Application of a bar adsorptive microextraction based methodology for doping control of alkylamine stimulants in urine matrices.

To comply with 'World Anti-Doping Agency' (WADA) guidelines, doping control laboratories must continuously adjust their analytical procedures. Therefore, sample preparation continues to play a critical step in modern analytical strategies, namely by replacing the tedious, time and solvent consuming commonly employed (e.g. liquid-liquid extraction). The present contribution proposes, for the first time in doping control, bar adsorptive microextraction (BAµE) as an alternative analytical technique for the qualitative determination of six alkyl amine stimulants (AAs; 1,3-dimethylbutylamine, 1,4-dimethylpentylamine, heptaminol, isometheptene, octodrine and tuaminoheptane) in urine matrices followed by derivatization prior to gas chromatography coupled to mass spectrometry, operating in the selected ion monitoring mode acquisition (GC-MS(SIM)). After selecting the most selective coating phase, i.e., a mixed-mode reversed phase/strong anion exchange sorbent (P2), assays performed under optimized experimental conditions [microextraction - BAµE(P2), 1 h (1,000 rpm), pH 11, 10 % NaCl; back-extraction - methanol (150 µL), 30 min, under sonication], allowed remarkable recoveries ranging from 48.7 % (heptaminol, 200 ng/mL) to 83.1 % (1,4-dimethylpentylamine, 200 ng/mL). The validation assessment assays of the proposed methodology showed suitable limits of identification (5.0-35.0 ng/mL), appropriate linear dynamic ranges (5.0-200.0 ng/mL) and good determination coefficients (r2 > 0.9937), as well as excellent selectivity, robustness, accuracy and precision. To check whether the methodology is fit-for-purpose, four previously analysed proficiency urine samples were successfully tested, in which were unequivocally detected and identified some of the target AAs. The present methodology showed to be a remarkable alternative in comparison to other dedicated analytical approaches to screen AAs in urine matrices, since it is cost-effective, user- and eco-friendly, requiring low volume of urine sample (1 mL). The great potential of this analytical technology in doping control lies in a very effective microextraction combined with the minimization of potential interferents, presenting itself as an added value to be applied to other types of substances and complex matrices.

Wild vs cultivated halophytes: Nutritional and functional differences.

Some halophyte plants are currently used in gourmet cuisine due to their unique organoleptic properties. Moreover, they exhibit excellent nutritional and functional properties, being rich in polyphenolics and vitamins. These compounds are associated to strong antioxidant activity and enhanced health benefits. This work compared the nutritional properties and antioxidant potential of three species (Mesembryanthemum nodiflorum, Suaeda maritima and Sarcocornia fruticosa) collected in saltmarshes from Portugal and Spain with those of cultivated plants. The latter were generally more succulent and had higher contents of minerals than plants obtained from the wild and contained less fibre. All species assayed are a good source of proteins, fibres and minerals. Additionally, they are good sources of carotenoids and vitamins A, C and B6 and showed good antioxidant potential particularly S. maritima. Chromatographic analysis of the phenolic profile revealed that ferulic and caffeic acids as the most relevant phenolic compounds detected in the halophytes tested.

High throughput bar adsorptive microextraction: A simple and effective analytical approach for the determination of nicotine and cotinine in urine samples.

A simple, effective, convenient and environmentally friendly methodology using high throughput bar adsorptive microextraction (HT-BAµE) with microliquid desorption in combination with large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode (LVI-GC-MS(SIM)) was applied for the determination of nicotine and cotinine in urine samples. Under optimized experimental conditions, the developed methodology allowed for linear dynamic ranges between 20.0 and 2000.0 µg L-1 with determination coefficients of 0.9991 and 0.9992, as well as average recovery yields of 61.7-67.5% and 53.9-57.8% for nicotine and cotine, respectively. The developed methodology was applied to monitor urine samples from 86 volunteers having different smoking habits, where nicotine and cotinine were quantified in the range from 23.6 to 2612.6 µg L-1. The target compounds were extracted in a HT-BAµE apparatus, which allows for simultaneous microextraction and subsequent back-extraction of up to 100 samples. This is a major improvement over other microextraction techniques. The data from the proposed methodology were satisfactory and in line with current green analytical chemistry guidelines, and proved to be an effective sample preparation alternative with substantial potential for high throughput bioanalysis.

