Aplicação da quimiometria e da espectrometria na determinação simultânea de ibuprofeno e paracetamol e para a detecção da adulteração de leite UHT

Abstract

This thesis comprises two different case studies: the first one is based on the development of a method for simultaneous determination of Ibuprofen (IBU) and Paracetamol (PAR) by spectrofluorimetric determination coupled with multivariate calibration in drugs and urine and validation by HPLC. The concentration range was from 2 to 7 mg.L-1 (IBU) and from 10 to 20 mg.L-1 (PAR) in both techniques. The results obtained for an aqueous standard for both methodologies were compared by using the orthogonal distance method, while the content of analytes in drugs was compared by using of F test, for a confidence level of 95%. In both cases, the methodologies were concordant. The LOD and LOQ were: 0.48 and 1.54 mg.L-1 (IBU); 1.40 and 4.20 mg.L-1 (PAR), respectively. Precision tests and accuracy tests of methodology showed that it was satisfactory. For determination in urine, it was used PARAFAC to perform the deconvolution of spectra. The figures of merit were also established in this case (LOD: 0.54 and 0.83 mg.L-1 for IBU and PAR; LOQ: 1.65 and 2.48 mg.L-1 for IBU and PAR). The second case study was based on the discrimination of adulterants in UHT milk by NIR spectroscopy coupled with chemometric discrimination techniques (SIMCA, PLS DA and SVM DA). The adulterants used were water (from 5 to 40 % v/v), urea and formaldehyde (from 1 to 5 g.L-1). The analysis was done in the range from 1100 to 2500 nm. The spectra of milk with and without adulteration did not show the significative visual difference. The SIMCA method was not able to discriminate the urea at any level. The PLS DA and SVM DA methods showed satisfactory results for adulterants discrimination even in a low degree of adulteration