Illumination of solutions of spiroquinoxazine 1 yields both a coloured species and a fluorescent species, both of which are reverse photochromic and both of which are trapped by bivalent metal ion complexation.When a photosensitive spiro-pyran or -0xazine is combined with a metal-ion coordinating moiety; then light may influence metal binding or metal binding may influence photochromism.1-3 We are interested in the design and application of fluorescent, metal-responsive photochomics for applications in sensors. We reasoned that the spiroquinoxazine l4 would be a good starting point for such a species; it has the fluorophore in the 6-hydroxyquinoline moiety, and the stable oxazin.2 Further, the nitrogen near the quinoline ring may lead to nitrogen-lonepair quenching of fluorescence, which is an excellent means of transduction for metal ion binding.5 However, 1 apparently has several potential metal-binding sites (2-4 among others). Previous demonstrations of light-induced metal binding have
Mass spectrometry was used to monitor vacuum-drying endpoints in the laboratory and pilot plant to demonstrate feasibility of its application. The technique is relatively simple to interface to existing equipment at minimal cost, requires no direct sample contact, and is generally applicable to multiple dryer configurations. Results of the feasibility study showing the monitoring of multiple solvents, along with correlation of the mass spectrometric technique to conventional percent loss on drying (LOD) measurements, are discussed.
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