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Analytical and Bioanalytical Chemistry (v.384, #4)

5th Mediterranean Basin Conference on Analytical Chemistry by Sergio Caroli (pp. 859-859).

Pervaporation membrane separation process for enhancing the selectivity of an artificial olfactory system (“electronic nose”) by Thomas Schäfer; Maria Belén Serrano-Santos; Santina Rocchi; Roger Fuoco (pp. 860-866).

This study investigates the potential of pervaporation (a selective membrane separation technique) combined with an electronic nose based on metal oxide sensors for analyzing wine model solutions. Choosing a suitable membrane polymer, it is shown that subtle variations in aroma composition can be detected by the metal oxide sensors, even when 12% (v/v) ethanol is present in the original sample. Simulations of the composition of the permeate demonstrate that, despite the low molecular density of the permeate, the respective solute concentrations are sufficiently high to generate a reproducible and significant response from the metal oxide sensors.

Keywords: Pervaporation; Electronic nose; Wine model solution; Sample work-up; Membrane; Analysis

Construction and evaluation of PVC and sol–gel sensor membranes based on Mn(III)TPP-Cl. Application to valproate determination in pharmaceutical preparations by Emília M. G. Santos; Alberto N. Araújo; Cristina M. C. M. Couto; M. Conceição B. S. M. Montenegro (pp. 867-875).

The construction and general performance of new valproate-selective electrodes based on manganese(III) tetraphenylporphyrin [Mn(III)TPP-Cl], as an ionophore, are presented. The ionophore was incorporated into PVC and ceramic membranes (sol–gel) based on methyltriethoxysilane. The influence of membrane composition and pH and the effect of lipophilic cationic and anionic additives in PVC membranes were investigated concerning their influence on the slope, response time, selectivity and lifetime of the electrodes. The PVC membrane without additive and the sol–gel membrane presented slopes and practical limits of detection of −60.8 mV dec⁻¹ and 5x10⁻⁶ mol l⁻¹ and −60.3 mV dec⁻¹ and 1×10⁻⁴ mol l⁻¹, respectively. The sol–gel membranes displayed higher selectivity for valproate when compared with PVC membranes. These two types of electrodes were coupled to a sequential-injection analysis (SIA) system for the direct determination of valproate in pharmaceutical formulations. The association of Mn(III)TPP-Cl with the sol–gel support inserted in a SIA system provided potentiometric sensors with an analytical range of 1x10⁻³–5x10⁻² mol l⁻¹, with a sample rate of 55 samples per hour and a sample and carrier consumption of 140 and 2,500 μl per determination, respectively.

Keywords: Valproate; Ion-selective electrodes; Potentiometry; Metalloporphyrins; Sol–gel; Sequential-injection analysis

In-depth profile analysis of thin films deposited on non-conducting glasses by radiofrequency glow-discharge–optical emission spectrometry by Beatriz Fernández; Antonio Martín; Nerea Bordel; Rosario Pereiro; Alfredo Sanz-Medel (pp. 876-886).

The potential of radiofrequency glow-discharge–optical emission spectrometry (rf-GD–OES) for quantification of thin films on non-conducting materials has been investigated. A commercial rf-GD chamber from Jobin Yvon operated at 13.56 MHz with Ar as discharge gas was used. The signal integration time was 0.1 s. The effect on emission yields of thin conducting layers on glasses of different thickness was studied in detail, using the rf-GD in the common operating mode “constant pressure–constant forward power”. Calibration curves were obtained for two types of material—conducting reference materials and a set of non-conductors comprising homogeneous glass of known composition and three different thicknesses coated (or not) with thin layers of gold. Qualitative and quantitative in-depth profile analyses of different coated non-conducting samples were investigated. A variety of samples, including different thick glass substrates (from 1.8 to 5.8 mm), different thin films deposited on homogeneous glasses (from 6 nm to 35 nm), and different kinds of coating (conductors such as Fe, Ni, Cr, Al, and Nb and non-conductors such as Si₃N₄) were studied at 450 Pa pressure and 20 W forward power. The quantitative in-depth profiles proved satisfactory and results for depths and concentrations were similar to nominal values.

