DETERMINATION OF CHLORFENVINPHOS, FIPRONIL, AND CYPERMETHRIN RESIDUES IN MEAT AND BOVINE FAT USING QUECHERS METHOD AND GAS CHROMATOGRAPHY-MASS SPECTROMETRY

Analytic methods were applied and validated to measure residues of chlorfenvinphos, fipronil, and cypermethrin in meat and bovine fat, using the QuEChERS method and gas chromatography-mass spectrometry. For the meat, 2 g of sample, 4mL of acetonitrile, 1.6 g of MgSO4, and 0.4 g of NaCl were used in the liquid-liquid partition, while 80 mg of C18, 80 mg of primary and secondary amine and 150 mg of MgSO4 were employed in the dispersive solid-phase extraction. For the fat, 1 g of sample, 5 mL of hexane, 10 mL of water, 10 mL of acetonitrile, 4 g of MgSO4, and 0.5 g of NaCl were used in the liquid-liquid partition and 50 mg of primary and secondary amine and 150 mg of MgSO4 were used in the dispersive solid-phase extraction. The recovery percentages obtained for the pesticides in meat at different concentrations ranged from 81 to 129% with relative standard deviation below 27%. The corresponding results from the fat ranged from 70 to 123% with relative standard deviation below 25%. The methods showed sensitivity, precision, and accuracy according to EPA standards and quantification limits below the maximum residue limit established by European Union, except for chlorfenvinphos in the fat.

Hollow-fiber liquid-phase microextraction and gas chromatography-mass spectrometry of barbiturates in whole blood samples

Here, we present a method for measuring barbiturates (butalbital, secobarbital, pentobarbital, and phenobarbital) in whole blood samples. To accomplish these measurements, analytes were extracted by means of hollow-fiber liquid-phase microextraction in the three-phase mode. Hollow-fiber pores were filled with decanol, and a solution of sodium hydroxide (pH 13) was introduced into the lumen of the fiber (acceptor phase). The fiber was submersed in the acidified blood sample, and the system was subjected to an ultrasonic bath. After a 5 min extraction, the acceptor phase was withdrawn from the fiber and dried under a nitrogen stream. The residue was reconstituted with ethyl acetate and trimethylanilinium hydroxide. An aliquot of 1.0 mu L of this solution was injected into the gas chromatograph/mass spectrometer, with the derivatization reaction occurring in the hot injector port (flash methylation). The method proved to be simple and rapid, and only a small amount of organic solvent (decanol) was needed for extraction. The detection limit was 0.5 mu g/mL for all the analyzed barbiturates. The calibration curves were linear over the specified range (1.0 to 10.0 mu g/mL). This method was successfully applied to postmortem samples (heart blood and femoral blood) collected from three deceased persons previously exposed to barbiturates.

Characterization of volatile composition of Laurencia dendroidea by gas chromatography-mass spectrometry

In this study we report the characterization of the volatile compounds of Laurencia dendroidea. Solvent extracts (dichloromethane and methanol), hydrodistillation extracts and headspace solid-phase microextraction samples were obtained and analyzed by GC-MS. Forty-six volatile components were identified in L. dendroidea, among them hydrocarbons, alcohols, phenols, aldehydes, ketones, acids, esters and terpenes.

Sensitive and fast determination of Sudan dyes in chilli powder by partial-filling micellar electrokinetic chromatography-tandem mass spectrometry

