Chinese Journal of Chemistry, 2005, 23, 160—165 Full Paper * E-mail: soruraddin@tabrizu.ac.ir Received March 18, 2004; revised August 9, 2004; accepted October 28, 2004. © 2005 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Spectrofluorimetric Determination of Cu 2＋ Using New Fluorogenic Reagent MOHAMMAD-HUSSEIN, Sorouraddin* ,a MOHAMMAD-REZA, Rashidi b BEHROOZ, Shabani c EBRAHIM, Ghorbani-Kalhor a a Analytical Chemistry Department, Faculty of Chemistry, Tabriz University, P. O. Box 51664, Tabriz, Iran b Drug Applied Research Center, Tabriz University of Medical Science, Tabriz, Iran c Inorganic Chemistry Department, Faculty of Chemistry, Tabriz University, Tabriz, Iran A new synthesized fluorogenic reagent, 8-[(2-pyridine)methylideneamino] quinoline (PMAQ), was utilized for spectrofluorimetric determination of Cu(II) at trace levels. PMAQ, a good fluorogenic reagent, though insoluble in water, but is soluble in ethanol and 20% ethanol-water. The excitation and the fluorescence wavelengths of PMAQ were 310 and 434 nm respectively. When the reagent was complexed with Cu(II), the fluorescence intensity de- creased proportionally with the concentration of Cu(II) at pH 4.5 by a static quenching effect. The highest sensitiv- ity to Cu 2＋ determination was shown to be at PMAQ concentration of 1.0×10 －5 mol•L －1 . In order to enhance the quenching effect, the Cu(II)-PMAQ complex solution was kept at 22 ℃ for 20 min. Though the interferences by Co(II) and Fe(III) were very serious, they were however, completely eliminated by being masked with oxalate and ascorbate ions respectively. The linear dynamic range for Cu(II) determination was between 25—441 μg•L －1 with the detection limit of 18 μg•L －1 (RSD＝3.7%, n＝6). The proposed method was successfully applied to the deter- mination of Cu(II) in real samples including human blood serum, commercial tea and wheat flour. Keywords copper determination, fluorogenic reagent, spectrofluorimetry Introduction Copper determination at trace levels has received widespread attention in the clinical and physiological studies. Copper as an essential trace element, plays a complex role in most living organisms. It is also known as one of the toxic elements in the environment. Some investigations have shown that copper-deficiency in the human body is chronically one of the reasons for result- ing in the cardiovascular disease, and, if copper is ex- cessively accumulated in the human body, it can cause poisoning. In general, a daily copper intake of 1.5—2 mg is essential. But, severe oral intoxication will affect mainly the blood and kidneys. 1 Therefore, the trace copper content in food and biological samples must be controlled on a daily basis. In order to assess copper accumulation or deficiency in biological and environ- mental samples, sensitive, reproducible and accurate analytical methods are required. 2 With spectrophotome- try, 3-5 electroanalytical methods, 6 chromatography, 7,8 and electrochemical analysis, 9,10 many new and modi- fied techniques that can be used to determine metal ions in real samples, have been studied. While these methods have some pros and cons, spectrofluorimetry has merit in a sense that it is more sensitive, convenient, and sim- pler than other techniques. The fact that in most fluorimetric determinations no pre-concentration step is needed, makes the analysis procedure simpler and faster than other techniques. Furthermore due to the inherent sensitivity, the fluorescence methods are increasingly being used in biochemical, medical, chemical research and determination of trace and ultra trace levels of metal ions. Although, there are a large number of published papers on spectrophotometric determination of Cu 2＋ , the spectrofluorimetric methods including the deter- mination of copper in food samples, 11 industrial and environmental applications, 12 ore and hair samples, 13 alloys and stream water, 14 industrial water and aqueous solution 15,16 are however, very limited. This is due to the fact that only very few metal ions exhibit a natural lu- minescence and most like Cu 2＋ do not. Hence, in the later cases, complexation with a suitable ligand (fluorophore) is required. In fluorimetric methods, the metal ions have often been determined with techniques that fluorescence intensity of the fluorophore (ligand) is enhanced when bound to a metal ion. In contrast, the quenching effect has also been utilized in some cases to determine metal ions, where the fluorescence intensity of fluorophore (ligand) decreases with the concentration of metal ion. The fluorescence quenching method using available or synthesized fluorogenic reagent has been applied to the determination of metal ions, 17-21 organic materials, 22 inorganic anions and biological materials. 23 In this work, therefore, for expanding the fluorimetric techniques, a new fluorogenic reagent, 8-[(2-pyridine)-