Determination of hydrogen peroxide and triacetone triperoxide (TATP) with a silver nanoparticles—based turn-on colorimetric sensor (original) (raw)
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Forensic Science International
The explosive triacetone triperoxide (TATP) can be easily manufactured from readily accessible reagents, and is extremely difficult to detect, owing to the lack of UV absorbance, fluorescence, or facile ionization. The developed method is based on the acidic hydrolysis of TATP into H 2 O 2 , pH adjustment to 3.6, and the addition of magnetite nanoparticles (Fe 3 O 4 MNPs) to the medium to produce hydroxyl radicals from H 2 O 2 , owing to the peroxidase-like activity of MNPs. The formed radicals converted the N,N-dimethyl-p-phenylene diamine (DMPD) probe to the colored DMPD + radical cation, the optical absorbance of which was measured at a wavelength of 554 nm. The molar absorptivity (ε) of the method for TATP was 21.06 x 10 3 L mol-1 cm-1. The colored DMPD + product in solution could be completely retained on a cation-exchanger Nafion membrane, constituting a colorimetric sensor for TATP and increasing the analytical sensitivity. The proposed method did not respond to a number of hand luggage items like detergent, sweetener, sugar, acetylsalicylic acid (aspirin) and paracetamol-caffeine based analgesic drugs. On the other hand, TATP could be almost quantitatively recovered from a household detergent and sweetener that can be used as camouflage for the analyte. Neither common soil and groundwater ions (e.g., Ca 2+ , Mg 2+ , K + , Cl-, SO 4 2-, and NO 3-) at 100-fold ratios nor nitro-explosives of TNT, RDX, and PETN at 10-fold amounts interfered with the proposed assay. The method was statistically validated against the standard GC-MS reference method.
Sensors
Titanium(IV) solutions are known to detect hydrogen peroxide in solutions by a colorimetric method. Xplosafe’s XploSens PS commercial titanium(IV)-based peroxide detection test strips are used to detect hydrogen peroxide in liquids. The use of these test strips as gas-phase detectors for peroxides was tested using low-cost hardware. The exposure of these strips to hydrogen peroxide liquid or gas leads to the development of an intense yellow color. For liquids, a digital single-lens reflex camera was used to quantify the color change using standardized solutions containing between 50 and 500 ppm peroxide by mass. Analysis of the images with color separation can provide a more quantitative determination than visual comparison to a color chart. For hydrogen peroxide gas, an inexpensive web camera and a tungsten lamp were used to measure the reflected light intensity as a function of exposure from a test strip held in a custom cell. First-order behavior in the color change with time was...
Analytica Chimica Acta, 2012
Titanium dioxide (i.e. TiO 2 ) in nano-form is a constituent of many nanomaterials that are used in sunscreens, cosmetics, industrial products and in biomedical applications. Quantification of TiO 2 nanoparticles in various matrixes is a topic of great interest for researchers studying the potential health and environmental impacts of nanoparticles. However, analysis of TiO 2 as Ti 4+ is difficult because current digestion techniques require use of strong acids that may be a health and safety risk in the laboratory. To overcome this problem, we developed a new method to digest TiO 2 nanoparticles using ammonium persulfate as a fusing reagent. The digestion technique requires short times to completion and optimally requires only 1 g of fusing reagent. The fusion method showed >95% recovery of Ti 4+ from 6 g mL −1 aqueous suspensions prepared from 10 g mL −1 suspension of different forms of TiO 2, including anatase, rutile and mixed nanosized crystals, and amorphous particles. These recoveries were greater than open hotplate digestion with a tri-acid solution and comparable to microwave digestion with a tri-acid solution. Cations and anions commonly found in natural waters showed no significant interferences when added to samples in amounts of 10 ng to 110 mg, which is a much broader range of these ions than expected in environmental samples. Using ICP-MS for analysis, the method detection limit (MDL) was determined to be 0.06 ng mL −1 , and the limit of quantification (LOQ) was 0.20 ng mL −1 . Analysis of samples of untreated and treated wastewater and biosolids collected from wastewater treatment plants yielded concentrations of TiO 2 of 1.8 and 1.6 ng mL −1 for the wastewater samples, respectively, and 317.4 ng mg −1 dry weights for the biosolids. The reactions between persulfate ions and TiO 2 were evaluated using stoichiometric methods and FTIR and XRD analysis. A formula for the fusing reaction is proposed that involves the formation of sulfate radicals.
This work is first report showed that supported TiO 2 NPs on alumina could act catalytic activity on peroxyoxalate chemiluminescence system. In this work the catalytic effect of supported Titanium dioxide nanoparticles (TiO 2 NPs) on the trichloroperoxy oxalate -hydrogen peroxide (PO-CL) reaction is investigated. Supported TiO 2 nanoparticles exhibited the better CL catalysis activity than SnO and Carbon nanotubes. Supported TiO 2 nanoparticles catalyze the chemiluminescence reaction between TCPO (bis-(2,4,6-trichlorophenyl) oxalate) and H 2 O 2 and produce a strong CL signal in the presence of triazinyl dye derivative as fluorophore. The CL signal intensity was linear with the hydrogen peroxide concentration in the range of 5 to 1000 nmol ml -1 with a detection limit of 1.2 nmol ml -1 and regression coefficient was 0.992 (n=4). The relative standard deviations for measurement of 300 and 500 nmol ml -1 hydrogen peroxide were 2.2 and 3.4%, respectively(n=4). Hydrogen peroxide concentration in river water was 8.7 nmol ml -1 with RSD=5.4%(n=3).
