Alejandra B. Camargo

Dispersive solid-phase extraction as a simplified clean-up technique for biological sample extracts. Determination of polybrominated diphenyl ethers by gas chromatography-tandem mass spectrometry

Dispersive solid-phase extraction (DSPE) is proposed for the first time as a simplified, fast and low cost clean-up technique of biological sample extracts for polybrominated diphenyl ethers (PBDEs) determination. The combination of a traditional extraction technique, such as ultrasound-assisted leaching (USAL) with DSPE was successfully applied for sample preparation prior to gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. The analytes were first extracted from 1g homogenized sample in n-hexane:dichloromethane (8:2) by applying USAL technique and further cleaned-up using DSPE with 0.20 g C(18)-silica as sorbent material. Different solvent mixtures, sorbent type and amount, and lipid digestion procedures were evaluated in terms of clean-up and extraction efficiency. Under optimum conditions, the method detection limits (MDLs) for PBDEs, calculated as three times the signal-to-noise ratio (S/N) were within the range 9-44 pg g(-1) wet weight. The calibration graphs were linear within the concentration range of 53-500,000 pg g(-1), 66-500,000 pg g(-1), 89-500,000 pg g(-1) and 151-500,000 pg g(-1) for BDE-47, BDE-100, BDE-99 and BDE-153, respectively; and the coefficient of determination (r(2)) exceeded 0.9992 for all analytes. The proposed methodology was compared with a reference solid-phase extraction technique. The applicability of the methodology for the screening of PBDEs has been demonstrated by analyzing spiked and real samples of biological nature (fish, egg and chicken) with different lipid content as well as reference material (WELL-WMF-01). Recovery values ranged between 75% and 114% and the measured concentrations in certified material showed a reasonable agreement with the certified ones. BDE-47, BDE-100 and BDE-99 were quantified in three of the seven analyzed samples and the concentrations ranged between 91 and 140 pg g(-1). In addition, this work is the first description of PBDEs detected in fish of Argentinean environment.

Coacervative microextraction ultrasound-assisted back-extraction technique for determination of organophosphates pesticides in honey samples by gas chromatography-mass spectrometry.

Coacervative microextraction ultrasound-assisted back-extraction technique (CME-UABE) is proposed for the first time for extracting and preconcentrating organophosphates pesticides (OPPs) from honey samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. The extraction/preconcentration technique is supported on the micellar organized medium based on non-ionic surfactant. To enable coupling the proposed technique with GC, it was required to back extract the analytes into hexane. Several variables including, surfactant type and concentration, equilibration temperature and time, matrix modifiers, pH and buffers nature were studied and optimized over the relative response of the analytes. The best working conditions were as follows: an aliquot of 10 mL 50 gL(-1) honey blend solution was conditioned by adding 100 μL 0.1 molL(-1) hydrochloric acid (pH 2) and finally extracted with 100 μL Triton X-114 100 gL(-1) at 85°C for 5 min using CME technique. Under optimal experimental conditions, the enrichment factor (EF) was 167 and limits of detection (LODs), calculated as three times the signal-to-noise ratio (S/N=3), ranged between 0.03 and 0.47 ngg(-1). The method precision was evaluated over five replicates at 1 ngg(-1) with RSDs ≤ 9.5%. The calibration graphs were linear within the concentration range of 0.3-1000 ngg(-1) for chlorpirifos; and 1-1000 ngg(-1) for fenitrothion, parathion and methidathion, respectively. The coefficients of correlation were ≥ 0.9992. Validation of the methodology was performed by standard addition method at two concentration levels (2 and 20 ngg(-1)). The recoveries were ≥ 90%, indicating satisfactory robustness of the methodology, which could be successfully applied for determination of OPPs in honey samples of different Argentinean regions. Two of the analyzed samples showed levels of methidathion ranged between 1.2 and 2.3 ngg(-1).

