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Analytica Chimica Acta (v.714, #)

Editorial Board (pp. iii).

Endogenous and exogenous hydrogen influence on amorphous silicon thin films analysis by pulsed radiofrequency glow discharge optical emission spectrometry by Pascal Sánchez; Deborah Alberts; Beatriz Fernández; Armando Menéndez; Rosario Pereiro; Alfredo Sanz-Medel (pp. 1-7).

Study of the influence of externally added hydrogen in the discharge or present as sample constituent in hydrogenated amorphous silicon thin films by pulsed rf-GD-OES.Display Omitted► A comparison for 2 modes of hydrogen introduction has been performed by rf-PGD-OES. ► Exogenous hydrogen (0.2% H₂) and endogenous hydrogen from the sample were employed. ► Enhanced emission intensities were measured for most elements in the presence of H. ► Exogenous H₂ play a more important role than hydrogen sputtered from the sample.During the last decade the photovoltaic industry has been growing rapidly. One major strategy to reduce the production costs is the use of thin film solar cells based on hydrogenated amorphous silicon (a-Si:H). The potential of pulsed radiofrequency glow discharge coupled to optical emission spectrometry (rf-PGD-OES) for the analysis of such type of materials has been investigated in this work. It is known that when hydrogen is present in the argon discharge, even in small quantities, significant changes can occur in the emission intensities and sputtering rates measured. Therefore, a critical comparison has been carried out by rf-PGD-OES, in terms of emission intensities, penetration rates and depth resolution for two modes of hydrogen introduction in the discharge, manually external hydrogen in gaseous form (0.2% H₂–Ar) or internal hydrogen, sputtered as a sample constituent. First, a comparative optimisation study (at 600Pa and 50W) was performed on conducting materials and on a silicon wafer varying the pulse parameters: pulse frequency (500Hz–20kHz) and duty cycle (12.5–50%). Finally, 600Pa, 50W, 10kHz and 25% duty cycle were selected as the optimum conditions to analyse three types of hydrogenated samples: an intrinsic, a B-doped and a P-doped layer based on a-Si:H. Enhanced emission intensities have been measured for most elements in the presence of hydrogen (especially for silicon) despite the observed reduced sputtering rate. The influence of externally added hydrogen and that of hydrogen sputtered as sample constituent from the analysed samples has been evaluated.

Keywords: Thin film solar cells; Hydrogenated amorphous silicon; Gas mixture argon–hydrogen; Pulsed radiofrequency glow discharge; Optical emission spectrometry

Green chemistry and the evolution of flow analysis. A review by Wanessa R. Melchert; Boaventura F. Reis; Fábio R.P. Rocha (pp. 8-19).

Display Omitted► Evolution of flow methods towards minimization of waste amount and toxicity. ► Reagentless procedures and replacement of toxic chemicals. ► Waste minimization through automation. ► Ingenious examples of reagents reuse and waste degradation. ► Applications focusing on the last 10 years.Flow analysis has achieved its majority as a well-established tool to solve analytical problems. Evolution of flow-based approaches has been analyzed by diverse points of view, including historical aspects, the commutation concept and the impact on analytical methodologies. In this overview, the evolution of flow analysis towards green analytical chemistry is demonstrated by comparing classical procedures implemented with different flow approaches. The potential to minimize reagent consumption and waste generation and the ability to implement processes unreliable in batch to replace toxic chemicals are also emphasized. Successful applications of greener approaches in flow analysis are also discussed, focusing on the last 10 years.

Keywords: Abbreviations; FIA; flow injection analysis; FT-IR; Fourier transform infrared spectrometry; GAC; green analytical chemistry; LLE; liquid–liquid extraction; LOV; lab-on-valve; MCFA; multicommutation in flow analysis; MSFA; monosegmented flow analysis; MSFIA; multisyringe flow injection analysis; SFA; segmented flow analysis; SIA; sequential injection analysis; SIC; sequential injection chromatography; SPE; solid-phase extractionFlow analysis; Green analytical chemistry; Multicommutation; Sequential injection analysis; Miniaturization

Surface-bonded ionic liquid stationary phases in high-performance liquid chromatography—A review by Verónica Pino; Ana M. Afonso (pp. 20-37).

