Study of carbon nanotubes and functionalized-carbon nanotubes as substrates for flow injection solid phase extraction associated to inductively coupled plasma with ultrasonic nebulization: Application to Cd monitoring in solid environmental samples

A research was performed to evaluate the capabilities of carbon nanotubes (CNTs) and modified CNTs to serve as sorbents for preconcentrating Cd together with on-line ultrasonic nebulization (USN)-inductively coupled plasma optical emission spectrometry (ICPOES). Three different carbon nanotubes sustrates namely, carbon nanotubes (CNTs), oxidized-carbon nanotubes (ox-CNTs) and l-alanine-carbon nanotubes (ala-CNTs) were studied systematically and the main factors influencing the preconcentration and determination of Cd were examined thoroughly. The CNTs evaluated showed dissimilar adsorption behaviors leading to increasing preconcentration factors when used in the proposed on-line solid phase extraction (SPE) system as follows: CNT < ala-CNT < ox-CNT. Aiming to achieve the best analytical performance, ox-CNTs were used as they enable quantitative retention of Cd at pH 7.0 and instantaneous elution of the analyte with 10% HNO₃. Under optimal conditions, the adsorption capacity on ox-CNTs was found to be 130 μmol g^?1 and the detection limit (3σ) achieved was 1.03 μg L^? 1. The precision of the method expressed as the relative standard deviation (RSD) turned to be 3.0%. The flow injection method involving use of ox-CNTs as sorbent and USN-ICPOES for detection was successfully applied to the determination of Cd in different kinds of environmental samples.     

Micro-electrodeposition in the presence of ionic liquid for the preconcentration of trace amounts of Fe,Co, Ni and Zn from aqueous samples

The paper presents the preconcentration of trace elements via electrodeposition onto a (micro)aluminum cathode in the presence of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] as a supporting electrolyte. The advantages of the proposed method include very simple instrumentation for the preconcentration of trace elements and low-cost reagents. The experiment showed that the use of ionic liquid in the electrodeposition process significantly improves sensitivity, recovery and detection limits for the determination of trace amounts of iron, cobalt, nickel and zinc. The preconcentrated metals were determined using X-ray fluorescence spectrometry. The optimum parameters for electrodeposition such as pH, the volume of the analyzed solution, the voltage and the deposition time were studied. Under the optimized conditions, the detection limits were 5, 2, 3 and 6 μg L^− 1 for iron, cobalt, nickel and zinc, respectively. The precision and recovery of the method were in the range of 3–5.5%, and 92–103%, respectively. The calibration was performed using aqueous standards of Fe(III), Co(II), Ni(II) and Zn(II) in the range 0.01–0.25 mg L^− 1. The method was applied successfully in water analysis.     

Quantitative analysis of single aerosol particles using polycapillary X-ray optics

A laboratory micro X-ray fluorescence spectrometer based on polycapillary X-ray optics (PXRO) was used to carry out the quantitative X-ray fluorescence analysis of single aerosol particles with smaller size than that of focal spot of PXRO. The minimum detection limits measured with the thin-film reference standards were in the range from 13.3 to 0.7 ng cm^? 2 when the operating current and voltage were 70 mA and 35 kV, respectively. In order to reduce the effects of the inhomogeneous distributions of the X-ray intensity in the focal spot of the PXRO on the analysis results, the sensitivities were corrected by using a Gaussian function for the quantitative analysis of single aerosol particles. The accuracy of the analysis of single standard solution drops was on average 25% depending on the element and concentration. The precision of the analysis was better than 5%.     

Wavelength dispersive X-ray fluorescence imaging using a high-sensitivity imaging sensor

A new wavelength-dispersive X-ray fluorescence (WD-XRF) imaging spectrometer equipped with a high-sensitivity imaging sensor was developed in our laboratory. In this instrument, a straight polycapillary optic was applied instead of a Soller slit as well as a 2D imaging X-ray detector instead of X-ray counters, which are used in conventional WD-XRF spectrometers. Therefore, images of elemental distribution were available after a short exposure time. Ni Kα images and Cu Kα images were clearly obtained at corresponding diffraction angles for a short exposure time of 10 s. By optimizing the spectrometer, the time required for imaging is reduced, leading to XRF image movies. It is difficult to distinguish two peaks (Ti Kα (4.508 keV) and Ba Lα (4.465 keV)) due to the poor energy resolution of EDXRS. However, Ti and Ba images could be successfully observed by the WD-XRF imaging spectrometer. The energy resolution of the developed spectrometer was 25 eV at the Ti Kα peak.     

