhang (pp. 239-246).

Molecular imprinting in polypyrrole (PPy) nanonecklaces have been achieved through the initial preoxidization of pyrrole by dissolved oxygen and subsequent quick polymerization by ammonium persulfate (APS), and the selective binding of imprinted sites to target species leads to the amplification of current response by a factor of 8 times toward the detection of trace herbicide.Display Omitted► Molecular imprinting in polypyrrole nanonecklaces can be facilely achieved through the initial preoxidization of pyrrole and subsequent quick polymerization. ► The resultant imprinted nanonecklaces exhibit the high capacity and fast kinetics to uptake herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). ► Importantly, the recognition and binding to 2,4-D significantly amplify the current response by a factor of 8 times in amperometric measurements, providing a sensitive detection of non-electrochemically active 2,4-D.Molecularly imprinted polypyrrole (PPy) nanonecklaces were facilely synthesized through a two-step oxidative polymerization route for the amperometric detection of non-electrochemically active herbicide. It has been demonstrated that dissolved oxygen can preoxidize pyrrole to form PPy oligomer bundles, which further self-assemble into necklace-like micelles in the presence of cetyltrimethylammonium bromide. Subsequently, these microstructures were immediately gelled through quick polymerization of residual pyrrole monomers, leading to the formation of PPy nanonecklaces. Meanwhile, herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was synchronously imprinted into the formed PPy and highly dense imprinted sites were generated in PPy nanonecklaces because the necklace-like structure with microgaps/pores provides the facile and complete removal of templates. The imprinted nanonecklaces exhibit the high capacity and fast kinetics to uptake 2,4-D molecules, and produce a imprinting factor of ∼4.2. Importantly, the recognition and binding to 2,4-D significantly amplify the current response by a factor of 8 times in amperometric measurements, providing a sensitive detection of 2,4-D. The molecular imprinting strategy opens a novel avenue to the direct detection of non-electrochemically active species in a more convenient, simpler and cheaper way than the traditional competition-displacing approaches.

Keywords: Molecularly imprinted; Polypyrrole; Electrochemical detection; Herbicide

Portable formaldehyde monitoring device using porous glass sensor and its applications in indoor air quality studies by Yasuko Yamada Maruo; Jiro Nakamura (pp. 247-253).

Display Omitted► Formaldehyde concentration analysis using developed portable device. ► Formaldehyde concentration analysis with both high sensitivity and high temporal resolution. ► Estimation of air exchange rate and formaldehyde adsorption rate in actual environment. ► A new term in the mass balance equation for formaldehyde.We have developed a portable device for formaldehyde monitoring with both high sensitivity and high temporal resolution, and carried out indoor air formaldehyde concentration analysis. The absorbance difference of the sensor element was measured in the monitoring device at regular intervals of, for example, one hour or 30min, and the result was converted into the formaldehyde concentration. This was possible because we found that the lutidine derivative that was formed as a yellow product of the reaction between 1-phenyl-1,3-butandione and formaldehyde was stable in porous glass for at least six months. We estimated the reaction rate and to be 0.049min⁻¹ and the reaction occurred quickly enough for us to monitor hourly changes in the formaldehyde concentration. The detection limit was 5μgm⁻³h. We achieved hourly formaldehyde monitoring using the developed device under several indoor conditions, and estimated the air exchange rate and formaldehyde adsorption rate, which we adopted as a new term in the mass balance equation for formaldehyde, in one office.

Keywords: Formaldehyde; Monitoring device; Air exchange rate; Mass balance equation; β-Diketone

Disposable luminol copolymer-based biosensor for uric acid in urine by J. Ballesta-Claver; I.F. Díaz Ortega; M.C. Valencia-Mirón; L.F. Capitán-Vallvey (pp. 254-261).

Display Omitted► Offering a biosensor for uric acid in urine based on the increase of ECL emission with analyte concentration. ► Presentation of a better ECL luminophore based on the formation of a copolymer of luminol. ► Preparation of a luminol copolymer by potentiodynamic mode using 3,3′,5,5′-tetramethylbenzidine. ► Low-cost alternative for the determination of uric acid in 24-h urine samples.A new electrochemiluminescent (ECL) disposable biosensor for uric acid was manufactured by immobilization in a double-layer design of luminol as a copolymer with 3,3′,5,5′-tetramethylbenzidine (TMB) and the enzyme uricase in chitosan on gold screen-printed cells. The good mechanical and improved electroluminescent characteristics of the new copolymer poly(luminol–TMB) make it possible to determine uric acid by measuring the growing ECL emission with the analyte concentration. The combination of enzymatic selectivity with ECL sensitivity results in a disposable analytical device with a linear range for uric acid from 1.5×10⁻⁶ to 1.0×10⁻⁴M, a limit of detection of 4.4×10⁻⁷M and a precision of 13.1% (1.0×10⁻⁵M, n=10) as relative standard deviation. Satisfactory results were obtained for uric acid determination in 24h-urine samples compared to a reference procedure. This uric acid biosensor can be used as a low-cost alternative to conventional methods.