Display Omitted► SCILs are very interesting stationary phases for HPLC. ► They show a multimodal behavior: hydrophobic, electrostatic, and hydrogen bonding. ► The state-of-the-art is reviewed: preparation, chromatographic behavior, and performance.Ionic liquids (ILs) are a class of ionic, nonmolecular solvents which remain in liquid state at temperatures below 100°C. ILs possess a variety of properties including low to negligible vapor pressure, high thermal stability, miscibility with water or a variety of organic solvents, and variable viscosity. IL-modified silica as novel high-performance liquid chromatography (HPLC) stationary phases have attracted considerable attention for their differential behavior and low free-silanol activity. Indeed, around 21 surface-confined ionic liquids (SCIL) stationary phases have been developed in the last six years. Their chromatographic behavior has been studied, and, despite the presence of a positive charge on the stationary phase, they showed considerable promise for the separation of neutral solutes (not only basic analytes), when operated in reversed phase mode. This aspect points to the potential for truly multimodal stationary phases. This review attempts to summarize the state-of-the-art about SCIL phases including their preparation, chromatographic behavior, and analytical performance.

Keywords: Ionic liquids; Surface confined ionic liquids; Stationary phases; High-performance liquid chromatography

Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry by S. García-Salgado; M.A. Quijano; M.M. Bonilla (pp. 38-46).

Display Omitted► Total As and As species were analyzed in edible marine algae. ► A microwave-assisted extraction method with deionized water was applied. ► As compounds identified comprised DMA, As(V) and four arsenosugars ► Considerably high As(V) concentrations were found in the most of the algae studied.Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9 Sargassum fulvellum were analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126μgg⁻¹. Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography–ultraviolet photo-oxidation–hydride generation atomic–fluorescence spectrometry (HPLC–(UV)–HG–AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22μgg⁻¹, whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2μgg⁻¹). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9μgg⁻¹) and generally high arsenate (As(V)) concentrations (up to 77μgg⁻¹) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.

Keywords: Arsenic speciation; Microwave-assisted extraction; Edible algae; Inductively coupled plasma atomic emission spectrometry; High performance liquid chromatography; Hydride generation–atomic fluorescence spectrometry

Usefulness of capability indices in the framework of analytical methods validation by A. Bouabidi; E. Ziemons; R. Marini; C. Hubert; M. Talbi; A. Bouklouze; H. Bourichi; M. El Karbane; B. Boulanger; Ph. Hubert; E. Rozet (pp. 47-56).

Display Omitted► A new capability index useful for small sample sizes like in method validation. ► Comparison of its improved performances with the classical Cpk index. ► A methodology to define method validation sample size is proposed. ► Examples of application to the validation of pharmaceutical analytical methods.Analytical methods capability evaluation can be a useful methodology to assess the fitness of purpose of these methods for their future routine application. However, care on how to compute the capability indices have to be made. Indeed, the commonly used formulas to compute capability indices such as Cpk, will highly overestimate the true capability of the methods. Especially during methods validation or transfer, there are only few experiments performed and, using in these situations the commonly applied capability indices to declare a method as valid or as transferable to a receiving laboratory will conduct to inadequate decisions.In this work, an improved capability index, namely Cpk- tol and the corresponding estimator of proportion of non-conforming results (πCpk-tol) have been proposed. Through Monte-Carlo simulations, they have been shown to greatly increase the estimation of analytical methods capability in particular in low sample size situations as encountered during methods validation or transfer. Additionally, the usefulness of this capability index has been illustrated through several case studies covering applications commonly encountered in the pharmaceutical industry. Finally a methodology to determine the optimal sample size required to validate analytical methods is also given using the proposed capability metric.

Keywords: Capability; Tolerance intervals; Drug products; Method validation; Fit for purpose

Prediction of some quality attributes of lamb meat using near-infrared hyperspectral imaging and multivariate analysis by Mohammed Kamruzzaman; Gamal ElMasry; Da-Wen Sun; Paul Allen (pp. 57-67).

