Potentiometric selectivity study of crown ethers containing four ring oxygen atoms and benzoxymethyl or carboxylic acid side chains as ionophores for lithium and potassium

Abstract

Five crown ethers with four ring oxygen atoms and different types of pendant groups were used t o prepare ion-selective electrodes by coating a membrane containing the crown ether on the tip o f a silver wire incorporated in a flow cell. A flow injection analysis study was conducted to determine the potentiometric selectivities of the crown ethers for lithium, sodium, potassium, magnesium, and calcium ions. It was found that crown ethers with neutral side arms show selectivities for lithium over other ions, while those of acidic side arms show selectivities for potassium over the other ions. The effect of the addition of trioctylphosphine oxide to the electrode matrix was also investigated. A comparison is made between the potentiometric selectivities of the crown ethers for certain metal ions and tlieir selectivities in extracting the ions into an organic phase.

Lithium Ion-selective Electrodes Employing Tetrahydrofuran-based 16-Crown-4 Derivatives as Neutral Carriers

“…After evaporation of the solvent, the residue was purified by fractional distillation at 65 °C (6 mmHg) to obtain a colorless oil in 18% yield. 5,10,15,4,6,9,11,14,16,3,6,8,11,13,16, To a solution of 105 ml of LiClO 4 •3H 2 O (32 g) in a mixture of 60% HClO 4 -H 2 O-ethanol (1 + 4 + 16 v/v) were added 4.7 ml (31 mmol) of 1 and 5 ml (90 mmol) of acetaldehyde at 0 °C. The mixture was stirred at room temperature for 41 h, then extracted with diethyl ether, washed with 10% NaHCO 3 , dried (MgSO 4 ) and concentrated.…”

“…The resulting yellow solid was recrystallized from hexanes three times and from light petroleum twice to obtain 2 as white crystals in 11% yield. 5,10,15,4,6,9,11,14,16,…”

“…After removal of the catalyst by filtration, the filtrate was concentrated and the residue was chromatographed using benzeneethyl acetate (1 + 1 v/v) to obtain glassy oil, which was a mixture of stereoisomers (THF-I). The isomeric mixture of almost identical physico-chemical properties was chromatographed several times using ethyl acetate-hexane (1 + 4 v/v) as eluent, resulting in the isolation of the cis-isomer (R f = 0.21) in a low yield ( 5, 4,6,9,11,14,16,3,6,8,11,13,16, To a solution of 105 ml of LiClO 4 •3H 2 O (32 g) in a mixture of 60% HClO 4 -H 2 O-ethanol (1 + 4 + 16 v/v) were added 6.7 ml (31 mmol) of 1,1-difuryl-2-phenylethane, which was prepared by a method similar to the method for 1, and 5 ml (90 mmol) of acetaldehyde at 0 °C. After 30 min at 0 °C, the mixture was stirred at room temperature for 60 h, then the product was extracted with diethyl ether, washed with 10% aqueous NaHCO 3 , dried (MgSO 4 ) and concentrated.…”

“…8 In this regard, considerable attention has been focused on the design and synthesis of lithium ionophores particularly with a high Li + /Na + selectivity. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] As with most other ISE systems, analytically useful lithium ISEs have been prepared with polymeric sensor membranes employing neutral carrier-type ionophores. Some highly selective ionophores used in lithium ISEs are N,Ndicyclohexyl-NA,NA-diisobutyl-cis-cyclohexane-1,2-dicarboxamide (ETH 1810; available as Lithium Ionophore III from Fluka, Buchs, Switzerland), 21,22 5-butyl-N,N,NA,NA-tetracyclohexyl-5-ethyl-3,7-dioxaazelaic acid diamide (ETH 2137; available as Lithium Ionophore IV from Fluka), 22 6,6-dibenzyl-1,4,8,11-tetraoxacyclotetradecane (Lithium Ionophore VI), 23 14-crown-4-dibutylamide, 24 2,2,3,3-tetramethyl-9-tetradecyl-1,4,8,11-tetraoxacyclotetradecane 25 and 2,9-dibutyl-1,10-phenanthroline.…”

Imprinted Polymeric Beads-Based Screen-Printed Potentiometric Platforms Modified with Multi-Walled Carbon Nanotubes (MWCNTs) for Selective Recognition of Fluoxetine

“…They are stable to extremes of pH, organic solvents and temperature, which provides for more flexibility in the development of analytical and bioanalytical methods [27][28][29]. MIPs have a valuable impact on the enhancement of ion-selective electrodes, in which the encapsulated molecules, attached via their high affinity three-dimensional cavities, act as tailor-made highly specific receptor sites for the desired molecule [30][31][32][33][34][35][36]. In addition, the developed membrane potential in ISEs does not require the extraction of the template from the molecular imprinting skeleton.…”