Optodes based on a calixarene ester for the determination of aldehydes via in situ generation of the Girard's reagent P derivative

Optode membranes for the general determination of aldehydes by visible spectroscopy were developed. A plasticized poly(vinyl chloride) membrane containing a calixarene ester which is used as a host molecule, a hydrogen ion-selective chromo-ionophore (ETH5294) and potassium tetrakis(4-chlorophenyl)borate (KTpClPB) responds reversibly to a guest molecule which is generated in situ from an aldehyde and a Girard's reagent P. The sensitivity of the optode can be modulated by changing the concentration of the calixarene ionophore in the membranes and the pH of the measuring solution. The proposed method shows a good correlation with the theoretically derived equation in the range 4 x 10^-5-0.2 mol l^-1 butyraldehyde with an error of < 6% and with a detection limit of 5 x 10^-7 mol l^-1. Typical response times (t₉₅) for the samples are 5 min.