Solvent selection for fatty acid residue analysis of archeologicial artifacts

Residue analysis has rapidly become one of the most useful techniques for determining an artifact function and revealing insight into paleodiets. The success of analytical residue analysis often lies with the first preparatory step, where the residue is extracted from the object. Detection of a residue requires effective solvation of the material, and there is a large range of potential solvents. One purpose of this study is to determine the efficiency of various solvents for the extraction of fatty acids from charcoal, a material that is ubiquitous, easily identified, remarkably stable in the archaeological record but, most importantly for this research, retains fats extremely well. This investigation examines the removal efficiency of model fatty acids from carbonized wood samples. The strong affinity of lipids to charcoal makes carbonized wood ideal for retaining them, but also makes their extraction extremely challenging and thus an ideal benchmark for solvent extraction characterization. Several solvents (benzene, chloroform, hexane, methanol and water) are used to determine the quantitative extraction efficiency of tripalmitin. While benzene and chloroform perform best for some wood types, neither solvent is better for all carbonized wood. Correlations between the chemical properties of the solvents and the effectiveness of the extraction provide guidance for solvents. Findings indicate solvent characteristics including dipole moment, dielectric constant, hydrogen bonding, and molecular weight all play an important role in extraction of fat from a charcoal matrix. Results presented should provide guidelines to allow for more effective residue extration and more accurate lipid analysis.

Preconcentration of nickel in waters by vortex assisted dispersive liquid-liquid microextraction

The present work describes the attempt for the preconcentration of nickel ions by using vortex assisted dispersive liquid-liquid microextraction from aqueous samples. In this method, a small amount of chloroform is rapidly injected by syringe into the water sample containing nickel ions complexed by diethyldithiocarbamate (DDTC).This forms a cloudy solution. The cloudy state is the result of chloroform fine droplets formation, which are dispersed in bulk aqueous sample. Therefore, Ni-DDTC complex is extracted into the fine chloroform droplets and vortex agitation takes place during six minutes. After optimization of experimental variables and determination of analytical characteristics, the method is evaluated for application in real samples. HPLC is used as separation and detection system.

Fast and accurate methodology for direct mercury determination in hair and nails

A solvent-free, easy, fast and waste-free methodology was developed for the determination of total mercury levels in hair and nails. Samples were taken from several volunteers and directly analysed, with levels of mercury in the range between 0.5 and 8 ng/mg. The influence of quantity of hair, as well as the addition of small amount of solvent and the necessity of previous treatment were studied. Also, a history of mercury exposure was provided by the distance of the hair from the scalp of each volunteer, the results of which were correlated with fish consumption. Furthermore, a short study of mercury in nails was carried out and correlated to the results from hair mercury levels. A small quantity of 5 mg of hair with an addition of 50 μL of water to the sample without previous treatment was adequate to get a representative result in less than 10 minutes. The accuracy of the proposed method was confirmed by analysing certified reference materials including Coal Fly Ash-NIST SRM 1633b, Fucus-IAEA 140 and three unpolished Rice Flour NIES-10. The observed results were found to be in good agreement with the certified values.

Ultrasound-assisted Matrix Solid Phase Dispersion for the HPLC-DAD analysis of amphenicols in shrimps

Ultrasound-assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of three amphenicol antibiotics, chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FFC) from shrimp. The target antibiotics were separated on a LiChroCART-LiChrospher® 100 RP-18 (5 μm, 250 × 4 mm) analytical column in less than 9 min, with isocratic elution using a mixture of 70% ammonium acetate (0.05 M) and 30% acetonitrile (v/v). Matrix Solid Phase Dispersion protocol was optimized in terms of extraction sorbent and elution solvent. Two polymer based (Oasis and Nexus) sorbents and one silica based (Lichrolut C18) were compared and different elution solvents such as methanol, acetone, acetonitrile and isopropanol were evaluated based on the achieved recovery rates as well as on the cleanup efficiency. The extraction procedure was performed with and without sonication to evaluate the impact of ultrasounds. TAP and FFC were monitored at 234 nm and CAP at 280 nm by a photodiode array detector. The method was validated according to the European Union Decision 2002/657/EC in terms of linearity, selectivity, stability, accuracy, precision and sensitivity. Detection capability values (CCb) were 64.6 μg/kg for TAP and 1046.8 μg/kg for FFC and 63.8 μg/ kg for CAP.