Display Omitted► We report prediction of meat quality attributes using NIR hyperspectral imaging. ► We develop and optimise multivariate prediction model. ► We conduct analysis to correlate between textural features and quality parameter. ► We derive prediction map to visualize the constituent concentration at pixel level.The goal of this study was to explore the potential of near-infrared (NIR) hyperspectral imaging in combination with multivariate analysis for the prediction of some quality attributes of lamb meat. In this study, samples from three different muscles ( semitendinosus (ST), semimembranosus (SM), longissimus dorsi (LD)) originated from Texel, Suffolk, Scottish Blackface and Charollais breeds were collected and used for image acquisition and quality measurements. Hyperspectral images were acquired using a pushbroom NIR hyperspectral imaging system in the spectral range of 900–1700nm. A partial least-squares (PLS) regression, as a multivariate calibration method, was used to correlate the NIR reflectance spectra with quality values of the tested muscles. The models performed well for predicting pH, colour and drip loss with the coefficient of determination ( R²) of 0.65, 0.91 and 0.77, respectively. Image processing algorithm was also developed to transfer the predictive model in every pixel to generate prediction maps that visualize the spatial distribution of quality parameter in the imaged lamb samples. In addition, textural analysis based on gray level co-occurrence matrix (GLCM) was also conducted to determine the correlation between textural features and drip loss. The results clearly indicated that NIR hyperspectral imaging technique has the potential as a fast and non-invasive method for predicting quality attributes of lamb meat.

Keywords: Near-infrared hyperspectral imaging; Lamb; Partial least square regression; pH; Colour and water holding capacity

Annular diffusion denuder for simultaneous removal of gaseous organic compounds and air oxidants during sampling of carbonaceous aerosols by Pavel Mikuška; Zbyněk Večeřa; Anna Bartošíková; Willy Maenhaut (pp. 68-75).

Display Omitted► Annular diffusion denuder for sampling of carbonaceous aerosols on filters. ► No positive sampling artefacts from VOCs and atmospheric oxidants. ► Optimum sorbent is a mixture of activated charcoal and sulfite on molecular sieve. ► The collection efficiency of VOCs and oxidants in denuder is better than 95%. ► Compatible with the collection of aerosol on 47-mm filter at flow rate of 1m³h⁻¹.A specially designed annular diffusion denuder for simultaneous removal of organic gaseous compounds and atmospheric oxidants in carbonaceous aerosol sampling is presented. Various kinds of denuder coatings were compared with respect to the collection efficiency of both organic gaseous compounds and NO₂ and ozone. The optimum sorbent is a mixture of activated charcoal and sulfite on molecular sieve. To ensure high collection efficiency over long-term field operation, two annular diffusion denuders are combined in series. The first half of the first denuder is filled with Na₂SO₃ on molecular sieve (23cm long layer) while the second half of the first denuder and the whole second denuder are filled with activated charcoal (the total length of the charcoal section is 67cm).At a flow rate of 16.6Lmin⁻¹, the collection efficiency of organic gaseous compounds and atmospheric oxidants in the annular diffusion denuder is better than 95%. Only small losses of aerosol particles (<3.6% in number concentration) were observed in the size range 0.12–2.26μm.The annular diffusion denuder is compatible with the collection of aerosols on 47-mm diameter quartz fiber filters at a flow rate of 16.6Lmin⁻¹. The use of this denuder enables one to sample carbonaceous aerosols on filters without positive sampling artefacts from volatile organic compounds and interferences from atmospheric oxidants. The annular diffusion denuder has been applied successfully for the sampling of carbonaceous aerosols during field campaigns of typically 1 month each at urban and forested sites in Europe.

Keywords: Annular diffusion denuder; Organic compounds; Oxidants; Carbonaceous aerosols; Sampling artefacts

Evaluation of single-walled carbon nanohorns as sorbent in dispersive micro solid-phase extraction by Juan Manuel Jiménez-Soto; Soledad Cárdenas; Miguel Valcárcel (pp. 76-81).