Variability of solids, organosulfur compounds, pungency and health-enhancing traits in garlic (Allium sativum L.) cultivars belonging to different ecophysiological groups.

Garlic is a vegetable mainly agamically propagated, and it has been dispersed all around the world. Garlic cultivars have been classified in different ecophysiological groups (EG) according to their bulbing requirements. The variability in organosulfur composition (ACSOs), solids content (SC), pungency (PC) and antiplatelet activity (IAA) and the correlation among these traits in garlic clones belonging to three EG was studied. We found variability for ACSOs, SC, PC and IAA between clones belonging to different EG and also among clones belonging to the same EG. Cutivars EG III presented more variability than EG IV for ACSOs, thiosulfinates, allicin and PC, while for SC, EG IV was the most variable. The correlations found suggested that IAA observed was mainly due to organosulfur composition. Finally recommendations about the most suitable cultivars for fresh consumption, pharmaceutical and dehydration industry are made.

Development of garlic bioactive compounds analytical methodology based on liquid phase microextraction using response surface design. Implications for dual analysis: Cooked and biological fluids samples.

Organosulphur compounds (OSCs) present in garlic (Allium sativum L.) are responsible of several biological properties. Functional foods researches indicate the importance of quantifying these compounds in food matrices and biological fluids. For this purpose, this paper introduces a novel methodology based on dispersive liquid-liquid microextraction (DLLME) coupled to high performance liquid chromatography with ultraviolet detector (HPLC-UV) for the extraction and determination of organosulphur compounds in different matrices. The target analytes were allicin, (E)- and (Z)-ajoene, 2-vinyl-4H-1,2-dithiin (2-VD), diallyl sulphide (DAS) and diallyl disulphide (DADS). The microextraction technique was optimized using an experimental design, and the analytical performance was evaluated under optimum conditions. The desirability function presented an optimal value for 600μL of chloroform as extraction solvent using acetonitrile as dispersant. The method proved to be reliable, precise and accurate. It was successfully applied to determine OSCs in cooked garlic samples as well as blood plasma and digestive fluids.

Molecular Factors Influencing the Affinity of Flavonoid Compounds on PGlycoprotein Efflux Transporter

The most common mechanism of the so-called multidrug resistance (MDR), is mainly associated with an over expression of P-glycoprotein (Pgp). It is an ATP-dependent transport protein that limits the intracellular accumulation of a variety of structurally unrelated compounds within various organs and normal tissues such as kidney, small intestine and the blood brain barrier. Thus, the expression of Pgp has a major impact on the pharmacokinetic profile of many therapeutic agents and therefore, overcoming Pgp-mediated efflux constitutes an attractive means of potentially enhancing their therapeutic efficacy. The flavonoids comprise a large group of polyphenolic compounds that occur in plants and vegetables, and they have been shown to display a wide variety of biological activities. For example, anti-inflammatory, antioxidant, antiallergic, hepatoprotective, antithrombotic, antiviral, and anticarcinogenic activities. The interactions between flavonoids and Pgp have also been extensively studied and some quantitative structure-activity relationships (QSAR) have been reported. In the present work, we have employed 2D-QSAR analysis to evaluate the interactions between Pgp and several flavonoid compounds with the aim of identifying the molecular factors responsible for the Pgp-binding affinity evidenced by these compounds. Thus, the reported data for dissociation constants (KD) between Pgp and 62 flavonoid compounds were modeled by means of multiple regression analysis (MLR), and structures of the compounds under study were characterized by means of calculated physicochemical properties and several topological and constitutional descriptors, as well as geometrical and quantum chemical indexes. The obtained results suggest that the hydrophobic and especially geometric factors are of prime importance for binding, whereas in the case of flavonoid derivatives with flavone (flavonols), flavanone and isoflavone nuclei, the electronic factors are also involved in electron donor/acceptor interactions. In addition, in the case of chalcones, the results suggest that the affinity toward P-gp of such compounds is mainly governed by intermolecular dispersive interactions at the binding site.

