H-point standard addition method applied to solid-state stripping voltammetry: quantitation of lead and tin in archaeological glazes

A solid-state electrochemical application of the H-point standard addition method to the quantification of two depositable metals A and B, which produce strongly overlapped stripping peaks, is described. The method is based on the mechanical transference of mixtures of the solid sample plus a selected compound, of a reference depositable metal R, and of known amounts of a reference material containing A or B, to paraffin-impregnated graphite electrodes. After a reductive deposition step, voltammograms recorded for those modified electrodes immersed into a suitable electrolyte produce stripping peaks for the oxidation of all of the metals deposited. Measurement of the currents at selected potentials in overlapping peaks corresponding to the stripping of A and B permits the quantitation of these metals in the solid sample, while avoiding matrix effects. The method was applied to the simultaneous determination of Pb and Sn in archaeological glazes using PbCO₃ and SnO₂ as standards and ZnO as a reference material.      

Headspace mass spectrometry methodology: application to oil spill identification in soils

In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment, the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach for oil spill identification in soils. Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for vertisol)     

Critical evaluation of sample pretreatment techniques

Sample preparation before chromatographic separation is the most time-consuming and error-prone part of the analytical procedure. Therefore, selecting and optimizing an appropriate sample preparation scheme is a key factor in the final success of the analysis, and the judicious choice of an appropriate procedure greatly influences the reliability and accuracy of a given analysis. The main objective of this review is to critically evaluate the applicability, disadvantages, and advantages of various sample preparation techniques. Particular emphasis is placed on extraction techniques suitable for both liquid and solid samples. Figure Miniaturised extraction techniques allow sensitive analysis of also small sample volumes.     

Study of the dynamics of surface molecules by time-resolved sum-frequency generation spectroscopy

Sum-frequency generation (SFG) is a nonlinear laser-spectroscopy technique suitable for analysis of adsorbed molecules. The sub-monolayer sensitivity of SFG spectroscopy enables vibrational spectra to be obtained with high specificity for a variety of molecules on a range of surfaces, including metals, oxides, and semiconductors. The use of ultra-short laser pulses on time-scales of picoseconds also makes time-resolved measurements possible; this can reveal ultrafast transient changes in molecular arrangements. This article reviews recent time-resolved SFG spectroscopy studies revealing site-hopping of adsorbed CO on metal surfaces and the dynamics of energy relaxation at water/metal interfaces. Time-resolved sum frequency generation spectroscopy at surfaces with non-resonant laser pulse irradiation     

Determination of the titanium content of human transferrin by inductively-coupled plasma-atomic-emission spectroscopy

We report a simple method that combines dialysis, as a purification method, with the multielement capability of ICP to determine the titanium-to-transferrin mole ratio at physiological pH, under buffer conditions. The method, by means of which titanium and transferrin are determined simultaneously, enabled us to assess the binding capacities of different titanocene complexes. Figure Titanocene dichloride     

SPME in environmental analysis

Recent advances in the use of solid-phase microextraction (SPME) in environmental analysis, including fiber coatings, derivatization techniques, and in-tube SPME, are reviewed in this article. Several calibration methods for SPME, including traditional calibration methods, the equilibrium extraction method, the exhaustive extraction method, and several diffusion-based calibration methods, are presented. Recent developed SPME devices for on-site sampling and several applications of SPME in environmental analysis are also introduced.      

Application of anodized aluminum in fluorescence detection of biological species

Thin nanoporous alumina obtained by anodization of aluminum films offers promising advantages for application in fluorescence-based biological sensors including convenient preparation, increased density of binding sites, and improved collection efficiency of fluorescence. These advantages are illustrated in the detection of streptavidin using biotin covalently bound to the surface of alumina nanopores. Fluorescence intensity enhancement as high as 7 times is observed in nanopores in comparison to flat glass surface.      

Arsine and selenium hydride trapping in a novel quartz device for atomic-absorption spectrometry

A novel quartz device has been designed to trap arsine and selenium hydride and subsequently to volatilize the collected analyte and atomize it for atomic-absorption spectrometric detection. The device is actually the multiple microflame quartz-tube atomizer (multiatomizer) with inlet arm modified to serve as the trap and to accommodate the oxygen-delivery capillary used to combust hydrogen during the trapping step. The effect of relevant experimental conditions (trap temperature during trapping and hydrogen flow rate and trap temperature during volatilization) on collection and volatilization efficiency was investigated. Under the optimum conditions collection and volatilization efficiency for arsenic and selenium were 50 and 70%, respectively.      

Analysis of biosensors by chemically specific optical techniques. Chemiluminescence-imaging and infrared spectroscopic mapping ellipsometry

The standard methods currently used to read out microarrays are fluorescent and chemiluminesent imaging techniques. These methods require labeling of a component with a marker and, usually, only the concentration of the marker molecule is detected. A label-free imaging method that also enables quantitative spectroscopic analysis of the composition and component interaction would be of great advantage. In this article it is shown for the first time that IR mapping ellipsometry enables label-free imaging of a biochip before and after incubation with peptide solution. The measurements prove that IR ellipsometry is a sensitive tool for laterally resolved identification of the different materials and determination of the composition of a biochip. The lateral resolution required was achieved by using radiation from an infrared synchrotron beamline.      