Profiling of antioxidant potential and phytoconstituents of Plantago coronopus / Avaliação do potencial antioxidante e perfil fitoquímico do Plantago coronopus

Abstract The halophyte species Plantago coronopus has several described ethnomedicinal uses, but few reported biological activities. This work carried out for the first time a comparative analysis of P. coronopus organs in terms of phenolic composition and antioxidant activity of organic and water extracts from roots, leaves and flowers. The leaves contents in selected nutrients, namely amino acids and minerals, are also described. Roots (ethyl acetate and methanol extracts) had the highest radical scavenging activity (RSA) towards 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, while leaves (hexane extract) had higher RSA on nitric oxide radical and iron chelating ability. High performance liquid chromatography (HPLC) analysis identified eighteen phenolics from which salicylic acid and epicatechin are here firstly described in Plantago species. Leaves had mineral levels similar to those of most vegetables, proving to be a good source for elements like calcium, sodium, iron and magnesium, and also for several of the essential amino acids justifying it use as food. Our results, especially those regarding the phenolics composition, can explain the main traditional uses given to this plantain and, altogether, emphasize the potential of P. coronopus as a source of bioactive molecules particularly useful for the prevention of oxidative stress-related diseases.

Resumo A espécie halófita Plantago coronopus tem vários usos etnomedicinais já descritos, mas em relação à bioatividade a informação é escassa. Este trabalho efetuou, pela primeira vez, uma análise comparativa dos órgãos de P. coronopus em termos de compostos fenólicos e atividade antioxidante de extratos orgânicos e aquosos provenientes das raízes, folhas e flores da planta, bem como o conteúdo de determinados nutrientes, aminoácidos e minerais, nas folhas da planta. As raízes (extratos de acetato de etila e metanol) apresentaram a maior atividade de captação para os radicais 1,1-difenil-2-picril hidrazil (DPPH) e 2,2'-azino-bis(3-etilbenzotiazolina-6-ácido sulfónico) (ABTS), enquanto as folhas (extrato de hexano) mostraram maior atividade captadora para o radical óxido nítrico bem como maior capacidade quelante do ferro. A análise por cromatografia liquida de alta eficiência (CLAE) identificou dezoito compostos fenólicos e, destes, o ácido salicílico e a epicatequina são aqui descritos pela primeira vez em espécies de Plantago. As folhas desta planta halófita mostraram ainda conter minerais em níveis semelhantes aos da maioria dos vegetais, provando ser uma boa fonte de elementos como o cálcio, sódio, ferro e magnésio, bem como de vários dos aminoácidos essenciais o que justifica seu uso na alimentação. Os resultados, particularmente aqueles relacionados à composição fenólica, podem justificar os principais usos medicinais atribuídos a esta espécie e, na sua totalidade, demonstram o potencial de P. coronopus como fonte de moléculas bioativas particularmente úteis na prevenção de doenças relacionadas com estresse oxidativo.

Profiling of antioxidant potential and phytoconstituents of Plantago coronopus.