Determination of polybrominated diphenyl ethers in milk samples. Development of green extraction coupled techniques for sample preparation

Ultrasound‐assisted extraction (UAE), cloud point extraction (CPE), and ultrasound back‐extraction (UABE) techniques have been coupled for lixiviation, preconcentration, and cleanup of polybrominated diphenyl ethers (PBDEs) from milk samples for determination by gas chromatography‐electron capture detection (GC‐ECD). Physicochemical parameters that affect the efficiency of the extraction system were investigated using a design of experiments based on multivariate statistical tools, and considering the sample matrix along the development. The coupling of the leaching step, UAE, enhanced ca. 3.5 times the extraction efficiency of the former sample preparation methodology (CPE‐UABE) leading to cleaner sample extracts suitable for GC analysis. Under optimum conditions, the proposed methodology exhibits successful performance in terms of linearity and precision, with recoveries in the range of 68–70% and LODs within the range 0.05–0.5 ng/g dry weight (d.w.). The proposed sample preparation methodology coupled three green analytical techniques. It expands the application frontiers of CPE for the analysis of biological samples by GC. The optimized methodology was used for determination of PBDEs in powder milk samples, from both commercial and human sources.

UAE-HPLC-UV: New Contribution for Fast Determination of Total Isothiocyanates in Brassicaceae Vegetables

Total isothiocyanates content (ITC) is considered a good indicator of bioactive compounds responsible for beneficial effects related to Brassicaceae vegetables. Analytical performance is a critical factor for routine analysis in plant tissues. The extraction technique for isolating phytochemicals from Brassicaceae vegetables is currently the bottleneck of the methodology. The aim of this work was to optimize this step in the analytical process. Fast and less expensive alternative, based on ultrasound-assisted extraction technique (UAE) for direct extraction of GLS into an aqueous phase and further analysis of the hydrolysis product, was optimized. Full factorial () design followed by Central Composite Design (CCD) was used to obtain the optimum extraction conditions. Selected conditions were homogenization time (9 min); ultrasound bath time (5 min); and sample-to-solvent ratio (1 : 5 w/v mg mL−1). The proposed analytical methodology exhibits satisfactory analytical performance in terms of linearity, precision (RSD < 2.4%), and limits of detection (26 nmol g−1 w.w.). The new analytical methodology was applied to cauliflower, cabbage, watercress, and broccoli samples with recoveries higher than 86%. The UAE extraction technique was showed to be efficient for real samples analysis leading to sensible, selective, and reproducible methodology for ITC analysis.

Coprecipitation-assisted coacervative extraction coupled to high-performance liquid chromatography: An approach for determining organophosphorus pesticides in water samples

An analytical methodology based on coprecipitation‐assisted coacervative extraction coupled to HPLC‐UV was developed for determination of five organophosphorus pesticides (OPPs), including fenitrothion, guthion, parathion, methidathion, and chlorpyrifos, in water samples. It involves a green technique leading to an efficient and simple analytical methodology suitable for high‐throughput analysis. Relevant physicochemical variables were studied and optimized on the analytical response of each OPP. Under optimized conditions, the resulting methodology was as follows: an aliquot of 9 mL of water sample was placed into a centrifuge tube and 0.5 mL sodium citrate 0.1 M, pH 4; 0.08 mL Al2(SO4)3 0.1 M; and 0.7 mL SDS 0.1 M were added and homogenized. After centrifugation the supernatant was discarded. A 700 μL aliquot of the coacervate‐rich phase obtained was dissolved with 300 μL of methanol and 20 μL of the resulting solution was analyzed by HPLC‐UV. The resulting LODs ranged within 0.7–2.5 ng/mL and the achieved RSD and recovery values were <8% (n = 3) and >81%, respectively. The proposed analytical methodology was successfully applied for the analysis of five OPPs in water samples for human consumption of different locations of Mendoza.