Amperometric ascorbic acid biosensor based on carbon nanoplatelets derived from ground cherry husks

In this work, a novel amperometric biosensor based on carbon nanoplatelets derived from ground cherry (Physalis peruviana) husks (GCHs-CNPTs) is reported for the sensitive and selective detection of ascorbic acid (AA). The structure of the nanoplatelets, the oxygen-containing groups and edge-plane-like defective sites (EPDSs) on the GCHs-CNPTs were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The presence of GCHs-CNPTs with a high density of EPDSs effectively enhances the electron transfer between AA and the glassy carbon electrode (GCE), and thus induces a substantial decrease in the overvoltage for AA oxidation compared with both a bare GCE and a GCE modified with carbon nanotubes (CNTs/GCE). In particular, an amperometric biosensor based on GCHs-CNPTs exhibited a wider linear range (0.01–3.57 mM), higher sensitivity (208.63 μA mM^− 1 cm^− 2), a lower detection limit (1.09 μM, S/N = 3) and better resistance to fouling for AA determination compared to a CNTs/GCE. The great potential of the GCHs-CNPTs/GCE for practical and reliable AA analysis was demonstrated by the successful determination of AA in samples taken from a medical injection dose and a soft drink.     

Advances with tungsten coil atomizers: Continuum source atomic absorption and emission spectrometry

Two new tungsten coil spectrometers are described: a continuum source tungsten coil atomic absorption spectrometer and a tungsten coil atomic emission spectrometer. Both devices use a 150 W tungsten coil extracted from a slide projector bulb. The power is provided by a computer-controlled, solid state, constant current 0–10 A supply. The heart of the optical system is a high-resolution spectrometer with a multi-channel detector. The continuum source system employs xenon or deuterium lamps, and is capable of multi-element analyses of complex samples like engine oil, urine, and polluted water. Spiked engine oil samples give mean percent recoveries of 98 ± 9, 104 ± 9, and 93 ± 0.8 for Al, V, and Ni, respectively. Copper, Zn, and Cd are determined in urine samples; while Cd, Co, Yb, and Sr are determined in water samples. Detection limits for Cd, Zn, Cu, Yb, Sr, and Co are: 8, 40, 1, 4, 1, and 4 μg l^− 1. The technique of tungsten coil atomic emission spectrometry using a 150 W commercial projector bulb is reported for the first time. Calcium, Ba, and Sr are determined with detection limits of 0.01, 0.5, and 0.1 μg l^− 1. Relative standard deviations are lower than 10% in each case, and Sr is determined in two water standard reference materials.     

Ti in dilute slurries of TiO2 nanoparticles by in-torch vaporization sector field inductively coupled plasma-mass spectrometry☆

A Re coil-filament in-torch vaporization (ITV) sample introduction system was interfaced to a sector field inductively coupled plasma-mass spectrometry (SFICP-MS) system. In this first report on an un-optimized ITV-SF-ICP-MS system, detection limits were established using 5 μL volumes of 100 pg mL^− 1 standard solutions, translating to 0.5 pg absolute. Such absolute amounts of a dried solution are near or below the detection limit of many ICP-based techniques. The absolute detection limits for Cd, Eu, Pb, Ti, U and Zn were in the 0.2–2 fg range (or, in the 10's of millions to millions of atoms for Pb, Cd, Zn and Ti, about one million atoms for U and about 800 thousand for Eu). These absolute detection limits along with the ability of ITV to handle minute amounts of discrete samples (thus eliminating memory effects from nanoparticles adhering to the walls of pneumatic nebulization sample introduction systems and from clogging of the mass spectrometer orifice), use of sonicated water-based slurries (that eliminated contamination from acid digestion reagents or from slurry stabilization reagents), and elimination of oxygen containing molecular ion interferences due to use of dry samples enabled concentration determinations of Ti (and consequently of TiO₂) in pg mL^− 1 concentrations of slurries of manufactured, 20 nm diameter TiO₂ nanoparticles.     

