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.

Bar Adsorptive Microextraction Coated with Carbon-based Phase Mixtures for Performance-Enhancement to Monitor Selected Benzotriazoles, Benzothiazoles, and Benzenesulfonamides in Environmental Water Matrices.

: In the present work we propose, for the first time, bar adsorptive microextraction coated with carbon-based phase mixtures, followed by microliquid desorption and high performance liquid chromatography-diode array detection (BAµE-µLD/HPLC-DAD) analysis, to enhance the performance of the determination of traces of benzotriazoles (BTRs), benzothiazoles (BTs), and benzenesulfonamide derivatives (BSDs) in environmental water matrices. Assessing six carbon-based sorbents (CA1, CN1, B test EUR, SX PLUS, SX 1, and R) with different selectivity properties allowed us to tailor the best phase mixture (R, 12.5%/CN1, 87.5%) that has convenient porosity, texture, and surface chemistry (pHPZC,mix ~6.5) for trace analysis of benzenesulfonamide, 1-hydroxybenzotriazole, 1H-benzotriazole, 5-methyl-1H-benzotriazole, benzothiazole, and 1,3-benzothiazol-2-ol chemicals in aqueous media. Optimized experimental conditions provided average recoveries ranging from 37.9% to 59.2%, appropriate linear dynamic ranges (5.0 to 120.0 µg L-1; r2 ≥ 0.9964), limits of detection between 1.0 and 1.4 µg L-1, and good precisions (relative standard deviation (RSD) ≤ 9.3%). The proposed methodology (BAµE(R, 12.5%/CN1, 87.5%)-µLD/HPLC-DAD) also proved to be a suitable sorption-based static microextraction alternative to monitor traces of BTRs, BTs, and BSDs in rain, waste, tap, and estuarine water samples. From the data obtained, the proposed approach showed that the BAµE technique with the addition of lab-made devices allows users to adapt the technique to use sorbents or mixtures of sorbents with the best selectivity characteristics whenever distinct classes of target analytes occur simultaneously in the same application.

A Fast and Validated High Throughput Bar Adsorptive Microextraction (HT-BAµE) Method for the Determination of Ketamine and Norketamine in Urine Samples.

We developed, optimized and validated a fast analytical cycle using high throughput bar adsorptive microextraction and microliquid desorption (HT-BAµE-µLD) for the extraction and desorption of ketamine and norketamine in up to 100 urine samples simultaneously, resulting in an assay time of only 0.45 min/sample. The identification and quantification were carried out using large volume injection-gas chromatography-mass spectrometry operating in the selected ion monitoring mode (LVI-GC-MS(SIM)). Several parameters that could influencing HT-BAµE were assayed and optimized in order to maximize the recovery yields of ketamine and norketamine from aqueous media. These included sorbent selectivity, desorption solvent and time, as well as shaking rate, microextraction time, matrix pH, ionic strength and polarity. Under optimized experimental conditions, suitable sensitivity (1.0 µg L-1), accuracy (85.5-112.1%), precision (≤15%) and recovery yields (84.9-105.0%) were achieved. Compared to existing methods, the herein described analytical cycle is much faster, environmentally friendly and cost-effective for the quantification of ketamine and norketamine in urine samples. To our knowledge, this is the first work that employs a high throughput based microextraction approach for the simultaneous extraction and subsequent desorption of ketamine and norketamine in up to 100 urine samples simultaneously.

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.

Bar adsorptive microextraction coated with multi-walled carbon nanotube phases - Application for trace analysis of pharmaceuticals in environmental waters.

Bar adsorptive microextraction devices were modified with multi-walled carbon nanotubes for the first time. A bar adsorptive microextraction method followed by microliquid desorption and high-performance liquid chromatography with diode array detection was developed for the determination of trace levels of ketoprofen, diclofenac, gemfibrozil and mefenamic acid in water samples. The mean parameters affecting the bar adsorptive microextraction and microliquid desorption efficiency were studied and optimized using a univariate optimization strategy. The methodology was validated in terms of linearity, limits of detection and quantification, recovery, intra- and inter-day precision, accuracy, and matrix effect. The developed method showed lower limits of quantification of 0.35 µg L-1, calibration curves from 0.35 up to 1000.0 µg L-1 and determination coefficients higher than 0.9917. Recoveries in tap, surface, sea and waste water samples at three spiking levels were between 70.2 and 117.3% for all the pharmaceuticals. The coefficients of variation values for intra- (n = 6) and inter-day precisions (n = 18) were below 9.7%. The proposed analytical methodology allowed preconcentration factors up to 250 and proved to be cost-effective, easy to operate and environmentally friendly.