A fast and sensitive method for the simultaneous determination of Sudan dyes (I, II, III, and IV) in food samples was developed for the first time using partial filling micellar electrokinectic chromatography-mass spectrometry (MEKC-MS). The use of MEKC was essential to achieve the separation of these neutral analytes, while the partial filling technique was necessary to avoid the contamination of the ion source with non-volatile micelles. MEKC separation and MS detection conditions were optimized in order to achieve a fast, efficient, and sensitive separation of the four dyes. Filling 25% of the capillary with an MEKC solution containing 40 mM ammonium bicarbonate, 25 mM SDS, and 32.5% (v/v) acetonitrile, a baseline separation of the four azo-dyes was obtained in 10 min. Tandem MS was investigated in order to improve the sensitivity and selectivity of the analysis. Limits of detection (LOD) values 5, 8, 15, and 29 times better were obtained for Sudan III, I, II, and IV, respectively, using partial filling MEKC-MS/MS instead of partial filling MEKC-MS. Under optimized conditions, LOD from 0.05 to 0.2 mu g/mL were obtained. The suitability of the developed method was demonstrated through the fast and sensitive determination of Sudan I, II, III, and IV in spiked chilli powder samples. This determination could not be achieved by MEKC-UV due to the existence of several interfering compounds from the matrix.

Optimization of in situ derivatization SPME by experimental design for GC-MS multi-residue analysis of pharmaceutical drugs in wastewater

This paper presents the development of a procedure, which enables the analysis of nine pharmaceutical drugs in wastewater using gas chromatography-mass spectrometry (GC-MS) associated with solid-phase microextraction (SPME) for the sample preparation. Experimental design was applied to optimize the in situ derivatization and the SPME extraction conditions. Ethyl chloroformate (ECF) was employed as derivatizing agent and polydimethylsiloxane-divinylbenzene (PDMS-DVB) as the SPME fiber coating. A fractional factorial design was used to evaluate the main factors for the in situ derivatization and SPME extraction. Thereafter, a Doehlert matrix design was applied to find out the best experimental conditions. The method presented a linear range from 0.5 to 10 mu g/L, and the intraday and interday precision were lower than 16%. Applicability of the method was verified from real influent and effluent samples of a wastewater treatment plant, as well as from samples of an industry wastewater and a river.

Determination of Tetradifon in Brazilian Green Bell Pepper by Differential Pulse Voltammetry

Tetradifon, a potentially carcinogenic and mutagenic pesticide, can contribute to environmental and human contamination when applied to green bell pepper crops. In this context, in this work, a reliable and sensitive method for determination of tetradifon in Brazilian green bell pepper samples involving a differential pulse voltammetry (DPV) technique on a glassy carbon electrode is proposed. The electrochemical behavior of tetradifon as followed by cyclic voltammetry (CV) suggests that its reduction occurs via an irreversible five-electron transfer vs. Ag vertical bar AgCl, KCl 3 M reference electrode. Very well-resolved diffusion controlled voltammetric peaks have been obtained in a supporting electrolyte solution composed of a mixture of 40% dimethylformamide (DMF), 30% methanol, and 30% NaOH 0.3 mol L-1 at -1.43, -1.57, -1.73, -1.88, and -2.05 V. The proposed DPV method has a good linear response in the 3.00 - 10.0 mu mol L-1 range, with a limit of detection (L.O.D) of 0.756 mu mol L-1 and 0.831 mu mol L-1 in the absence and in the presence of the matrix, respectively. Moreover, improved L.O.D results (0.607 mu mol L-1) have been achieved in the absence of DMF from the supporting electrolyte solution. Recovery has been evaluated in five commercial green bell pepper samples, and recovery percentages ranging from 91.0 to 109 have been obtained for tetradifon determinations. The proposed voltammetric method has also been tested for reproducibility, repeatability, and potential interferents, and the results obtained for these three analytical parameters are satisfactory for electroanalytical purposes. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.024207jes] All rights reserved.