Keywords: Radiofrequency; Glow discharge; Depth profiling; Thin films; Coated glass

Element fingerprinting of marine organisms by dynamic reaction cell inductively coupled plasma mass spectrometry by Francesco Cubadda; Andrea Raggi; Ettore Coni (pp. 887-896).

A method for the determination of sixteen elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) in seafood by dynamic reaction cell inductively coupled plasma mass spectrometry (ICP–DRC–MS) is presented. A preliminary study of polyatomic interferences was carried out in relation to the chemical composition of marine organisms belonging to different taxa. Acid effects and other matrix effects in marine organisms submitted to closed-vessel microwave digestion were investigated as well. Ammonia was the reactive gas used in the DRC to remove polyatomic ions interfering with ²⁷Al, ⁵²Cr, ⁵⁶Fe and ⁵¹V. Optimal conditions for the simultaneous determination of analytes were identified in order to develop a fast multielement method. A suite of real samples (mussels and various fish species) were used during method development along with three certified reference materials: BCR CRM 278R (mussel tissue), BCR CRM 422 (cod muscle) and DORM-2 (dogfish muscle). The proposed analytical approach can be used in conjunction with suitable chemometric procedures to address quality and safety issues in aquaculture and fisheries. As an example, a case study is described in which mussels from three farming sites in the Venice Lagoon were distinguished by multivariate analysis of element fingerprints.

Keywords: Dynamic reaction cell inductively coupled plasma mass spectrometry; Seafood; Multielement analysis; Principal component analysis; Discriminant analysis

Development and field evaluation of a new diffusive sampler for Hydrogen Sulphide in the ambient air by F. De Santis; I. Allegrini; R. Bellagotti; F. Vichi; D. Zona (pp. 897-901).

A diffusive sampler for the determination of hydrogen sulphide (H₂S) based on collection on a paper filter coated with silver nitrate followed by optical densitometric determination of the metal sulphide was developed. Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity and of interferents, precision and accuracy. The measured uptake rate for H₂S was determined in experiments involving sampling at different concentration levels in comparison to a wet standard colorimetric technique. The precision of the measurements for co-located passive samplers was lower than 15%. The accuracy of the data collected is within 20% of the actual value measured by the wet method. The sampler is capable of reliable measurements of H₂S at common levels of a polluted atmosphere in urban settings yielding average concentration levels over one month and beyond. Diffusive sampling can be adopted to analyse in detail the temporal and spatial trends of H₂S concentration in ambient air and in specific historic buildings or in museums. Figure At the end of sampling cap #2 is removed and optical density is measured

Keywords: Atmospheric pollution; Diffusive sampling; Hydrogen sulphide

An attempt to differentiate HPLC-ICP-MS selenium speciation in natural and selenised Agaricus mushrooms using different species extraction procedures by Vanesa Díaz Huerta; María Luisa Fernández Sánchez; Alfredo Sanz-Medel (pp. 902-907).

Total determination and speciation analysis of Se in commercial and selenised Agaricus mushrooms have been performed to investigate the Se species naturally occurring in non-enriched mushrooms as well as those present in specimens grown in a Se-enriched medium. Mushroom aqueous and enzymatic extracts have been analysed by three complementary chromatographic separation mechanisms (size-exclusion, anion-exchange and reversed-phase) coupled to an inductively coupled plasma mass spectrometer with an octopole reaction system. Post-column isotope dilution analysis has been used on-line with the separations for quantification of the Se species eluted. The ⁷⁸Se-to-⁷⁷Se isotope ratio was monitored after adequate corrections for both total determinations and Se species quantitative speciation. The results showed marked differences not only in total Se contents but also in Se species found in the two types of Agaricus mushrooms investigated. Selenomethionine was detected in both of them (free in commercial mushrooms and incorporated into proteins in selenised ones) together with a number of unknown selenocompounds.