High throughput bar adsorptive microextraction: A novel cost-effective tool for monitoring benzodiazepines in large number of biological samples.

In this work, we propose an innovative high throughput (HT) apparatus using the bar adsorptive microextraction (BAµE) technique, which enables the simultaneous enrichment of up to 100 samples. This novel configuration was combined with microliquid desorption and high-performance liquid chromatography-diode array detection to monitor trace levels of eight benzodiazepines (diazepam, prazepam, bromazepam, oxazepam, lorazepam, alprazolam, temazepam and loflazepate) in biological samples. The proposed methodology was fully developed, optimized and validated, resulting in suitable intraday and interday precision (RSD ≤ 15%), with recovery yields ranging from 33.0% to 104.5%. The lower limits of quantification were between 20.0 and 100.0 µg L-1, using 1.0 mL of urine and 0.5 mL of plasma or serum samples. The application of the proposed methodology to real matrices resulted in average sample preparation time of around 2 min per sample, demonstrating that it is user-friendly, cost-effective and a rapid decision-making tool, whenever large number of samples are involved.

Secondary hypertension due to a juxtaglomerular cell tumor.

Juxtaglomerular cell tumors are rare, generally benign, and they are one of the secondary surgically treatable causes of arterial hypertension. There are about 100 reported cases on literature, and the diagnosis is usually carried out based on a high clinic suspicion index, mostly in patients with hypokalemia and arterial hypertension. The diagnosis involves blood tests and imaging studies, but it is only definite with histopathological exam after surgical treatment. We present a case of a 22-year-old woman with resistant arterial hypertension and renal and cardiovascular target-organ lesions. High plasmatic renin and a nodular renal mass on magnetic resonance imaging were present. A tumorectomy was performed and the histological exam confirmed a reninoma. After surgery, blood pressure and serum renin values returned to normal without medication. This work focuses on the need to exclude rare secondary causes of hypertension in young patients with resistant forms of this disease.

New-generation bar adsorptive microextraction (BAµE) devices for a better eco-user-friendly analytical approach-Application for the determination of antidepressant pharmaceuticals in biological fluids.

The present contribution aims to design new-generation bar adsorptive microextraction (BAµE) devices that promote an innovative and much better user-friendly analytical approach. The novel BAµE devices were lab-made prepared having smaller dimensions by using flexible nylon-based supports (7.5 × 1.0 mm) coated with convenient sorbents (≈ 0.5 mg). This novel advance allows effective microextraction and back-extraction ('only single liquid desorption step') stages as well as interfacing enhancement with the instrumental systems dedicated for routine analysis. To evaluate the achievements of these improvements, four antidepressant agents (bupropion, citalopram, amitriptyline and trazodone) were used as model compounds in aqueous media combined with liquid chromatography (LC) systems. By using an N-vinylpyrrolidone based-polymer phase good selectivity and efficiency were obtained. Assays performed on 25 mL spiked aqueous samples, yielded average recoveries in between 67.8 ±â€¯12.4% (bupropion) and 88.3 ±â€¯12.1% (citalopram), under optimized experimental conditions. The analytical performance also showed convenient precision (RSD < 12%) and detection limits (50 ng L-1), as well as linear dynamic ranges (160-2000 ng L-1) with suitable determination coefficients (r2 > 0.9820). The application of the proposed analytical approach on biological fluids showed negligible matrix effects by using the standard addition methodology. From the data obtained, the new-generation BAµE devices presented herein provide an innovative and robust analytical cycle, are simple to prepare, cost-effective, user-friendly and compatible with the current LC autosampler systems. Furthermore, the novel devices were designed to be disposable and used together with negligible amounts of organic solvents (100 µL) during back-extraction, in compliance with the green analytical chemistry principles. In short, the new-generation BAµE devices showed to be an eco-user-friendly approach for trace analysis of priority compounds in biological fluids and a versatile alternative over other well-stablished sorption-based microextraction techniques.