Display Omitted► The potential of single walled carbon nanohorns in dispersive solid phase microextraction has been evaluated. ► The method was characterized for the extraction of PAHs from waters. ► Single walled carbon nanohorns were better extractant than carbon nanotubes and carbon nanocones. ► The limits of detection were adequate for the target analytes in environmental waters.A new dispersive micro solid-phase extraction method which uses single-walled carbon nanohorns (SWNHs) as sorbent is proposed. The procedure combines the excellent sorbent properties of the nanoparticles with the efficiency of the dispersion of the material in the sample matrix. Under these conditions, the interaction with the analytes is maximized. The determination of polycyclic aromatic hydrocarbons was selected as model analytical problem. Two dispersion strategies were evaluated, being the functionalization via microwave irradiation better than the use of a surfactant. The extraction was accomplished by adding 1mL of oxidized SWHNs (o-SWNHs) dispersion to 10mL of water sample. After extraction, the mixture was passed through a disposable Nylon filter were the nanoparticles enriched with the PAHs were retained. The elution was carried out with 100μL of hexane. The limits of detection achieved were between 30 and 60ngL⁻¹ with a precision (as repeatability) better than 12.5%. The recoveries obtained for the analytes in three different water samples were acceptable in all instances. The performance of o-SWNHs was favourably compared with that provided by carboxylated single-walled carbon nanotubes and thermally treated carbon nanocones.

Keywords: Single-walled carbon nanohorns; Dispersive micro solid-phase extraction; Polycyclic aromatic hydrocarbons; Waters

Comparison of ultrasound-assisted emulsification and dispersive liquid–liquid microextraction methods for the speciation of inorganic selenium in environmental water samples using low density extraction solvents by Nahid Mashkouri Najafi; Hamed Tavakoli; Yaser Abdollahzadeh; Reza Alizadeh (pp. 82-88).

Display Omitted► USAEME and DLLME have been applied for the speciation of inorganic selenium. ► Low density organic solvents have been used as extraction solvent in the two methods. ► Response surface methodology has been applied for optimization of the two methods. ► The advantages and disadvantages of both methods have been discussed.Herein, ultrasound-assisted emulsification microextraction (USAEME) and dispersive liquid–liquid microextraction (DLLME) methods based on applying low-density organic solvents have been critically compared for the speciation of inorganic selenium, Se(IV) (selenite) and Se(VI) (selenate) in environmental water samples by gas chromatography-flame ionization detection (GC-FID). At pH 2 and T=75°C for 7min, only Se(IV) was able to form the piazselenol complex with 4-nitro- o-phenylenediamine. Piazselenol was extracted using an extraction solvent and was injected into a GC-FID instrument for the determination of Se(IV). Conveniently, Se(VI) remained in the aqueous phase. Total inorganic selenium was determined after the reduction of Se(VI) to Se(IV) and prior to the above procedures. The Se(VI) concentration was calculated as the difference between the measured total inorganic selenium and Se(IV) content. The effect of various experimental parameters on the efficiencies of the two methods and their optimum values were studied with the aid of response surface methodology and experimental design. Under the optimal conditions, the limit of detections (LODs) for Se(IV) obtained by USAEME-GC-FID and DLLME-GC-FID were 0.05 and 0.11ngmL⁻¹, respectively. The relative standard deviations (RSDs, n=6) for the measurement 10ngmL⁻¹ of Se(IV) were 5.32% and 4.57% with the enrichment factors of 2491 and 1129 for USAEME-GC-FID and DLLME-GC-FID, respectively. Both methods were successfully applied to the analysis of inorganic selenium in different environmental water samples and certified reference material (NIST SRM 1643e).

Keywords: Dispersive liquid–liquid microextraction; Environmental water samples; Inorganic selenium; Low density organic solvents; Ultrasound-assisted emulsification microextraction

Application of sulfur microparticles for solid-phase extraction of polycyclic aromatic hydrocarbons from sea water and wastewater samples by Vahid Khalili-Fard; Kamal Ghanemi; Yadollah Nikpour; Mehdi Fallah-Mehrjardi (pp. 89-97).

