Determinação e avaliação da concentração de ânions por cromatografia líquida de alta eficiência com pareamento iônico em águas superficiais

Abstract

The ion chromatography (IC) is the most widely used analytical technique to perform ion analysis in environmental samples. Nowadays, the ionpair high performance liquid chromatography (ion-pair HPLC) has been used to perform this kind of analysis due to the stability and efficiency of reverse phase (RP) column. The ion-pair HLPC is more complex than the reverse phase chromatography, since the equilibrium between the ion-pairing reagent (IPR) and stationary phase (SP) is slow, the separation is more sensitive to variations in temperature and pH. A variation in the concentration of IPR also affects the separation of the analytes. In ion-pair HPLC, several parameters must be optimized such as: mobile phase (MP) composition, type IPR, the concentration of the IPR in MP and pH of the MP. The present work aims to develop an analytical methodology for the separation and quantification of anions (chloride, nitrite, nitrate and sulfate) in surface water samples from Paraibuna River by ion-pair HPLC. The method of analysis of anions was optimized using RP chromatography column octadecylsilane (C18) with indirect detection in the ultraviolet region (UV). During the execution of this work the composition and flow rate of the MP for isocratic elution were studied as well with the wavelength for detection. We tested four different ion-pairing reagents to from the mobile phase. The best condition for separation of ions was achieved with the use of reagent cetyltrimethylammonium bromide. Once completed, the process of separation of anions the methodology was applied in the analyses of water samples from Paraibuna River. The parameters used for evaluate the accuracy and precision of method presented satisfactory values. The concentration levels found for the anions in the samples were below the limit allowed by brazilian legislation for water used for human consume.