Taylor dispersion analysis of metallic-based nanoparticles – A short review

Taylor dispersion analysis (TDA) is an interesting tool for nanoparticle (NP) size determination, feasible using simple capillary electrophoresis apparatus. Based upon the radial diffusion of analytes upon a laminar stream, the diffusion coefficient of species is easily estimable. Moreover, TDA is generally more adequate than conventional dynamic light scattering methodologies as it is less dependent on the polydispersity of the sample, leading to accurate measurement and reliable results. This review provides every paper mentioning the use of TDA for metallic-based NPs size determination. Diverse strategies for the detection of metallic NPs (like UV–visible and inductively coupled plasma–mass spectrometry – ICP–MS – for instance) and interpretation of the Taylorgrams are discussed. Based upon the literature, advices on future prospects are also indicated, especially for the comparison of TDA results with other classical techniques.     

Synthesis of diastereomeric,deoxy and ring-expanded sulfone analogues of aigialomycin D

Several analogues of the fungal natural product aigialomycin D (AmD) have been synthesised. These include the stereoisomer 5′R,6′S-AmD, 2,4-di-deoxyAmD, 1′,2′,7′,8′-tetrahydroAmD and a 15-membered macrocyclic sulfone. Growth inhibitory activities of these compounds against the HL-60 leukaemic cell line were measured. The ring-expanded sulfone and tetrahydro-analogue were found to have similar IC₅₀ values to the natural product, whereas the 5′R,6′S-stereoisomer was inactive. Energy minimisation of AmD and the synthesised analogues resulted in a range of lowest energy conformers, from planar, open arrangements of the macrocycle in AmD and tetrahydroAmD to bent, L-shaped structures for the sulfone. The synthesis of methyl orsellinate was investigated and optimised as part of this work. A stereodivergent route to both enantiomers of the diol fragment from d-ribose was also achieved.     

MALDI-TOF-MS Directly Combined with TLC: A Review of the Current State

Thin-layer chromatography (TLC) is a widely used, fast and inexpensive method for separating complex mixtures. Unfortunately, the quality of achievable separation represents only one side. An additional problem is the unambiguous assignment of the obtained spots to defined compounds. Clear identification of spots is often not possible by common staining methods and comparison with a known reference compound. Therefore, further analytical techniques are mostly required for further structural elucidation. Mass spectrometry (MS) is a suitable method due to its high sensitivity. In particular, matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) MS is a modern soft-ionization technique that may be easily combined with TLC. This review summarizes the so far available knowledge about direct TLC–MALDI combination and gives an overview about different molecule classes that have already been successfully analyzed by this approach. This review critically summarizes the capabilities and limitations of the direct MALDI–TLC combination and highlights in particular the problems related to sample preparation and instrumentation.     

An improved cryogen for plunge freezing

The use of an alkane mixture that remains liquid at 77 K to freeze specimens has advantages over the use of a pure alkane that is solid at 77 K. It was found that a mixture of methane and ethane did not give a cooling rate adequate to produce vitreous ice, but a mixture of propane and ethane did result in vitreous ice. Furthermore, the latter mixture produced less damage to specimens mounted on a very thin, fragile holey carbon substrate.     

LC‐MS/MS analysis of Δ9‐tetrahydrocannabinolic acid A in serum after protein precipitation using an in‐house synthesized deuterated internal standard

