Anion-Selective Electrodes Based on Long-Chain Methyltrialkylammonium Salts

Abstract

A new series of methyltrialkylammonium salts with an alkyl chain length (n) longer than the conventional methyltridodecylammonium (MTDDA, n = 12) has been developed, and these materials were examined for use as the ion-sensing component (ligand) in anion-selective electrodes (ISEs). Syntheses of the higher ammoniums with n = 16, 18, and 20 were carried out. In combination with an alcoholic plasticizer, the ammoniums with n = 12, 16, and 18 led to ISEs with fundamental characteristics, such as slope sensitivity, impedance, and time response, that were sufficient for practical applications. Compared with the conventional MTDDA, the ISEs based on the ligands of n = 16 and 18 showed marked improvement in chloride selectivity over both lipophilic and hydrophilic anions, deviating from the Hofmeister regime in some cases. Taking perchlorate as an example, the magnitude of the improvement was a factor of 20 for n = 16 and 15 for n = 18. When the new ISEs were applied to chloride analysis in blood serum, they improved the accuracy by a factor of 2-6. Therefore, the methyltrialkylammonium salts with alkyl chain lengths of 16 and 18 offer definite advantages over the conventional alternative and are strong candidates to become the standard compounds for use in future chloride ISEs.

Potentiometric Membrane Electrode for Salicylate Based on an Organotin Complex with a Salicylal Schiff Base of Amino Acid

“…22,23 A study of the effect of a plasticizer on the potentiometric response characteristics involved four kinds of plasticizer, DOP, DDS, DBP and o-NPOE were used. The composition of the membranes was 30.53 wt% PVC, 65.65 wt% membrane plasticizer, and 3.82 wt% ionophore.…”

Highly Selective Triiodide Polymeric Membrane Electrode Based on Tetra(p-chlorophenyl)porphyrinato Manganese (Ⅲ) Acetate

“…Metalloporphyrins, as ionophores for anions, show such specific metal-ligand interactions and also it is well stablished that the central metal and the bulkiness of the side chains that surround the porphyrin ring control the selectivity of the ISEs. 24 In this work, we were interested in investigating the possibility of the use of tetra(p-chlorophenyl)porphyrinato manganese(III) acetate, recently synthesized in our research laboratories, as an ionophore in PVC-based membranes for I 3 − ion. Thus, in preliminary experiments the mentioned ionophore was used to prepare PVC membrane ion-selective electrodes for a wide variety of anions.…”

“…The proposed electrode system was very stable and could be used over a period of at least 2 months without any significant change in its response characteristics. Under optimal conditions, the emf response of the sensor at varying activity of I 3 − indicates a rectilinear range from 1.0 × 10 −2 to 7.5 × 10 −6 M (Figure 3). The slopes of calibration curves were -59.6 ± 0.9 mV per decade of I 3 − concentration.…”

“…The useful anion selective electrodes reported in recent years have been mainly based on quaternary ammonium salts, [1][2][3] vitamin B 12 derivatives, [4][5][6] metal ion complexes, 7,8 organometallic compounds 9,10 and metalloporphyrin derivatives. [11][12][13][14][15][16][17][18] Metalloporphyrins are a class of molecules which, in preliminary studies, have proven useful for such purposes.…”

Polymethacrylate polymers with appended aluminum(III)-tetraphenylporphyrins: Synthesis, characterization and evaluation as macromolecular ionophores for electrochemical and optical fluoride sensors

“…However, historically, the majority of anionselective electrodes and optodes described in the literature are based on dissociated anionexchangers such as lipophilic quaternary ammonium salts [8,9]. Selectivity coefficients of such membrane electrodes are related to the ability of the anion to partition from the aqueous phase into the organic phase since specific interactions between the anion-exchanger and target anions do not exist.…”