Analytica

Gravimetric mass loss in polymer–biogenic filler systems is often reported as polymer biodegradation without establishing which phase of the material is lost. This study proposes and applies an analytical framework that combines FTIR identification of the starting material, a phase balance ceiling, and removable inventory kinetics to assess such claims. Post-consumer cup plastic was blended with pyroconverted cassava (Manihot esculenta) peel dextrin in four matrix/dextrin/turpentine formulations (70/10/20 to 30/50/20% w/w) and exposed for 30 days to Aspergillus niger and A. fumigatus in Rivalier moist chambers with Sabouraud dextrose broth. FTIR revealed that the material sold as polypropylene contained polystyrene: the matrix ranged from essentially polystyrene (formulation B) to polypropylene-rich (C and D), as shown by the aromatic 755/697 ${\mathrm{cm}}^{-1}$ doublet and a PS/PP spectral index spanning more than one order of magnitude. Mass loss profiles followed a first-order removable inventory model with rate constants $\kappa$ of $9.9\times {10}^{-3}$ to $67.8\times {10}^{-3}$${\mathrm{d}}^{-1}$ (nominal residual solvent scenario) and inventory half-lives of 10–70 d. The removal rate increased with dextrin content ($\rho =0.80$ for both species) with a reproducible reversal between 30 and 40% dextrin that survives explicit bounding of the specimen surface-to-volume covariate. Five of the eight conditions remained below the removable fraction ceiling even on a dry basis; the other three required residual solvent fractions of only 1.2, 1.9, and 11.9% w/w, below the 20% nominal loading, so that no observation requires degradation of the PP/PS matrix. A greenness assessment of the framework with AGREE (0.62), MoGAPI (77%), and AGSA (66.7%) places it above the confirmatory methods it is intended to gate (respirometry, high-temperature GPC), with low throughput, manual operation, and the biosafety of the fungal assay as its main remaining limitations. The framework provides a reproducible, low-burden basis for separating selective removal of biodegradable or volatile phases from evidence that can legitimately support polymer biodegradation claims.

A targeted method for the determination of 10 active components in 4 characteristic honeys from Yunnan, China, was established using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). The lower calibration limit differed among analytes, ranging from 0.01 to 0.5 μg·mL⁻¹. The detection limits and quantification limits ranged from 0.03–1.5 mg·kg⁻¹ and 0.1–5.0 mg·kg⁻¹, respectively. The precision, stability, and repeatability were satisfactory. After partial least squares discriminant analysis (PLS-DA) discriminant analysis was applied to four honey varieties, Brassica rapa var. oleifera DC. honey (BRH) and Hevea brasiliensis honey (HBH) clustered into one group but were clearly distinguishable from Amomum tsao-ko Crevost et Lemarié honey (ATH) and Apis cerana honey (ACH). BRH and HBH could be further differentiated using the OPLS-DA model. Gentisic acid, trigonelline, and naringenin were differentially abundant active components among the four honeys, whereas trigonelline and naringenin exhibited differential abundance between BRH and HBH. Volcano plot analysis revealed that homoeriodictyol, quercetin, and naringenin may serve as key compounds for distinguishing ACH and ATH, BRH, and HBH honeys; that trigonelline may be a key compound for differentiating ATH and HBH, ACH, and BRH honeys; and that quercetin and apigenin may be key compounds for distinguishing HBH and ATH, ACH, and BRH honeys.

Calixarenes lacking additionally introduced fluorophores have long been considered insufficiently fluorescent for fluorimetric sensing. We have recently shown that simple calix[4]arene derivatives possess weak intrinsic fluorescence which significantly changes upon cation binding, raising a question whether the same holds for their larger and more flexible analogs. The aim of this work was to investigate the intrinsic fluorescence of the tertiary-amide calix[6]arene derivative L and to establish whether the changes accompanying complexation can be used for quantitative characterization of alkali and alkaline earth metal cation complexation. Stability constants of the 1:1 and 2:1 (cation:ligand) complexes in acetonitrile were determined by spectrofluorimetric titrations and validated by UV absorption spectrophotometry and isothermal titration calorimetry. Compared with the latter techniques, fluorimetry could be performed at much lower receptor concentrations, in some cases in the micromolar range. Complex stoichiometries and structures were further examined by NMR spectroscopy, mass spectrometry, and molecular dynamics simulations. Although L contains no additional fluorophore, it exhibits relatively weak intrinsic fluorescence which is strongly affected by cation binding. Among the alkali metal ions, pronounced fluorescence enhancement was observed for K⁺ and to a slightly lesser extent Rb⁺, whereas Li⁺ and Cs⁺ caused fluorescence quenching. Sodium ions induced both effects, depending on concentration. In contrast, all alkaline earth metal cations reduced the fluorescence intensity. The emission changes were interpreted in terms of variations in the absorption spectra and conformational rigidification upon complexation, as well as possible suppression of the photoinduced electron transfer and involvement of charge-transfer character of the excited state. Fluorimetry based on the intrinsic fluorescence of L proved superior to absorption spectrophotometry and microcalorimetry for the quantitative characterization of complexation reactions, offering a valuable advantage for poorly soluble systems and highly stable complexes.