Determination of organochlorine pesticides (OCPs) in breast milk from Rio Grande do Sul,Brazil, using a modified QuEChERS method and gas chromatography-negative chemical ionisation-mass spectrometry

ABSTRACT

The food chain is the main source of exposure to humans by organochlorine pesticides (OCPs) due to the bioaccumulation. Breast milk can accumulate OCPs, so this matrix is often used as an environmental bioindicator. The currently available methods for the determination of several OCPs and metabolites in breast milk involve, in general, multi-step sample preparation and quantification techniques with low selectivity, high cost and much time and labour. Thus, a fast and efficient method based on sample preparation using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with gas chromatography coupled to mass spectrometry with negative chemical ionisation (GC-NCI-MS) was developed, validated and applied for determination of 16 OCPs and metabolites in breast milk samples. The extract was cleaned by dispersive solid-phase extraction (d-SPE) using MgSO₄ and C18, evaporated in a Turbovap® system, redissolved and analysed by GC-NCI-MS. The method was validated showing acceptable recoveries (72–118%) and precision (RSD <19%). Method limits of detection (LODs) and quantification (LOQs) ranged from 0.75 to 7.5 ng g^?1 and from 2.5 to 25 ng g^?1 lipid, respectively. The method was successfully applied to 20 samples of breast milk from different regions of the Rio Grande do Sul state, Brazil, of which 75% contained residues below the LOQs.     

Highly sensitive ion preconcentration method based on flow sorbent extraction using multiwall carbon nanotubes

In this work a solid phase on-line uranium ion preconcentration system coupled with spectrophotometry has been developed. The method is based on uranyl ion preconcentration at pH 3.75 onto multiwall carbon nanotubes treated with HNO₃. After preconcentration, the uranyl ions are eluted with 0.32?mol?L^?1HCl followed by reaction with 3,6-bis[(2-arsonophenyl)-azo]-4,5-dihydroxy-2,7-naphthalendisulfonic acid 0.08%[w/v] (Arsenazo III), which had maximum monitored absorbance of 650?nm. Effects of the pertinent experimental parameters on the system were investigated by means of 2^6?2 fractional factorial design, while optimization was carried out using the Doehlert matrix. Under optimized conditions, detection and quantification limits were found to be 0.21 and 0.7?µg?L^?1, respectively. The analytical curve ranged from 5 to 150?µg?L^?1 (r?=?0.998), while the relative standard deviations (RSD) were 3.27 and 2.56% for the respective uranium concentrations of 10 and 100?µg?L^?1 (n?=?10). The features obtained for the on-line preconcentration system were: preconcentration factor of 228, concentration efficiency of 57?min^?1, consumption index of 0.13?mL and sample throughput of 15?h^?1. In order to assess the accuracy of the proposed method, addition and recovery studies were carried out on spring water samples from different sources and synthetic seawater with satisfactory results ranging from 94.85 up to 103.65%.     

The Influence of Hydrogen Loading Temperature on the Mechanical Strength of Optical Fibers

The influence of hydrogen loading temperature on the mechanical strength of optical fibers is investigated. Fibers subjected to high-pressure hydrogen loading at different temperatures were submitted to bend tests, and the results compared with those for pristine fibers. The Weibull probability distribution function was used to analyze the data of the mechanical bending strength of the fibers. Fiber strength is reduced by the presence of hydrogen, and this decrease is greater for higher hydrogen loading temperatures. The mechanical properties of the polymers used to coat fibers are affected by the hydrogen loading process and also by the increase in temperature. However, there is no evidence of cracks formation that might allow water to penetrate to the surface of the glass. Observation using scanning electron microscopy revealed that the morphology of fractures in nonhydrogen-loaded fibers have distinct fracture characteristics to that of fibers that are hydrogen loaded at 90°C and 120°C.     

Non-oxo vanadium(IV) alkoxide chemistry: solid state structures, aggregation equilibria and thermochromic behaviour in solution

The reversible thermochromic behaviour of homoleptic [{V(OR)(4)}(n)] complexes in solution [R = Pr(i) (product I), Bu(s) (B(s)), Nep (N) and Cy (C)] is accounted for the existence of an aggregation equilibrium involving dimeric and monomeric species in which vanadium(iv) is respectively five- and four-coordinate. Bulky R groups such as Bu(t) and Pe(t) (tert-pentoxide) prevent aggregation and therefore give rise to exclusively mononuclear compounds (B(t) and P(t), respectively) that are not thermochromic. The complexes and their temperature-dependent interconversion were characterised by single crystal X-ray diffractometry, magnetic susceptibility measurements and electronic, FTIR and EPR spectroscopies in a wide temperature range. Equilibrium constants and enthalpy and entropy changes for the dimerization reactions have been determined and compared with literature data.     

Antimicrobial activities of indole alkaloids from Tabernaemontana catharinensis

Tabernaemontana catharinensis root bark ethanol extract, EB2 fraction and the MMV alkaloid (12-methoxy-4-methylvoachalotine) were evaluated for their antimicrobial activities. T. catharinensis ethanol extract was effective against both strains of the dermatophyte Trichophyton rubrum at concentrations of 2.5 mg/mL (wild strain) and 1.25 mg/mL (mutant strain), while the EB2 fraction and MMV alkaloid showed a strong antifungal activity against wild and mutant strains with MIC values of <0.02 and 0.16 mg/mL, respectively. The EB2 fraction showed a strong antibacterial activity against ATCC strains of S. aureus, S. epidermidis, E. coli and P. aeruginosa with MICs from <0.02 to 0.04 mg/mL, as well as against resistant clinical isolates species of Enterococcus sp, Klebsiella oxytoca, Citrobacter, K. pneumoniae, P. mirabilis, S. aureus, S. epidermidis, E. coli and P. aeruginosa with MIC values ranging from 0.04 to 0.08 mg/mL. The MMV alkaloid presented a MIC of 0.16 mg/mL against the strains of S. aureus and E. coli ATCC. For the resistant clinical isolates Enterococcus sp, Citrobacter, S. aureus, S. epidermidis, E. coli and P. aeruginosa the MIC of MMV ranged from 0.08 to 0.31 mg/mL. The chromatography analysis of the EB2 fraction revealed the presence of indole alkaloids, including MMV, possibly responsible for the observed antimicrobial activity.     

