Electrochemical Detection of Gunshot Residue for Forensic Analysis: A Review

Current demands for detection of Gunshot Residue (GSR) require a reliable and rapid decentralized detection system with high sensitivity and specificity. This article reviews the use of electrochemical devices for GSR detection over the last 35 years and highlights recent advances associated with the demands of GSR field detection such as portability, speed, cost and power. Anodic stripping voltammetry (ASV) has been widely implemented for the detection of the metallic components of GSR at a variety of working electrodes. Efforts toward the detection of the organic components of GSR have also been reported using cyclic‐ and square‐wave voltammetry. The simultaneous detection of both organic and inorganic GSR constituents has recently been examined to increase the overall information content in a single voltammetric scan. As well as this, exploitation of screen‐printing fabrication allows replacement of conventional electrochemical cells with easy‐to‐use sensor strips Sampling methods for electrochemical GSR analysis are also advancing from acid washes or swabs to simpler abrasive methods which integrate sampling and analysis obviating the need for intermediate processing steps. The latest direction of electrochemical detection of GSR involves chemometric treatment to evaluate data allowing for more objective conclusions and increasing the automation of the system. These advances indicate great promise for investigating firearm‐related crimes, and bring significant changes to the detection of GSR making electroanalysis a powerful tool for decentralized forensic analysis.     

Simultaneous determination of elemental content in water samples by total reflection X-ray fluorescence and atomic absorption spectrometry

An analytical exercise between two laboratories was performed in order to compare the elemental composition of a water sample. The metal concentration of Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the water sample was analyzed by Total Reflection X-Ray Fluorescence and Atomic Absorption Spectrometry. The analysis by Total Reflection X-Ray Spectrometry was realized by an Ital Structures TX-2000 and the analysis by Atomic Absorption Spectrometry was made by a Perkin Elmer Spectrophotometer Model 3110. Results show a good agreement in the metal concentrations obtained by both techniques. The variation coefficient between the results with both techniques was less than 14%. Therefore, it is possible to conclude that both techniques are reliable and adequate for the determination of these elements in environmental water samples.     

Determination of trace level of selenium and mercury in photographic emulsions by atomic spectroscopy techniques

Trace level of selenium and mercury in photographic emulsion are used to improve photographic properties. The presence of silver halide in photographic emulsion does not allow the application of the most common analytical methods such as Hydride Generation Atomic Absorption Spectrometry (HG-AAS) and cold vapour Atomic Absorption Spectrometry (CV-AAS). Besides, silver removal was not quantitative, leading to a significant loss of the analytes and low reproducibility. The present work suggest the use of inductively coupled plasma Atomic Emission Spectrometry (ICP-AES) equipped with Ultrasonic Nebulizer (USN) for direct aqueous samples analysis at microgram l-1 level (d.l. 5.1 ppb for Hg and 6.1 ppb for Se).     

Trends in Preconcentration Procedures for Metal Determination Using Atomic Spectrometry Techniques

 Methods for metal preconcentration are often described in the literature. However, purposes are often different, depending on whether the methods are applied in environmental, clinical or technological fields. The respective method needs to be efficient, give high sensitivity, and ideally also is selective which is useful when used in combination with atomic spectroscopy. This review presents the actual tendencies in metal preconcentration using techniques such as Flame Atomic Absorption Spectrometry (FAAS), Electrothermal Atomic Absorption Spectrometry (ETAAS), Hydride Generation Atomic Absorption Spectrometry (HGAAS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Procedures based on related to electrochemical, coprecipitation/precipitation, liquid–liquid and solid–liquid extraction and atom trapping mechanisms are presented. Correspondence: Department of Analytical Chemistry, Universidade Estadual de Campinas – UNICAMP, P.O. Box 6154, 13083-970 Campinas, Brazil. e-mail: zezzi@iqm.unicamp.br Received December 20, 2001; accepted October 11, 2002     

