Tetramethyl orthosilicate tmos

Concentrated nitric acid (65%), methyl isobutyl ketone (MIBK) and stock standard solutions (1000 mg L⁻¹) of Cd(II), Cu(II) and Pb(II) were purchased from Merck (Merck, Darmstadt, Germany). Ultra-pure water produced by a Milli-Q system, also by Merck (Merck, Darmstadt, Germany), was used throughout the study. Working solutions for the target analytes were prepared on a daily basis through appropriate dilution of the stock standards. Ammonium pyrrolidine dithiocarbamate (APDC) and sol-gel precursors, methyl trimethoxysilane (MTMS) and tetramethyl orthosilicate (TMOS), were purchased from Sigma Aldrich (St. Louis, MO, USA). Aqueous solutions of APDC were prepared daily at appropriate concentration levels. The polyester fabric substrate was purchased from Joanne Fabrics (Miami, FL, USA). Isopropanol, HCl, NH₄OH, and methylene chloride were purchased from Fisher Scientific (Milwaukie, WI, USA). A single-layer graphene oxide dispersion in ethanol (5 mg mL⁻¹) was purchased from ACS Material (Pasadena, CA, USA). The preparation of the coated polyester fabric membranes is described in the Supplementary Materials.
The proposed method was applied to the analysis of different types of alcoholic beverages (i.e., rum, vodka, gin, and tsipouro) with an ethanol content up to 40%. All samples were randomly purchased during April 2022 from the local market of Thessaloniki.

Mitomycin C, ampicillin, and tetramethyl orthosilicate (TMOS) were purchased from Sigma Aldrich (Zwijndrecht, The Netherlands). Nalidixic acid, lysogeny broth (LB) powder, agar, dimethyl sulfoxide, acetone, glycerol, NaCl, KCl, NaHPO₄·2H₂O, KH₂PO₄, HCl, and NaOH were purchased from Boom (Meppel, The Netherlands). All chemicals were of analytical grade and stored as suggested by the manufacturer’s instructions.

The solvents methanol, ethanol and n-hexane, as well as the concentrated ammonium water (25 wt%) and the silica gel precursor, tetramethylorthosilicate (TMOS), were purchased from Sigma-Aldrich/MERCK. Acetic acid was also obtained from Sigma-Aldrich/MERCK. Glucose was procured from a local grocery. The silver-lined capillaries were purchased from DOKO Engineering Japan. They are 20 cm long and have inner diameters of 700 µm. The fused silica capillaries with circular cross sections were obtained from MOLEX and have inner/outer diameters of 530 ± 10 µm/700 ± 20 µm and 700 ± 10 µm/850 ± 20 µm, respectively. The borosilicate glass capillary with an internal diameter of 1000 µm possesses a steel body and has a circular cross section. It was purchased from Chemietechnik Reichelt. Hexamethyldisilazane (HMDS) was provided by Sigma-Aldrich/MERCK and utilised as a hydrophobising agent.

Tetramethylorthosilicate (TMOS) (≥99%, CAS: 681-84-5) was obtained from Sigma Aldrich, USA.
TMOS (as obtained) was poured into the 20 mL of a stirring ultra-pure water. Three aqueous solutions were prepared by adding 2, 4 and 6 mL of TMOS, respectively. Solutions were transferred to moulds and left for 24 h. After the gelation methanol was added on the top of a gel and replaced after 5 h.