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.

Application of polyurethane-based devices as sorption-desorption phases for microextraction analysis - The all-in-one microextraction concept.

In this work, polyurethane-based (PU) devices having cylindrical geometry soaked with suitable organic solvents are proposed for microextraction analysis. This novel analytical approach (PU microextraction; PUµE) operates under the floating sampling technology for extraction, followed by mechanical compression using a manual syringe for back-extraction. To test the performance of the PUµE method, two series of priority contaminants were used as model compounds (group #1: metalaxyl-M, penconazole and tebuconazole; group #2: atrazine, terbuthylazine, alachlor and benzo[a]pyrene) and extracted from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. The preparation of the PUµE devices and the device handling procedures are described. Also, the optimization experiments as well as the application of the new method to real matrices are discussed. Assays performed on 25mL water samples spiked at trace levels yielded average recoveries ranging from (50.1±6.7) % to (93.3±1.6) %, under optimized experimental conditions. The analytical performance showed good detection limits (0.01-0.50µg/L) and linear dynamic ranges (0.1-50.0µg/L) with acceptable determination coefficients (r2>0.9937). Excellent repeatability was also achieved in both intraday (RSD<3.5%) and inter-day (RSD<7.0%) experiments. With standard addition quantification, the proposed analytical approach revealed good sensitivity and selectivity at trace levels with absence of matrix effects for environmental water and wine samples. The PUµE technique is simple, cost-effective and very easy to apply, using an all-in-one microextraction concept.

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.

Enhancement for trace analysis of sulfonamide antibiotics in water matrices using bar adsorptive microextraction (BAµE).

In this study, the enhancement for trace analysis of sulfonamide antibiotics (sulfathiazole, sulfamethoxazole and sulfadimethoxine) and trimethoprim in water matrices is proposed using bar adsorptive microextraction combined with micro-liquid desorption followed by high-performance liquid chromatography with diode array detection (BAµE-µLD/HPLC-DAD). By comparing different polymers and activated carbons as sorbent coatings for BAµE, the polystyrene-divinylbenzene polymer (PS-DVB) showed the best selectivity for the compounds under study. Assays performed through BAµE(PS-DVB)-µLD on 25mL of ultrapure water samples spiked at the 8.0µgL(-1) level showed recoveries ranging from 63.8±1.5% to 84.2±1.9%, under optimized experimental conditions. The validated method provided satisfactory limits of detection (0.08-0.16µgL(-1)) and good linear dynamic ranges (0.16-8.00µgL(-1)) with determination coefficients higher than 0.9958. The proposed analytical methodology was applied to real matrices, such as tap, estuarine and wastewater samples using the standard addition method. It showed to be easy to implement, with good reproducibility, sensitivity and requiring small amount of sample. Furthermore, negligible consumption of organic solvents was used in compliance with the green analytical chemistry principles. When compared to other well-established microextraction approaches, BAµE demonstrated better performance concerning recovery yields and sensitivity.

Bar adsorptive microextraction (BAµE) coated with mixed sorbent phases-Enhanced selectivity for the determination of non-steroidal anti-inflammatory drugs in real matrices in combination with capillary electrophoresis.

The present work proposes the application of bar adsorptive microextraction coated with mixed sorbent phases (n-vinylpyrrolidone and divinylbenzene polymers with strong and weak anion exchangers), combined with liquid desorption followed by capillary electrophoresis with diode array detection (BAµE(PMIX)-LD/CE-DAD) for the determination of trace levels of non-steroidal anti-inflammatory drugs (NSAIDs: salicylic acid, mefenamic acid, diclofenac and naproxen as model compounds) in urine and water matrices. Assays performed on 25mL of water samples spiked at the 80.0µg/L level, yielded average recoveries between 86.6 and 104.% for all the NSAIDs under study using optimized experimental conditions. The proposed analytical methodology demonstrated suitable detection limits (0.3µg/L) and good linear dynamic ranges (2.5-320.0µg/L) with determination coefficients higher than 0.9981. By using the standard addition methodology, the present analytical approach was applied on urine and water samples, where good selectivity and sensitivity were achieved. The proposed method, which operated under the floating sampling technology, proved to be a suitable sorption-based static microextraction alternative for monitoring trace levels of NSAIDs in urine and water samples. The methodology showed to be easy to implement, demonstrating good reproducibility and robustness, allowing the possibility to choose the most selective sorbent, or mixed sorbent phases, according to the compounds of interest.