Measurement of Lα, Lβ and Total L X-ray fluorescence cross-sections for some elements with 40≤Z≤53

Lα, Lβ and total L X-ray fluorescence (XRF) cross-sections have been measured for the nine elements (Zr, Nb, Mo, Ag, Cd, In, Sn, Sb and I) using photon energy 5.96 keV. In these the elements, Lα and Lβ spectra were derived from the measured L-shell spectra by fitting process. Experimental results of Lα, Lβ and total L X-ray fluorescence cross-sections have been compared with theoretical results. The experimental results of L XRF cross-section are found to be in agreement with the theoretical values.     

Determination of lead,cadmium and mercury in blood for assessment of environmental exposure: A comparison between inductively coupled plasma–mass spectrometry and atomic absorption spectrometry

A biomonitoring method for the determination of Pb, Cd, and Hg at background levels in whole blood by inductively coupled plasma-mass spectrometry is described. While this method was optimized for assessing Pb, Cd and Hg at environmental levels, it also proved suitable for assessing concentrations associated with occupational exposure. The method requires as little as 200 μl of blood that is diluted 1 + 49 for direct analysis in the inductively coupled plasma-mass spectrometer. Method performance is compared to well-established AAS methods. Initial method validation was accomplished using National Institute of Standards and Technology (NIST) Standard Reference Material 966, Toxic Metals in Bovine Blood. Method detection limits (3s) are 0.05 μg dl^− 1 for Pb, 0.09 μg l^− 1 for Cd; and 0.17 μg l^− 1 for Hg. Repeatability ranged from 1.4% to 2.8% for Pb; 3% to 10% for Cd; and 2.6% to 8.8% for Hg. In contrast, AAS method detection limits were 1 μg dl^− 1, 0.54 μg l^− 1, and 0.6 μg l^− 1, for Pb, Cd, and Hg, respectively. Further performance assessments were conducted over a 2-year period via participation in four international External Quality Assessment Schemes (EQAS) operated specifically for toxic metals in blood. This includes schemes operated by (a) the New York State Department of Health's Wadsworth Center, Albany, NY, USA (b) L′Institut National de Santé Publique du Québec, Centre de Toxicologie du Québec, Canada, (c) Friedrich-Alexander University, Erlangen, Germany, and (d) the University of Surrey, Guildford, UK Trace Elements scheme. The EQAS data reflect analytical performance for blind samples analyzed independently by both inductively coupled plasma-mass spectrometry and AAS methods.     

Analysis of catecholamines and related compounds in one whole metabolic pathway with high performance liquid chromatography based on derivatization

The simultaneous determination of Tyr, catecholamines and their metabolites in one whole metabolic pathway using high performance liquid chromatography coupled with fluorescence detection (HPLC–FLD) based on pre-column derivatization has been achieved successfully. 1,3,5,7-Tetramethyl-8-(N-hydroxysuccinimidyl butyric ester)-difluoroboradiaza-s-indacene (TMBB-Su), a highly reactive fluorescent reagent synthesized in our previous work, was used for the labeling of tyrosine (Tyr), l-3,4-dihydroxyphenylalanine (l-DOPA), dopamine (DA), norepinephrine (NE), epinephrine (E) and metanephrine (MN). Derivatization conditions including reagent concentration, buffer, reaction temperature and reaction time were also investigated to improve the derivatization efficiency and thus the sensitivity of the detection. The separation of the derivatives was obtained on C₁₈ column with the mobile phase of 20 mM pH 3.5 citric acid (H₃Cit)–sodium hydrogen phosphate (Na₂HPO₄) buffer and methanol. Good linearities with correlation coefficients square (R²) greater than 0.998 in the corresponding concentration ranges were observed and the detection limits (S/N = 3) were found in the range from 0.10 to 0.40 nM (l-DOPA: 1.45 nM). The proposed method has been applied to the detection of catecholamines and related compounds in mice liver and brain samples without tedious extraction or purification procedure, which exhibits excellent selectivity and sensitivity in the analysis of complex samples. This work provides an alternative approach in the metabolic research of catecholamines and is helpful for the study of catecholamine metabolism.     