Inorganic constituents in aerosols, cloud water and precipitation collected at the high alpine measurement station Sonnblick: Sampling, analysis and exemplary results

Background measurements at the high alpine station of the Sonnblick (altitude 3106 m) are reported. For a period of 13 months samples have been collected during 4 campaigns of 1–2 weeks duration each and analysed for their ionic and elemental composition, pH and conductivity. These samples were aerosols collected with filters, cloud water and precipitation. The samples were mainly analysed with ion chromatography (IC) and atomic absorption spectrometry (AAS). Analysis proved to be difficult due to the low amounts of aerosols collected and the low concentrations of components in cloud water and wet precipitation. Also major problems arose in sampling due to the extreme climatic conditions. The analytical techniques, particularly those for sampling the materials, are critically evaluated and results on pollutant levels, their variation with time and the distribution of the components between the gaseous and liquid phases are presented.Abbreviations ET-AAS Electrothermal Atomic Absorption Spectrometry - F-AAS Flame Atomic Absorption Spectrometry - FIA Flow Injection Analysis - IC Ion Chromatography Dedicated to Prof. Dr. Dieter Klockow on the occasion of his 60th birthday     

Chemometric evaluation of different experimental conditions on wheat (Triticum aestivum L.) development using liquid chromatography mass spectrometry (LC–MS) profiles of benzoxazinone derivatives

Different chemometric techniques have been used to evaluate the effect of distinct experimental conditions and factors on Triticum aestivum L. plant development. The study was conducted using three wheat varieties, Astron, Ritmo and Stakado. These varieties were grown under organic and conventional cultivation systems. Samples were collected at five growth stages. Shoots and roots of each plant at these stages were analysed. Three replicates of each analysed sample were performed to improve representativeness and to allow for the evaluation of natural variability and interaction effects. All samples were analysed using Liquid Chromatography Mass–Spectrometry (LC–MS), and the Total Ion Current (TIC) profiles of benzoxazinone derivatives obtained for each sample were investigated. Qualitative and quantitative assessments of these TIC profiles and of their changes in the analysed samples were carried out using different chemometric techniques. Estimation of main effects, and of their possible interaction, was performed by means of Analysis of Variance combined to Principal Component Analysis (ANOVA–PCA) and of Analysis of Variance combined to Simultaneous Component Analysis (ASCA).     

Application of MATLAB package for the automation of the chemometric processing of spectrometric signals in the analysis of complex mixtures

We describe three types of automatic software for the chemometric processing of spectrometric data. The software was developed in the MATLAB working environment and includes data import, mathematical preprocessing, chemometric analysis, and generation of a report file. The software is designed to solve problems regarding identification of some components of multicomponent mixtures, determination of compounds with overlapping signals, and differentiation of samples by their spectral responses. To test the software, we present examples of spectrometric analyses of coffee, fruit juices, and alcoholic beverages using chemometric methods of independent component analysis (ICA) and partial least squares–discriminant analysis (PLS–DA). In particular, we simulated electronic absorption spectra for the identification of three artificial colors (E110, E102, and E122) in alcoholic beverages, NMR spectra for the simultaneous determination of five components (acetic acid, γ-aminobutyric acid, arginine, acetaldehyde, and proline) in orange juice without using reference standards, and NMR spectra of coffee samples to determine its varietal authenticity (Arabica or Robusta). The duration of automatic chemometric processing did not exceed 1 min per sample. The developed software can be optimized for other matrices and/or brands of spectrometers.     