Determination of mitragynine in urine matrices by bar adsorptive microextraction and HPLC analysis.

Bar adsorptive microextraction combined with liquid desorption followed by high performance liquid chromatography with diode array detection (BAµE-LD/HPLC-DAD) is proposed for the determination of the psychoactive alkaloid mitragynine (MG) in human urine matrices. By using a modified N-vinylpyrrolidone polymer (P2) sorbent phase, high selectivity and efficiency is achieved. Assays performed by BAµE(P2)-LD/HPLC-DAD on 25 mL water samples spiked at the 8.0 µg L(-1) level yielded average recoveries around 100% of MG, under optimized experimental conditions. The analytical performance showed good precision (RSD<15%), appropriated detection limits of 0.10 µg L(-1) and linear dynamic ranges (0.6-24.0 µg L(-1)) with convenient determination coefficients of 0.9924. By using the standard addition method, the application of the present methodology for the determination of MG in human urine matrices after Kratom consumer, allowed very good performances. The proposed methodology proved to be a suitable alternative to monitor MG in biological fluid matrices, showing to be easy to implement, reliable, sensitive and requiring low sample volumes, when compared with other sorbent-based methods.

Determination of steroid sex hormones in real matrices by bar adsorptive microextraction (BAµE).

In the present work, the development of a novel analytical approach which combines a miniaturized bar adsorptive microextraction device with a micro-liquid desorption in one single step, followed by high performance liquid chromatography with diode array detection (BAµE-µLD/HPLC-DAD), is proposed for the determination of trace levels of nine steroid hormones (estriol, 17ß-estradiol, 17α-estradiol, 19-northisterone, 17α-ethynylestradiol, estrone, D-(-)-norgestrel, progesterone and mestranol) in environmental and biological matrices. From the comparison of ten different coating phases (five polymeric and five activated carbon sorbents), the modified pyrrolidone polymer (P2) showed the best compromise between selectivity and efficiency. Assays performed through BAµE(P2, 1.3mg)-µLD(100µL)/HPLC-DAD on 25mL of ultrapure water samples spiked at the 6.0µg/L level, yielded recoveries ranging from 93±9% to 101±8%, under optimized experimental conditions. The analytical performance showed convenient detection (50.0-100.0ng/L) and quantification limits (165.0-330.0ng/L), as well as good linear dynamic ranges (0.2-24.0µg/L) with remarkable determination coefficients (r(2)>0.9968). Excellent repeatability were also achieved through intraday (RSD<14%) and interday (RSD<12%) experiments. The application of the proposed analytical approach on environmental water and urine samples, using the standard addition methodology (SAM), revealed good linearity and sensitivity at trace level, with the detection of some of the target compounds. In short, the miniaturization of the analytical device for microextraction combined with the minimization of the solvent volume for back-extraction in one single step demonstrated remarkable performance, increasing the enrichment factor, being simultaneously more easier to implement and environment friendly.

Application of bar adsorptive microextraction (BAµE) for anti-doping control screening of anabolic steroids in urine matrices.

This study proposes a new analytical methodology for the determination of trace levels of testosterone (T) and epitestosterone (E) in urine matrices using bar adsorptive microextraction combined with liquid desorption followed by high-performance liquid chromatography with diode array detection (BAµE-LD/HPLC-DAD). The comparison of different sorbent coatings (five activated carbons, one styrene-divinylbenzene, two modified pyrrolidone, one ciano and one n-vinylpyrrolidone polymers) through BAµE showed that the latter phase presented much higher selectivity and capacity offering multiple mechanisms of interaction. Assays using this phase were performed on 25mL of water samples spiked at the 8.0µg/L level, yielded average recoveries of 92.1 and 93.4% for T and E, respectively, under optimized experimental conditions; BAµE (n-vinylpyrrolidone): 16h (1000rpm), pH 5.5; LD: acetonitrile, 30min under sonication treatment. From the developed analytical methodology, suitable detection limits were achieved (0.4µg/L) and good linear dynamic ranges (1.4-16.0µg/L) with remarkable determination coefficients (r(2)>0.9978). By using the standard addition methodology, the application of the present analytical approach on urine samples revealed good sensitivity. The proposed method, which operated under the floating sampling technology, proved to be a suitable sorption-based static microextraction alternative for screening T, E and the T/E ratio in urine samples for doping control purposes. The methodology showed to be easy to implement, demonstrating good reproducibility, sensitivity and robustness, allowing the possibility to choose the most selective sorbent coating according to the compounds of interest.