The halophyte species Plantago coronopus has several described ethnomedicinal uses, but few reported biological activities. This work carried out for the first time a comparative analysis of P. coronopus organs in terms of phenolic composition and antioxidant activity of organic and water extracts from roots, leaves and flowers. The leaves contents in selected nutrients, namely amino acids and minerals, are also described. Roots (ethyl acetate and methanol extracts) had the highest radical scavenging activity (RSA) towards 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, while leaves (hexane extract) had higher RSA on nitric oxide radical and iron chelating ability. High performance liquid chromatography (HPLC) analysis identified eighteen phenolics from which salicylic acid and epicatechin are here firstly described in Plantago species. Leaves had mineral levels similar to those of most vegetables, proving to be a good source for elements like calcium, sodium, iron and magnesium, and also for several of the essential amino acids justifying it use as food. Our results, especially those regarding the phenolics composition, can explain the main traditional uses given to this plantain and, altogether, emphasize the potential of P. coronopus as a source of bioactive molecules particularly useful for the prevention of oxidative stress-related diseases.

Determination of tributyltin in environmental water matrices using stir bar sorptive extraction with in-situ derivatisation and large volume injection-gas chromatography-mass spectrometry.

Stir bar sorptive extraction with in-situ derivatization using sodium tetrahydridoborate (NaBH4) followed by liquid desorption and large volume injection-gas chromatography-mass spectrometry detection under the selected ion monitoring mode (SBSE(NaBH4)in-situ-LD/LVI-GC-MS(SIM)) was successfully developed for the determination of tributyltin (TBT) in environmental water matrices. NaBH4 proved to be an effective and easy in-situ speciation agent for TBT in aqueous media, allowing the formation of adducts with enough stability and suitable polarity for SBSE analysis. Assays performed on water samples spiked at the 10.0µg/L, yielded convenient recoveries (68.2±3.0%), showed good accuracy, suitable precision (RSD<9.0%), low detection limits (23ng/L) and excellent linear dynamic range (r(2)=0.9999) from 0.1 to 170.0µg/L, under optimized experimental conditions. By using the standard addition method, the application of the present methodology to real surface water samples allowed very good performance at the trace level. The proposed methodology proved to be a feasible alternative for routine quality control analysis, easy to implement, reliable and sensitive to monitor TBT in environmental water matrices.

Development of a bar adsorptive micro-extraction-large-volume injection-gas chromatography-mass spectrometric method for pharmaceuticals and personal care products in environmental water matrices.

The combination of bar adsorptive micro-extraction using activated carbon (AC) and polystyrene-divinylbenzene copolymer (PS-DVB) sorbent phases, followed by liquid desorption and large-volume injection gas chromatography coupled to mass spectrometry, under selected ion monitoring mode acquisition, was developed for the first time to monitor pharmaceutical and personal care products (PPCPs) in environmental water matrices. Assays performed on 25 mL water samples spiked (100 ng L(-1)) with caffeine, gemfibrozil, triclosan, propranolol, carbamazepine and diazepam, selected as model compounds, yielded recoveries ranging from 74% to 99% under optimised experimental conditions (equilibrium time, 16 h (1,000 rpm); matrix characteristics: pH 5, 5% NaCl for AC phase; LD: methanol/acetonitrile (1:1), 45 min). The analytical performance showed good precision (RSD < 18%), convenient detection limits (5-20 ng L(-1)) and excellent linear dynamic range (20-800 ng L(-1)) with remarkable determination coefficients (r(2) > 0.99), where the PS-DVB sorbent phase showed a much better efficiency. By using the standard addition methodology, the application of the present analytical approach on tap, ground, sea, estuary and wastewater samples allowed very good performance at the trace level. The proposed method proved to be a suitable sorption-based micro-extraction alternative for the analysis of priority pollutants with medium-polar to polar characteristics, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor PPCPs in water matrices.

Antioxidant and antibacterial activity of essential oil and extracts of bay laurel Laurus nobilis Linnaeus (Lauraceae) from Portugal.