Characterization of Food-Grade Titanium Dioxide: The Presence of Nanosized Particles
Titanium dioxide (TiO 2 ) is widely used in food products, which will eventually enter wastewater treatment plants and terrestrial or aquatic environments, yet little is known about the fraction of this TiO 2 that is nanoscale, or the physical and chemical properties of TiO 2 that influence its human and environmental fate or toxicity. Instead of analyzing TiO 2 properties in complex food or environmental samples, we procured samples of food-grade TiO 2 obtained from global food suppliers and then, using spectroscopic and other analytical techniques, quantified several parameters (elemental composition, crystal structure, size, and surface composition) that are reported to influence environmental fate and toxicity. Another sample of nano-TiO 2 that is generally sold for catalytic applications (P25) and widely used in toxicity studies, was analyzed for comparison. Food-grade and P25 TiO 2 are engineered products, frequently synthesized from purified titanium precursors, and not milled from bulk scale minerals. Nanosized materials were present in all of the food-grade TiO 2 samples, and transmission electron microscopy showed that samples 1−5 contained 35, 23, 21, 17, and 19% of nanosized primary particles (<100 nm in diameter) by number, respectively (all primary P25 particles were <100 nm in diameter). Both types of TiO 2 aggregated in water with an average hydrodynamic diameter of >100 nm. Food-grade samples contained phosphorus (P), with concentrations ranging from 0.5 to 1.8 mg of P/g of TiO 2 . The phosphorus content of P25 was below inductively coupled plasma mass spectrometry detection limits. Presumably because of a P-based coating detected by X-ray photoelectron spectroscopy, the ζ potential of the food-grade TiO 2 suspension in deionized water ranged from −10 to −45 mV around pH 7, and the iso-electric point for food-grade TiO 2 (<pH 4) was significantly lower than that for P25. The presence of other elements in or on the TiO 2 (Si content of 0.026− 0.062% and Al content of 0.0006−0.810%) was also different from the case for P25 and would influence the environmental fate of TiO 2 . X-ray diffraction analysis confirmed the presence of anatase and/or rutile in the food-grade materials, and although the presence of amorphous TiO 2 could not be ruled out, it is unlikely on the basis of Raman analysis. The food-grade TiO 2 was solar photoactive. Cationic dyes adsorbed more readily to food-grade TiO 2 than P25, indicating very different potentials for interaction with organics in the environment. This research shows that food-grade TiO 2 contains engineered nanomaterials with properties quite different from those of P25, which has previously been used in many ecotoxicity studies, and because food-grade TiO 2 is more likely than P25 to enter the environment (i.e., potentially higher exposure levels), there is a need to design environmental (and human) fate and toxicity studies comparing food-grade to catalytic TiO 2 .
Characterization of Food-Grade Titanium Dioxide: Presence of Nano-Sized Particles
Environmental Science & Technology, 2014
Titanium dioxide (TiO 2 ) is widely used in food products, which will eventually enter wastewater treatment plants and terrestrial or aquatic environments, yet little is known about the fraction of this TiO 2 that is nanoscale, or the physical and chemical properties of TiO 2 that influence its human and environmental fate or toxicity. Instead of analyzing TiO 2 properties in complex food or environmental samples, we procured samples of food-grade TiO 2 obtained from global food suppliers and then, using spectroscopic and other analytical techniques, quantified several parameters (elemental composition, crystal structure, size, and surface composition) that are reported to influence environmental fate and toxicity. Another sample of nano-TiO 2 that is generally sold for catalytic applications (P25) and widely used in toxicity studies, was analyzed for comparison. Food-grade and P25 TiO 2 are engineered products, frequently synthesized from purified titanium precursors, and not milled from bulk scale minerals. Nanosized materials were present in all of the food-grade TiO 2 samples, and transmission electron microscopy showed that samples 1−5 contained 35, 23, 21, 17, and 19% of nanosized primary particles (<100 nm in diameter) by number, respectively (all primary P25 particles were <100 nm in diameter). Both types of TiO 2 aggregated in water with an average hydrodynamic diameter of >100 nm. Food-grade samples contained phosphorus (P), with concentrations ranging from 0.5 to 1.8 mg of P/g of TiO 2 . The phosphorus content of P25 was below inductively coupled plasma mass spectrometry detection limits. Presumably because of a P-based coating detected by X-ray photoelectron spectroscopy, the ζ potential of the food-grade TiO 2 suspension in deionized water ranged from −10 to −45 mV around pH 7, and the iso-electric point for food-grade TiO 2 (<pH 4) was significantly lower than that for P25. The presence of other elements in or on the TiO 2 (Si content of 0.026− 0.062% and Al content of 0.0006−0.810%) was also different from the case for P25 and would influence the environmental fate of TiO 2 . X-ray diffraction analysis confirmed the presence of anatase and/or rutile in the food-grade materials, and although the presence of amorphous TiO 2 could not be ruled out, it is unlikely on the basis of Raman analysis. The food-grade TiO 2 was solar photoactive. Cationic dyes adsorbed more readily to food-grade TiO 2 than P25, indicating very different potentials for interaction with organics in the environment. This research shows that food-grade TiO 2 contains engineered nanomaterials with properties quite different from those of P25, which has previously been used in many ecotoxicity studies, and because food-grade TiO 2 is more likely than P25 to enter the environment (i.e., potentially higher exposure levels), there is a need to design environmental (and human) fate and toxicity studies comparing food-grade to catalytic TiO 2 .