Source term identification of environmental radioactive Pu/U particles by their characterization with non-destructive spectrochemical analytical techniques

Six radioactive particles stemming from Thule area (NW-Greenland) were investigated by gamma-ray and L X-ray spectrometry based on radioactive disintegration, scanning electron microscopy coupled with energy-dispersive and wavelength-dispersive X-ray spectrometer, synchrotron radiation based techniques as microscopic X-ray fluorescence, microscopic X-ray absorption near-edge structure (μ-XANES) as well as combined X-ray absorption and fluorescence microtomography. Additionally, one particle from Mururoa atoll was examined by microtomography. From the results obtained, it was found out that the U and Pu were mixed in the particles. The U/Pu intensity ratios in the Thule particles varied between 0.05 and 0.36. The results from the microtomography showed that U/Pu ratio was not homogeneously distributed. The ²⁴¹Am/^{238 + 239 + 240}Pu activity ratios varied between 0.13 and 0.17, indicating that the particles originate from different source terms. The oxidation states of U and Pu as determined by μ-XANES showed that U(IV) is the preponderant species and for Pu, two types of particles could be evidenced. One set had about 90% Pu(IV) while in the other the ratio Pu(IV)/Pu(VI) was about one third.     

Determination of highly polar catecholamine with liquid chromatography–tandem mass spectrometry using weak cation-exchange stationary phase to increase retention time

This paper reports method development and validation work to determine highly polar bases, catecholamine compounds, using weak cation-exchange liquid chromatography of low ionic strength mobile phase with electrospray tandem mass spectrometry. Catecholamine compounds, such as epinephrine and norepinephrine, well-known biomarkers to diagnose hypertension disease, spiked in saline solutions are purified with solid phase extraction (SPE) using alumina powders. The extracts are loaded into a weak cation-exchange liquid chromatographic column via an injection loop and analyzed with electrospray-mass spectrometer. The de-salted extracts contain only small amounts of electrolytes to avoid saturating weak cation-exchange sites in the stationary phase with sodium ions. Using carefully selected mobile-phase solvents with optimized compositions (acetonitrile and water 10:90 v/v) and with dilute acid additives (acetic acid 0.1% v/v), we are able to elute catecholamine at sufficient retention times to avoid co-elution of saline matrix residues while maintaining adequate electrospray ionization efficiency of these compounds. Using epinephrine and norepinephrine standards, these methods are validated at the range of 5 to 500 ng mL^− 1. The measurement accuracy and precision of using epinephrine standards are within 12% and 5.3% respectively, whereas the accuracy and precision are within 6.0% and 4.2% respectively using epinephrine standards.The detection limits of epinephrine and norepinephrine are 0.10 ng mL^− 1 and 0.45 ng mL^− 1 respectively. The recovery percentages of our solid phase extraction methods using alumina powders are higher than 74%. When the validated calibration curves are used to determine epinephrine and norepinephrine in rat blood dialysates, the determination errors of accuracy and precision are both within 4%, while the determination errors are within 3% in rat blood plasma samples.     

Microwave-radiated synthesis of gold nanoparticles/carbon nanotubes composites and its application to voltammetric detection of trace mercury(II)

Gold nanoparticles/carbon nanotubes (Au-NPs/CNTs) composites were rapidly synthesized by microwave radiation, and firstly applied for the determination of trace mercury(II) by anodic stripping voltammetry (ASV). The structure and composition of the synthesized Au-NPs/CNTs nanocomposites were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV–vis absorption spectroscopy and cyclic voltammetry. Au-NPs/CNTs nanocomposites modified glassy carbon electrode (Au-NPs/CNTs/GCE) exhibited excellent performance for Hg(II) analysis. A wide linear range (5 × 10⁻¹⁰–1.25 × 10⁻⁶ mol/L) and good repeatability (relative standard deviation of 1.84%) were obtained for Hg(II) detection. The limit of detection was found to be 3 × 10⁻¹⁰ mol/L (0.06 μg/L) at 2 min accumulation, while the World Health Organization’s guideline value of mercury for drinking water is 1 μg/L, suggesting the proposed method may have practical utility.     