Keywords: Agaricus ; Mushroom; Se speciation; Hybrid high-performance liquid chromatography inductively coupled plasma mass spectrometry; Isotope dilution analysis

Isotope dilution GC-MS routine method for the determination of butyltin compounds in water by Giuseppe Centineo; Pablo Rodríguez-González; Elisa Blanco González; J. Ignacio García Alonso; Alfredo Sanz-Medel; Nuria Font Cardona; José Luis Aranda Mares; Salomé Ballester Nebot (pp. 908-914).

A standard GC-MS instrument with electron impact ionisation has been used to develop a fast, simple and reliable method for the simultaneous determination of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in water samples. Isotope dilution analysis (IDA) is used for the determination of species, taking advantage of a commercially available spike solution containing a mixture of MBT, DBT and TBT enriched in ¹¹⁹Sn. Method detection limits for 100-mL samples were between 0.18 and 0.25 ng L⁻¹ for the three butyltin compounds with typical RSD between 2 and 4% at levels between 100 and 10 ng L⁻¹, respectively. Recovery of tin species in spiked samples (natural water, wastewater and seawater) was quantitative. The stability of butyltin compounds in collected seawater samples was also studied. The addition of a 1% (v/v) glacial acetic acid preserved tin species in the samples for at least 5 days at room temperature. The IDA method was finally implemented in a routine testing laboratory and it was subsequently accredited by the Spanish National Accreditation Body according to the requirements of UNE-EN ISO/IEC 17025.

Keywords: Butyltin compounds; Isotope dilution; Gas chromatography-mass spectrometry; Water samples; Implementation and accreditation in routine testing laboratories

Tyrosinase inhibition organic phase biosensor for triazinic and benzotriazinic pesticide analysis (part two) by L. Campanella; R. Dragone; D. Lelo; E. Martini; M. Tomassetti (pp. 915-921).

Several triazine pesticides, such as atrazine, are much more soluble in several organic solvents, such as chloroform, than in water. Our recent research was aimed at analyzing this class of pesticides using tyrosinase OPEE (organic phase enzyme electrodes), exploiting their inhibiting action on the tyrosinase enzyme when operating in water-saturated chloroform medium. In this work we studied the response of a tyrosinase inhibition enzyme sensor to several triazinic (simazine, propazine, terbuthylazine) and benzotriazinic (azinphos-ethyl and azinphos-methyl) pesticides (LOD=0.5×10⁻⁹ mol l⁻¹). Recovery trials were also performed in vegetal matrixes (corn, barley, lentils). Lastly, the effect of the solvent (chloroform or water) on the inhibition process was investigated via Hill’s equation and the diffusion of analyte from the solvent to the enzyme membrane.

Keywords: Triazine; Benzotriazine; Pesticide analysis; OPEE; Tyrosinase inhibition

Development of an SdFFF–ETAAS hyphenated technique for dimensional and elemental characterization of colloids by G. Blo; A. Ceccarini; C. Conato; C. Contado; F. Fagioli; R. Fuoco; A. Pagnoni; F. Dondi (pp. 922-930).

