Succinic acid

Generally, the chemicals for the obtaining of Mg₂SiO₄ nanostructures, including Mg(NO₃)₂·6H₂O (98%), tetraethyl orthosilicate (TEOS) (99%), citric acid anhydrous, maleic acid and succinic acid were purchased from Merck and Sigma-Aldrich Company and used without further purification. Also, de-ionized water was used as the solvent. XRD patterns were recorded using a Philips X-ray diffractometer using Ni-filtered Cu Kα radiation. SEM images were taken using an LEO instrument model 1455VP. Before capturing images, the samples were coated by a thin layer of Au to make the sample surface a conductor and prevent charge accumulation to obtain a better contrast. FT-IR spectra were recorded on a Galaxy series FTIR 5000 spectrophotometer. The electronic spectra of the complexes were taken on a UV-visible scanning spectrometer (Shimadzu, UV-2550, Japan).

The following materials and chemicals were purchased from Merck, Johannesburg, South Africa: standards (98%) of glycolic acid, α-ketoglutaric acid, succinic acid, lactic acid, malonic acid, succinylacetone, glutaconic acid, adipic acid, methylmalonic acid, fumaric acid, ethylmalonic acid, phenyllactic acid, vanillylmandelic acid, 4-hydroxyphenylpyruvic acid, sebacic acid, 4-phenylbutyric acid, stearic acid, 3-methylglutaconic acid, phenylacetic acid, glutaric acid, citric acid, pyruvic acid, 3-phenylbutyric acid, and sorbitol, hexane, diethyl ether, and butanol, derivatization reagents, namely N-bis (trimethylsilyl) trifluoroacetamide (BSTFA) with trimethylchlorosilane (TMCS), and pyridine. Spectrometry-grade solvents, including methanol, acetonitrile, water, acetone, isopropyl alcohol, and ethyl acetate, were obtained from Honeywell Burdick & Jackson, Anatech, Johannesburg, South Africa. Sodium and magnesium sulphate were obtained from Merck, South Africa. Synthetic urine (SurineTM Lot 72110) was purchased from Dyna-tek industries, Johannesburg, South Africa. For validation experiments, ERNDIM External Quality Assurance Samples (EQAS) 2016 Quantitative Organic Acids samples were utilized.

The predominant organic acids found in kombucha tea were determined by high performance liquid chromatography (HPLC). Six organic acids including glucuronic acid (Sigma-Aldich, Darmstadt, Germany), gluconic acid (Merck, Darmstadt, Germany), d-saccharic acid 1,4-lactone (Sigma-Aldich, Germany), acetic acid (Merck, Germany), ascorbic acid (Merck, Germany), and succinic acid (Merck, Germany) in kombucha tea were optimized for detection by isocratic HPLC systems with a conventional C18 column. The kombucha tea samples were filtered through a 0.22 µm sterile microfilter and 50 μL of the filtrate was injected into the HPLC system (Agilent technologies 1200 series, Santa Clara, CA, USA). The C-18 column (4.6 × 150 mm, 5 µm; GL Sciences, Tokyo, Japan) employing a UV detector (210 nm) was used for the analysis. Moreover, the HPLC system was controlled with a flow rate of 0.8 mL per minute and a running time of 40 min at 25 °C. Six organic acids in kombucha tea were separated by 20 mM KH₂PO₄ elution buffer at pH 2.4 and the standards of organic acids were used for comparison with kombucha tea. The peak area of each organic acid was calculated by Agilent ChemStation level-5 program, and then standard graphs of each organic acid were generated. Thus, the content of each organic acid in kombucha tea was calculated from the standard graph of each organic acid.

