Two new coumarin-based “turn-off” fluorescent probes, (E)-3-((3,4-dihydroxybenzylidene)amino)-7-hydroxy-2H-chromen-2-one (BS1) and (E)-3-((2,4-dihydroxybenzylidene)amino)-7-hydroxy-2H-chromen-2-one (BS2), were synthesized and their detection of copper(II) and iron(III) ions was studied. Results show that both compounds are highly selective for Cu2+ and Fe3+ ions over other metal ions. However, BS2 is detected directly, while detection of BS1 involves a hydrolysis reaction to regenerate 3-amino-7-hydroxycoumarin (3) and 3,4-dihydroxybenzaldehyde, of which 3 is able to react with copper(II) or iron(III) ions. The interaction between the tested compounds and copper or iron ions is associated with a large fluorescence decrease, showing detection limits of ca. 10−5 M. Preliminary studies employing epifluorescence microscopy demonstrate that Cu2+ and Fe3+ ions can be imaged in human neuroblastoma SH-SY5Y cells treated with the tested probes.

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Keywords 1 Chloride micro-determination ; biological @ids ; spectrophotometry ; chromyl chlorideAbnormal levels of chloride ion in biological fluids, such as serum, urine and cerebrospinal fluid, indicate disorders in the metabolism that are caused by some diseases, so the determination of chloride ion in biological fluids is routine work in clinical laboratories. Numerous methods have been reported for the determination of chloride in these fluids, including volumetric,l polarographic2 and ion-selective electrode method^.^ Spectrophotometric methods are commonly used for the determination of chloride ions in biological fluids as they are readily automated and require small amounts of ample.^ Most of these spectrophotometric methods are indirect and are based on displacement reactions. We have recently developed a direct method for the spectrophotometric determination of chloride, based on the formation of chromyl chloride and its subsequent extraction into carbon tetrachloride.6 In this paper we summarise the results obtained when the chromyl chloride method is applied to the determination of chloride ions in biological fluids. The method proposed involves a slight modification of our previous method. The results are compared with those obtained by two established methods; the mercury(I1) titrimetric method and the iron(II1) -mercury(I1) thiocyanate spectrophotometric method. Experimental SamplesUniversity of Salamanca and were obtained by the use of conventional methods. Samples of serum, urine and cerebrospinal fluid were supplied by the Clinical Hospital of the ReagentsAll reagents were of analytical-reagent grade.Potassizcm dichromate solution, 0.1 N. Concentrated suLphuric acid. Carbon tetrachloride.Hydrogen peroxide solution, 30% mlm. Standard sodium chloride solution, 14.69 g 1-l. dilutions, to prepare a calibration graph. This solution was used, after appropriate ApparatusA Unicam SP 1800 spectrophotometer equipped with a Unicam AR 25 linear recorder and 1.0-cm silica cells was used.Glass-stoppered conical $?asks, 100 ml. Syringes, 25 and 50 p1. ProceduresEstablished methods mercury(I1) thiocyanate spectrophotometric method4 were used.The mercury(I1) titrimetric method (with diphenylcarbazide as indicator)l and the iron(II1)* Presented a t the Fourth SAC Conference, Birmingham, July 17th to 22nd, 1977.