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Optimization of experimental conditions for measurements of perfluorinated organic acids by GC
Ston, Martin ; Čabala, Radomír (advisor) ; Coufal, Pavel (referee)
Commercial software Pro ezGC was used for calculation of optimal temperature program for analysis of isobutylesters of perfluorinated organic acids (C6 - C12) by gas chromatography with flame ionization detector. Optimization was done with respect to the complete resolution of all peaks of analytes. The calculated temperature program was also applied to the analysis of substances of interest on GC-MS. The calculated and measured values have been compared. The measured resolutions were higher than the calculated ones in all cases. Keywords: perfluorinated organic acids, isobutylesters, peak resolution Subject words: gas chromatography, numerical optimization
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Development of separation methods for determination of perfluoroalkyl carboxylic acids in envirnonmental samples
Dufková, Veronika ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee) ; Kubinec, Róbert (referee)
A complete, sensitive and selective procedure was developed for gas chromatographic determination of perfluoroalkyl carboxylic acids (PFCAs, C5 - C12) in river water samples. A rapid and simple derivatization procedure was developed and optimized at first, using isobutyl chloroformate (IBCF) to convert the acids into the more volatile isobutyl esters. The second task was to find the most suitable stationary phase for separation of perfluoroalkyl carboxylic acids by GC. The retention characteristics of PFCA isobutyl esters were measured and compared on 9 different stationary phases. The physical-chemical parameters of analyte interactions with stationary phase were monitored on selected column Rtx-200MS, and these parameters were compared with a non-fluorinated homologue - octanoic acid. A sensitive GC-MS system was used with negative chemical ionization, which is suitable for the selected type of fluorinated analytes. The developed method exhibits very low limits of detection and determination of PFCA isobutyl esters: 0.05 - 9.7 ng mL-1 (LOD) and 0.16 - 32.2 ng mL-1 (LOQ). An optimum pre-concentration technique was found for real water samples, where SPE SupelTM-Select HLB cartridges were used. In these cartridges, PFCAs were captured as ion- pairs with enrichment factor of 400. The recoveries of...
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Stanovení perfluorovaných organických kyselin v půdách metodou plynové chromatografie
Okáľová, Zuzana ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee)
A method employing solid-liquid extraction with methanol and solid-phase extraction (SPE) clean-up step using Supelco SupelcleanTM ENVITM -Carb 3 mL cartridges (0.25 g graphitized carbon adsorbent) followed by gas chromatography - mass spectrometry with negative chemical ionization (GC-NCI-MS) has been optimized and applied for determination of ultratrace concentrations of C6 - C12 perfluorinated carboxylic acids (PFCAs) in soil samples. A sophisticated multifactorial statistic method, response surface methodology, employing 1/16 fractional factorial design and the face centered central composite design as well has been applied to find the significant parameters which influence the extraction procedure of PFCAs and SPE clean-up step and to set the optimum extraction and clean-up levels of eight parameters evaluated yielding the maximum extraction recovery of all PFCAs. The analyte extraction recoveries and the limits of detection and quantification have been obtained. The recoveries of individual PFCAs were within a range from 85 to 100 % for analyte spiked concentration level of 1.1 ng g−1 and within a range from 91 to 107 % for analyte spiked level of 2.1 ng g−1 . The values of limits of detection were 1.9 - 3.0 pg g−1 and limits of quantification 6.4 - 10.1 pg g−1 . This analytical method has...
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Development of separation methods for determination of perfluoroalkyl carboxylic acids in envirnonmental samples
Dufková, Veronika ; Čabala, Radomír (advisor) ; Feltl, Ladislav (referee) ; Kubinec, Róbert (referee)
A complete, sensitive and selective procedure was developed for gas chromatographic determination of perfluoroalkyl carboxylic acids (PFCAs, C5 - C12) in river water samples. A rapid and simple derivatization procedure was developed and optimized at first, using isobutyl chloroformate (IBCF) to convert the acids into the more volatile isobutyl esters. The second task was to find the most suitable stationary phase for separation of perfluoroalkyl carboxylic acids by GC. The retention characteristics of PFCA isobutyl esters were measured and compared on 9 different stationary phases. The physical-chemical parameters of analyte interactions with stationary phase were monitored on selected column Rtx-200MS, and these parameters were compared with a non-fluorinated homologue - octanoic acid. A sensitive GC-MS system was used with negative chemical ionization, which is suitable for the selected type of fluorinated analytes. The developed method exhibits very low limits of detection and determination of PFCA isobutyl esters: 0.05 - 9.7 ng mL-1 (LOD) and 0.16 - 32.2 ng mL-1 (LOQ). An optimum pre-concentration technique was found for real water samples, where SPE SupelTM-Select HLB cartridges were used. In these cartridges, PFCAs were captured as ion- pairs with enrichment factor of 400. The recoveries of...
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Determination of selected chromatographic and thermodynamic parameters of perfluorinated organic acids by gas chromatography
Vrzal, Tomáš ; Čabala, Radomír (advisor) ; Pacáková, Věra (referee)
Chromatographic and thermodynamic parameters (specific retention volume, distribution coefficient, standard molar enthalpy, entropy and Gibbs energy) has been determined for retention of isobutyl esters of homological set of perfluorinated carboxylic acids C6 - C12 on the fluorinated stationary phase Rtx-200MS. Determined data has shown, that distribution of solutes between stationary and mobile phase is driven neither by the enthalpy nor entropy, but both these contributors play the same role in the retention mechanism. Helium and hydrogen has been used as a mobile phases during analysis. Their influence on thermodynamic behavior of isobutyl esters of PFCAs is insignificant.
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SPE optimization for determination of perfluorinated organic acids
Ševčík, Václav ; Čabala, Radomír (advisor) ; Pacáková, Věra (referee)
This thesis is focused on optimization of preparation of aqueous environmental samples for determination of persistent pollutants - perfluorinated organic acids, which are potentially dangerous for living organisms. The goal of the thesis is optimization of SPE conditions for preconcentration of these compounds for their determination by GC-MS. Perfluorinated organic acids with carbon chain lenghts of C6-C12 were selected as analytes. Effect of sample pH value, effect of type and elution solvent volume, addition of indifferent salt and ion pair reagent have been studied during the optimization. The results show that the extraction efficiency depends on analyte carbon chain length and reaches values from 75 to 110 % for C6 - C8 and 55 to 95 % for C9 - C12 acids. The overall increase in extraction efficiency was more pronounced for acids with shorter chain length (for C6 up to ten times), whereas for long chain acids the improvement was only moderate.
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Optimization of experimental conditions for measurements of perfluorinated organic acids by GC
Ston, Martin ; Coufal, Pavel (referee) ; Čabala, Radomír (advisor)
Commercial software Pro ezGC was used for calculation of optimal temperature program for analysis of isobutylesters of perfluorinated organic acids (C6 - C12) by gas chromatography with flame ionization detector. Optimization was done with respect to the complete resolution of all peaks of analytes. The calculated temperature program was also applied to the analysis of substances of interest on GC-MS. The calculated and measured values have been compared. The measured resolutions were higher than the calculated ones in all cases. Keywords: perfluorinated organic acids, isobutylesters, peak resolution Subject words: gas chromatography, numerical optimization
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