Bienzyme sensors based on novel polymethylferrocenyl dendrimers

Amperometric bienzyme electrodes with horseradish peroxidase (HRP) and glucose oxidase (GOx) co-immobilized on polymethylferrocenyl dendrimers deposited onto platinum electrodes have been used for determination of the hydrogen peroxide produced by the oxidase during the enzymatic reaction. The redox dendrimers consist of flexible poly(propylenimine) dendrimer cores functionalised with octamethylferrocenyl units. The effects of dendrimer generation, the thickness of the dendrimer layer, substrate concentration, interferences, and reproducibility on the response of the sensors were investigated. The new bienzyme biosensors respond to substrate at work potential values between 200 and 50 mV (vs. SCE), have good sensitivity, and are resistant to interferences. Figure     

Noninvasive methods for the investigation of ancient Chinese jades: an integrated analytical approach

This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples, encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions, as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western and Eastern hemispheres.      

Recent advances in capillary electrophoretic analysis of individual cells

Because variability exists within populations of cells, single-cell analysis has become increasingly important for probing complex cellular environments. Capillary electrophoresis (CE) is an excellent technique for identifying and quantifying the contents of single cells owing to its small volume requirements and fast, efficient separations with highly sensitive detection. Recent progress in both whole-cell and subcellular sampling has allowed researchers to study cellular function in the areas of neuroscience, oncology, enzymology, immunology, and gene expression.      

Fluorescence determination of metoprolol in human plasma by trilinear decomposition-based calibration techniques

In this study a new spectrofluorimetric method for the direct determination of metoprolol in human plasma is presented and discussed. It is based on the use of fluorescence excitation–emission matrices (EEMs) and second-order calibration performed with parallel factor analysis (PARAFAC) or alternating trilinear decomposition (ATLD). This methodology enables accurate and reliable discrimination of the analyte signal, even in the presence of unknown and uncalibrated fluorescent component(s), which is often referred to as the second-order advantage. No separation or sample pretreatment steps were required. Satisfactory results were obtained. Metoprolol recoveries in plasma were determined as 87±2% and 90±4% with PARAFAC and ATLD, respectively. All RSD values of intra- and interday assays were below 5%. Figure A three-dimensional plot of EEMs for a plasma sample and metoprolol solution     

Fluoroquinolones in soil—risks and challenges

Fluoroquinolones (FQs) are among the most important antibacterial agents used in human and veterinary medicine. Because of the growing practice of adding manure and sewage sludge to agricultural fields these drugs end up in soils, where they can accumulate and have adverse effects on organisms. This paper presents an overview of recent developments in the determination of FQs in solid environmental matrices and describes the risks and challenges (persistence, fate, effects, and remediation) which result from their presence in soil. Figure Pathways into the environment for FQs     

Impedimetric genosensors for the detection of DNA hybridization

Impedance spectroscopy is proposed as the transduction principle for detecting the hybridization of DNA complementary strands. In our experiments, different DNA oligonucleotides were used as model gene substances. The gene probe is first immobilized on a graphite-epoxy composite working electrode based genosensor. Detection principle is based on changes of impedance spectra of a redox marker, the ferro/ferricyanide couple, after hybridization with target DNA. Resistance offered to the electrochemical reaction serves as the working signal, allowing for an unlabelled gene assay.      

Modì: a new mobile instrument for in situ double-pulse LIBS analysis

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ elemental analysis. A new mobile instrument for LIBS analysis, developed in a collaboration between Marwan Technology s.r.l. and the Applied Laser Spectroscopy Laboratory in Pisa, is presented, and some applications of it and results from it are outlined. The innovative experimental set-up, based on the use of two suitably retarded laser pulses and a standardless analysis procedure, which overcomes problems related to matrix effects, greatly improves the potential of this technique for accurate quantitative analysis.      

Spatially resolved element analysis of historical violin varnishes by use of μPIXE

External μPIXE has been used for characterisation of small samples of varnish from historical violins, and pieces of varnished wood from historical and modern stringed instruments. To obtain spatially resolved information about the distribution of elements across the varnish layers single-spot analysis, line-scans, and area-mapping were performed. Local resolution of approximately 20 μm was obtained from the 3 MeV, 1 nA proton micro-probe. Results from simultaneous multi-element determination of Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Rb, Sr, Ag, Cd, Sn, Ba, and Pb in historical varnishes are presented. Semi-quantitative evaluation of line-scans recorded on diverse historical varnishes is reported. The applied method is discussed in detail and the results obtained are critically reviewed and compared with those in the literature.      

Current role of liquid chromatography–mass spectrometry in clinical and forensic toxicology

This paper reviews multi-analyte single-stage and tandem liquid chromatography–mass spectrometry (LC-MS) procedures using different mass analyzers (quadrupole, ion trap, time-of-flight) for screening, identification, and/or quantification of drugs, poisons, and/or their metabolites in blood, plasma, serum, or urine published after 2004. Basic information about the biosample assayed, work-up, LC column, mobile phase, ionization type, mass spectral detection mode, and validation data of each procedure is summarized in tables. The following analytes are covered: drugs of abuse, analgesics, opioids, sedative-hypnotics, benzodiazepines, antidepressants including selective-serotonin reuptake inhibitors (SSRIs), herbal phenalkylamines (ephedrines), oral antidiabetics, antiarrhythmics and other cardiovascular drugs, antiretroviral drugs, toxic alkaloids, quaternary ammonium drugs and herbicides, and dialkylphosphate pesticides. The pros and cons of the reviewed procedures are critically discussed, particularly, the need for studies on matrix effects, selectivity, analyte stability, and the use of stable-isotope labeled internal standards instead of unlabeled therapeutic drugs. In conclusion, LC-MS will probably become a gold standard for detection of very low concentrations particularly in alternative matrices and for quantification in clinical and forensic toxicology. However, some drawbacks still need to be addressed and finally overcome. Photos of LC-MS apparatus and typical samples suitable for toxicological analysis