Display Omitted► Outstanding features of sulfur: low cost, readily available and low back-pressure. ► The recoveries of PAHs were unaffected by salinity and solution pH. ► Analytical features: high recovery, good detection limit and broad-range linearity. ► PAHs were successfully determined in sea water and petrochemical wastewater.The application of sulfur microparticles as efficient adsorbents for the solid-phase extraction (SPE) and determination of trace amounts of 10 polycyclic aromatic hydrocarbons (PAHs) was investigated in sea water and wastewater samples using high performance liquid chromatography coupled with an ultraviolet detector (HPLC–UV). Parameters influencing the preconcentration of PAHs such as the amount of sulfur, solution flow rate and volume, elution solvent, type and concentration of organic modifier, and salt effect were examined. The results showed that at a flow rate of 10mLmin⁻¹ for the sample solutions (100mL), the PAHs could be adsorbed on the sulfur microparticles and then eluted by 2.0mL of acetonitrile. For HPLC–UV analysis of extracted PAHs, the calibration curves were linear in the range of 0.05–80.0μgL⁻¹; the coefficients of determinations ( r²) were between 0.9934 and 0.9995. The relative standard deviations (RSDs) for eight replicates at two concentration levels (0.5 and 4.0μgL⁻¹) of PAHs were lower than 7.3%, under optimized conditions. The limits of detection (LODs, S/N=3) of the proposed method for the studied PAHs were 0.007–0.048μgL⁻¹. The recoveries of spiked PAHs (0.5 and 4μgL⁻¹) in the wastewater and sea water samples ranged from 78% to 108%. The simplicity of experimental procedure, high extraction efficiency, short sample analysis, and using of low cost sorbent demonstrate the potential of this approach for routine trace PAH analysis in water and wastewater samples.

Keywords: High-performance liquid chromatography (HPLC); Sulfur microparticles; Solid-phase extraction; Water and wastewater samples; Polycyclic aromatic hydrocarbons (PAHs)

Effect of standard phase differences between gas and liquid and the resulting experimental bias in the analysis of gaseous volatile organic compounds by Yong-Hyun Kim; Ki-Hyun Kim (pp. 98-103).

Comparison of experimental bias (expressed in percent difference (PD)) against liquid phase standard: (1) gas-phase standard and (2) gaseous samples prepared at two concentration levels of low (L) and high (H).Display Omitted► Experimental bias often becomes inevitable due to phase differences between standard and sample. ► The use of gas-phase standard is ideal to analyze gas-phase samples with the least matrix effect. ► The experimental bias in VOC analysis was assessed in relation to phase differences in standards. ► The bias can be reduced significantly for many VOCs with the proper control of experimental conditions.Liquid- or gas-phase standards can be used for the analysis of VOCs in air. Once the accuracy is secured in the standard preparation stage, the use of gas-phase standard should be more reliable with the least matrix effect. However, it is not difficult to find that the liquid-phase standard is used more preferably in many laboratories for several reasons (e.g., low expense, easy handling, etc.). As such, one needs to accurately evaluate any possible bias stemming from the use of different standard phases. To this end, standards for 8 VOCs consisting of 4 aromatic compounds (benzene (B), toluene (T), styrene (S) and p-xylene (p-X)) and 4 others (methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), butyl acetate (BuAc), and isobutyl alcohol (i-BuAl)) were prepared in both liquid and gas phases. Each standard was analyzed by the initial collection on the adsorption tube and by the combined application of thermal-desorption–gas chromatography–mass spectrometry (TD/GC/MS). The results indicated that experimental bias between the two phases, if expressed in terms of percent difference (PD), was very low in many target VOCs (B (1.09%), T (2.41%), p-X (3.64%), MEK (6.76%), and MIBK (0.17%)), while it was not in some targets (e.g., >10%: e.g., S, i-BuAl, and BuAc). In an ancillary experiment, biases were evaluated further by (1) calibrating gaseous samples against liquid phase standard and via (2) comparison between two different types of gas phase standards. In conclusion, treatment of different standards (e.g., between the same or different phases) will inevitably induce biases in most VOCs, although certain volatiles (e.g., benzene, MIBK, etc.) are virtually unaffected by such variables in a practical sense.

