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| Author(s): |
Felipe Manfroi Fortunato
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Araraquara. 2017-03-17. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara |
| Defense date: | 2017-02-22 |
| Advisor: | José Anchieta Gomes Neto |
| Abstract | |
The aim of this Doctoral Thesis was to evaluation of the internal standard addition method employing spectroscopic techniques. Initially, traditional standard addition method was applied for Ca and Mg determination in biodiesel and urine samples by high-resolution continuum source flame atomic absorption spectrometry and for urea determination in urine samples by Raman spectroscopy. For comparison purposes, all samples and certified materials were also analyzed by external calibration, standard addition and internal standardization methods. Nitrate, Sr and Mn were selected as internal standards for urea, Ca and Mg, respectively. In order to verify the accuracy for Ca and Mg determination were analyzed nine certified reference materials (CRM), the results were in agreement with certified values at the 95% confidence level (t-test). For urea, the accuracy was evaluated by comparison of the results obtained by internal standard addition and a reference method. All results were in agreement at 95% confidence level (paired t-test) with each other. The accuracy was also checked by addition and recovery tests: Ca (93 - 119%), Mg (100 - 116%) and urea (99 - 105%). The drawbacks of traditional internal standard addition were the total volume of sample used, the amount of analytical solutions employed and the lower sample throughput. However, these problems were solved with the development of flow systems and the use of a concentration gradient. The internal standard addition by flow gradient concentration was evaluated for Na and K determination in biodiesel and urine samples by flame emission atomic spectrometry and for ethanol determination in gasoline by Raman spectroscopy. Lithium was selected as internal standard for Na and K, and acetone was selected as internal standard for ethanol. The accuracy of the method for Na and K determination was evaluated by five CRMs analysis, and the results obtained for Na were in agreement with certified values at the 95% confidence level (t-test), for K the results presented underestimated values throughout the study (around 80% recovery). The accuracy for ethanol determination in gasoline was evaluated comparing the results obtained by the proposed method with the reference method. All results were in agreement at 95% confidence level (paired t-test) with each other. The accuracy of internal standard addition by flow gradient concertation method was also evaluated by addition and recovery tests: Na (94 - 110%), K (73 - 86%) e ethanol (99 - 104%). The results obtained by internal standard addition (traditional and flow modes) for all applications showed accuracy and precision better or comparable with traditional calibration methods (standard addition, internal standardization and external calibration), revealing to be an efficient calibration strategy for spectroscopic techniques. (AU) | |
| FAPESP's process: | 12/23323-7 - Internal standard addition method using flowing gradient concentration in spectroscopic techniques |
| Grantee: | Felipe Manfroi Fortunato |
| Support Opportunities: | Scholarships in Brazil - Doctorate |