Journal of Zhejiang University SCIENCE
(ISSN 1009-3095, Monthly)
2005 Vol. 6B No. 6 p.514-522
Application of derivative ratio spectrophotometry for determination of β-carotene and astaxanthin from Phaffia rhodozyma extract
NI Hui1, HE Guo-qing†1, RUAN Hui1, CHEN Qi-he1, CHEN Feng2
(1Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310029, China)
(2Department of Food Science and Human Nutrition, Clemson University, Clemson, South Carolina 29634, USA)
†E-mail: gqhe@zju.edu.cn
Received Dec. 1, 2004; revision accepted Feb. 1, 2005
Abstract: A derivative ratio spectrophotometric method was used for the simultaneous determination of β-carotene and astaxanthin produced from Phaffia rhodozyma. Absorbencies of a series of the standard carotenoids in the range of 441 nm to 490 nm demonstrated that their absorptive spectra accorded with Beer’s law and that the additivity when the concentrations of β-carotene and astaxanthin and their mixture were within the range of 0 to 5 µg/ml, 0 to 6 µg/ml, and 0 to 6 µg/ml, respectively. When the wavelength interval (∆λ) at 2 nm was selected to calculate the first derivative ratio spectra values, the first derivative amplitudes at 461 nm and 466 nm were suitable for quantitatively determining β-carotene and astaxanthin, respectively. Effect of divisor on derivative ratio spectra could be neglected; any concentration used as divisor in range of 1.0 to 4.0 µg/ml is ideal for calculating the derivative ratio spectra values of the two carotenoids. Calibration graphs were established for β-carotene within 0−6.0 µg/ml and for astaxanthin within 0−5.0 µg/ml with their corresponding regressive equations in: y=−0.0082x−0.0002 and y=0.0146x−0.0006, respectively. R-square values in excess of 0.999 indicated the good linearity of the calibration graphs. Sample recovery rates were found satisfactory (>99%) with relative standard deviations (RSD) of less than 5%. This method was successfully applied to simultaneous determination of β-carotene and astaxanthin in the laboratory-prepared mixtures and the extract from the Phaffia rhodozyma culture.
Key words: Derivative ratio spectrum, β-carotene, Astaxanthin, Spectrophotometry
doi:10.1631/jzus.2005.B0514 CLC number: TQ926.4; O657; Q939.97