Sevencompact ph meter s220

The pH values were measured by SevenCompact™ S220 pH meter (METTLER TOLEDO, Zurich, Switzerland) (pH = 0~14).

A portion of fecal sample was heated in an air-oven at 105 ± 2°C to a constant weight. The water content of the feces was calculated from the mass of the feces before and after drying. The other part of fecal sample was diluted with distilled water at a ratio of 1:10 (w/v) and the pH value was determined using a SevenCompact™ S220 pH meter (Mettler Toledo, Switzerland).

The hydrodynamic diameter and zeta potential values of the nanoparticles were determined using the Zetasizer Nano ZS instrument, (Malvern Panalytical Ltd., Malvern, UK).
The stability of aqueous suspensions of metal nanoparticles was evaluated by the sedimentation rate of NPs. The sedimentation rates of the suspensions were determined spectrophotometrically (NanoPhotometer NP80, Implen, München, Germany) over 7 days at a concentration of 0.25 mg/mL. The measurements were performed in a 10 mm quartz cuvette at the following wavelengths, corresponding to the adsorption maximum of the suspensions: 420 nm for extract-stabilized AgNP, 425 nm for citrate-stabilized AgNP, 272 nm for extract-stabilized FeNP, and 350 nm for non-stabilized FeNP.
The stability of aqueous suspensions at different pH values was also evaluated. The required pH value (pH 3.0, 7.4, and 9.0 at 25 °C) of the solutions was set by adding hydrochloric acid or sodium hydroxide solutions (0.1 mol/L) and monitored using a SevenCompact S220 pH meter (Mettler Toledo, Schwerzenbach, Switzerland).

pH was measured using a S220 SevenCompact pH meter (Mettler-Toledo, Port Melbourne, Australia). Density was measured by pre-calibrated pycnometer at room temperature.

The semi-purified chokeberry extract, the isolated cyanidin-3-galactoside, and the purified 5-Carboxypyranocyanidin-3-galactoside were diluted in pH 3.0 citrate buffer (0.1 M adjusted with HCl) until an absorbance of 1.0 at their respective λ_vis-max was reached. Levels of AA of 250, 500, and 1000 mg/L were added using a concentrated ascorbic acid stock solution, and a control consisting of each pigment with the absence of AA was maintained. All samples were brought to the same final volume with additional citrate buffer. The pH of all samples were evaluted using a S220 SevenCompact pH meter (Mettler Toledo, Columbus, OH, USA) and were found to have a pH of 3.0 ± 0.05. Samples were stored in the dark at 25 °C in an incubator (listed in Section 3.2.2). UV-Vis spectrophotometry, colorimetry, and HPLC analyses were conducted over a 5-day period following the addition of ascorbic acid. UV-Vis spectral data was collected every hour for the first 8 h, and then at 12 h, and daily from that point on for 5 days. Spectra and color were eveluated with this data. HPLC analyses were conducted on days 0, 1, 3, and 5. All treatments were run in triplicate.

Potentiometric
titrations to determine acid–base constants were carried out
at 298 K. At acidic pH, the compounds were found to be very soluble
in water, with solubilities higher than 25 mg mL^–1 in all cases (the solubility limit was not determined). In a typical
experiment, 7 mL of a solution of the corresponding compound (15 mg)
in HCl (0.1 M) was titrated with standardized 0.1 M NaOH under stirring.
Next, the base was added with a NE-300 Just Infusion Syringe Pump
(0.04 mL min^–1, inner diameter 14.57 mm) using an
SGE Analytical Science syringe (10 mL), which had a connected needle
of stainless steel (Luer Look, 0.7 mm × 300 mm). The pH was monitored
every 10 s (S220 Seven Compact pH-meter, Mettler Toledo). The pK_a values were calculated by fitting the experimental
data to calculated titration curves with the program HYPERQUAD.
The ionization degree was calculated from the pK_a values by using the speciation program HYSS.