Direct hyphenation of electrothermal atomic-absorption spectroscopy (ETAAS) to sedimentation field-flow fractionation (SdFFF) has been developed to enable elemental characterization of submicron particles as a function of size. This hyphenation is particularly suitable for characterizing colloidal particles of environmental interest, for example water-borne particles. The interface is an automatic capillary injection device (CID) which enables direct introduction of large and variable volumes of colloidal particle suspensions into a hot graphite furnace, thus preconcentrating the colloidal particles on the furnace walls. The method was validated by determination of Fe in certified submicron Fe₂O₃. The procedure was set up by first optimizing the SdFFF fractionation under programmed field conditions, thus enabling optimum fractionation of particle size. The ETAAS procedure was then tested to determine whether it could be used for direct analysis of Fe₂O₃ slurries without the need for a mineralization step. CID coupled to ETAAS was subsequently exploited for its ability to enhance the sensitivity, because of the increased injection volume. Statistical tests and data handling were conducted to prove the suitability of the ETAAS-CID module. Finally, off-line and on-line ETAAS-CID-SdFFF hyphenation were investigated. These experiments emphasized the advantages of the on-line coupling, because it enables synchronized sampling, enrichment, and elemental analysis of the flowing eluate. The benefits of the proposed hyphenation are the high specificity of analytical detection, increased sensitivity, reduction of analysis time, and minimum sample handling and contamination.

Keywords: Colloids; SdFFF analysis; ETAAS element analysis; Capillary injection device

Quantification of trimethylsilyl derivatives of amino acid disease biomarkers in neonatal blood samples by gas chromatography-mass spectrometry by Xizhong Shen; Chunhui Deng; Ben Wang; Ling Dong (pp. 931-938).

A novel analytical procedure was developed for the rapid determination of disease biomarkers of maple syrup urine disease (MSUD),L-valine,L-leucine,L-isoleucine, andL-phenylalanine in dried blood spots. Amino acids extracted from neonatal dried blood spots were rapidly derivatized with bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and then analyzed by gas chromatography-mass spectrometry (GC-MS). Derivatization conditions and the method validation were studied: optimal derivatization conditions were acetonitrile as reaction solvent, a temperature of 100°C, and a reaction time of 30 min. The proposed method provided a detection limit lower than 2.0 μM, recovery between 92% and 106%, and relative standard deviation less than 8.0%. The method was further tested in screening for neonatal MSUD by determination ofL-valine,L-leucineL-isoleucine, andL-phenylalanine in blood samples. The experimental results show that GC-MS following BSTFA derivatization is a rapid, simple, and sensitive method for the determination of amino acid disease biomarkers in blood samples, and is a potential tool for fast screening of MSUD. Figure

Keywords: Bis-(trimethylsilyl)trifluoroacetamide; Maple syrup urine disease; Amino acids; Derivatization; Gas chromatography-mass spectrometry

Chiral high-performance liquid chromatographic separation of the enantiomers of tetrahydropalmatine and tetrahydroberberine, isolated from Corydalis yanhusuo by Zong-De Zhai; Yan-Ping Shi; Xiao-Mei Wu; Xing-Ping Luo (pp. 939-945).

HPLC methods have been developed for chiral resolution of the enantiomers of dl-tetrahydropalmatine (THP) and dl-tetrahydroberberine (THB), two active constituents of Corydalis yanhusuo W.T. Wang. On the analytical scale, good baseline separation of the enantiomers was achieved using cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases in both normal-phase and polar organic modes. Validation of the analytical methods, including linearity, limits of detection, recovery, and precision, and semipreparative resolution of dl-THP and dl-THB, were achieved with methanol as mobile phase, without any basic additives, in polar organic mode using cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases. On the semipreparative scale, small quantities of the individual enantiomers of THP and THB were isolated for study of the chiroptical properties of the individual enantiomers.

Keywords: Enantiomer separation; Polysaccharide carbamate phase; Specific rotation; Circular dichroism; Tetrahydropalmatine; Tetrahydroberberine

2-D PAGE analysis of pesticide-induced stress proteins of E. coli by Muhammad Nadeem Asghar; Muhammad Ashfaq; Zahoor Ahmad; Islam Ullah Khan (pp. 946-950).

