A sensor based on the electrochemiluminescence (ECL) of the Ru(bpy) 3 2+ complex is attractive in analytical chemistry because of its high substrate selectivity and high sensitivity. 1 -4 It is desired that the ECL sensor has a higher selectivity compared to ECL-based flow-through detectors for HPLC which have been reported by many reseachers. 5 We have prepared an ECL-optic oxalic acid sensor having a Pt electrode coated with chitosan to which Ru(bpy) 3 2+ complex moieties are covalently bonded. 6 The oxalic acid sensor takes advantage of some characteristic properties of chitosan: the high content of a basic amino group, the high hydrophilicity and the ability to form a transparent thin film. The selectivity toward oxalic acid, however, is not very satisfactory for applications to practical samples. The sol-gel method, on the other hand, gives a simple process which can be used to prepare gel materials that can immobilize different functional reagents in working electrodes. For example, Glezer and Lev 7 have prepared a glucose sensor having a Pt electrode coated with a vanadium pentaoxide matrix entrapping glucose oxidase. Dvorak and Armond 8 have reported a determination of Ru(bpy) 3 2+ by preconcentration into Pt and ITO electrodes coated with silica gel. Dominguez et al. 9 have studied the electrochemical behaviors of graphite electrodes coated with an ionexchange polymers/silica gel. We have recently prepared a Pt electrode coated doubly with Ru(bpy) 3 2+ -modified chitosan and silica-gel layers, which has been successfully applied to an ECL optic sensor with improved selectivity toward oxalic acid. 10 In the present paper we report on the fundamental behaviors, such as the potential dependence and the decay of the responses. Experimental Materials and apparatusRu(bpy) 3 2+ complex-modified chitosan was prepared from chitosan and bis(2,2¢-bipyridine)[4-methyl-4¢-(6-bromohexyl)-2,2¢-(bipyridine)]ruthenium(II) perchlorate.6 Tetramethoxysilane (TMOS) was purchased from Shin-etsu Chem. Co. All other chemicals were of reagent grade or better and used without further purification.Voltammetric experiments were performed using a system constructed by a Hokuto Denko HB 104 function generator, a Hokuto Denko HA 301 potentiostat and a Yokogawa 3086 X-Y recorder. The standard three-electrode arrangement consisted of a coated Pt disk (1.6 mmf), a Pt counter electrode and a Ag/AgCl reference electrode. A solution containing 0.1 M KNO 3 and 0.05 M phosphate buffer of pH 6.8 was used as the supporting electrolyte. Highly pure nitrogen was passed through an electrolytic cell thermostated at 25.0±0.2˚C prior to a measurement. ECL experiments were carried out using the same apparatus as reported previously 6,10 at room temperature; the potential applied to the photomultiplier was 900 V. The thickness of the membranes on the working electrode was determined by a Surfcom 575A surface texture measuring instrument (Tokyo Seimitsu Co., Japan). Preparation of sensor probeTMOS, water and methanol were mixed with a 2% ethanol solut...

Crosslinking metal-complexed chitosans (metal ions=Cu(II), Cd(II), Zn(II), Ni(II), and Fe(III)) with (chloromethyl)oxirane yields resins having higher abilities to adsorb Cu2+ than a resin obtained from chitosan in the absence of metal ion. Resins from Cd(II)–chitosan complex can act as effective adsorbents for Hg2+; their Langmuir’s adsorption parameters depend on the quantity of (chloromethyl)oxirane used.

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Various writing implements have often been used at crime scenes in Japan. One of the purposes for the examination of writing ink is to specify writing implements. A number of papers have been published regarding techniques for forensic examinations, including visible spectrophotometry 1,2 , thin-layer chromatography (TLC) 1-4 , X-ray microanalysis 1 , microspectrophotometry 3,5 , high-performance liquid chromatography (HPLC) 6 , gel electrophoresis 7 and capillary zone electrophoresis. 8,9 TLC is the simplest of those methods, and is effective for separating dyestuff components. A systematic TLC study, however, has been pursued only slightly concerning the analysis of Japanese writing inks. In the present paper we describe a preliminary preparation of a standard TLC library for inks, and also discuss the effectiveness and limitation of TLC for the identification of writing implements. We also report on a microsampling technique, that is often requested in the analysis of inks on questioned documents, and the application of a pin-point condensation technique 10 to the identification of dye TLC bands by microscope/Fourier transform infrared spectroscopy (FT-IR). Experimental Pens and reagentsIn this work were used 161 kinds of black, red and blue pens, which were classified for convenience into four groups, as shown in Table 1: oil-based ball-point and marking pens as well as aqueous roller-ball and marking pens. They are now on the market, and some of them were kindly supplied by their manufacturers. Reference dyestuffs were obtained from manufacturers and the Identification Reference Data Center, National Police Agency, Tokyo, Japan. Water was purified by reverse osmosis (Millipore Milli RO15) and deionization. Developing organic solvents for TLC were of reagent grade, and were distilled before use. All other chemicals were also of reagent grade and were used 269 ANALYTICAL SCIENCES APRIL 1998, VOL. 14 1998 © The Japan Society for Analytical Chemistry Black, blue and red writing pens were classified into various groups using the Rf values and color tones of dyestuff bands separated by normal-phase thin-layer chromatography (TLC) of their inks. The classification is effective for the preliminary identification of pens used in crime scenes. A microsampling technique was proposed for the TLC analysis of minute quantities of inks on questioned documents. Furthermore, a combination of reflectance-mode microscope/Fourier transform infrared spectroscopy and the pin-point condensation technique was proved to be useful for the precise discrimination of trace amounts of analogous water-soluble dyestuffs on TLC plates. Analysis of Writing Ink Dyestuffs by TLC and FT-IR and Its

Exploratory studies have uncovered novel photoaddition reactions occurring upon irradiation of 1-methyl-2-phenyl-l-pyrrolinium perchlorate (4) in the presence of a variety of allylsilanes 5-10 and leading to production of 2-allylpyrrolidine photoadducts. Mechanistic studies demonstrate that the reactions occur from the singlet excited state of 4. The effects of substituents on the allylsilane component on the reaction quantum efficiencies