2 nitrophenyl octyl ether npoe

The lipophilicity values (log P_TLC) of chromoionophores 1–4 were estimated by TLC method [31 (link),32 (link)] using reverse phase chromatography (RP18) with a mixture of methanol: water (9:1, v/v) as the mobile phase. As standards bis(1-butylpentyl)adipate (BBPA) (≥98.0%, Sigma Aldrich, Switzerland), 2-nitrophenyl octyl ether (NPOE) (≥99.0%, Sigma Aldrich, Switzerland), bis(2-ethylhexyl)sebacate (DOS) (≥97.0%, Sigma Aldrich, Germany), bis(2-ethylhexyl)phthalate (DOP) (≥97.0%, Fluka, Switzerland) and di-n-butylphthalate (DBP) (≥97.0%, Fluka, Switzerland) were used.

Aqueous solutions were prepared by dissolving salts and acids in distilled and deionized water. Standard solutions of fixed pH value were prepared by dissolving citric acid (POCH, Gliwice, Poland) and boric acid (POCH). The buffer solution of 1 mM citric acid and 1 mM boric acid was titrated with 1M sodium hydroxide and 1M hydrochloric acid. NaOH (POCH) and HCl (POCH) were added to meet the desired pH value that is 4-12 and 2-3, respectively. All chemicals used for solution preparation were of analytical grade and were used as received without any further purification.
Designed pH sensors are ion-selective electrodes characterized by a sandwich structure with ion-selective membrane placed on the solid-contact layer. The solid-contact layer consisted of hydrous iridium dioxide (hIrO₂) (Alfa Aesar, Haverhill, MA, USA), multiwalled carbon nanotubes (NTs) (Nanostructured & Amorphous Materials, Inc., Houston, TX, USA), and Poly(3- octylthiophene-2,5-diyl) (POT) (Sigma Aldrich, St. Louis, MO, USA). The ion-selective membrane consisted of hydrogen ionophore V (Calix[4]-aza-crown), sodium tetrakis(4-fluorophenyl)borate dihydrate, 2-Nitrophenyl octyl ether (NPOE), and poly(vinyl chloride) (PVC) of high molecular weight were purchased from Sigma-Aldrich. Dimethylformamide (DMF) and Tetrahydrofuran (THF) used as solvents were also purchased from Sigma-Aldrich.

Phosphoric acid di-n-decyl ester (PADE) was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). Tetrakis [3,5-bis(trifluoromethyl)phenyl] borate sodium salt dehydrate (TFPB) and polyvinyl chloride (PVC) were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). 2-Nitrophenyl octyl ether (NPOE) and tetrahydrofuran (THF), which were used as the supporting material and the organic solvent, were purchased from Sigma-Aldrich Japan G.K. (Tokyo, Japan. Figure 1 shows the structures of these substances used to make up the membrane.
Measurement samples are as follows. Potassium chloride (KCl) and sodium chloride (NaCl) were purchased from Kanto Chemical Co., Inc. (Tokyo Japan). Lithium chloride (LiCl) and cesium chloride (CsCl) were purchased from FUJIFILM Wako Pure Chemical Corporation. All samples to be tested were dissolved in pure water. The details of sample solutions will be recorded in Section 2.4.

The chemical reagents utilized to cast the PIMs were Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) pellets (Castle Hill, NSW, Australia), di(2-ethylhexyl)phosphoric acid (D2EHPA) (≥ 97%, Sigma-Aldrich, MO, USA), and tetrahydrofuran (THF) (≥ 99.8, Merck, Darmstadt, Germany). The investigated plasticizers were 2-nitrophenyl octyl ether (NPOE) (99%, Sigma Aldrich, Hamburg, Germany), tris(2-ethylhexyl)phosphate (TEHP) (≥ 97%, Sigma Aldrich, Germany), bis(2-ethylhexyl) phthalate (DEHP) (99.5%, Fluka, Buchs, Switzerland), 1-tetradecanol (≥ 98%, Merck, Germany),Tri-n-butyl phosphate (TBP) (> 98%, Merck, Darmstadt, Germany), and phthalic acid dibutyl ester (DBP) (99%, Sigma-Aldrich, USA).
Sulfuric acid (98%, Neutron, Iran), Bi(NO₃)₃ 0.5H₂O (> 99%, Alfa Aesar, ACS), Fe(NO₃)₃·9H₂O (≥ 98%, Alpha Chemika, Maharashtra, India), ZnSO₄·7H₂O (≥ 99%, Sigma-Aldrich, MO, USA), Ni(NO₃)₂ 0.6H₂O (≥ 99%, Carlo Erba, Italy), Cu(NO₃)₂ 0.3H₂O (≥ 99.5%, Avantor, Gliwice, Poland), Na₂SO₄ (≥ 99%, Neutron, Iran), AlCl₃ (≥ 99%), CrCl₃ (99%), Co(NO₃)₃·6H₂O (≥ 98%), Mn(NO₃)₂. 4H₂O (≥ 98%), NaF(≥ 99.5%), NaOH (≥ 98%), and CdSO₄ 0.8H₂O (≥ 98%,), all from Merck (Darmstadt, Germany). All aqueous solutions were prepared in ultrapure water (resistivity ≥ 18.2 MΩ cm, Zolalan, m-uv-3⁺, Iran).

Membrane components: hydrogen ionophore V (Calix[4]-aza-crown), sodium tetrakis(4-fluorophenyl)borate dihydrate, 2-Nitrophenyl octyl ether (NPOE) and high molecular weight poly(vinyl chloride) were purchased from Sigma-Aldrich (www.sigmaaldrich.com). Dimethylformamide (DMF) and Tetrahydrofuran (THF) used as solvents were also purchased from Sigma-Aldrich. Ruthenium dioxide (RuO₂) used as solid-contact layer was purchased from Acros Organics (www.acros.com). Other chemicals (including TRIS, citric acid, boric acid, sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium chloride) were used for further analysis in form of aqueous solutions. Aqueous solutions were prepared by dissolving salts and acids in distilled and deionized water and then titrated with sodium hydroxide and hydrochloric acid to meet the desired pH values. All chemicals were of analytical grade and were used as received without any further purification.