Determination of triclosan,triclocarban and methyl-triclosan in aqueous samples by dispersive liquid–liquid microextraction combined with rapid liquid chromatography

In this study, dispersive liquid–liquid microextraction (DLLME) combined with ultra-high-pressure liquid chromatography (UHPLC)–tunable ultraviolet detection (TUV), has been developed for pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in aqueous samples. The key factors, including the kind and volume of extraction solvent and dispersive solvent, extraction time, salt effect and pH, which probably affect the extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.0500–100 μg L^?1 for TCS, 0.0250–50.0 μg L^?1 for TCC, and 0.500–100 μg L^?1 for M-TCS, respectively, with correlation coefficients (r²) > 0.9945. The limits of detection (LODs) ranged from 45.1 to 236 ng L^?1. TCS in domestic waters was detected with the concentration of 2.08 μg L^?1. The spiked recoveries of three target compounds in river water, irrigating water, reclaimed water and domestic water samples were achieved in the range of 96.4–121%, 64.3–84.9%, 77.2–115% and 75.5–106%, respectively. As a result, this method can be successfully applied for the rapid and convenient determination of TCS, TCC and M-TCS in real water samples.     

Determination of nicotine and N-nitrosamines in house dust by pressurized liquid extraction and comprehensive gas chromatography—Nitrogen chemiluminiscence detection

A novel, highly selective method for the determination of nicotine, N-nitrosamines and tobacco-specific nitrosamines (TSNAs) in indoor dust samples is presented in this study. Samples were extracted by in-cell clean-up pressurized liquid extraction (PLE) that allows high extraction efficiency with moderate consumption of organic solvents. The extracts were analyzed by comprehensive gas chromatography and detected with a nitrogen chemiluminiscence detector (GC × GC-NCD) that provided enhanced selectivity and sensitivity for organic nitrogen containing compounds. Method validation showed good linearity, repeatability and reproducibility (%RSD < 8%). Recovery was higher than 80% for most target compounds and limits of detection lower than 16 ng g^?1. The method was used for the determination of the nitrosamine target compounds in house dust samples from both smoking and non-smoking households. All the analytes were found in the samples, nicotine being the most abundant compound in smokers’ dust and one of the most abundant in non-smokers’ dust. To our knowledge this is the first time that volatile N-nitrosamines and TSNAs have been determined in indoor dust samples. The results demonstrate the presence of these highly carcinogenic compounds in house dust, with inherent human exposure through inhalation and/or involuntary ingestion of house dust.     

Liquid chromatography methodologies for the determination of steroid hormones in aquatic environmental systems

Steroid hormones are a diverse group of natural and synthetic compounds. Their wide use in human and veterinary medicine results in their continual introduction into the environment. In recent years, environmental concern over steroids that act as endocrine disruptors has increased because of their adverse effects on organisms or their progeny. Moreover, as these compounds are not totally removed from sewage in wastewater treatment plants, they can reach the aquatic environment and persist due to their physicochemical characteristics.For this reason, a major trend in analytical chemistry is the development of rapid and efficient procedures for the extraction, determination and quantification of steroid hormones in environmental samples. Over the past few decades, the significant expansion of liquid chromatography technology utilizing mass spectrometry detection has led to applications with increased selectivity and sensitivity. Optimized extraction and microextraction techniques combined to these liquid chromatography techniques have lowered detection and quantification limits to the ng L⁻¹–μg L⁻¹ range, which is the concentration of steroid hormones in liquid, solid and biota samples.In this paper, the state-of-the-art techniques for the analysis of steroid hormones focused mainly in based liquid chromatography methods in liquid and aquatic solid and biota samples are reviewed. Handling, storage, extraction and detection methodologies are reviewed and compared for all families of steroid hormones.     