Logarithmically growing batch cultures of Escherichia coli were exposed to sublethal concentrations of pyrethroid and carbamate pesticides of four different technical grades. This induced 17–20 stress proteins, as observed using two-dimensional polyacrylamide gel electrophoresis. An E. coli culture growing exponentially in Luria Bertani medium (cell density ~2.3×10⁹ cells/ml) was exposed to predetermined sublethal doses of individual pesticides. The cells were harvested after 30 minutes of induction and the stress response was developed in fresh LB medium for three hours under the same growth conditions. Cell pellets were obtained and stored in sonication buffer. Two-dimensional polyacrylamide gel electrophoresis was performed to resolve the proteins. Visualization of the protein spots by rapid silver staining showed 17–20 stress proteins which were absent in the standard protein profile of E. coli. On average 29% of these stress proteins were unique to the pollutant, while the remaining stress proteins overlapped with those of other pesticides. The iso-electric points (PIs) and molecular weights of the proteins were determined by comparing with protein markers with known PIs and molecular weights. Furthermore, upon comparing the pesticide-induced proteins within the same class and between the two different classes (pyrethroid and carbamate), it was apparent that the general nature of the stress remained the same throughout, which indirectly proved that the gene or set of genes responsible for stress expression are also the same, irrespective of the chemical nature of the substituents of the pesticides.

Keywords: Stress proteins; 2-D PAGE; Pesticides; E. coli

Elemental mapping and quantitative analysis of Cu, Zn, and Fe in rat brain sections by laser ablation ICP-MS by Brian Jackson; Steve Harper; Laura Smith; Jane Flinn (pp. 951-957).

This report details the application of laser ablation quadrupole ICP-MS for the (multi)elemental mapping of 100-μm-thick sections of rat brain. The laser spot size used was 60 μm, and the laser scan speed was 120 μm s⁻¹. The analysis was relatively rapid, allowing mapping of a whole brain thin section (≈1 cm²) in about 2 h. Furthermore, the method was amenable to multi-element data collection including the physiologically important elements P and S and afforded sub μg g⁻¹ detection limits for the important trace elements Cu and Zn. Calibrations were performed with pressed pellets of biological certified reference materials, and the elemental distributions and concentrations of Cu, Zn, and Fe were determined in whole rat brain sections. The distributions and concentration ranges for these elements were consistent with previous studies and demonstrate the utility of this technique for rapid mapping of brain thin sections.

Keywords: Laser ablation ICP-MS; Rat brain sections; Elemental imaging

Simultaneous determination of MHD and DMD in dog plasma by high-performance liquid chromatography with fluorescence detection and its application to pharmacokinetic studies by Xiaoyu Li; Guangji Wang; Haitang Xie; Rui Wang; Meijuan XU; Wei Wang; Jining Tao; Jianguo Sun (pp. 958-963).

A rapid, reproducible high-performance liquid chromatographic (HPLC) method with fluorescence detection for the simultaneous determination of 3(or 8)-(1-methoxyethyl)-8(or 3)-(1-hydroxyethyl)-deuteroporphyrin IX (MHD) and 3,8-di-(1-methoxyethyl)-deuteroporphyrin IX (DMD) in dog plasma was described. Fluorescein was used as an internal standard. A simple extraction step with ethyl acetate was performed before chromatography on a Diamonsil C₁₈ column (5 μm, 4.6 mm×150 mm). The chromatography used 0.02 mol L⁻¹ sodium acetate/tetrahydrofuran (66:34 v/v). The analytical curve was linear over the concentration range 0.025– 2.5 μg mL⁻¹. For a 100 μL dog plasma sample, the limit of determination for both MHD and DMD was 0.025 μg mL⁻¹. The recoveries of MHD and DMD were more than 76% and 89%, respectively. The intra-assay (within-run) and interassay (between-run) coefficients of variation (precisions) for MHD and DMD were less than 15%. This method was found to be suitable for the analysis of biosamples and was successfully applied to pharmacokinetic studies of Deuxemether in dogs.

