Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.18/2311
Título: Accuracy in niacin quantification in food matrices, by an RP-HPLC method
Autor: Flores, Cristina
Dias, M. Graça
Santos, Mariana
Palavras-chave: Composição de Alimentos
Data: Mai-2014
Editora: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP
Resumo: Aim: This work intended to evaluate accuracy of niacin quantification in food matrices, by an RP-HPLC method, in order to validate it for four different food groups: legumes, grains, dairy products and fish. Material and methods: Analytical methodology The analytical method was a RP-HPLC with fluorometric detection, based on EN 15652:2009. Samples (1 to 10 g) were submitted to an acid hydrolysis with 0.1 mol/l HCl for 30 min in an autoclave at 121ºC. After filtration, 50 µl of the solutions, were injected and separated at 37 ºC on a HPLC system. The stationary phase was the Fortis C18 5 µm (150 x 4,6 mm) column and the mobile phase consisted of 0.07 mol/l phosphate buffer, 0.075 mol/l hydrogen peroxide and 5x10-6 mol/l copper sulphate, at a flow rate of 1 ml/min. Excitation and emission wavelengths were 322 nm and 380 nm, respectively. Quantification was made with five external standards. Results were expressed in mg/100g. Accuracy evaluation To evaluate precision, at least one matrix of each food group was chosen: roasted peanuts, canned green peas, wheat bran, powder milk and canned tuna. Method trueness was assessed by testing five different reference materials from FAPAS and NIST. Each of the FAPAS samples 2160, 2166, 2172, 2176 (Breakfast Cereals) were tested once over a period of 14 months and, NIST 1849 (Infant/Adult Formula) was tested twice in the same period. In the precision study, the five matrices were tested in triplicate in four different days. Repeatability and intermediate precision standard deviations (Sr and SPi) were calculated, for each matrix, trough ANOVA (p < 0.05). Repeatability and Intermediate precision limits; r and Pi were calculated using the following formulas: r=2.8*S_r and Pi=2.8*S_Pi . Trueness was evaluated from the z-scores obtained. Results: The values of niacin concentration obtained were: peanuts – 13.4 mg/100 g, green peas – 0.59 mg/100 g, wheat bran – 18.2 mg/100 g, powder milk – 0.73 mg/100 g and tuna – 9.5 mg/100 g. The Sr and SPi (mg/100g) were respectively 0.52 / 1.25 (peanuts), 0.02 / 0.05 (green peas), 0.23 / 0.78 (wheat bran), 0.02 / 0.06 (powder milk) and 0.24 / 0.60 (tuna). The r and Pi values obtained ranged from 0.05 to 1.46 for r and 0.14 to 3.50for Pi. All the │z-scores│ obtained for FAPAS samples were < 1 and, the │z-scores│ obtained for NIST reference material were both < 2. Conclusion: The repeatability data obtained in this study, for niacin in different food matrices were in accordance with the ones presented in the method standard EN 15652:2009. Trueness evaluation using breakfast cereals and formulas revealed a good method/laboratory performance. Accuracy evaluation, using representative matrices and niacin contents, showed the method suitable to its purpose and fit to be submitted to accreditation by an external entity.
Peer review: yes
URI: http://hdl.handle.net/10400.18/2311
Aparece nas colecções:DAN - Posters/abstracts em congressos internacionais

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