Laurus nobilis L. is an aromatic plant frequently used as a spice in Mediterranean cookery and as a traditional medicine for the treatment of several infectious diseases. The aim of this study was to characterise the antibacterial and antioxidant activities of bay laurel essential oil (EO), ethanolic extract (EE) and hot/cold aqueous extract (AE). The major components detected in bay laurel EO were eucalyptol (27.2%), α-terpinenyl acetate (10.2%), linalool (8.4%), methyleugenol (5.4%), sabinene (4.0%) and carvacrol (3.2%). The EO exhibited strong antibacterial activity against all tested foodborne spoilage and pathogenic bacteria, whereas this activity was less pronounced or even nonexistent in the EE and AE. In contrast, EO exhibited low antioxidant activity compared to extracts (EX), and among the EX, the hot AE revealed the highest antioxidant ability. The results show that bay laurel EO and its EX have potential as natural alternatives to synthetic food preservatives, in order to enhance food safety and increase food shelf life.

Antioxidant and cytotoxic activities of carob tree fruit pulps are strongly influenced by gender and cultivar.

Extracts from fruit pulps of six female cultivars and two hermaphrodite Portuguese carob trees [(Ceratonia siliqua L., Fabaceae)] exhibited strong antioxidant activity and were rich in phenolic compounds. The extracts decreased the viability of different human cancer cell lines on a dose- and time-dependent manner. Gender and cultivar significantly influenced the chemical content and the biological activities of the extracts. Extracts from hermaphrodite trees had a higher content of phenolic compounds, and exhibited higher antioxidant and cytotoxic activities. Among females, cv. Aida had the highest radical scavenging activity and total content of phenolics, Mulata the highest capacity to inhibit lipid oxidation and Gasparinha the strongest cytotoxic activity on HeLa cells. The decrease in cell viability was associated with apoptosis on HeLa and MDA-MB-231 lines. (+)-Catechin and gallic acid (GA) were the main compounds identified in the extracts, and GA contributed to the antioxidant activity. Our results show that the antioxidant and cytotoxic activities of carob tree fruit pulps are strongly influenced by gender and cultivar, and provide new knowledge about the advantages of hermaphrodite trees over female cultivars, namely, as a source of compounds with biological interest, which may represent an increase of their agronomic interest.

Stir-bar-sorptive extraction and liquid desorption combined with large-volume injection gas chromatography-mass spectrometry for ultra-trace analysis of musk compounds in environmental water matrices.

Stir-bar-sorptive extraction with liquid desorption followed by large-volume injection and capillary gas chromatography coupled to mass spectrometry in selected ion monitoring acquisition mode (SBSE-LD/LVI-GC-MS(SIM)) has been developed to monitor ultra-traces of four musks (celestolide (ADBI), galaxolide (HHCB), tonalide (AHTN) and musk ketone (MK)) in environmental water matrices. Instrumental calibration (LVI-GC-MS(SIM)) and experimental conditions that could affect the SBSE-LD efficiency are discussed. Assays performed on 30-mL water samples spiked at 200 ng L(-1) under optimized experimental conditions yielded recoveries ranging from 83.7 ± 8.1% (MK) to 107.6 ± 10.8% (HHCB). Furthermore, the experimental data were in very good agreement with predicted theoretical equilibria described by octanol-water partition coefficients (K (PDMS/W) ≈ K (O/W)). The methodology also showed excellent linear dynamic ranges for the four musks studied, with correlation coefficients higher than 0.9961, limits of detection and quantification between 12 and 19 ng L(-1) and between 41 and 62 ng L(-1), respectively, and suitable precision (< 20%). Application of this method for analysis of the musks in real water matrices such as tap, river, sea, and urban wastewater samples resulted in convenient selectivity, high sensitivity and accuracy using the standard addition methodology. The proposed method (SBSE-LD/LVI-GC-MS(SIM)) was shown to be feasible and sensitive, with a low-sample volume requirement, for determination of musk compounds in environmental water matrices at the ultra-trace level, overcoming several disadvantages presented by other sample-preparation techniques.

Determination of organochlorine pesticides in vegetable matrices by stir bar sorptive extraction with liquid desorption and large volume injection-gas chromatography-mass spectrometry towards compliance with European Union directives.

