Journal of Chemical Metrology

Aronia melanocarpa (black chokeberry) is a fruit rich in phenolic compounds and well-known for its potent antioxidant capacity; however, comparative investigations comparing fresh berries and their processed counterparts remain scarce. In this work, microwave-assisted extraction (MAE) was optimized via response surface methodology (RSM) to enhance the recovery of antioxidant constituents from Aronia fruits cultivated in Türkiye. Extraction time (5–30 min), temperature (40–100 °C), solvent-to-solid ratio (mL/0.1 g dry sample, DS), and solvent composition (20–100%) were systematically modeled, while antioxidant performance was assessed using the CUPRAC assay. The optimal conditions (100 °C, 24 min, 34% ethanol, 14 mL per 0.1 g DS) yielded a maximum TAC value of 0.998 mmol TE/g DS. Both raw fruits and commercial preparations (juice, concentrate, dried fruit, jam, vinegar, gummies, herbal capsules) were then characterized by spectrophotometric assays (CUPRAC, Folin–Ciocalteu, pH differential) and by chromatographic analysis (HPLC-PDA). Major anthocyanins—including cyanidin-3-O-xyloside, cyanidin-3-O-arabinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-galactoside—and phenolics such as chlorogenic acid, neochlorogenic acid, epicatechin, and gallic acid were identified and quantified. Substantial compositional differences were observed between fresh fruit and processed products, with pronounced losses of anthocyanins attributed to industrial processing. This study provides the first integrated assessment of Turkish Aronia fruits and related commercial products, by uniting MAE optimization with comprehensive antioxidant and phytochemical profiling, and offering new insights into their nutritional and functional potential.

The accuracy and reliability of conductivity measurements in analytical laboratories depend significantly on the availability of quality control materials. This study addresses the preparation, homogeneity, stability and characterization of a potassium chloride (KCl) quality control material (QCM) of 1414 µS/cm based on ISO/TR 33402. OIML R-56 does not contain this conductivity value as a secondary standard, so the mass of KCl required to prepare such a solution was experimentally defined. The conductivity measurements were carried out at 25 °C using a conductivity meter calibrated by a CRM produced by the the Slovak Institute of Metrology (SMU), a signatory to the mutual recognition arrangement (MRA) of the International Committee of Weights and Measures (CIPM). The homogeneity study was carried out in accordance with ISO 33405 using 10% of the batch bottles and the analysis of variance (ANOVA) showed that the QCM batch is homogeneous. The short-term stability was carried out over 4 weeks storage time at 4°C and 40°C and the isochronous measurements showed no significant deviations over time. The characterization of the QCM along three days showed that, its conductivity was 1414.11 µS/cm. The uncertainty associated with the conductivity measurements was assessed based on the requirements of the Guide to the expression of uncertainty in measurement (ISO GUM) and the EURACHEM/CITAC Guide, CG4 (Quantifying uncertainty in analytical measurement). It was found to be 23.10 µS/cm or 1.63%. A control chart was developed using the prepared QCM and the measured values remained within the control limits over the control time of six weeks. The prepared KCl QCM will be useful for use in quality control and instrumental validation in food, drug and environmental conductivity testing.