An assay based on liquid chromatography/tandem mass spectrometry is presented for the fast, precise and sensitive quantitation of Δ9‐tetrahydrocannabinolic acid A (THCA) in serum. THCA is the biogenetic precursor of Δ9‐tetrahydrocannabinol in cannabis and has aroused interest in the pharmacological and forensic field especially as a potential marker for recent cannabis use. After addition of deuterated THCA, synthesized from D₃‐THC as starting material, and protein precipitation, the analytes were separated using gradient elution on a Luna C18 column (150 × 2.0 mm × 5 µm) with 0.1% formic acid and acetonitrile/0.1% formic acid. Data acquisition was performed on a triple quadrupole linear ion trap mass spectrometer in multiple reaction monitoring mode with negative electrospray ionization. After optimization, the following sample preparation procedure was used: 200 μL serum was spiked with internal standard solution and methanol and then precipitated ‘in fractions’ with 500 μL ice‐cold acetonitrile. After storage and centrifugation, the supernatant was evaporated and the residue redissolved in mobile phase. The assay was fully validated according to international guidelines including, for the first time, the assessment of matrix effects and stability experiments. Limit of detection was 0.1 ng/mL, and limit of quantification was 1.0 ng/mL. The method was found to be selective and proved to be linear over a range of 1.0 to 100 ng/mL using a 1/x weighted calibration model with regression coefficients >0.9996. Accuracy and precision data were within the required limits (RSD ≤ 8.6%, bias: 2.4 to 11.4%), extractive yield was greater than 84%. The analytes were stable in serum samples after three freeze/thaw cycles and storage at ?20 °C for one month. Copyright © 2012 John Wiley & Sons, Ltd.     

A state-of-the-science review of analytical methods for urinary dialkylphosphate metabolites in the assessment of exposure to organophosphate pesticides: From 2000 to 2022

The general population and workers are exposed to organophosphate insecticides, one of the leading chemical classes of pesticides used in rural and urban areas. This paper aims to conduct an integrative review of the most used analytical methods for identifying and quantifying dialkylphosphate—which are metabolites of organophosphate insecticides—in the urine of exposed workers, discussing their advantages, limitations and applicability. Searches utilized the PubMed, the Scientific Electronic Library Online and the Brazilian Digital Library of Theses and Dissertations databases between 2000 and 2021. Twenty-five studies were selected. The extraction methods most used were liquid–liquid extraction (LLE) (36%) and solid-phase extraction (SPE) (36%), with the SPE being more economical in terms of time and amount of solvents needed, and presenting the best percentage of recovery of analytes, when compared with LLE. Nineteen studies (76%) used the gas chromatography method of separation, and among these, 12 records (63%) indicated mass spectrometry used as a detection technology (analyzer). Studies demonstrate that dialkylphosphates are sensitive and representative exposure biomarkers for environmental and occupational organophosphate exposure.     

Preparation of Functionalized Ayous Sawdust-carbon Nanotubes Composite for the Electrochemical Determination of Carbendazim Pesticide

Fine particles of Ayous sawdust (AS) were successfully modified by maleic anhydride to increase their accumulation capability towards carbendazim (Cbz). For a more efficient use of the biosourced material as electrode modifier for electrochemical detection, the functionalized particles were mixed with carbon nanotubes to yield a conductive composite. After electrochemical characterization, the modified GCE was applied to Cbz detection. A sensitivity of (2.61±0.08) μA M⁻¹ and a detection limit of 0.04 μM were obtained under optimized experimental conditions. Moreover, the designed sensor was found efficient for Cbz determination in real samples (spring water and commercial pesticide product).     

Ex vivo fluorescence imaging of normal and malignant urothelial cells to enhance early diagnosis

Urinary cytology is a noninvasive and unconstraining technique for urothelial cancer diagnosis but lacks sensitivity for detecting low-grade lesions. In this study, the fluorescence properties of classical Papanicolaou-stained urothelial cytological slides from patients or from cell lines were monitored to investigate metabolic changes in normal and tumoral cells. Time- and spectrally-resolved fluorescence imaging was performed at the single cell level to assess the spectral and temporal properties as well as the spatial distribution of the fluorescence emitted by urothelial cells. The results reveal quite different fluorescence distributions between tumoral urothelial cells, characterized by a perimembrane fluorescence localization, and the normal cells which exhibit an intracellular fluorescence. This is not caused by differences in the fluorescence emission of the endogenous fluorophores NAD(P)H, flavoproteins or porphyrins but by various localization of the EA 50 Papanicolaou stain as revealed by both the spectral and time-resolved parameters. The present results demonstrate that the use of single-cell endofluorescence emission of Papanicolaou-stained urothelial cytological slides can allow an early ex vivo diagnosis of low-grade bladder cancers.