Amino-calixarene-modified graphitic carbon as a novel electrochemical interface for simultaneous measurement of lead and cadmium ions at picomolar level

Amino-calixarene-derivatized graphitic carbon electrode has been used in the simultaneous quantification of lead and cadmium ions at picomolar level. The graphitic carbon has been chemically modified using amino-calixarene as an indicator molecule through microwave irradiation, and it has been characterized by NMR, mass, and Fourier transform infrared spectroscopy (FTIR) techniques. The proposed sensor has shown linearity in the concentration range 10–120 pM with detection limits of 3.3 and 3.5 pM for lead and cadmium, respectively. The proposed sensor has been successfully applied to quantify lead and cadmium levels in battery effluents, alloy materials, and sewage water sample matrices. The results obtained by the proposed sensor are in agreement with the results of the standard protocols.     

Isomerism and decoherence

In the present paper we address the problem of optical isomerism embodied in the socalled “Hund’s paradox”, which points to the difficulty to account for chirality by means of quantum mechanics. In particular, we explain the answer to the problem proposed by the theory of decoherence. The purpose of this article is to challenge this answer on the basis of a conceptual analysis of the phenomenon of decoherence, that reveals the limitations of the theory of decoherence to solve the difficulties posed by optical isomerism and, in general, by quantum measurement.     

Precipitation of mixed Ca–Ba,Ca–Cd and Ca–Mn carbonates with distinct morphologies under cooperativity of divalent metal ions and protein

According to the basic principles of biomineralization, a homogeneous precipitation process involving BSA as the matrix was used to precipitate mixed Ca–Ba, Ca–Cd and Ca–Mn carbonate particles with distinct morphologies and structures at room temperature. The structures and morphologies of these carbonates were investigated using SEM and XRD. It was found that there were distinct differences when two different kinds of divalent metal ions were simultaneously precipitated in the reacting solutions. Moreover, according to the results of FT-IR and TG-DTA, we could conclude that bovine serum albumin also affected the diverse morphologies of Ca–M carbonates besides the influence of divalent metal ions. A self-assembly process coupled with an Ostwald ripening mechanism was also discussed based on a series of time-dependent SEM observations.     

Determination of oxygenated and native polycyclic aromatic hydrocarbons in urban dust and diesel particulate matter standard reference materials using pressurized liquid extraction and LC–GC/MS

The objective of this study was to develop a novel analytical chemistry method, comprised of a coupled high-performance liquid chromatography–gas chromatography/mass spectrometry system (LC–GC/MS) with low detection limits and high selectivity, for the identification and determination of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and polycyclic aromatic hydrocarbons (PAHs) in urban air and diesel particulate matter. The linear range of the four OPAHs, which include 9,10-anthraquinone, 4H-cyclopenta[def]phenanthrene-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, was 0.7 pg–43.3 ng with limits of detection (LODs) and limits of quantification (LOQs) on the order of 0.2–0.8 and 0.7–1.3 pg, respectively. The LODs in this study are generally lower than values reported in the literature, which can be explained by using large-volume injection. The recoveries of the OPAHs spiked onto glass fiber filters using two different pressurized liquid extraction (PLE) methods were in the ranges of 84–107 and 67–110 %, respectively. The analytical protocols were validated using the following National Institute of Standards and Technology standard reference materials: SRM 1649a (Urban Dust), SRM 1650b (Diesel Particulate Matter), and SRM 2975 (Diesel Particulate Matter, Industrial Forklift). The measured mass fractions of the OPAHs in the standard reference materials (SRMs) in this present study are higher than the values from the literature, except for benzanthrone in SRM 1649a (Urban Dust). In addition to the OPAHs, 44 PAHs could be detected and quantified from the same particulate extract used in this protocol. Using data from the literature and applying a two-sided t test at the 5 % level using Bonferroni correction, significant differences were found between the tested PLE methods for individual PAHs. However, the measured mass fractions of the PAHs were comparable, similar to, or higher than those previously reported in the literature.     

Study of the distribution of actinides in human tissues using synchrotron radiation micro X-ray fluorescence spectrometry

This study aims at evaluating the capabilities of synchrotron radiation micro X-ray fluorescence spectrometry (SR micro-XRF) for qualitative and semi-quantitative elemental mapping of the distribution of actinides in human tissues originating from individuals with documented occupational exposure. The investigated lymph node tissues were provided by the United States Transuranium and Uranium Registries (USTUR) and were analyzed following appropriate sample pre-treatment. Semi-quantitative results were obtained via calibration by external standards and demonstrated that the uranium concentration level in the detected actinide hot spots reaches more than 100 μg/g. For the plutonium hot spots, concentration levels up to 31 μg/g were found. As illustrated by this case study on these unique samples, SR micro-XRF has a high potential for this type of elemental bio-imaging owing to its high sensitivity, high spatial resolution, and non-destructive character.

