Organotin speciation in French brandies and wines by solid-phase microextraction and gas chromatography--pulsed flame photometric detection

An analytical method devoted to organotin compounds (OTC) determination in brandy and wine was developed. It is based on solid-phase microextraction (SPME) of ethylated organotins. The following operating factors were examined: SPME mode/nature of fibre coating, sample volume/dilution, and sampling time. The optimisation work led to dilute the sample in an aqueous buffer (1/11, v/v ratio) in order to satisfactorily decrease the matrix effects due to competitive sorption of non-OTC species onto/into fibre coating. The optimised operating conditions consist of polydimethylsiloxane (PDMS) coated fibre used in headspace mode for 30 min. In wines, the limits of detection (LOD) and quantification (LOQ) ranged from 1 to 40 and 3 to 80 ng(Sn)L(-1) respectively, according to the species. The analytical validation was made by evaluating the accuracy of OTC determination in spiked samples with various concentrations over the whole calibration range, i.e. from LOQ to 1000 ng(Sn)L(-1). Recovery was around 80-110% and precision (relative standard deviation, RSD) was between 12% and 25%. Despite the presence of two chromatographic peaks corresponding to sulphur compounds during brandy analysis, the selectivity of the method is adequate. The analysis confirmed the analytical performances and applicability of the method to wine and brandy samples. The obtained results emphasise the contamination of brandy and wine by organotins, the storage in plastic container seeming to be confirmed as the main OTC source.     

Volatile components of vine leaves from two Portuguese grape varieties (Vitis vinifera L.), Touriga Nacional and Tinta Roriz,analysed by solid-phase microextraction

The purpose of this work was to study the volatile composition of vine leaves and vine leaf infusion prepared from vine leaves collected at 30 and 60 days after grape harvest of two Vitis vinifera L. species. Eighteen volatile compounds were identified by gas chromatography–mass spectrometry in vine leaves and in vine leaf infusions. It was observed that the volatile compounds present in vine leaves are dependent on the time of harvest, with benzaldehyde being the major volatile present in vine leaves collected at 30 days after harvesting. There are significant differences in the volatile composition of the leaves from the two grape cultivars, especially in the sample collected at 60 days after grape harvest. This is not reflected in the volatile composition of the vine leaf infusion made from this two cultivars, the more important being the harvesting date for the volatile profile of vine leaf infusion than the vine leaves grape cultivar.     

Calibration transfer employing univariate correction and robust regression

This paper proposes a new method for calibration transfer, which was specifically designed to work with isolated variables, rather than the full spectrum or spectral windows. For this purpose, a univariate procedure is initially employed to correct the spectral measurements of the secondary instrument, given a set of transfer samples. A robust regression technique is then used to obtain a model with low sensitivity with respect to the univariate correction residuals. The proposed method is employed in two case studies involving near infrared spectrometric determination of specific mass, research octane number and naphthenes in gasoline, and moisture and oil in corn. In both cases, better calibration transfer results were obtained in comparison with piecewise direct standardization (PDS). The proposed method should be of a particular value for use with application-targeted instruments that monitor only a small set of spectral variables.     

Evaluation of the cytotoxicity on breast cancer cell of extracts and compounds isolated from Hyptis pectinata (L.) poit

Abstract

Hyptis pectinata is a herb popularly used in Brazil for the treatment of inflammations, pain, bacterial infections and cancer. In the present study, inflorescences (MPIn), leaves (MPL), branches (MPB), root (MPR) extracts and three compounds isolated from MPIn were assayed against breast tumor cell lines. The structures of the three compounds (pectinolide J, hyptolide and pectinolide E) were determined by means of spectroscopic analysis. Pectinolide J was isolated for the first time. The MPIn, MPL and MPR exhibited specific antiproliferative activity on tumor cell lines when compared to normal cell lines with IC₅₀ of 52.01?±?0.64, 45.91?±?0.02?μg/mL and 82.84?±?0.03?μg/mL, respectively. Although the isolated substances did not present good antiproliferative activity, when the three were associated, a greater biological effect was observed, suggesting a synergistic effect. Hyptolide (5.6?±?0.4?μg/mL) showed IC₅₀ sufficiently low to be considered as a drug prototype.     