Keywords: Standard; Thermal desorption; Bias; Calibration; Odorant; Matrix effect

Microprobe sampling—Photo ionization-time-of-flight mass spectrometry for in situ chemical analysis of pyrolysis and combustion gases: Examination of the thermo-chemical processes within a burning cigarette by Romy Hertz; Thorsten Streibel; Chuan Liu; Kevin McAdam; Ralf Zimmermann (pp. 104-113).

.Display Omitted► Analysis of the changes of VOC inside a burning cigarette. ► Analysis of VOC formed by smoldering and puffing in real-time. ► Discrimination between VOC formed under combustion or pyrolysis conditions.A microprobe sampling device (μ-probe) has been developed for in situ on-line photo ionization mass spectrometric analysis of volatile chemical species formed within objects consisting of organic matter during thermal processing. With this approach the chemical signature occurring during heating, pyrolysis, combustion, roasting and charring of organic material within burning objects such as burning fuel particles (e.g., biomass or coal pieces), lit cigarettes or thermally processed food products (e.g., roasting of coffee beans) can be investigated. Due to its dynamic changes between combustion and pyrolysis phases the cigarette smoking process is particularly interesting and has been chosen as first application. For this investigation the tip of the μ-probe is inserted directly into the tobacco rod and volatile organic compounds from inside the burning cigarette are extracted and real-time analyzed as the glowing front (or coal) approaches and passes the μ-probe sampling position. The combination of micro-sampling with photo ionization time-of-flight mass spectrometry (PI-TOFMS) allows on-line intrapuff-resolved analysis of species formation inside a burning cigarette. Monitoring volatile smoke compounds during cigarette puffing and smoldering cycles in this way provides unparalleled insights into formation mechanisms and their time-dependent change. Using this technique the changes from pyrolysis conditions to combustion conditions inside the coal of a cigarette could be observed directly. A comparative analysis of species formation within a burning Kentucky 2R4F reference cigarette with μ-probe analysis reveals different patterns and behaviors for nicotine, and a range of semi-volatile aromatic and aliphatic species.

Keywords: Cigarette smoke; Photo ionization; Mass spectrometry; Micro sampling; Pyrolysis; Combustion

Amperometricl-lactate biosensor based on screen-printed carbon electrode containing cobalt phthalocyanine, coated with lactate oxidase-mesoporous silica conjugate layer by Takeshi Shimomura; Touru Sumiya; Masatoshi Ono; Tetsuji Ito; Taka-aki Hanaoka (pp. 114-120).

Display Omitted►l-lactate biosensor based on screen-printed electrode, simple to fabricate and use, has been developed. ► Activated electrode containing cobalt-phthalocyanine lowers operating potential of the biosensor. ► Mesoporous silica and nafion layers ensure excellent stability and high selectivity. ► Only a small sample volume is required for the measurement. ► High-performancel-lactate biosensor is obtained with a simple and cost effective way.A novel amperometric biosensor for the measurement ofl-lactate has been developed. The device comprises a screen-printed carbon electrode containing cobalt phthalocyanine (CoPC-SPCE), coated with lactate oxidase (LOD) that is immobilized in mesoporous silica (FSM8.0) using a polymer matrix of denatured polyvinyl alcohol; a Nafion layer on the electrode surface acts as a barrier to interferents. The sampling unit attached to the SPCE requires only a small sample volume of 100μL for each measurement. The measurement ofl-lactate is based on the signal produced by hydrogen peroxide, the product of the enzymatic reaction. The behavior of the biosensor, LOD-FSM8.0/Naf/CoPC-SPCE, was examined in terms of pH, applied potential, sensitivity and operational range, selectivity, and storage stability. The sensor showed an optimum response at a pH of 7.4 and an applied potential of +450mV. The determination range and the response time forl-lactate were 18.3μM to 1.5mM and approximately 90s, respectively. In addition, the sensor exhibited high selectivity forl-lactate and was quite stable in storage, showing no noticeable change in its initial response after being stored for over 9 months. These results indicate that our method provides a simple, cost-effective, high-performance biosensor forl-lactate.