Keywords: Deuxemether; MHD; DMD; HPLC; Pharmacokinetics

Quantitative analysis and evaluation of the solubility of hydrophobic proteins recovered from brain, heart and urine using UV-visible spectrophotometry by Visith Thongboonkerd; Napat Songtawee; Rattiyaporn Kanlaya; Somchai Chutipongtanate (pp. 964-971).

There is a need for a simple method that can directly quantify hydrophobic proteins. UV-visible spectrophotometry was applied in the present study for this purpose. Absorbance at λ=280 nm (A ₂₈₀) was detected for both Escherichia coli membrane proteins and bovine serum albumin, whereas absorbance at λ=620 nm (A ₆₂₀) was only detected for E. coli membrane proteins. The A ₆₂₀ values of the brain samples were greater than those of heart samples when equal concentrations were used, regardless of the type of solubilizing agent employed. Because hydrophobic proteins tend to form colloidal microparticles in solution, we also applied UV-visible spectrophotometry to evaluate the efficacies of different extraction protocols for solubilizing hydrophobic proteins. For brain protein extraction, the highest A ₆₂₀ was observed in samples recovered using Tris, whereas the lowest was from samples recovered using SDS. Solubilizing brain tissue with 0.25% SDS (above the CMC) gave a lower A ₆₂₀ than extraction with 0.025% SDS (below the CMC). Addition of 0.25% SDS to samples recovered with Triton caused A ₆₂₀ to drop. A ₆₂₀ could also be used to distinguish between the hydrophobic fractions (pellets) of brain and urine proteins and their hydrophilic fractions (supernatants) prefractionated using high-speed centrifugation. Additionally, an A ₆₂₀/A ₂₈₀ ratio exceeding 0.12 appears to denote highly hydrophobic samples. Our data suggest that direct UV-visible spectrophotometry can be used as a simple method to quantify and evaluate the solubilities of hydrophobic proteins.

Keywords: Spectrophotometry; Hydrophobicity; Hydropathicity; Membrane proteins; Solubility; Critical micelle concentration

Phospholipids from some common fungi associated with damp building materials by Taiwo O. Womiloju; J. David Miller; Paul Mayer (pp. 972-979).

Methods for the analysis of fungal biomass in contaminated building materials have been limited to methods that use viable propagules as well as indicators of total biomass such as fungal glucan and ergosterol. Because of large differences in the survival times of spores, and limitations imposed by the use of agar media to assess fungal cells for the former approach, no quantitative information and poor qualitative information is obtained. The use of the biochemical indicators provides reliable quantitative information but no qualitative data. Analysis of phospholipids of various bacteria and, recently, of fungi common in outdoor air has provided both qualitative and quantitative data on their distributions in various substrates including in outdoor air samples. In this report, we provide new data on the signature lipids of some fungi common on moldy building materials. Using the LC/MS/MS analysis described, an estimate can be made of the fresh weight of fungal cells and the relative abundance of the common genera of fungi typically found on moldy materials.

Keywords: Fungi; Spores; Damp buildings; Phospholipids; Liquid chromatography; Mass spectrometry

Detection of emissions from surfaces using ion mobility spectrometry by Wolfgang Vautz; Jörg Ingo Baumbach; Erik Uhde (pp. 980-986).

Emissions from surfaces (from furniture, wall paintings or floor coverings for instance) significantly influence indoor air quality and therefore the wellbeing or even the health of the occupants. Together with metabolites from mold they are responsible for the well-known “sick building syndrome”. Therefore, it is in the interest of the manufacturer as well as of the occupants to have a fast and accurate method for the detection of substances relevant to this syndrome in order to be able to monitor and control product quality and indoor air quality. The use of small and easy-to-transport ion mobility spectrometers that use UV light as the ionization source enables rapid in situ detection of such substances with high selectivity and sensitivity (detection limits in the lower ppb range). If a multicapillary column is used for preseparation as well, the selectivity is increased and the unwanted influence of humidity on the spectra can be eliminated, thus enabling the use of the instruments under normal ambient conditions. Furthermore, the use of air as carrier gas avoids the need for other sources of high-purity gas. An emission cell with a homogeneous and constant air flow over the surface to be investigated was developed in order to ensure reproducible results. Investigations of emissions from wooden surfaces with and without additional contamination as well as from complex mixtures are presented. The results demonstrate that relevant emissions can be identified and quantified with high sensitivity and selectivity in under five minutes. Therefore, the method is useful for indoor air quality monitoring, especially when miniaturized instruments are applied. Figure