A simple,low cost,multielement atomic absorption spectrometer with a tungsten coil atomizer

An inexpensive, multielement atomic absorption spectrometer utilizing a tungsten coil atomizer has been developed. The novel optical arrangement employs three 60° beam combiners to blend the spectral output from four light sources such as electrodeless discharge lamps, or hollow cathode lamps, and then direct that output over an atomizer. This instrument uses an inexpensive tungsten coil atomizer that is extracted from a standard 150 W projector bulb. The temperature of the coil is computer-controlled by changing the voltage across the coil. A low voltage is first used to dry the sample then a higher voltage is used to atomize the sample. Simultaneous detection of the analyte absorption signals is accomplished using a charge-coupled device. The elements of interest in this study were Cd, Pb, and Cu. Near-line background correction was used to correct for nonspecific analyte absorption.     

Pyrohydrolysis of carbon nanotubes for Br and I determination by ICP-MS

Bromine and iodine determination was performed in carbon nanotubes (CNTs) by inductively coupled plasma mass spectrometry (ICP-MS) after sample preparation using pyrohydrolysis. Samples of CNTs (up to 500 mg) were mixed with 750 mg of V₂O₅ and heated at 950 °C during 12.5 min in a quartz tube under water vapor and air. The main operational conditions of pyrohydrolysis (carrier gas, absorbing solution, heating time, sample mass and use of V₂O₅) were evaluated. Accuracy was evaluated using certified reference materials (CRM) with similar matrix and also by comparison of results obtained after digestion of samples by microwave-induced combustion (MIC) and determination by ICP-MS. Agreement with CRM values was higher than 97% for Br and better than 96% in comparison with reference values (MIC/ICP-MS) of Br and I in CNTs samples. The limit of detection of the method for Br and I determination by ICP-MS was 0.05 and 0.004 μg g^? 1, respectively. Using a relatively simple and low cost pyrohydrolysis apparatus up to four samples can be processed per hour. The pyrohydrolysis sample preparation procedure is easy to be performed and provide a clean solution for analysis by ICP-MS, which is very attractive for Br and I control in CNTs.     

Dithizone–chloroform single drop microextraction system combined with electrothermal atomic absorption spectrometry using Ir as permanent modifier for the determination of Cd in water and biological samples

A simple and sensitive method using dithizone–chloroform single drop microextraction has been developed for separation and preconcentration of trace Cd prior to its determination by electrothermal atomic absorption spectrometry with Ir as permanent modifier. Parameters, such as pyrolysis and atomization temperature, solvent type, pH, dithizone concentration, extraction time, organic drop volume, stirring rate and sample volume were investigated. Under the optimized conditions, a detection limit (3σ) of 0.7 ng/l and enrichment factor of 65 were achieved. The relative standard deviation was 7.4% (c = 0.2 μg/l, n = 5). The developed method has been applied to the determination of trace Cd in water samples and biological reference materials with satisfactory results.     

Fluorescence detection and identification of eight sulphonamides using capillary electrophoresis on released excipients in lake water

A simple and sensitive capillary electrophoresis method with fluorescence detection was developed for the determination of sulphanilamide, sulphamerazine, sulphacetamide and sulphanilic acid, sulphathiazole, Sulphisomidine, sulphadoxine and sulphadiazine in lake water. The sulphonamides were extracted from lake water, derivatized with fluorescamine and determination of sulphonamide was achieved using 20 mM borate buffer of pH 9.5 at an applied voltage of 25 kV. Detection was performed using UG-11 excitation filter of 405 nm and 495 nm emission filters. A fast, simple and sensitive method with limit of detection in the range 0.89–1.43 n mol L⁻¹ for all the eight sulphonamides with good recoveries of 80–110% is seen. Inter-day and intra-day validation of the separation method shows fairly good results. The detection and quantification limits for this newly developed method are too low to determine drug residues in lake water.