A novel analytical approach to determine trace levels of 20 organochlorine pesticides (OCPs) in nine vegetable matrices (lettuce, spinach, green bean, green pepper, tomato, broccoli, potato, carrot and onion) is proposed, based on stir bar sorptive extraction followed by liquid desorption and large volume injection-gas chromatography coupled to mass spectrometry using the selected-ion monitoring mode acquisition (SBSE-LD/LVI-GC-MS(SIM)). The experimental procedure consists of a previous ultrasonic extraction of the freeze-dried vegetable samples (100.0mg) with methanol (2mL) followed by centrifugation and dissolution in aqueous media prior to SBSE-LD/LVI-GC-MS(SIM) under optimised conditions. Assays were performed on 30mL aqueous samples using stir bars coated with 47microL of polydimethylsiloxane, an equilibrium time of 180min (1000rpm; 20 degrees C) and acetonitrile as back-extraction solvent, providing convenient analytical performance to monitor OCPs in vegetable matrices at the trace level. Besides the selectivity reached, the data obtained clearly demonstrate that the matrices involved have a strong effect on the recovery yields (10-110%) of the OCPs under study, in particular the green vegetables especially the leafy ones. By using the standard addition methodology, good linearity (r(2)>0.99) and convenient precisions (RSD<20%) were found for almost all cases, depending on the particular OCP and vegetable matrix involved. Furthermore enough sensitivity was also achieved (limit of detection <10microgkg(-1)) for all OCPs under study towards compliance with the European Union regulations for the maximum residue limits of pesticides in agricultural vegetables. The methodology showed to be easy of work-up, fast, almost solventless with low sample amount requirement, when compared with conventional methods of sample preparation to screen pesticides in vegetable matrices.

Plant extracts with anti-inflammatory properties--a new approach for characterization of their bioactive compounds and establishment of structure-antioxidant activity relationships.

Geranium robertianum L. (Geraniacea) and Uncaria tomentosa (Willd.) DC. (Rubiaceae) plant extracts, frequently used in traditional medicine for treatment of inflammatory and cancer diseases, were studied to identify potential bioactive compounds that may justify their therapeutic use and their underlying mechanisms of action. Since some of the pharmacological properties of these plant extracts may be linked to their antioxidant potential, the antioxidant activity, in relation to free radical scavenging, was measured by the ABTS/HRP and DPPH() assays, presenting U. tomentosa the higher activity. The antioxidant activity was also evaluated by scavenging of HOCl, the major strong oxidant produced by neutrophils and a potent pro-inflammatory agent. U. tomentosa was found to be a better protector against HOCl, which may justify its effectiveness against inflammatory diseases. SPE/LC-DAD was used for separation/purification purposes and ESI-MS/MS for identification/characterization of the major non-volatile components, mainly flavonoids and phenolic acids. The ESI-MS/MS methodology proposed can be used as a model procedure for identification/characterization of unknowns without the prerequisite for standard compounds analysis. The ESI-MS/MS data obtained were consistent with the antioxidant activity results and structure-activity relationships for the compounds identified were discussed.

Optimisation of stir bar sorptive extraction and liquid desorption combined with large volume injection-gas chromatography-quadrupole mass spectrometry for the determination of volatile compounds in wines.