Keywords: Electrochemiluminescence; Disposable biosensor; Conducting polymers; Luminol copolymer; Uric acid determination; Urine samples

Development of an efficient protein phosphatase-based colorimetric test for okadaic acid detection by Audrey Sassolas; Gaëlle Catanante; Akhtar Hayat; Jean-Louis Marty (pp. 262-268).

Display Omitted► Development of protein phosphatase-based colorimetric test for okadaic acid detection. ► Rapid and sensitive detection of okadaic acid. ► Enzyme immobilization to stabilize protein phosphatase activity. ► Analysis of contaminated mussels.Okadaic acid (OA), responsible for gastrointestinal problems, inhibits protein phosphatase 2A (PP2A). Therefore, the inhibition exerted by the toxin on PP2A could be used to detect the presence of OA in aqueous solution and in shellfish sample.In this work, two commercial PP2As (from ZEU Immunotec and Millipore) and one produced by molecular engineering (from GTP Technology) were tested. Enzymes were used in solution and also immobilized within a polymeric gel. In solution, best performances were obtained using PP2A purchased from ZEU Immunotec (Spain). OA was detected in aqueous solution in concentration as low as 0.0124μgL⁻¹ using the enzyme from ZEU Immunotec whereas the detection limits were 0.47μgL⁻¹ and 0.123μgL⁻¹ with PP2As from Millipore and GTP Technology, respectively. Considering that the immobilization step contributes to stabilize the PP2A activity, enzymes were entrapped within a photopolymer and an agarose gel. These different polymeric matrices were optimized, tested and compared. Agarose gel seems to be a good alternative to the photopolymer largely used in our group. For instance, the IC₅₀ value obtained with the test based on PP2A from ZEU Immunotec immobilized within an agarose gel was 1.98μgL⁻¹. This value was 1.8-fold lower than those obtained with the photopolymer test using the same enzyme. The proposed test is sensitive, fast and does not require expensive equipment. To evaluate the efficiency of the assay, PP inhibition tests based on PP2A from ZEU Immunotec in solution or immobilized within a gel were used for OA detection in contaminated shellfish.

Keywords: Okadaic acid; Protein phosphatase; Colorimetric assays; Photopolymer; Agarose gel; Mussels

Thin-film oxygen sensors using a luminescent polynuclear gold(I) complex by A. Mills; C. Tommons; R.T. Bailey; P. Crilly; M.C. Tedford (pp. 269-273).

Display Omitted► Thin film sensors fabricated for gaseous and dissolved oxygen. ► Polynuclear gold complex encapsulated in polystyrene and ormosil matrices. ► Ormosil sensor showed linear Stern–Volmer plot for dissolved oxygen. ► Gaseous oxygen Stern–Volmer plots were downward turning. ► Sensors were stable, reversible, with fast response times.Robust thin-film oxygen sensors were fabricated by encapsulating a lipophilic, polynuclear gold(I) complex, bis{m-(bis(diphenylphosphino)octadecylamine-P,P′)}dichlorodigold(I), in oxygen permeable polystyrene and ormosil matrices. Strong phosphorescence, which was quenched by gaseous and dissolved oxygen, was observed from both matrices. The polystyrene encapsulated dye exhibited downward-turning Stern–Volmer plots which were well fitted by a two-site model. The ormosil trapped complex showed linear Stern–Volmer plots for dissolved oxygen quenching but was downward turning for gaseous oxygen. No leaching was observed when the ormosil based sensors were immersed in flowing water over an 8h period. Both films exhibited fully reversible response and recovery to changing oxygen concentration with rapid response times.

Keywords: Gold complex; Oxygen sensor; Phosphorescence; Polystyrene; Ormosil

New method based on combining ultrasonic assisted miniaturized matrix solid-phase dispersion and homogeneous liquid–liquid extraction for the determination of some organochlorinated pesticides in fish by Farahnaz Rezaei; Mohammad-Reza Milani Hosseini (pp. 274-279).

Display Omitted► Ultrasonic assisted miniaturized matrix solid-phase dispersion combined with HLLE was developed as a new method for the extraction of OCPs in fish. ► The goal of this combination was to enhance the selectivity of HLLE procedure and to extend its application in biological samples. ► This method proposed the advantages of good detection limits, lower consumption of reagents, and does not need any special instrumentation.In this study, ultrasonic assisted miniaturized matrix solid-phase dispersion (US-MMSPD) combined with homogeneous liquid–liquid extraction (HLLE) has been developed as a new method for the extraction of organochlorinated pesticides (OCPs) in fish prior to gas chromatography with electron capture detector (GC-ECD). In the proposed method, OCPs (heptachlor, aldrin, DDE, DDD, lindane and endrin) were first extracted from fish sample into acetonitrile by US-MMSPD procedure, and the extract was then used as consolute solvent in HLLE process. Optimal condition for US-MMSPD step was as follows: volume of acetonitrile, 1.5mL; temperature of ultrasound, 40°C; time of ultrasound, 10min. For HLLE step, optimal results were obtained at the following conditions: volume of chloroform, 35μL; volume of aqueous phase, 1.5mL; volume of double distilled water, 0.5mL; time of centrifuge, 10min. Under the optimum conditions, the enrichment factors for the studied compounds were obtained in the range of 185–240, and the overall recoveries were ranged from 39.1% to 81.5%. The limits of detection were 0.4–1.2ngg⁻¹ and the relative standard deviations for 20ngg⁻¹ of the OCPs, varied from 3.2% to 8% ( n=4). Finally, the proposed method has been successfully applied to the analysis of the OCPs in real fish sample, and satisfactory results were obtained.