Hollow-fiber liquid-phase microextraction of amphetamine-type stimulants in human hair samples

A fast method was optimized and validated in order to quantify amphetamine-type stimulants (amphetamine, AMP; methamphetamine, MAMP; fenproporex, FPX; 3,4-methylenedioxymethamphetamine, MDMA; and 3,4-methylenedioxyamphetamine, MDA) in human hair samples. The method was based in an initial procedure of decontamination of hair samples (50 mg) with dichloromethane, followed by alkaline hydrolysis and extraction of the amphetamines using hollow-fiber liquid-phase micro extraction (HF-LPME) in the three-phase mode. Gas chromatography-mass spectrometry (GC-MS) was used for identification and quantification of the analytes. The LoQs obtained for all amphetamines (around 0.05 ng/mg) were below the cut-off value (0.2 ng/mg) established by the Society of Hair Testing (SoHT). The method showed to be simple and precise. The intra-day and inter-day precisions were within 10.6% and 11.4%, respectively, with the use of only two deuteratecl internal standards (AMP-d5 and MDMA-d5). By using the weighted least squares linear regression (1/x(2)), the accuracy of the method was satisfied in the lower concentration levels (accuracy values better than 87%). Hair samples collected from six volunteers who reported regular use of amphetamines were submitted to the developed method. Drug detection was observed in all samples of the volunteers. (c) 2012 Elsevier B.V. All rights reserved.

Characterization of cuticular hydrocarbons of diploid and haploid males, workers and queens of the stingless bee Melipona quadrifasciata

Males, queens and workers of stingless bees show differences in external morphology, behaviour and roles within a colony. In addition, each individual has a cuticular chemical signature responsible for mutual communication that is essential for maintaining the integrity of the colony. In this paper we characterize the cuticular hydrocarbon composition of newly emerged diploid and haploid males, workers and virgin queens of Melipona quadrifasciata by gas chromatography-mass spectrometry (GC/MS) analysis. This is the first time that the cuticular profile of diploid males in a species of stingless bee has been characterized. We found differences in the cuticular hydrocarbon composition among males, workers and virgin queens, recording both qualitative and quantitative differences among individuals of different phenotypes. However, no compound was found exclusively in diploid males. The cuticular chemical profiles of haploid and diploid males were very similar to those of workers. Moreover, the cuticular lipids of males and workers were significantly different from those of queens. Tricosane, pentacosene-2 and 7-methyl-heptacosane were the compounds responsible for this significant separation. This result correlates with the behavioural and morphological differences among these phenotypes.

Exhaled Acetone as a New Biomarker of Heart Failure Severity

Background: Heart failure (HF) is associated with poor prognosis, and the identification of biomarkers of its severity could help in its treatment. In a pilot study, we observed high levels of acetone in the exhaled breath of patients with HF. The present study was designed to evaluate exhaled acetone as a biomarker of HF diagnosis and HF severity. Methods: Of 235 patients with systolic dysfunction evaluated between May 2009 and September 2010, 89 patients (HF group) fulfilled inclusion criteria and were compared with sex- and age-matched healthy subjects (control group, n = 20). Patients with HF were grouped according to clinical stability (acute decompensated HF [ADHF], n = 59; chronic HF, n = 30) and submitted to exhaled breath collection. Identification of chemical species was done by gas chromatography-mass spectrometry and quantification by spectrophotometry. Patients with diabetes were excluded. Results: The concentration of exhaled breath acetone (EBA) was higher in the HF group (median, 3.7 mu g/L; interquartile range [IQR], 1.69-10.45 mu g/L) than in the control group (median, 0.39 mu g/L; IQR, 0.30-0.79 mu g/L; P < .001) and higher in the ADHF group (median, 7.8 mu g/L; IQR, 3.6-15.2 mu g/L) than in the chronic HF group (median, 1.22 mu g/L; IQR, 0.68-2.19 P < .001). The accuracy and sensitivity of this method in the diagnosis of HF and ADHF were about 85%, a value similar to that obtained with B-type natriuretic peptide (BNP). EBA levels differed significantly as a function of severity of HF (New York Heart Association classification, P < .001). There was a positive correlation between EBA and BNP (r = 0.772, P < .001). Conclusions: EBA not only is a promising noninvasive diagnostic method of HF with an accuracy equivalent to BNP but also a new biomarker of HF severity. CHEST 2012; 142(2):457-466