Stir bar sorptive extraction and liquid desorption followed by large volume injection coupled to gas chromatography-quadrupole mass spectrometry (SBSE-LD/LVI-GC-qMS) had been applied for the determination of volatiles in wines. The methodology was optimised in terms of extraction time and influence of ethanol in the matrix; LD conditions, and instrumental settings. The optimisation was carried out by using 10 standards representative of the main chemical families of wine, i.e. guaiazulene, E,E-farnesol, beta-ionone, geranylacetone, ethyl decanoate, beta-citronellol, 2-phenylethanol, linalool, hexyl acetate and hexanol. The methodology shows good linearity over the concentration range tested, with correlation coefficients higher than 0.9821, a good reproducibility was attained (8.9-17.8%), and low detection limits were achieved for nine volatile compounds (0.05-9.09 microg L(-1)), with the exception of 2-phenylethanol due to low recovery by SBSE. The analytical ability of the SBSE-LD/LVI-GC-qMS methodology was tested in real matrices, such as sparkling and table wines using analytical curves prepared by using the 10 standards where each one was applied to quantify the structurally related compounds. This methodology allowed, in a single run, the quantification of 67 wine volatiles at levels lower than their respective olfactory thresholds. The proposed methodology demonstrated to be easy to work-up, reliable, sensitive and with low sample requirement to monitor the volatile fraction of wine.

New strategies to screen for endocrine-disrupting chemicals in the Portuguese marine environment utilizing large volume injection-capillary gas chromatography-mass spectrometry combined with retention time locking libraries (LVI-GC-MS-RTL).

A new analytical strategy to screen for endocrine-disrupting chemicals (EDCs) in environmental matrices is presented. The strategy uses solid-phase extraction followed by large volume injection and capillary gas chromatography coupled to mass spectrometry combined with retention time locking libraries (SPE-LVI-GC-MS-RTL). Characterization of the proposed methodology (SPE-LVI-GC-MS) for selected classes of EDCs enabled high reproducibility and robustness at the ultratrace level. The RTL databases used allowed hundreds of non-target semivolatiles (i.e., pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls and other classes of suspected EDCs from a great number of unknown environmental matrices) to be simultaneously screened for in an easy, fast and remarkable manner. The application of the proposed methodology to real environmental samples demonstrated its remarkable selectivity and sensitivity at the ultratrace level. Screening assessments performed on water and sediment matrices from eight Portuguese estuaries and coastal waters identified EDC "hotspots." These EDCs mainly come from agricultural and a wide variety of industrial sources, and include pesticides and pesticide metabolites, phenolic derivatives and polycyclic aromatic hydrocarbons, which are included in the lists of priority substances published by international environmental agencies. The estuaries that contained relatively high levels of pesticides were Guadiana, Sado and Mondego, while Minho, Douro and Formosa showed enhanced levels of phenolic derivatives. Dibutyltin and tributyltin, selected as target compounds to be monitored by SPE-LVI-GC-MS in the selected ion monitoring mode, were shown to be widespread contaminants at trace levels in almost all of the sediment matrices assessed. The reliability of the proposed methodology undoubtedly makes it a valuable tool that could replace other analytical strategies currently used to screen for EDCs present in the environment at ultratrace levels.

Organotin speciation in environmental matrices by automated on-line hydride generation-programmed temperature vaporization-capillary gas chromatography-mass spectrometry detection.

In the present contribution, a new automated on-line hydride generation methodology was developed for dibutyltin and tributyltin speciation at the trace level, using a programmable temperature-vaporizing inlet followed by capillary gas chromatography coupled to mass spectrometry in the selected ion-monitoring mode acquisition (PTV-GC/MS(SIM)). The methodology involves a sequence defined by two running methods, the first one configured for hydride generation with sodium tetrahydroborate as derivatising agent and the second configured for speciation purposes, using a conventional autosampler and data acquisition controlled by the instrument's software. From the method-development experiments, it had been established that injector configuration has a great effect on the speciation of the actual methodology, particularly, the initial inlet temperature (-20 degrees C; He: 150 ml/min), injection volume (2 microl) and solvent characteristics using the solvent venting mode. Under optimized conditions, a remarkable instrumental performance including very good precision (RSD < 4%), excellent linear dynamic range (up to 50 microg/ml) and limits of detection of 0.12 microg/ml and 9 ng/ml, were obtained for dibutyltin and tributyltin, respectively. The feasibility of the present methodology was validated through assays upon in-house spiked water (2 ng/ml) and a certified reference sediment matrix (Community Bureau of Reference, CRM 462, Nr. 330 dibutyltin: 68+/-12 ng/g; tributyltin: 54+/-15 ng/g on dry mass basis), using liquid-liquid extraction (LLE) and solid-phase extraction (SPE) sample enrichment and multiple injections (2 x 5 microl) for sensitivity enhancement. The methodology evidenced high reproducibility, is easy to work-up, sensitive and showed to be a suitable alternative to replace the currently dedicated analytical systems for organotin speciation in environmental matrices at the trace level.