International Journal of Scientific Research in Science and Technology, 2019
A simple method has been developed for the determination of trace toxic elements like arsenic, lead and chromium in titanium dioxide pigment samples by ICP OES attached with a Concomitant Metals Analyser. Open mineral acid decomposition was used for sample dissolution employing a mixture of nitric and hydrofluoric acids. The continuous online generation of hydrides into the plasma was achieved through a concomitant metals analyser. The recovery of arsenic, lead and chromium and the matrix effects of titanium on these elements have been studied with spiking experiments. The proposed method has been successfully applied to the determination of arsenic and other elements in titanium pigment samples. The continuous hydride generating system, Concomitant Metals Analyser (CMA) improved the sensitivity of analysis nearly five times in pigment samples. The precision of the measurements was found to be less than 10% RSD.
Talanta, 2009
The determination of hydrogen peroxide (H 2 O 2 ) and the evaluation of scavenging capacity against this species were performed using five colorimetric reactions, which were adapted to flow injection analysis. The reactions chosen were based on the oxidation of iodide (I − method), on the formation of titaniumperoxide complex (TiP method), on the formation of titanium-xylenol orange-peroxide complex (TiXoP method), on the oxidation of 3,3 ,5,5 -tetramethylbenzidine (TMB method) and on the co-oxidation of phenol-4-sulfonic acid and 4-aminoantipyrine (PSA/4-AAP method). The operational conditions were studied in order to improve the sensitivity of each method. Concerning to the method sensitivity, the ranking order was TMB method > I − method > TiXoP method ∼PSA/4-AAP method > TiP method. All methods showed an excellent repeatability (RSD < 2%) and, except for I − method, relative deviations from the reference method were <1.9%. The FIA manifolds were adapted to perform the determination of scavenging capacity against H 2 O 2 and glutathione (GSH) was applied as model compound. TiP and TiXoP methods were not suitable as no inhibition or an increase of analytical signal was attained. PSA/4-AAP method was chosen for further application to dietary phenolics and pharmaceutical compounds, providing IC 50 values for those compounds that are fast reacting antioxidants. (M.A. Segundo).
Journal of the Brazilian Chemical Society, 2012
Recentemente, o dióxido de titânio foi classificado como potencialmente carcinogênico pela International Agency for Research on Cancer (IARC). Dióxido de titânio é um pigmento geralmente utilizado como opacificante em cremes dentais, porém sua concentração não é indicada nos rótulos dos produtos. Neste estudo, 22 amostras de cremes dentais foram calcinadas a 800 ºC e o teor de TiO 2 foi determinado por fluorescência de raios X por energia dispersiva (EDXRF) através do método de parâmetros fundamentais (FP). As mesmas amostras foram irradiadas in natura por 100 s e, através da correlação dos espectros e das concentrações anteriormente determinadas, um modelo multivariado de calibração foi construído. Oito variáveis latentes descreveram o modelo de regressão de mínimos quadrados parciais (PLS) com erros médios de 9,5%, indicando que além do pico referente ao titânio, as informações do espalhamento da radiação também são importantes para minimizar os erros ao usar uma calibração univariada. A rapidez das análises, com mínimo pré-tratamento das amostras, é a grande vantagem do método, que tem frequência analítica de 24 determinações por hora. Recently, the International Agency for Research on Cancer (IARC) has classified titanium dioxide as potentially carcinogenic. Titanium dioxide is a pigment generally used as opacifying agent in toothpastes, but there is no indication of the percentage of this oxide in these products. In this work, 22 distinct toothpaste samples were calcinated at 800 °C and TiO 2 concentration was determined with energy dispersive X-Ray fluorescence (EDXRF) via fundamental parameter (FP) method. The same samples were irradiated in natura for 100 s and through the correlation of spectra and concentrations formerly determined, a multivariate calibration model was constructed. Eight latent variables described the partial least square regression (PLS) model with average errors of 9.5%, indicating that beyond the peak of titanium, the information of the X-Ray scattering irradiation is also important to minimize errors when using an univariate calibration. As a major advantage, the method allows analysis without pretreatment of the samples, with a throughput of 24 determinations per hour.