Influence of different banana cultivars on volatile compounds during ripening in cold storage

The aroma responsible for the flavor of fruits is highly susceptible to low temperatures in storage. The present study investigated the volatile composition of the Nanicao and Prata banana cultivars by testing pulp and whole fruit under cold storage conditions. The volatile fractions were characterized using headspace solid phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). The cold storage induced changes in the volatile profile relative to the profile of the control group. The result of principal component analysis revealed that cold storage more strongly affects the Nanicao than the Prata cultivar. Esters such as 2-pentanol acetate, 3-methyl-1-butanol acetate, 2-methylpropyl butanoate, 3-methylbutyl butanoate, 2-methylpropyl 3-methylbutanoate and butyl butanoate were drastically reduced in the cold group of the Nanicao cultivar. Our results suggest that the metabolism responsible for the production of volatile compounds is related to the ability to tolerate low temperatures. (C) 2012 Elsevier Ltd. All rights reserved.

Mixed colonies of two species of congeneric stingless bees (Hymenoptera: Apinae, Meliponini) display environmentally-acquired and endogenously-produced recognition signals

Nestmate recognition is fundamental for the maintenance of social organization in insect nests. It is becoming well recognized that cuticle hydrocarbons mediate the recognition process, although the origin of recognition cues in stingless bees remains poorly explored. The present study investigates the effects of endogenously-produced and environmentally-acquired components in cuticular hydrocarbons in stingless bees. The tests are conducted using colonies of Plebeia droryana Friese and Plebeia remota Holmberg. Recognition tests are performed with four different groups: conspecific nestmates, conspecific non-nestmates, heterospecifics and conspecific, genetically-related individuals that emerge in a heterospecific nest. This last group is produced by introducing brood cells of P. droryana into a P. remota colony, and the resulting adult bees are tested for acceptance 10 days after emergence. For all groups, 15 individuals are sampled for chemical analysis. The results show the acceptance of all conspecific nestmates, and the rejection of almost every conspecific non-nestmate and every heterospecific bee. Genetically-related individuals emerging from heterospecific nests present intermediate rejection (66.7% rejection). Chemical analysis shows that P. droryana individuals emerging in a P. remota nest have small amounts of alkene and diene isomers found in P. remota cuticle that are not found in workers from the natal nest. The data clearly show that the majority of the compounds present in P. droryana cuticle are endogenously produced, although a few unsaturated compounds are acquired from the environment, increasing the chemical differences and, consequently, the rejection percentages.

Effects of the antimycobacterial compound 2-phenoxy-1-phenylethanone on rat hepatocytes and formation of metabolites

Context: Neolignans are usually dimers formed by oxidative coupling of allyl and propenyl phenols, and the neolignan analogue, 2-phenoxy-1-phenylethanone (LS-2) is a promising antimycobacterial compound showing very weak cytotoxicity in mammalian cells and lack of acute toxicity in murine models. Objectives: To investigate the mechanism of action of LS-2 in rat hepatocytes by evaluating the activity levels of enzymes related to oxidation status and drug-metabolizing activity. Materials and methods: Hepatocytes were treated with LS-2 from 0.05 up to 1 mM, for 24 and 48 h, and reduced glutathione (GSH), lipid peroxidation and cytochrome P450 enzyme (CYP450) activity were assayed. A homologous series of phenoxazone ethers were used as substrates to measure the enzymatic profile. The biotransformation of LS-2 was studied in hepatocytes by gas chromatography-mass spectrometry (GC-MS) for detection and analysis of possible metabolites. Results: Hepatocytes treated with LS-2 up to 1 mM for 24 or 48 h did not induce the formation of GSH and lipid peroxidation. O-Dealkylation activities of the isoenzymes CYP4501A1, CYP4501A2, CYP4502B1 and CYP4502B2 were also not detected in the hepatocytes treated with LS-2 for 24 or 48 h. Discussion and conclusion: The results indicate that LS-2 or its two detected metabolites, 2-phenoxy-1-phenylethanol and 2,4-(2-hydroxy-2-phenylethoxy) phenol, are not cytotoxic to rat hepatocytes. These compounds maintain a balance between the production of pro-oxidant agents and their respective antioxidant systems. The data show that enzymes related to oxidation status and drug-metabolizing activities are not involved in the mechanism of action of LS-2.

