Fast determination of toxic diethylene glycol in toothpaste by ultra-performance liquid chromatography–time of flight mass spectrometry

A rapid method for determining diethylene glycol (DEG) in toothpaste based on the use of ultra-performance liquid chromatography (UPLC) coupled to time-of-flight mass spectrometry (TOF-MS) has been developed. The method has been validated in toothpaste samples spiked at different levels, 0.005, 0.1 and 5%, obtaining satisfactory recoveries (74–98%) and relative standard deviations (<4%). Quantification was carried out by using matrix-matched standards calibration. The developed method was applied to several types of toothpaste, making identification and quantification of DEG and other polyethylene glycols (PEG) feasible with very little sample manipulation, as only extraction with water is required. The excellent sensitivity of TOF-MS analysis performed in full-scan acquisition mode allowed the determination of DEG at concentration levels as low as 0.005% in samples and its reliable identification via the mass accuracy measurements provided by this instrument (<5 ppm).     

Studies on toxic oil syndrome: development of an enzyme-linked immunosorbent assay for 3-(<Emphasis Type="Italic">N</Emphasis>-phenylamino)propane-1,2-diol in human urine

The fatty acid esters of 3-(N-phenylamino)propane-1,2-diol (PAP) are biomarkers of toxic oil batches that caused toxic oil syndrome (TOS), an intoxication that caused over 400 deaths and affected 20,000 people in Spain in 1981. PAP esters are converted into PAP by human pancreatic lipase. The in vivo biotransformation of PAP in two mouse strains generated potentially toxic metabolites. Here we report an enzyme-linked immunosorbent assay (ELISA) for PAP detection incorporating antibodies generated using PAP-hapten derivatives 1 and 2. The immunizing haptens were designed to recognize the phenylamino and hydroxymethylene moieties of the PAP structure. The antisera raised against 1-HCH showed greater affinity for free PAP, as demonstrated in competitive experiments using either 1-BSA or 2-BSA as coating antigens. The developed ELISA detects PAP at a threshold of 130 μg L⁻¹ and can be used over a wide range of pH and ionic strength values. The assay can be applied to human urine samples, after a simple treatment method, with good recovery according to the correlation obtained when analyzing blind spiked urine samples. Figure Development of an ELISA for PAP in human urine     

Mercury binding by ferrocenoyl peptides with sulfur-containing side chains: Electrochemical, spectroscopic and structural studies

Ferrocenoyl peptides incorporating amino acids derived from either l-methionine, l-cysteine or dl-homocysteine have been synthesised and investigated as agents for heavy metal binding and detection. Heavy metal-peptide interactions have been characterised using cyclic voltammetry to follow changes in the potential of the Fe(II)/Fe(III) redox couple, revealing that these systems interact with mercury(II) ions more strongly than with other thiophilic heavy metals such as cadmium(II), silver(I) and lead(II). Proton NMR experiments have demonstrated 1:1 peptide:mercury binding and enabled quantitative characterisation of this binding interaction. Crystal structures for two of these ferrocenoyl peptide derivatives have been elucidated, revealing that these compounds adopt a P-1,3′ open solid state conformation in the absence of mercury; this arrangement precludes intramolecular hydrogen bonding between chains, while extensive intermolecular hydrogen bonding is evident. The particular affinity of these systems for mercury(II) opens the possibility of incorporating them in new, biologically inspired sensors for detecting this toxic pollutant.     

Determination of toxic elements in coal by ICP-MS after digestion using microwave-induced combustion

A microwave-induced combustion (MIC) procedure was applied for coal digestion for subsequent determination of As, Cd and Pb by inductively coupled plasma mass spectrometry (ICP-MS) and Hg using cold vapor (CV) generation coupled to ICP-MS. Pellets of coal (500 mg) were combusted using 20 bar of oxygen and ammonium nitrate as aid for ignition. The use of nitric acid as absorbing solution (1.7, 3.5, 5.0, 7.0 and 14 mol L⁻¹) was evaluated. For coal samples with higher ash content, better results were found using 7.0 mol L⁻¹ HNO₃ and an additional reflux step of 5 min after combustion step. For coal samples with ash content lower than 8%, 5.0 mol L⁻¹ nitric acid was suitable to the absorption of all analytes. Accuracy was evaluated using certified reference material (CRM) of coal and spikes. Agreement with certified values and recoveries was better than 95 and 97%, respectively, for all the analytes. For comparison of results, a procedure recommended by the American Society of Testing and Materials (ASTM) was used. Additionally, a conventional microwave-assisted digestion (MAD) in pressurized vessels was also performed. Using ASTM procedure, analyte losses were observed and a relatively long time was necessary for digestion (>6 h). By comparison with MAD procedure, higher sample mass can be digested using MIC allowing better limits of detection. Additionally, the use of concentrated acids was not necessary that is an important aspect in order to obtain low blank levels and lower limits of detection, respectively. The residual carbon content in digests obtained by MAD and MIC was about 15% and <1%, respectively, showing the better digestion efficiency of MIC procedure. Using MIC it was possible to digest completely and simultaneously up to eight samples in only 25 min with relatively lower generation of laboratory effluents.     

The application of ICP-MS and ICP-OES in determination of micronutrients in wood ashes used as soil conditioners

In the present paper, the elemental composition of wood ashes obtained by the combustion of wood in a fireplace was determined with the use of ICP-MS and ICP-OES techniques. Wood ashes may find a potential application as deacidifying agents and soil conditioners, since they contain calcium (in the form of CaCO₃ and CaO), potassium (in the form of K₂SO₄ and K₂CO₃) and significant levels of micronutrients. However, if applied to soil, it is important to assess the bioavailability of particular elements to plants. This process can be simulated by proper extraction procedures.

