Selective metals determination with a photoreversible spirobenzopyran

The photoreversible metal-ion complexation behavior of nitroquinolinospirop yranindoline (NQSP) was studied in combination with the selective identific ation of six different transition-metal ions, Zn2+, Co2+, Hg2+, Cu2+, Cd2+, and Ni2+, in single- and binary-component mixtures via partial least squar es discriminant (PLSD) analysis. The plasticizer, dicapryl phthalate, was c hosen as the support medium for this study on the basis of (1) its enhancem ent of the photoreversibility and hypsochromic shifts seen in metal complex ation and (2) its potential application to supported liquid membranes for e ventual sensor applications. Complexation of divalent transition-metal ions by NQSP in dicapryl phthalate produced variable hypsochromic shifts in the absorption spectra (30-60 nm), requiring chemometric techniques in order t o overcome the spectral overlaps. PLSD analysis was used to build classific ation analysis models to differentiate between the six divalent transition- metal ions. The feasibility of performing mixture analysis was studied usin g the concept of net analyte signal prior to experimental verification. Sin gle- and binary-component mixtures of metals were identified with 100 and 9 7.4% accuracy, respectively, which included no false positives in either th e training or prediction sets.