Keywords: Emissions; Furniture; Indoor air quality; Ion mobility spectrometry; Sick building syndrome

SEM–FTIR spectroscopic evaluation of deterioration in an historic coffered ceiling by C. Genestar; J. Palou (pp. 987-993).

Microorganisms generally degrade wood when moisture, oxygen and other environmental factors provide favorable growing conditions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to study the development and transformation of the products formed during the biomineralization process that follows the deterioration of wood from an historical coffered ceiling (Cloister of St Francesc (XIV century), Palma de Mallorca, Spain). After fungi colonization, cellulose and lignin disappear and inorganic salts are formed. Thus, the secretion of numerous acids (initially oxalic acid) by fungal hyphae also leads to the precipitation of authigenic salts. Damaged cells or tissues enhance the formation and growth of crystals, which is strongly favored by fungi that function as calcification nuclei. Finally, the presence of dihydrated calcium sulfate reveals the contribution of environmental factors to the weathering of wood.

Keywords: Wood decay; Fungi; Scanning electron microscopy (SEM-EDS); Fourier transform infrared spectroscopy (FTIR); X-ray diffraction (XRD)

O-Alkylation of a lignite humic acid by phase-transfer catalysis by A. Piccolo; P. Conte; A. F. Patti (pp. 994-1001).

A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides—methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and ¹H NMR, CPMAS ¹³C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete removal of the phase-transfer catalyst after purification of the alkylated HA. ¹H NMR and CPMAS ¹³C NMR spectra of alkylated products provided evidence of the successful occurrence of the alkylation reactions. Infrared spectra confirmed the NMR results, revealing the characteristic absorption of newly formed alkyl and aryl ethers and esters in the alkylated products and C–H stretching in the aromatic ring of the benzylated derivative. These findings indicate that humic matter can be successfully alkylated with several different alkylating groups by catalysed phase-transfer reaction. This O-alkylation reaction has the advantage of being mild, versatile, and high-yielding compared with traditional methylation reactions applied to HA. The possibility of introducing different alkyl groups into the HA by a mild phase-transfer reaction may become useful by enabling improved fractionation of humic supramolecular associations and further understanding of the molecular nature of humic substances.

Keywords: Humic substances; O-Alkylation; Phase-transfer catalysis; Tetrabutylammonium hydroxide; NMR; FTIR

Determination of pesticides by solid phase extraction followed by gas chromatography with nitrogen–phosphorous detection in natural water and comparison with solvent drop microextraction by C. López-Blanco; S. Gómez-Álvarez; M. Rey-Garrote; B. Cancho-Grande; J. Simal-Gándara (pp. 1002-1006).

The European Union specificies that drinking water can contain pesticide residues at concentrations of up to 0.1 μg/L each and 0.5 μg/L in total, and that 1–3 μg/L of pesticides can be present in surface water, but the general idea is to keep discharges, emissions and losses of priority hazardous substances close to zero for synthetic substances. Therefore, in order to monitor pesticide levels in water, analytical methods with low quantification limits are required. The method proposed here is based on solid phase extraction (SPE) followed by gas chromatography with a nitrogen–phosphorous detector (GC-NPD). During method development, six organophosphate pesticides (azinphos-ethyl, chlorfenvinphos, chlorpyriphos, ethoprophos, fenamiphos and malathion) and two organonitrogen pesticides (alachlor and deltamethrin) were considered as target analytes. Elution conditions that could influence the efficiency of the SPE were studied. The optimized methodology exhibited good linearity, with determination coefficients of better than 0.996. The analytical recovery for the target analytes ranged from 70 to 100%, while the within-day precision was 4.0–11.5 %. The data also showed that the nature of the aqueous matrice (ultrapure, surface or drinking water) had no significant effect on the recovery. The quantification limits for the analytes were found to be 0.01–0.13 μg/L (except for deltamethrin, which was 1.0 μg/L). The present methodology is easy, rapid and gives better sensitivity than solvent drop microextraction for the determination of organonitrogen and organophosphate pesticides in drinking water at levels associated with the legislation.