Various species of wood were combusted in a firestove in a single-family house. The ashes underwent multielemental analyses with ICP-MS Varian Ultra Mass 700 (Australia) and ICP-OES Vista-MPX from Varian (Australia) in order to determine the content of macro- and micronutrients as well as toxic elements. Ashes were also extracted with solutions of 0.1 M NaNO₃ and water in order to simulate the process of elemental transfer from ash (used as soil conditioner) to soil solution and consequently to plants. Also, the environmental impact of ash supplementation to soil was assessed in these experiments. Soil was supplemented with 0–20% of ash. After elution, the eluent underwent multielemental analysis by ICP-MS and ICP-OES techniques to determine the content of macronutrients (P, K, Mg), micronutrients (Fe, Mn, Co, Mo, Zn, Cu and Ti) and toxic elements (Hg, Pb, As and Cd).

It was shown that fireplace ashes can be applied for deacidification of homestead gardens. Ash may be described as a valuable soil conditioner with N:P:K formula 0:1:3. It is concluded therefore that in order to achieve full fertilization, additional supplementation with nitrogen fertilizer would be necessary.     

Functionalized Cellulosic Fibers for Removal of Toxic Metal Ions From Contaminated Water

Functionalization of cellulosic okra fibers was carried out by graft copolymerization of acrylamide in the presence of ascorbic acid and hydrogen peroxide as redox initiator in aqueous medium. Different reaction parameters such as time, temperature, initiator concentration, and monomer concentration were optimized to obtain the maximum graft yield. The graft copolymerized fibers were characterized by FT-IR, TGA, and X-ray diffraction techniques. Further, chemically modified fibers were used for removal of Zn²⁺ and Cd²⁺ toxic metal ions from contaminated water. The effect of pH, contact time, and metal ion concentration was studied in batch mode experiments. The kinetics of adsorption were studied using pseudo-first and pseudo-second-order kinetic models. The adsorption isotherm was studied using Langmuir and Freundlich isotherm models. The Langmuir model was found to fit the equilibrium data well.     

Nanostructured metal oxides/hydroxides-based electrochemical sensor for monitoring environmental micropollutants

Nanostructured metal oxides/hydroxides (NMOs/HOs) with unique optical, electrical and molecular properties, chemical and photochemical stability, electrochemical activity, large surface area along with desired functionalities have recently become important as materials to construct electrochemical sensor for monitoring environmental micropollutants. In this review, we present and discuss the NMOs/HOs-based electrochemical sensor for detection of micropollutants including toxic organic micropollutants, heavy metal ions (HMIs), and anions in water. The analytical performance of a NMOs/HOs-based electrochemical sensor can be improved by tailoring the properties of the NMOs/HOs through engineering of morphology, particle size, exposed crystal facets, effective surface area, functionality, adsorption capability and electron-transfer properties. These interesting NMOs/HOs are expected to find potential applications in a new generation of miniaturized, smart electrochemical environmental monitoring devices.     

Molecular and structural characteristics in toxic algae cultures of Ostreopsis ovata and Ostreopsis spp. evidenced by FTIR and FTNIR spectroscopy

In this article we investigated the compositional and structural characteristics of the principal biomolecules such as carbohydrates, proteins, lipids, nucleic acids and chlorophyll pigments present in biofilm cultures of Ostreopsis spp. and in batch cultures of Ostreopsis ovata. Our approach based on the use of infrared (FTIR) and near infrared (FTNIR) spectroscopy showed the marked differences existing between biofilm cultures and batch cultures. FTIR spectroscopy showed the higher contents of polysaccharides and chlorophyll pigments in O. ovata from batch cultures with respect to Ostreopsis spp. Second derivative FTIR spectroscopy showed different features concerning the secondary structure of proteins because in O. ovata samples the beta sheet and beta turn structures were observed whereas in Ostreopsis spp. samples the alpha helix structure was the most evident. FTNIR spectroscopy showed other structural differences observed existing between O. ovata and Ostreopsis spp. mainly related to hydrogen bond interactions determining more packed structures in the nucleus of O. ovata. In addition, the interpretation of FTIR and FTNIR spectral information was also supported by the application of two statistical methods, the independent component analysis (ICA) and the spectral cross correlation analysis (SCCA). ICA was used as spectral deconvolution technique to separate the effects of the interference bicarbonate ion from algal FTIR spectra so to verify the high similar qualitative composition of the three biofilm samples of Ostreopsis spp. At last, SCCA applied to FTIR and FTNIR spectra was useful to evidence some structural differences involving -CH and CH(2) groups of aliphatic chains in O. ovata and Ostreopsis spp. samples. Though preliminary, these results agree with some previous studies suggesting that the presence of different ecophysiological characteristics in O. ovata and Ostreopsis spp. depending on the parameters related to the condition growth.     

不同底物体系下漆酶的失活动力学研究

本文对三种体系的漆酶热失活动力学进行了研究,并对动力学参数进行了相应的分析。结果显示,漆酶在纯水溶液中的失活符合一级动力学模型,其失活方程为lnA=-0. 1353t-2. 2522。在有毒有机物体系(2,4-二氯酚和吲哚溶液)中漆酶的失活仍符合一级失活动力学模型,失活速率常数减小,但半衰期增大。在极性溶液(乙醇)中,漆酶的反应速率常数最小,可能是因为漆酶分子内部作用力的变化导致了漆酶反应变缓;在非极性体系(异辛烷溶液)中,水-疏水体系减少了对酶的伤害,利于酶的稳定,延长了漆酶半衰期;极性或非极性体系中的漆酶失活均符合一级动力学失活模型。