Selective Metals Determination with a Photoreversible Spirobenzopyran

Abstract

The photoreversible metal-ion complexation behavior of nitroquinolinospiropyranindoline (NQSP) was studied in combination with the selective identification of six different transition-metal ions, Zn(2+), Co(2+), Hg(2+), Cu(2+), Cd(2+), and Ni(2+), in single- and binary-component mixtures via partial least squares discriminant (PLSD) analysis. The plasticizer, dicapryl phthalate, was chosen as the support medium for this study on the basis of (1) its enhancement of the photoreversibility and hypsochromic shifts seen in metal complexation and (2) its potential application to supported liquid membranes for eventual 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 to overcome the spectral overlaps. PLSD analysis was used to build classification analysis models to differentiate between the six divalent transition-metal ions. The feasibility of performing mixture analysis was studied using the concept of net analyte signal prior to experimental verification. Single- and binary-component mixtures of metals were identified with 100 and 97.4% accuracy, respectively, which included no false positives in either the training or prediction sets.

Chemo/bio-sensor networks

“…In contrast, the spiropyran form is colourless, and has no absorbance in the visible spectrum (1, figure 3). Furthermore, the presence of the charged centres in the merocyanine form renders it capable of binding a number of guest species, including metal ions at the phenolate oxygen anion [8,9], and amino acids [10] that complement the zwitterionic charges.…”

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“…[15] Furthermore, the MC isomer has a phenolate anion site to which ions, protons and amino acids can bind, giving rise to new absorption bands in the visible spectrum. [16][17][18] By shining white light on the colored complex, the guest species is released, and the spiropyran form is regenerated.…”

Spiropyran modified micro-fluidic chip channels as photonically controlled self-indicating system for metal ion accumulation and release

“…Spiropyran functionalised micro-channels offer interesting possibilities for controlling metal ion uptake using light, as only the MC form binds with metal ions since the phenolate group of the MC form exhibits ion-binding behaviour, particularly for heavy metals [13,14,43,44]. Moreover, plenty of carboxylic groups of SP-COOH remain free for extra coordination, enhancing the ion-binding behaviour.…”

“…In Figure 5b Based on previous solution studies, Ca 2+ [36], Zn 2+ [13], Hg 2+ [14], Cu 2+ [17,28], As blank experiments, a micro-fluidic device functionalised with non-carboxylated spiropyran (SP) was also fabricated following the same procedure described above necessary as it appears to stabilise the whole molecule inside the hydrophobic porous PDMS polymeric network [46]. A third PDMS micro-reactor (non-functionalised)…”

“…Furthermore, they can be easily incorporated into membranes for improved robustness and ease of handling [11], but from our perspective, most interesting of all, they have metal ion-binding and molecular recognition properties which are only manifested by the MC form [12][13][14][15][16][17][18][19].…”