The isolation and characterisation of the synthetic cannabinoid AM-2201 from commercial products using purification by HPLC-DAD

A total of six products containing legal highs were purchased via the internet from the UK- based retailers and screened for the presence of synthetic cannabinoids using a fast GC-MS method and identified, in the absence of reference materials, by comparing the mass spectra with the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) mass spectral library. Four synthetic cannabinoids were detected: RCS-4, CP-47, 497, UR-144 and AM-2201. The active ingredient (1-(5-fluoropentyl)-3-(1-naphthoyl) indole), with the street name AM-2201, detected in the product named Doob was isolated and purified from the methanolic extract of the product using preparative HPLC with analytical column (column overloading method). The structure of the substance was confirmed using NMR. This approach used common analytical equipment found in forensic and other analytical laboratories (except for the NMR), therefore can be useful for the identification of unknown psychoactive substances in drugs of abuse.

Non-chromatographic methods focused on speciation of arsenic and selenium in food and environmental samples

Speciation is a promising and essential tool in the evaluation of the contamination of metals in food and environmental samples. In this context, information about the species of these elements is important considering that toxic effects are directly related to their chemical forms. The enormous progress in combining separation and detection techniques has enabled the effective chemical speciation. However, a possible source of error in studies of speciation occurs during sample preparation. Appropriate treatment of samples is necessary in order to ensure that interconversion between the species does not occur during the experimental procedure prior to the final analysis. In this review, methods of sample preparation for the determination of arsenic and selenium in food and environmental samples are discussed. We decided to focus on these elements since they account for around 50% of all speciation studies. Procedures including conventional extraction, microwave-assisted extraction and sonolysis are discussed as simple ways to ensure species selectivity. The main purpose of this review is to provide an update on the recent literature concerning the strategies for arsenic and selenium speciation and to critically discuss their advantages and weaknesses compared with the commonly accepted approach of combining non-chromatographic and spectroscopic techniques. The problems focused on involve sampling, sample preparation and storage, as well as changes in ‘species information’ that occur during the use of various separation technologies. These difficulties are described along with recent developments aimed at overcoming these potential issues.

Design of experiment in the development of spme method for the determination of pesticide residues in fruits and vegetables

The various microextraction techniques have been developed in order to reduce sample preparation time, improve sensitivity and selectivity as well as to corroborate the recent advances in the development of highly sensitive and efficient analytical instrumentation. The current trend is aimed at the simplification and miniaturization of extraction steps, which has led to the combination of multi-step extraction and analytical analysis into single uninterrupted step. The method development involves the screening and subsequent optimization of both gas chromatography-mass spectrometry (GC-MS) and solid phase microextraction (SPME) parameters using multivariate experimental design, which has been shown to be efficient and effective with little experimental runs. The use of microextraction has been very effective in the analysis of contaminants in food, water and the environments to ensure they are safe and does not pose any health risk to human.

Solid Phase Extraction and Solid Phase Microextraction in grape and wine volatile compounds analysis

Volatile compounds determine the organoleptic characteristics of grapes and wines. The main grape aroma compounds are monoterpenols and volatile benzene compounds. Aroma precursors, such as glycoside compounds and C

Effect of pre-stain methanol washing on the sensitivity of CBBR-250 staining in SDS-polyacrylamide gels

Coomassie Brilliant Blue R-250 (CBBR-250) is the most frequently used dye stain in protein research. However, relatively poor sensitivity and long application durations are the major limitations of this stain. In the present study, we have investigated the effect of pre-stain methanol washing on the sensitivity of the conventional CBB staining method. Concentrations of methanol ranging from 5 to 30% were prepared in 5% acetic acid. Pre-stain washing of SDS-gels using acetic acid (5%) and methanol were assessed at various timings and temperatures. Our results demonstrate that pre-stain washing by methanol greatly improves the sensitivity of the CBB stain and facilitates the visualization of low molecular weight components present in a complex muscle protein, actomyosin. The outcome of this study also revealed duration of pre-stain washing and temperature as other factors that determine the sensitivity of CBB staining method. Therefore, it is suggested that pre-stain washing with methanol may improve the sensitivity of CBB stain in SDS-PA gels.

Miniaturized sample preparation based on carbon nanostructures

The evolution of analytical methodologies has been driven by the objective to reduce the complexity of sample treatment while increasing the efficiency of the overall analytical process. For this reason, the analytical chemist takes into consideration advances in other scientific areas and systematically evaluates the potential influence that such discoveries might have on its own discipline. This is the present situation with nanostructured materials, which have already been recognized as a revolution in many scientific and technological fields, including analytical chemistry. Carbon nanoparticles have been a cornerstone in the advance of miniaturization of analytical processes. This review article considers the contribution of four reference carbon nanoparticles: nanotubes, graphene, nanohorns/ cones and fullerenes, in the context of miniaturized sample treatment, where their outstanding sorbent properties are by far the most exploited in (micro) solid phase extraction.