Development of a stir-bar-sorptive extraction-liquid desorption-large-volume injection capillary gas chromatographic-mass spectrometric method for pyrethroid pesticides in water samples.

Stir-bar-sorptive extraction followed by liquid desorption and large-volume injection capillary gas chromatography with mass spectrometric detection (SBSE-LD-LVI-GC-MS), had been applied for the determination of ultra-traces of eight pyrethroid pesticides (acrinathrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, fenvalerate, and permethrin cis and trans isomers) in water samples. Instrumental calibration for selected-ion monitoring acquisition and conditions that could affect the SBSE-LD efficiency are fully discussed. By performing systematic assays on 30-mL water samples spiked at the 0.10 microg L(-1) level it was established that stir-bars coated with 47 microL polydimethylsiloxane, an equilibrium time of 60 min (750 rpm), 5% methanol as organic modifier, and acetonitrile as back-extraction solvent, provided the best analytical performance to monitor pyrethroid pesticides in water matrices. Good accuracy (81.8-105.0%) and remarkable reproducibility (<11.7%) were obtained, and the experimental recovery data were in good agreement with the theoretical equilibrium described by octanol-water partition coefficients (log K(O/W)), with the exception of acrinathrin for which lower yields were measured. Excellent linear dynamic ranges between 25 and 400 ng L(-1) (r2>0.994), low quantification (3.0-7.5 ng L(-1)) and detection (1.0-2.5 ng L(-1)) limits were also achieved for the eight pyrethroid pesticides studied. The method was successfully used for analysis of tap-water and groundwater matrices spiked at the 0.10 microg L(-1), revealing the suitability of the method for determination of pyrethroid pesticides in real samples. The method was shown be reliable and sensitive and a small volume of sample was required to monitor pyrethroids at ultra-trace levels, in compliance with international regulatory directives on water quality.

An amperometric biosensor for polyphenolic compounds in red wine.

In the present work, a biosensor was developed with Laccase Coriolus Versicolor as the biological reconnaissance element immobilized on derivatized polyethersulphone membranes and applied to a Pt-Ag, AgCl US electrode base. Its application to several polyphenols usually found in red wine (caffeic acid, gallic acid, catechin, rutin, trans-resveratrol, quercetin and malvidin) was tested. It was observed that an amperometric response was obtained for catechin at +100 mV (versus Ag, AgCl) and caffeic acid at -50 mV in acetate buffer solutions (pH 4.5) having 12% ethanol. At pH 3.5 and +100 mV the biosensor was sensitive to both substrates and their response was additive. A limit of detection of 1.0 x 10(-6) M, linearity ranging from 2.0 to 14.0 x 10(-6) M, high sensitivity (0.0566 mAM(-1)) and reproducibility (R.S.D. <10%) were achieved for equimolar mixed solutions of catechin and caffeic acid. Under the same experimental conditions the other polyphenols tested individually did not yield any biosensor response. The application of the biosensor to red wine samples required a previous solid phase extraction for polyphenols enrichment. In fact, attempts to apply the biosensor in red wine using the "standard addition" methodology showed that large interferences occurred, as was to be expected. Reduction currents of -0.33 +/- 0.03 nA were obtained when the biosensor was used with the wine extract at +100 mV. This current could be ascribed to catechin and caffeic acid, although some interference by other polyphenols at the matrix level seemed to persist. The present biosensor showed promising applications for the wine analysis in future.