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.

Determination of trace levels of parabens in real matrices by bar adsorptive microextraction using selective sorbent phases.

In the present work, the development of an analytical methodology which combines bar adsorptive microextraction with microliquid desorption followed by high performance liquid chromatography-diode array detection (BAµE-µLD/HPLC-DAD) is proposed for the determination of trace levels of four parabens (methyl, ethyl, propyl and buthyl paraben) in real matrices. By comparing six polymer (P1, P2, P3, P4, P5 and P6) and five activated carbon (AC1, AC2, AC3, AC4 and AC5) coatings through BAµE, AC2 exhibited much higher selectivity and efficiency from all the sorbent phases tested, even when compared with the commercial stir bar sorptive extraction with polydimethylsiloxane. Assays performed through BAµE(AC2, 1.7mg) on 25mL of ultrapure water samples spiked at the 8.0µg/L level, yielded recoveries ranging from 85.6±6.3% to 100.6±11.8%, under optimized experimental conditions. The analytical performance showed also convenient limits of detection (0.1µg/L) and quantification (0.3µg/L), as well as good linear dynamic ranges (0.5-28.0µg/L) with remarkable determination coefficients (r(2)>0.9982). Excellent repeatability was also achieved through intraday (RSD<10.2%) and interday (RSD<10.0%) assays. By downsizing the analytical device to half-length (BAµE(AC2, 0.9mg)), similar analytical data was also achieved for the four parabens, under optimized experimental conditions, showing that this analytical technology can be design to operate with lower volumes of sample and desorption solvent, thus increasing the sensitivity and effectiveness. The application of the proposed analytical approach using the standard addition methodology on tap, underground, estuarine, swimming pool and waste water samples, as well as on commercial cosmetic products and urine samples, revealed good sensitivity, absence of matrix effects and the occurrence of levels of some parabens. Moreover, the present methodology is easy to implement, reliable, sensitive, requiring low sample and minimized desorption solvent volume, having the possibility to tune the most selective sorbent coating, according to the target compounds involved.

Improvements on bar adsorptive microextraction (BAµE) technique--application for the determination of insecticide repellents in environmental water matrices.

Bar adsorptive microextraction combined with micro-liquid desorption followed by large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode (BAµE-µLD/LVI-GC-MS(SIM)), is proposed for the determination of trace levels of three insecticide repellents (N,N-diethyl-meta-toluamide (DEET), cis and trans permethrin (PERM)) in environmental water matrices. By comparing different sorbent coatings (five activated carbons and six polymers) through BAµE, an activated carbon (AC2) proved to be the best compromise between selectivity and efficiency, even against polydimethylsiloxane through stir bar sorptive extraction. The novel improvement proposed on the back-extraction stage performed in a single step, by reducing the desorption solvent volume at the microliter level, demonstrated remarkable performance turning possible to save time, making easier the practical manipulation and more environmentally friendly. Assays performed by BAµE(AC2)-µLD/LVI-GC-MS(SIM) on 25 mL of ultrapure water samples spiked at the 1.0 µg/L level, yielded recoveries ranging from 73.8±8.8% (trans-PERM) to 96.4±9.9% (DEET), under optimised experimental conditions. The analytical performance showed convenient detection limits (8-20 ng/L) and good linear dynamic ranges (0.04-4.0 µg/L) with suitable determination coefficients (r(2)>0.9963, DEET). Excellent repeatability were also achieved through intraday (RSD<14.9%) and interday (RSD<11.9%) experiments. The novel improvement on downsizing the BAµE device to half-size proved to be either a promising option in forthcoming to reduce still more the desorption solvent volume without losing microextraction efficiency. By using the standard addition methodology, the application of the present analytical approach on tap, ground, river, swimming-pool and estuary water samples revealed good sensitivity at trace level and absence of matrix effects.