Keywords: Screen-printed carbon electrode; Cobalt phthalocyanine; Lactate oxidase; Mesoporous silica; Nafion; Sampling unit

Ion chromatographic determination of hydrolysis products of hexafluorophosphate salts in aqueous solution by Lydia Terborg; Sascha Nowak; Stefano Passerini; Martin Winter; Uwe Karst; Paul R. Haddad; Pavel N. Nesterenko (pp. 121-126).

Display Omitted► Ion chromatography – a key tool to the analysis of purity of hexafluorophosphates. ► Hexafluorophosphates are not stable in aqueous solutions. ► Hexafluorophosphates cannot be considered as a part of green chemistry anymore.In this work, hydrolysis of three different hexafluorophosphate salts in purified water was investigated. Aqueous samples of lithium hexafluorophosphate (LiPF₆), sodium hexafluorophosphate (NaPF₆) and potassium hexafluorophosphate (KPF₆) were prepared and stored for different times. Ion chromatography (IC) with UV as well as non-suppressed and suppressed conductivity detection was used for the analysis of the reaction products. For the detection and identification of the formed decomposition products, an IC method using IonPac AS14A 250mm×4.0mm i.d. column and 2.5mM KHCO₃–2.5mM K₂CO₃ eluent was established. Besides hexafluorophosphate, four other anionic species were detected in fresh and matured aqueous solutions. The hydrolysis products fluoride (F⁻), monofluorophosphate (HPO₃F⁻), phosphate (HPO₄²⁻) and difluorophosphate (PO₂F₂⁻) were found and were unambiguously identified by means of standards or electrospray ionization mass spectrometry (ESI-MS). It was shown that stability of hexafluorophosphate solutions depends on the nature of the counter ion and decreases in the order potassium>sodium>lithium.

Keywords: Hexafluorophosphate salts; Ion chromatography; Hydrolysis; Photometric detection; Conductivity

Dual polarization interferometric and capillary electrophoretic analysis of supported lipid bilayer constructed on silica-based surface: Evaluation of its anti-protein adsorption effect by Ja-an Annie Ho; Ting-Yang Kuo; Liang-Gui Yu (pp. 127-133).

Display Omitted► Applicability of DPI in monitoring formation of SLBs on Si surface was demonstrated. ► Formulation of SLB decides the resistance towards nonspecific protein adsorption. ► The further application of SLB enables separation of 4 alkaline proteins in CE.Supported lipid bilayer (SLB) has been demonstrated as a model of cell membranes with prospective bioanalytical or biotechnological applications. In this study, the formation of SLB and their potential biofunctionality against protein adsorption were investigated by Dual Polarization Interferometry (DPI) and Capillary Electrophoresis (CE). DPI studies on different formulations of double-chained, zwitterionic phospholipidlipids, allow the process of bilayer formation to be followed in situ and in real time. Furthermore the anti-protein adsorption effect provided by the various formulated SLBs was examined by DPI. In addition, the SLB coatings of the same lipid formulations were subsequently employed in CE experiments as a pseudo-stationary phase for demonstrating more efficient separation of alkaline protein standard mixtures. SLB-assisted CE was found to be capable of separating 4 alkaline proteins (protonated at neutral pH). This study demonstrates the applicability of DPI to monitor the process of SLB formation; and our findings, obtained by both DPI and CE, confirm that the presence of the SLB reduced drastically the problematic interactions between cationic, alkaline proteins and the negatively charged silica capillary wall, leading to better recovery and efficient separation of the proteins under investigation.

Keywords: Dual polarization interferometry (DPI); Supported lipid bilayer (SLB); Liposome; Capillary electrophoresis (CE); SLB-assisted capillary electrophoresis analysis (SACE)

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Analytica Chimica Acta (v.714, #)