Classical analysis including trace-matrix separation versus solid state mass spectrometry: A comparative study for the analysis of high purity Mo,W and Cr

The applicability of GDMS, SIMS, SSMS, NAA and TMS with AAS, ICP-OES and ICP-MS end determination for routine bulk ultratrace analysis of high purity refractory metals was investigated. Due to the heterogeneous distribution of trace elements in the sub-ppm range, sample consumption and analysis time have a tremendous influence on quantification with procedures of low sample consumption. As an example, GDMS, which is commonly used for ultrapure material certification by most of the manufacturers in Europe and the USA, exhibits discrepancies by more than one order of magnitude for repetitive analyses of a series of trace components in the same sample. Furthermore, results of different laboratories using the same instrument are frequently not comparable. Due to easy standardization and large sample consumption TMS procedures combined with FAAS, GFAAS, ICP-AES and ICP-MS as methods of end determination exhibit better precision and accuracy than GDMS and SIMS. Detection limits are comparably low or even better in case of ICP-MS end determination. TMS procedures are less expensive and less time consuming than highly sophisticated analytical techniques like GDMS, SIMS or NAA. Additionally, they can be easily applied by experienced personnel in a well equipped industrial analytical laboratory.List of Acronyms Used AAS Atomic Absorption Spectrometry - FAAS Flame Atomic Absorption Spectrometry - GDMB Gesellschaft Deutscher Metallhütten- und Bergleute - GDMS Glow Discharge Mass Spectrometry - GFAAS Graphite Furnace Atomic Absorption Spectrometry - ICP-AES Inductively Coupled Plasma Atomic Emission Spectrometry - ICP-MS Inductively Coupled Plasma Mass Spectrometry - IDMS Isotope Dilution Mass Spectrometry - NAA Neutron Activation Analysis - SIMS Secondary Ion Mass Spectrometry - SSMS Spark Source Mass Spectrometry - TMS Trace-Matrix Separation - VLSI Very Large Scale Integration - XRFS X-Ray fluorescence Spectroscopy Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Recent developments in methods of chemical analysis in investigations of firearm-related events

A review of recent (approximately the last ten years) developments in the methods used for chemical analysis in investigations of firearm-related events is provided. This review discusses:examination of gunshot (primer) residues (GSR) and gunpowder (propellant) residues on suspects and their clothing;detection of firearm imprints on the hands of suspects;identification of the bullet entry holes and estimation of shooting distance;linking weapons and/or fired ammunition to the gunshot entries, and estimation of the time since discharge.     

Trends in surface and interface analysis

Summary The rapid progress in high technology constantly poses new challenges for Analytical Chemistry and prompts the development of new techniques and procedures. The influence is particularly strong in surface and interface analysis, which is developing at a rapid pace. This paper discusses some of the frontier areas like high-resolution depth-distribution analysis of trace elements, quantitative depth distribution analysis of ultra thin-layer systems, quantitative trace element analysis in monolayers, 3-dimensional stereometric analysis, molecular analysis, in-situ atomic resolution analysis of surfaces (chemical nanoscopy). Methodological approaches are discussed as well as results obtained mainly with solid state mass spectrometry and atomic force microscopy.Abbreviations and acronyms AES Auger Electron Spectrometry - AEM Analytical Electron Microscopy - AFM Atomic Force Microscopy - BSE Back Scattered Electrons - EPMA Electron Probe Micro Analysis - LRI-SNMS Laser Resonance Ionization Sputtered Neutrals Mass Spectrometry - SE Secondary Electrons - SEM Scanning Electron Microscopy - SIMS Secondary Ion Mass Spectrometry - STM Scanning Tunneling Microscopy - TEM Transmission Electron Microscopy - TOF-MS Time-of-Flight Mass Spectrometer - TXRF Total Reflection X-Ray Spectrometry - XPS X-Ray Photoelectron Spectroscopy Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

A comparison between ICP-MS and AFS detection for arsenic speciation in environmental samples