Fine graphite powder (<50 μm) was received from Sigma-Aldrich, India. Tetrachloroauric (III) acid trihydrate, chitosan, sulfuric acid (AR grade), potassium permanganate, hydrogen peroxide (30%), sodium nitrate, sodium nitrite, sodium fluoride, sodium bromide, sodium thiocyanate, calcium oxalate, disodium phosphate, sodium bicarbonate, sodium sulphate, and succinic acid were obtained from Merck, India. All chemicals were of analytical grade and used as received. The stock solutions were prepared using doubly distilled water and the experiments were performed under ambient conditions.
UV–vis spectral measurements were performed using a Jasco (V-560) spectrometer. The morphological studies of the as-synthesized composite were characterized by FEI Tecnai G2 20 S-TWIN TEM with an accelerating voltage of 200 kV. FEI Tecnai G2 20 S-TWIN TEM attached BRUKER AXS elemental analyzer was used for the EDS and elemental mapping of the composite. XRD analysis was performed using from Panalytical X′ per PRO X-ray diffractometer equipped with Cu Kα radiation (λ = 0.15406 nm). FTIR was performed by a Shimadzu model FT-IR spectrometer.

Carbon black C-45 (CB, Imerys Graphite & Carbon, Bironico, Switzerland), Picactif BP10 (PICA Co., Levallois-Perret, France), LiFePO₄ (LFP, Aleees Co. Ltd., Taoyuan, Taiwan), NaH₂PO₄∙2H₂O (Caesar & Loretz GmbH, Hilden, Germany), TiO₂ (>99%, Sigma Aldrich, Merck KGaA, Darmstadt, Germany), (NH₄)₂HPO₄ (>99%, Merck KGaA, Darmstadt, Germany), succinic acid (99.5%, Merck KGaA, Darmstadt, Germany), chitosan (>75% deacetylated from shrimp shells, Merck KGaA, Darmstadt, Germany), polytetrafluoroethylene (PTFE) suspension (solid content 60.2% w/w, DuPont de Nemours and Co. BV Nederland, Dordrecht, The Netherlands,), Na₂SO₄∙10H₂O (99%, Merck KGaA, Darmstadt, Germany), Li₂SO₄∙H₂O (ACS, Carlo Erba S.r.l., Milan, Italy), N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC, 98%, Merck KGaA, Darmstadt, Germany), 1 M LiPF₆ in 1:1 (w:w) ethylene carbonate (EC): dimethyl carbonate (DMC) (LP30, 99.9%, Solvionic, Toulouse, France), and Graphite MAGE (D₅₀ 22.8 µm, Hitachi Chemical Co. Ltd., Tokyo, Japan) were used without further purifications. Glass fibre membranes (GF/D, Whatman, GE Healthcare Ltd., Little Chalfont, UK) were used as separators.

For the purposes of determining the total phenolic and flavonoid components, analytical-grade chemicals and reagents were procured from Merck (Darmstadt, Germany) and Carl Roth GmbH (Karlsruhe, Germany). N-hexane, ethyl acetate, and ethanol were obtained from Merck (Darmstadt, Germany). The required acarbose, 3,5-Dinitrosalicylic acid (DNSA), 1,1-Diphenyl-2-picrylhydrazyl (DPPH•), β-carotene, α-glucosidase, and α-amylase were purchased from Merck (Sigma-Aldrich, St. Louis, MA, USA). Ascorbic acid, kojic acid, gallic acid, apigenin, succinic acid, cholesterol, and tannic acid, which served as phenolic standards, were obtained from Merck and Carl Roth GmbH (Karlsruhe, Germany).

Citric acid monohydrate (Roth, Karlsruhe, Germany, ≥99.5%), fumaric acid (Merck, Darmstadt, Germany, >98%), itaconic acid (Merck, ≥99%) linseed oil epoxy (ELO, EPOL-L Traditem, Hilden, Germany), maleic acid (TCl, Zwijndrecht, Belgium, >99%), malic acid (Merck, ≥98%), methyltetrahydrophthalic anhydride (TCl, >80%), oxalic acid dihydrate (VWR, Darmstadt, Germany, ≥99%), pyromellitic dianhydride (TCl, >99%), succinic acid (Merck, ≥99%) and tartaric acid (Aldrich, Steinheim, Germany, ≥99.5%) were used as received.