Keywords: Organonitrogen pesticides; Organophosphate pesticides; Water analysis; Microextraction; Gas chromatography with nitrogen-phosphorous detector

Comparison of traditional cloud-point extraction and on-line flow-injection cloud-point extraction with a chemiluminescence method using benzo[a]pyrene as a marker by Guan Qun Song; Chao Lu; Kazuichi Hayakawa; Jin-Ming Lin (pp. 1007-1012).

In this work, using benzo(a)pyrene (BaP) as marker, the analytical merits of on-line flow-injection cloud-point extraction (FI CPE), including preconcentration factor, extraction efficiency, sample throughput, and analysis time were evaluated by use of peroxyoxalate chemiluminescence (CL) detection. Moreover, by detailed discussion of several preconcentration conditions for traditional and on-line FI CPE the advantages of on-line FI CPE became conspicuously apparent. When coupled with separation techniques such as high-performance liquid chromatography (HPLC) or capillary electrophoresis (CE), on-line FI CPE–CL has much potential for analysis of low concentrations of polycyclic aromatic hydrocarbons (PAH) in environmental samples.

Keywords: On-line flow-injection cloud-point extraction; Traditional cloud-point extraction; Chemiluminescence; Benzo(a)pyrene

Development of a fast spectroscopic enzyme assay for on-site measurement of total polyphenol content in grapes and wine by Daniela Harkensee; Sascha Beutel; Manuel Young; Roland Ulber (pp. 1013-1018).

In recent years interest in polyphenols as a nutrient in vegetables and fruits has increased because of polyphenols’ positive effects on human health. The interest focuses on the sensory properties of polyphenols and their influence on the taste of fruits and derived products. This article presents the development of a bioanalytical measurement technique enabling the determination of the total polyphenol content (TPC) of fresh grapes within a few minutes. Furthermore this technique allows the control of TPC during production processes, e. g. fermentation of wine.

Keywords: Polyphenols; Enzyme assay; Wine; Grapes; Analysis

Fluidized beds in flow analysis: use with ion-exchange separation for spectrophotometric determination of zinc in plant digests by Marta F. T. Ribeiro; Ana C. B. Dias; João L. M. Santos; José L. F. C. Lima; Elias A. G. Zagatto (pp. 1019-1024).

A novel strategy for utilization of solid reagents in flow analysis is proposed. Establishment of diffuse and reproducible geometry enables the solid particles to be maintained in constant floating, reflux, and circulating motion inside a mini-chamber. This is efficiently accomplished with pulsed flows, a characteristic of multi-pumping flow systems. Drawbacks inherent in solid-phase packed columns, for example backpressure, preferential pathways, swelling, etc., and some limitations inherent in immobilized reagents are minimised. Spectrophotometric determination of zinc in plants was selected as an application of the technique. Dowex 1-X8 anionic resin was kept freely inside a mini-chamber. Zinc chloro-complexes were adsorbed on the moving particles and derivatization with zincon was performed after elution. Analytical figures of merit and the potential and limitations of the approach are discussed.

Keywords: Fluidized bed; Ion exchange; Multi-pumping flow system; Flow analysis

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Analytical and Bioanalytical Chemistry (v.384, #4)