Amperometric Detection of Ethanol Vapors by Screen Printed Electrodes Modified by Paper Crowns Soaked with Room Temperature Ionic Liquids

A convenient assembly recently proposed for screen printed gold electrodes (SPEs) suitable for measurements in gaseous samples is here tested for the analysis of the ethanol content in alcoholic drinks. This assembly involves the use of a circular crown of filter paper, soaked in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hydrogen sulfate, which is simply placed upon a disposable screen printed cell, so as to contact the outer edge of the gold disc working electrode, as well as peripheral counter and reference electrodes. The electrical contact between the paper crown soaked in RTIL and the SPE electrode is assured by a gasket and all components are installed in a polylactic acid holder. This assembly provides a portable and disposable electrochemical platform, assembled by the easy immobilization onto a porous and inexpensive supporting material such as paper of a RTIL characterized by profitable electrical conductivity and negligible vapor pressure. The electroanalytical performance of this device was assayed for the flow injection analysis of the ethanol concentration in some real samples of wine and beer and the results obtained are compared with the alcoholic degree reported in the relevant bottle-labels, thus highlighting a substantially satisfactory agreement. Repeatable sharp peaks (RSD=6–8 %) were detected for ethanol over a wide linear range (1–20 % v/v in water) and a detection and quantitation limit of 0.55 % v/v and 1.60 % v/v were inferred for a signal-to-noise ratio of 3 and 10, respectively.     

A practical synthesis of 2,4(5)-diarylimidazoles from simple building blocks

A simple and efficient approach to selectively obtain 2,4(5)-diarylimidazoles suppressing formation of 2-aroyl-4(5)-arylimidazoles is described. The yield of each of the two products strongly depends on the reaction conditions employed. This reaction provides a simple method to prepare small libraries of biologically active compounds by parallel synthesis.     

Replica Symmetry Breaking in Short-Range Spin Glasses: Theoretical Foundations and Numerical Evidences

We discuss replica symmetry breaking (RSB) in spin glasses. We update work in this area, from both the analytical and numerical points of view. We give particular attention to the difficulties stressed by Newman and Stein concerning the problem of constructing pure states in spin glass systems. We mainly discuss what happens in finite-dimensional, realistic spin glasses. Together with a detailed review of some of the most important features, facts, data, and phenomena, we present some new theoretical ideas and numerical results. We discuss among others the basic idea of the RSB theory, correlation functions, interfaces, overlaps, pure states, random field, and the dynamical approach. We present new numerical results for the behaviors of coupled replicas and about the numerical verification of sum rules, and we review some of the available numerical results that we consider of larger importance (for example, the determination of the phase transition point, the correlation functions, the window overlaps, and the dynamical behavior of the system).     

Propanediol (and) Caprylic Acid (and) Xylitol as a New Single Topical Active Ingredient against Acne: In Vitro and In Vivo Efficacy Assays

In addition to dermatological complications, acne can affect the quality of life of individuals in numerous ways, such as employment, social habits and body dissatisfaction. According to our expertise, caprylic acid and propanediol would not have a direct action on Cutibacterium acnes. Despite this, we investigated the existence of a synergistic effect among xylitol, caprylic acid and propanediol as a mixture of compounds representing a single topical active ingredient that could benefit the treatment against acne. In vitro and in vivo assays were performed to challenge and to prove the efficacy of propanediol, xylitol and caprylic acid (PXCA) against acne. PXCA had its MIC challenged against C. acnes (formerly Propionibacterium acnes) and Staphylococcus aureus, resulting in concentrations of 0.125% and 0.25%, respectively, and it also developed antimicrobial activity against C. acnes (time-kill test). PXCA was able to reduce the 5-alpha reductase expression in 24% (p < 0.01) in comparison with the testosterone group. By the end of 28 days of treatment, the compound reduced the skin oiliness, porphyrin amount and the quantity of inflammatory lesions in participants. According to the dermatologist evaluation, PXCA improved the skin’s general appearance, acne presence and size.     

Influence of the soil matrices on the analytical performance of headspace solid-phase microextraction for organotin analysis by gas chromatography-pulsed flame photometric detection

Organotin compounds (OTCs) have been identified in a variety of environmental media (air, surface water, groundwater, soil and sediments). In the past, much attention was assigned to the study of the OTCs content in biological samples, water and sediments. Little information about OTCs in soil is available. In this work, a procedure for butyl and phenyltin determination in soils by headspace-solid-phase microextraction (HS-SPME) gas chromatography-pulsed flame photometric detection (GC-PFPD) was investigated. For SPME analysis, a polydimethylsiloxane (PDMS) coating was applied. Peat soil rich in organic matter and with a high cation-exchange capacity (CEC), and clay soil low in organic matter and with a low CEC were analysed. The influence of these different soil matrices on HS-SPME analysis was evaluated by spiking of samples. In general, the recoveries for the two spiked soils exceeded 80%. The repeatability of the method was better than 10%. The limits of detection (LODs) and limits of quantification (LOQs) were in the ng S ng(-1) range. The technique may be reliably applied for the determination of butyltins and monophenyltin in soils, while it shows some limitations for the analysis of di- and triphenyltin (TPhT).