Performances of two atomic detectors, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Atomic Fluorescence Spectrometry (AFS) have been compared for arsenic speciation in environmental samples. Instrumental couplings, based on the use of high performance liquid chromatography (HPLC), hydride generation (HG), and the two atomic detectors were used for the speciation of arsenite, arsenate, dimethylarsinic acid and monomethylarsonic acid. Optionally, arsenobetaine was also determined using on-line ultraviolet (UV) photooxidation. The detection limits ranging from 0.1 to 0.3 mug l(-1) (as As) and the precision >10% RSD obtained with HPLC-(UV)-HG-AFS were comparable with those obtained with HPLC-(UV)-HG-ICP-MS. Both instrumental coupling were applied to the NRCC-TORT-1 and several environmental samples, such as seawater, freshwater, sediments, bivalves and bird eggs, taken from two areas with different degrees of pollution. No influence of the sample matrix was observed on the results using external calibration and standard additions methods, for both coupled techniques.     

Electrochemical Analysis of Mercury Using a Kryptofix Carbon‐Paste Electrode

Abstract

Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV‐AAS), X‐Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES), or Inductively Coupled Plasma Mass Spectrometry (ICP‐MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon‐paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l.     

A field aluminium speciation method to study the aluminium hazard in water

The toxicity of aluminium is governed by its bioavailability. Therefore, the speciation of aluminium in drinking water becomes of prime importance to understand its fate and the population exposure, and to develop guidelines for the concentration levels. At Health Canada, a field speciation method has been developed to perform on-site speciation followed by measurement of Al in the laboratory. The following species are generated: 1) total recoverable; 2) total acid-leacheable; 3) total dissolved; 4) dissolved extracted; and 5) dissolved non extracted. The field extractions are performed by percolation through chelation columns, which are later processed in the laboratory. Aluminium determinations can then be performed by numerous methods, such as by Inductively Coupled Plasma Mass Spectrometry (ICPMS), Graphite Furnace Atomic Absorption Spectrometry (GFAAS) or Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Examples of results for raw or treated/ distributed surface waters, as well as for groundwaters, are used to illustrate the validity of the method, and the importance of considering aluminium speciation in characterizing the aluminium hazard in water.     

Chemometric tools for identification of volatile aroma-active compounds in oregano

One of the purposes of chemical analysis is to find quick and efficient methods to answer complex analytical questions in the life sciences. New analytical methods, in particular, produce a flood of data which are often very badly arranged. An effective way to overcome this problem is to apply chemometric methods. As part of the following investigations, three brands of oregano were analysed to identify their volatile aroma-active compounds. Two techniques were applied—gas chromatograpy–olfactometry (GC–O) and human sensory evaluation. Aroma-impact compounds could be identified in the main brands of oregano with the aid of chemometric methods (principal-components analysis, hierarchical cluster analysis, linear discriminant analysis, partial least-squares regression). Therefore, it is possible to reduce the analysis of sensory and olfactometry to relevant attributes. This makes classifying new species easier, much faster, and less expensive and is the premise for quick and more economic identification of new potential genotypes for oregano plant breeding. A comprehensive list of oregano key odourants, determined by GC–O and human sensory evaluation using different methods of supervised and unsupervised pattern cognition, has not previously been published.      

A metabonomic investigation of hepatotoxicity using diffusion-edited 1H NMR spectroscopy of blood serum

It has been shown extensively, that chemometric investigations of 1H NMR spectra of rat urine taken from animals dosed with model toxins produce characteristic patterns of metabolic responses and that this permits the identification of biomarkers of toxic response and regeneration. To date, metabonomic methods have been mainly optimised for urine which contains mainly low molecular weight moieties, and thus a conventional 1-dimensional 1H NMR pulse sequence is an efficient means of obtaining information-rich data. In the case of biofluids such as blood plasma or serum, which contain a wide range of macromolecules the resonances of which can overlap with peaks from small molecule metabolites, the information giving rise to sample classification can be concealed in a conventional NMR spectrum andthis presents a different analytical challenge in terms of chemometric analysis of spectral profiles. Here, the use of other types of NMR data have been investigated and it is shown that by using spectra where the peak intensities are edited according to their molecular diffusion coefficients, it is possible to improve differentiation of control animals and those treated with the model hepatotoxin, alpha-naphthylisothiocyanate (ANIT). By using diffusion-edited spectroscopy, plasma lipid moieties are less attenuated than those from small endogenous metabolites and thus the toxin-induced changes to the lipoprotein profiles are more easily detectable.     