Keywords: Organochlorinated pesticides; Ultrasonic assisted extraction; Miniaturized sample preparation; Matrix solid-phase dispersion; Homogeneous liquid–liquid extraction

Combined liquid chromatography–coulometric detection and microextraction by packed sorbent for the plasma analysis of long acting opioids in heroin addicted patients by Lorenzo Somaini; Maria Addolorata Saracino; Chiara Marcheselli; Silvia Zanchini; Gilberto Gerra; Maria Augusta Raggi (pp. 280-287).

Display Omitted► We developed a combined HPLC method–microextraction by packed sorbent procedure. ► Coulometric detection was used for the first time. ► We examined long-acting opioids in plasma from former heroin addicts. ► MEPS approach reduced time analysis and sample and organic solvent consumption.The sublingual combination of buprenorphine and naloxone (Suboxone^®) and Methadone Maintenance Therapy have been found effective in treating heroin addiction. A new analytical method suitable for the simultaneous determination of buprenorphine, norbuprenorphine, methadone and naloxone in human plasma by means of liquid chromatography with coulometric detection has been developed. The chromatographic separation was achieved with a phosphate buffer–acetonitrile mixture as the mobile phase on a cyano column. The monitoring cell of the coulometric detector was set at an oxidation potential of +0.600V. A rapid clean-up procedure of the biological samples using a microextraction by packed sorbent technique has been implemented, employing a C8 sorbent inserted into a syringe needle. The extraction yield values were satisfactory for all analytes (>85%). The calibration curves were linear over a range of 0.25–20.0ngmL⁻¹ for buprenorphine and norbuprenorphine, 3.0–1000.0ngmL⁻¹ for methadone and 0.13–10.0ngmL⁻¹ for naloxone. The sensitivity was also high with limits of detection of 0.08ngmL⁻¹ for both buprenorphine and norbuprenorphine, 0.9ngmL⁻¹ for methadone and 0.04ngmL⁻¹ for naloxone. The intraday and interday precision data were always satisfactory.The method was successfully applied to plasma samples obtained from former heroin addicts treated with opioid replacement therapy.

Keywords: Abbreviations; NLX; naloxone; BPN; buprenorphine; N-BPN; norbuprenorphine; MTD; methadone; ORT; opioid replacement therapy; MMT; Methadone Maintenance Therapy; IS; internal standard; MEPS; microextraction by packed sorbentBuprenorphine; Norbuprenorphine; Methadone; Naloxone; Liquid chromatography–coulometric detection; Microextraction by packed sorbent

Mixture designs for exploring class diversity and metabolite fingerprinting: An efficient column chromatographic strategy by Daniely Xavier Soares; Ieda S. Scarminio; Roy Edward Bruns (pp. 288-294).

Display Omitted► Ternary mixtures are efficient for studying metabolite diversity. ► Pure solvents are best to investigate the same class of metabolites. ► Statistical mixture design elution for fingerprint characterization.The effects of four solvents, hexane, dichloromethane, ethyl acetate, methanol, and their mixtures on the separation of metabolites in crude extracts of Erythrina speciosa Andrews leaves were investigated using two strategies for open column chromatography. The classical extraction procedure was compared with mobile phases prepared according to a mixture design in order to explore the effects of solvent interactions on metabolite separations. Principal component analysis was used to compare the UV spectra obtained from RP-HPLC-DAD and to estimate the number of independent factors contained in the chromatographic data of the extracts. The results showed that, in addition to solvent polarity, solvent mixtures play an important role in metabolite separation. When pure solvents are used, larger groups of similar spectra are observed in the factor analysis score graphs indicating the same or a limited number of metabolite classes. In contrast solvent mixtures produced score graphs with a larger number of clusters indicating greater metabolic diversity. Besides resulting in more peaks than the pure solvents the chromatographic data of the design mixtures resulted in larger numbers of significant principal components confirming the greater chemical diversity of their extracts. Thus, if the objective of an analysis is to obtain metabolites of the same class, one should use pure solvents. On the other hand, binary and ternary solvent mixtures are recommended for more efficient investigations of class diversity and richer metabolite fingerprints.

Keywords: Mixture design; Column chromatography; Solvent mixtures; Erythrina speciosa; Andrews; Metabolites

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Analytica Chimica Acta (v.702, #2)

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Analytica Chimica Acta (v.702, #2)