Talanta 64 (2004) 853–856 Flame atomic absorption determination of manganese(II) in natural water after cloud point extraction V.O. Doroschuk ∗ , S.O. Lelyushok, V.B. Ishchenko, S.A. Kulichenko Analytical Chemistry Department, Taras Shevchenko Kyiv University, Volodymyrska Str. 64, Kyiv 01033, Ukraine Received 1 December 2003; received in revised form 29 January 2004; accepted 11 March 2004 Available online 26 June 2004 Abstract The possibility to use 4-(2-pyridylazo)resorcinol (PAR) and 1-(2-pyridylazo)-2-naphthol (PAN) for manganese(II) concentrating by the micellar extraction at cloud point (CP) temperature and subsequent atomic absorption spectrometry (AAS) determination was investigated. Under the optimum conditions, preconcentration of 100 ml of water sample in the presence of 1% non-ionic surfactant (NS) OP-7, 1 × 10 -4 M 1-(2-pyridylazo)-2-naphthol permitted the detection 5 gl -1 manganese. The proposed method has been applied to the AAS determination of manganese in water samples after cloud point extraction. © 2004 Elsevier B.V. All rights reserved. Keywords: Non-ionic surfactant; Cloud point extraction; Manganese determination 1. Introduction The general trend of the modern analytical chemistry is the elaboration of simple, ecologically safe, sensitive, and selective methods for microcomponents determination com- bining previous concentration and further determination by physical or physico-chemical methods [1]. Micellar extrac- tion with non-ionic surfactants (NS) at cloud point (CP) is a high effective, ecologically safe method for microcompo- nents preconcentration which has been developed intensively recent years [2,3]. High concentration coefficients, selec- tivity, simple combination with spectral, atomic absorption, chromatographic, and electrochemical analysis allow to use extraction with NS phases for elaborating high-sensitive and convenient analytical methods [4–7]. NS dissolves in water due to the hydrogen bonds forma- tion between oxygen atoms of polyoxyethyl chain and water molecules [4]. Heating of aqueous NS solutions till definite temperature; namely, cloud point results in destruction of these bonds and further separation of the system into phases. Hence, the two phases are formed. The first one is the NS phase, which consists of large hydratated micelles, and the second one is the aqueous solution of NS with the concen- ∗ Corresponding author. Tel.: +380-44-239-33-98. E-mail address: doroschuk@univ.kiev.ua (V.O. Doroschuk). tration level near critical micelle concentration. The micellar phase is used for concentrating. Manganese(II) is a biometal with low contents in nat- ural waters. Thus, Mn 2+ ions present in natural waters always participate biocycles. Lack of the manganese in the human organism leads to the bones and cartilages de- formation and destroys platelet aggregation. As a rule, the overall manganese content in natural waters is deter- mined by photometric method after oxidation of Mn 2+ ions into MnO 4 - with peroxysulfate. However, this method is of low sensitivity (limit of determination, 50 gl -1 ) and labour-consuming [8]. The extraction–spectrophotometric procedures have been applied for manganese determination in water samples [9,10]. However, used organic solvents are hazardous causing damage to human health and the en- vironment. On another hand, the application of cloud point extraction method is used for manganese preconcentration with 1-(2-thiazolylazo)-2-naphtol into the NS Triton X-114 phases [11]. The using of 0.05% Triton X-114 solution for the extraction of manganese allows to decrease the limit of metal determination to 0.28 ppb by the AAS. Herein, the micellar extraction of manganese(II) with 4-(2-pyridylazo)resorcinol (PAR) and 1-(2-pyridylazo)-2- naphthol (PAN) into phase of non-ionic SAS OP-7 has been investigated. The reagents choice was caused by high sta- bility of their complexes with manganese [12]. Also, it was possible to examine the influence of the ligand structure 0039-9140/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2004.03.056