Determination of Copper,Cadmium, Zinc And Lead In ArgeŞ River In Romania During Four Seasons By Inductively Coupled Plasma Atomic Emission Spectrometry And Anodic Stripping Voltammetry

ABSTRACT

The paper represents a continued study of selected heavy metals concentration in the Arge? River, the fifth river in length from Romania.

For the determination of metal ion concentration in Arge? river was used Atomic Absorption Spectrometry for sodium, potassium and magnesium; Direct Coupled Plasma Atomic Emission Spectrometry for calcium; Inductively Coupled Plasma Atomic Emission Spectrometry for copper, cadmium, zinc, aluminium, lead, titanium, zirconium, chromium, molybdenum, manganese, iron and nickel.

Copper, cadmium, zinc and lead concentration were determined by ICP–AES and ASV and results were reliable.

By comparison of the results a good agreement between these two techniques is observed.     

Determination of Thallium in Antarctic Snow by Means of Laser Induced Atomic Fluorescence and High Resolution Inductively Coupled Plasma Mass Spectrometry

Abstract

Measurements of thallium levels in Antarctic snow samples collected in an area surrounding the Italian Station at Terra Nova Bay in different campaigns have been performed without preconcentration by means of Laser Induced Atomic Fluorescence Spectroscopy (LIAF) as well as by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR ICP-MS).

The data obtained by both methods compare favourably and are of the order of tenths of pg/g. The data is discussed taking into account the effect of the marine aerosol and the crustal contribution to the thallium content in samples.     

Mapping of lead,magnesium and copper accumulation in plant tissues by laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass spectrometry

Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were utilized for mapping the accumulation of Pb, Mg and Cu with a resolution up to 200 μm in a up to cm × cm area of sunflower (Helianthus annuus L.) leaves. The results obtained by LIBS and LA-ICP-MS are compared with the outcomes from Atomic Absorption Spectrometry (AAS) and Thin-Layer Chromatography (TLC). It is shown that laser-ablation based analytical methods can substitute or supplement these techniques mainly in the cases when a fast multi-elemental mapping of a large sample area is needed.     

Ultrasound-assisted emulsification of cosmetic samples prior to elemental analysis by different atomic spectrometric techniques

In this work, ultrasound-assisted emulsification with a probe system is proposed as a rapid and simple sample treatment for atomic spectrometric determinations (Electrothermal Atomic Absorption Spectrometry, Inductively Coupled Plasma Optical Emission Spectrometry, Flame Atomic Absorption Spectrometry and Cold Vapour Atomic Absorption Spectrometry) of trace elements (As, Cd, Cr, Cu, Hg, Mg, Mn, Ni, Sr and Zn) in cosmetic samples such as shampoos, gel (hair gel), crèmes (body milk, hair conditioner) and oil (body oil). The type of dispersion medium, the sample mass-to-dispersion medium volume ratio, as well as the parameters related to the ultrasound-assisted emulsification (sonication amplitude and treatment time) were exhaustively studied. Only 1 min of ultrasonic shaking and a dispersion medium containing 0.5% (w/v) of SDS + 3% (v/v) of HNO₃ or HCl allows obtaining a stable emulsion at least for 3 months. Thermal programs, nebulization of emulsions, speed of pumps and concentration of reagents used in cold vapour generation were optimized. Calibration using aqueous standards was feasible in all cases. Calibration by the standard addition method and recovery studies was also applied for validation. Microwave-assisted digestion and Inductively Coupled Plasma Mass Spectrometry were used for comparison purposes. Relative standard deviations from analysis of five independent emulsions were less than 9% in all cases.