Optode membrane for continuous measurement of silver ions

Abstract

Abstract. An optical sensor (optode) membrane for continuous monitoring of silver ion is presented. It is composed of plasticized poly(vinyl chloride) (PVC), a silver-sensitive chromo-ionophore, and a lipophilic borate salt acting as an anionic site. The membrane selectively responds to silver ion in the concentration range from 50 pM to 10 raM, giving a reversible colour change from blue to pink, with response times of the order of 2 min. The acridinium dye acts as both the recognition element and the chromo-ionophore. Its long-wave absorption band is at around 680 nm, which makes it compatible with existing LED light sources and diode lasers. A lipophilic octadecyl side chain renders it highly lipophilic and this prevents its leakage out of the PVC membrane. Hence, the operational lifetime exceeds 1 week, without any changes in the work function.Key words: silver sensor, optical sensors, chromo-ionophore, spectrophotometry, PVC membrane.Silver is widely used in conventional photography, the production of electrical conductors, and in electroplating. It has been estimated that the total annual loss of silver to the environment from industrial wastes exceeds 2500 metric tons [1], a fact that clearly points to the importance of monitoring and recycling of silver, both from a commercial and an environmental point of view.Numerous analytical procedures (including single-shot tests and field tests) have been described for determination of silver. However, in order to enable continuous monitoring, sensors rather than discontinuous methods are required. Among them, solid-state sensors based on silver sulphide are predominant. In addition, electrochemical ion-selective sensors (ISEs and ISFETs) based on plasticized PVC membranes, modified with various silver-selective ionophores such as thia-crown ethers [2][3][4][5][6][7], calixarenes [8,9], and pyridinophanes [10] have been reported. The

Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 2. Ionophores for Potentiometric and Optical Sensors

“…The idea for a Ag + optode based on a TEHPplasticized PVC membrane containing KTpClPB and an acridine chromoionophore (H + -37; see Koncki et al 101 for a use of this compound as H + ionophore) came from the observation that the latter gives three distinctly different absorbance spectra in the neutral, the protonated, and the Ag + complex form. 102 Due to this peculiar response mechanism, interfering ions mimic a lower Ag + sample activity instead of a higher one, as usually observed for optodes with two ionophores. While interferences from a series of alkali, alkaline earth, and transition metal ions are quite small, Hg 2+ again poisons the optode.…”

“…Bulk optodes based on an acridine derivative as H + ionophore ( H + -37 ) were found to respond to H + in the range from pH 6 to 9 but the response mechanism and possible influence and nature of a coextracted anion was not discussed . The same compound was also reported as Ag + chromoionophore …”

“…The idea for a Ag + optode based on a TEHP-plasticized PVC membrane containing KTpClPB and an acridine chromoionophore ( H + -37 ; see Koncki et al . for a use of this compound as H + ionophore) came from the observation that the latter gives three distinctly different absorbance spectra in the neutral, the protonated, and the Ag + complex form …”

Naphthalimide-Piperazine Derivatives as Multifunctional “On” and “Off” Fluorescent Switches for pH, Hg2+ and Cu2+ Ions

“…Fluorescence-based optical sensors and molecular probes in particular have attracted interest as metal ion sensors due to favorable properties such as high sensitivity and selectivity, the relatively simple detection process and intrinsic low cost. Various fluorescent chemosensors have been synthesized and investigated for heavy metal ion-determination based on photophysical mechanisms such as chelation-induced enhanced fluorescence (CHEF), chelation enhancement quenching (CHEQ), intramolecular charge transfer (ICT), photo-induced electron transfer (PET) and aggregation-induced emission (AIE) [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

A two-component polymeric optode membrane based on a multifunctional ionic liquid

“…Another interesting approach to simplification of sensors is to make them capable of performing simultaneous and/or multianalyte measurements [10][11][12][13] . Clearly, through the combination of these strategies, significant simplification of sensor fabrication can be achieved.…”