?

Open image in new window

Graphical Abstract SR micro-XRF study of the distribution of actinitides in human tissues. Left Location of the U-contaminated tissue sample in the human body. Middle U distribution derived from the high resolution SR micro-XRF scan on the tissue sample, indication of five U hot spots. Right Detail of the point measurement spectrum of U hot spot 3, intense U-L_α fluorescence peak located at 13.6 keV.

     

Nanometer-sized materials for solid-phase extraction of trace elements

This review presents a comprehensive update on the state-of-the-art of nanometer-sized materials in solid-phase extraction (SPE) of trace elements followed by atomic-spectrometry detection. Zero-dimensional nanomaterials (fullerene), one-dimensional nanomaterials (carbon nanotubes, inorganic nanotubes, and nanowires), two-dimensional nanomaterials (nanofibers), and three-dimensional nanomaterials (nanoparticles, mesoporous nanoparticles, magnetic nanoparticles, and dendrimers) for SPE are discussed, with their application for trace-element analysis and their speciation in different matrices. A variety of other novel SPE sorbents, including restricted-access sorbents, ion-imprinted polymers, and metal–organic frameworks, are also discussed, although their applications in trace-element analysis are relatively scarce so far.

Open image in new window

Graphical Abstract Nanometer-sized materials for solid-phaseextraction of trace elements and their species

     

High-internal-phase-emulsion polymeric monolith coupled with liquid chromatography–electrospray tandem mass spectrometry for enrichment and sensitive detection of trace cytokinins in plant samples

High-internal-phase-emulsion polymers (polyHIPEs) show great promise as solid-phase-extraction (SPE) materials because of the tremendous porosity and highly interconnected framework afforded by the high-internal-phase-emulsion (HIPE) technique. In this work, polyHIPE monolithic columns as novel SPE materials were prepared and applied to trace enrichment of cytokinins (CKs) from complex plant samples. The polyHIPE monoliths were synthesized via the in-situ polymerization of the continuous phase of a HIPE containing styrene (STY) and divinylbenzene (DVB) in a stainless column, and revealed highly efficient and selective enrichment ability for aromatic compounds. Under the optimized experimental conditions, a method using a monolithic polyHIPE column combined with liquid chromatography–electrospray tandem mass spectrometry (LC–MS–MS) was developed for the simultaneous extraction and sensitive determination of trans-zeatin (tZ), meta-topolin (mT), kinetin (K), and kinetin riboside (KR). The proposed method had good linearity, with correlation coefficients (R ²) from 0.9957 to 0.9984, and low detection limits (LODs, S/N?=?3) in the range 2.4–47 pg mL^?1 for the four CKs. The method was successfully applied to the determination of CKs in real plant samples, and obtained good recoveries ranging from 68.8 % to 103.0 % and relative standard deviations (RSDs) lower than 16 %.     

A cationic cysteine-hydrazide as an enrichment tool for the mass spectrometric characterization of bacterial free oligosaccharides

In Campylobacterales and related ε-proteobacteria with N-linked glycosylation (NLG) pathways, free oligosaccharides (fOS) are released into the periplasmic space from lipid-linked precursors by the bacterial oligosaccharyltransferase (PglB). This hydrolysis results in the same molecular structure as the oligosaccharide that is transferred to a protein to be glycosylated. This allowed for the general elucidation of the fOS-branched structures and monosaccharides from a number of species using standard enrichment and mass spectrometry methods. To aid characterization of fOS, hydrazide chemistry has often been used for chemical modification of the reducing part of oligosaccharides resulting in better selectivity and sensitivity in mass spectrometry; however, the removal of the unreacted reagents used for the modification often causes the loss of the sample. Here, we develop a more robust method for fOS purification and characterize glycostructures using complementary tandem mass spectrometry (MS/MS) analysis. A cationic cysteine hydrazide derivative was synthesized to selectively isolate fOS from periplasmic fractions of bacteria. The cysteine hydrazide nicotinamide (Cyhn) probe possesses both thiol and cationic moieties. The former enables reversible conjugation to a thiol-activated solid support, while the latter improves the ionization signal during MS analysis. This enrichment was validated on the well-studied Campylobacter jejuni by identifying fOS from the periplasmic extracts. Using complementary MS/MS analysis, we approximated data of a known structure of the fOS from Campylobacter concisus. This versatile enrichment technique allows for the exploration of a diversity of protein glycosylation pathways.