Evaluation of porous graphitic carbon stationary phase for simultaneous preconcentration and separation of organic and inorganic selenium species in "clean" water systems

A high performance liquid chromatography procedure, based on porous graphitic carbon stationary phase, was evaluated for simultaneous on-line preconcentration and separation of organic and inorganic selenium species. Detection was achieved by inductively coupled plasma mass spectrometry with collision/reaction cell (ICP-CRC-MS). Different concentrations of formic acid were tested as mobile phase. A 240 mmol L(-1) concentration with pH adjusted to 2.6, allowed the separation of five species, i.e. selenite, selenate, selenomethionine, selenocystine and selenoethionine. On-line preconcentration of these five species was achieved when heptafluorobutyric acid was used as injection medium, inducing an enrichment of solutes at the top of the column which allowed large volumes (up to 1 mL) to be injected. Combining these injection conditions and 80Se monitoring with ICP-CRC-MS, detection limits between 2 and 8 ng (Se)L(-1), depending on the species, were obtained. Because of the extremely low detection limits obtained, the method was successfully applied to mineral waters.     

Coupling and cycloaddition of ynamides: homo- and Negishi coupling of tosylynamides and intramolecular [4+2] cycloaddition of N-(o-ethynyl)phenyl ynamides and arylynamides

N,N′-aryl- and N,N′-alkyl-buta-1,3-diyne-1,4-ditosylamides have been synthesized for the first time, in good to excellent yields, by copper-catalyzed dimerization of the corresponding N-aryl or N-alkyl tosylynamides. Negishi coupling of N-ethynylzinc tosylamides derivatives with (hetero)aryl iodides in the presence of Pd₂dba₃ and triphenylphosphine affords N-aryl and N-alkyl arylynamides in yields of up to 90%. Intramolecular [4+2] cycloaddition reactions of N-ethynylphenyl ynamides and arylynamides allow the synthesis of carbazoles and benzannulated and heteroannulated carbazoles in moderate-to-good yields.     

Flow injection system for hydrolysable tannin determination

A flow injection system was proposed to evaluate the transient product of a colorimetric reaction between hydrolysable tannin and potassium iodate (KIO₃) solution. The system optimization was accomplished by using statistical methods based on experimental design. Flow rate of KIO₃ solution, sample volume, carrier flow rate, and reaction coil were the selected factors for evaluation. On screening step, complete factorial 2⁴ was used and two levels for each selected factor were studied. For the optimization phase, a centered face composite design 2² + star was employed to evaluate sample volume and flow rate of KIO₃ solution, which were the factors identified in the screening phase as having more influence on the absorbance signal. After optimization, the proposed system was compared with batch determination. Some characteristics, such as analytical frequency, reagent consumption and chemical residues generation presented better results by the use of the proposed system if compared with batch method. The system presented good repeatability with standard deviation lower than 3%, for n = 10, linearity (R² = 0.9974) for tannic acid standard, analytical frequency of 15 injections h^− 1 and limit of quantification of 24 mg L^− 1 of tannic acid. Good results were obtained when the proposed system was applied to hydrolysable tannin determination in Stryphnodendron barbatimão, Eucalyptus citriodora and Phyllanthus niruri, samples of plants commonly used in popular medicine.     

Raman microspectroscopic chemical mapping and chemometric classification for the identification of gunshot residue on adhesive tape

A novel approach utilizing automated Raman microspectroscopic mapping for gunshot residue (GSR) detection was investigated. A well-established technique for GSR recovery (tape lifting) was utilized for GSR particle collection. Uncontaminated samples of the substrate (tape), organic GSR (OGSR), and inorganic GSR (IGSR) particles were characterized to generate three respective Raman spectroscopic training sets. Automated Raman mapping was used to rapidly collect spectra over areas of the tape substrate populated with GSR particles. Raman spectra collected from the maps were classified against the training sets via partial least squares discriminant analysis (PLS-DA) to determine if GSR was present. We report the application of Raman chemical mapping as a proof of concept for the positive detection of GSR particles of varying morphologies. The estimated size of GSR particles, which could be readily detected by this method, is about 3.4 μm. The efficiency of the classification was quantitated with rates of true positives and negatives. Validation studies scrutinizing the practicality of this approach as a viable tool for potential forensics investigations are currently in progress.