Automated analysis of lidocaine and its metabolite in plasma by in-tube solid-phase microextraction coupled with LC-UV for pharmacokinetic study

A sensitive, selective, and reproducible in-tube solid-phase microextraction and liquid chromatographic (in-tube SPME/LC-UV) method for determination of lidocaine and its metabolite monoethylglycinexylidide (MEGX) in human plasma has been developed, validated, and further applied to pharmacokinetic study in pregnant women with gestational diabetes mellitus (GDM) subjected to epidural anesthesia. Important factors in the optimization of in-tube SPME performance are discussed, including the draw/eject sample volume, draw/eject cycle number, draw/eject flow rate, sample pH, and influence of plasma proteins. The limits of quantification of the in-tube SPME/LC method were 50 ng/mL for both metabolite and lidocaine. The interday and intraday precision had coefficients of variation lower than 8%, and accuracy ranged from 95 to 117%. The response of the in-tube SPME/LC method for analytes was linear over a dynamic range from 50 to 5000 ng/mL, with correlation coefficients higher than 0.9976. The developed in-tube SPME/LC method was successfully used to analyze lidocaine and its metabolite in plasma samples from pregnant women with GDM subjected to epidural anesthesia for pharmacokinetic study.

Antimicrobial Activity of Essential Oils against Streptococcus mutans and their Antiproliferative Effects

This study aimed to evaluate the activity of essential oils (EOs) against Streptococcus mutans biofilm by chemically characterizing their fractions responsible for biological and antiproliferative activity. Twenty EO were obtained by hydrodistillation and submitted to the antimicrobial assay (minimum inhibitory (MIC) and bactericidal (MBC) concentrations) against S. mutans UA159. Thin-layer chromatography and gas chromatography/mass spectrometry were used for phytochemical analyses. EOs were selected according to predetermined criteria and fractionated using dry column; the resulting fractions were assessed by MIC and MBC, selected as active fractions, and evaluated against S. mutans biofilm. Biofilms formed were examined using scanning electron microscopy. Selected EOs and their selected active fractions were evaluated for their antiproliferative activity against keratinocytes and seven human tumor cell lines. MIC and MBC values obtained for EO and their active fractions showed strong antimicrobial activity. Chemical analyses mainly showed the presence of terpenes. The selected active fractions inhibited S. mutans biofilm formation (P < 0.05) did not affect glycolytic pH drop and were inactive against keratinocytes, normal cell line. In conclusion, EO showed activity at low concentrations, and their selected active fractions were also effective against biofilm formed by S. mutans and human tumor cell lines.

The effects of extrusion conditions and the addition of volatile compounds and flavour enhancers to corn grits on the retention of the volatile compounds and texture of the extrudates

Corn grits that were supplemented with isovaleraldehyde, ethyl butyrate, butyric acid and flavour enhancers were extruded under different processing conditions. Volatile compounds retained in the extrudates were isolated by dynamic headspace and analysed using gas chromatographymass spectrometry. The expansion ratio, density and cut force to break down the extrudates were evaluated and aroma intensity was assessed using a multisample difference test. Butyric acid showed the greatest retention (96.4%), regardless of the extrusion conditions. All compounds were better retained when samples were extruded at 20% feed moisture and 90 degrees C processing temperature (2.981.0%), conditions that also resulted in greater aromatic intensity (moderate to moderate-strong intensity). The addition of volatile compounds reduced the expansion ratio and cut force, whereas the addition of flavour enhancers increased the expansion ratio but reduced ethyl butyrate and butyric acid retention.