Multivariate Optimization of Nitrophenol Quantification

PATRICIA ORTIZ; RODRIGO NUÑEZ; VALERIA PFAFFEN

Congreso; IUPAC 49th General Assembly; 2017

Aromatic compounds containing nitro groups are very important chemical substances, nitrophenols, are used in a variety of industries ranging from paint coloring to rubber chemicals and are breakdown products of pesticides including parathion and dinoseb. However, their high toxicity has become of special interest due to these compounds propagation through lixiviation and industrial residuals filtration in many water resources [1].Electrochemical methods, offer in general high sensitivity, low limit of detection, easy operation and the use of simple instrumentation. Bibliographic research on electrochemical analysis of nitro containing compounds indicates that classic polarography has been mainly used, as well as carbon electrodes. Since 2000, bismuth films electrodes (BiFEs) have been presented as an alternative to mercury electrodes for metals determination. Nevertheless, only a few reports can be found for nitrophenols quantification [2-5].When developing an analytical method, several experimental factors, either chemical or instrumental, affecting the analytical signal, must be considered. For that reason, it is necessary to optimize all these factors in a proper way, in order to obtain the best analytical signal. Particularly, factors affecting the electroanaytical signal are usually not independent, so if univariate optimization is used, a biased interpretation can be obtained. Keeping this in mind one of the purposes of the present work was using chemometrics tools for the optimization of nitrophenol quantification using an electroanalytical method. Furthermore, a study has been done on the SWV optimization by using statistical experimental design [6].Nitrophenol electrochemical behavior was performed by cyclic voltammetry either with carbon and bismuth film electrodes. Results show that both electrodes present only one reduction peak, and when comparing these cathodic peaks intensity higher response was obtained with the bismuth film electrode. All the different stages from BiFE preparation up to nitrophenol quantification were optimized using factorial design to obtain the best analytical signal and a BiFE with a stable film that can be used more than once. Concerning the BiFE preparation three factors were evaluated: Bi(III) solution concentration, deposition time and potential. The optimized parameters are: deposition time 67 s and potential -0,600 V and 2.7 mg/L Bi(III) solution. Furthermore, square wave voltammetry (SWV) was chosen as the electroanalytical technique. A glassy carbon electrode was modified with a bismuth film according to the optimized electrodeposition method, and the experimental parameters affecting the current peak were evaluated using experimental design considering current value as the signal. The experimental design was build accounting the following instrumental parameters: frequency, wave amplitude and step potential, being the optima 45.00 Hz, 0.02 V and 0.008 V, respectively. A lineal model for the calibration curve was determined in the (1.0 to 100.0) 10-6 M concentration range, being the limits of detection and quantification 3.4 x 10-6 M and 1.0 x 10-5 M, respectively. Also the precision and accuracy were evaluated resulting that the optimized and validated method can be used for nitrophenol quantification.