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Intra‐laboratory validation of microplate methods for total phenolic content and antioxidant activity on polyphenolic extracts, and comparison with conventional spectrophotometric methods
Author(s) -
BoboGarcía Gloria,
DavidovPardo Gabriel,
Arroqui Cristina,
Vírseda Paloma,
MarínArroyo María R,
Navarro Montserrat
Publication year - 2015
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.6706
Subject(s) - repeatability , gallic acid , trolox , dpph , chromatography , chemistry , relative standard deviation , reproducibility , detection limit , standard curve , antioxidant , organic chemistry
BACKGROUND Total phenolic content ( TPC ) and antioxidant activity ( AA ) assays in microplates save resources and time, therefore they can be useful to overcome the fact that the conventional methods are time‐consuming, labour intensive and use large amounts of reagents. An intra‐laboratory validation of the Folin–Ciocalteu microplate method to measure TPC and the 2,2‐diphenyl‐1‐picrylhydrazyl ( DPPH ) microplate method to measure AA was performed and compared with conventional spectrophotometric methods. RESULTS To compare the TPC methods, the confidence intervals of a linear regression were used. In the range of 10–70 mg L −1 of gallic acid equivalents ( GAE ), both methods were equivalent. To compare the AA methodologies, the F ‐test and t ‐test were used in a range from 220 to 320 µmol L −1 of Trolox equivalents. Both methods had homogeneous variances, and the means were not significantively different. The limits of detection and quantification for the TPC microplate method were 0.74 and 2.24 mg L −1 GAE and for the DPPH 12.07 and 36.58 µmol L −1 of Trolox equivalents. The relative standard deviation of the repeatability and reproducibility for both microplate methods were ≤6.1%. The accuracy ranged from 88% to 100%. CONCLUSION The microplate and the conventional methods are equals in a 95% confidence level. © 2014 Society of Chemical Industry