Method for estimating the content of the chloroform-extractable green fraction (CEGF) in HCI-DMSO extract of soils
2005
Kobayashi, T.(Kobe Univ. (Japan)) | Asakawa, D. | Yanagi, Y. | Suzuki, T. | Watanabe, M. | Ohta, H. | Fujitake, N.
Chloroform-extractable green fraction (CEGF) was detected in the supernatant obtained by alkali precipitation from the HCl-dimethylsulfoxide (DMSO) extract of Pg-rich soil. In the alkaline solution, the color of CEGF was green and CEGF showed strong Pg-like absorption bands. Ultraviolet and visible (UV-VIS) spectral analysis and gel chromatography on Sephadex G-50 were performed to compare several properties between CEGF and Pg. CEGF, which was purified by gel chromatography on Bio-Beads SX-1, displayed strong absorption bands at 609, 562, 445 and 280 nm in the alkaline solution. These absorption bands were almost similar to those of Pg. Furthermore, the UV-VIS spectrum of CEGF in the organic solvents showed a similar characteristic pattern of 4,9-dihydroxyperylene-3,10-quinone (DHPQ), which was considered to be a chromophore of Pg. Based on the results of gel chromatography on Sephadex G-50, CEGF mainly consisted of two fractions, corresponding to the G2 and G3 fractions of Pg. These results indicated that the method for extracting CEGF from Pg-rich soil in the present study was easy and selective and that CEGF was one of the components of, or a closely related substance to Pg. A colorimetric method for the estimation of the CEGF content in soils was developed. The calibration curve of CEGF was linear over a wide range of contents from 2.75 to 220 mg L(-1). The CEGF content in twelve samples of various soils was examined. CEGF was detected in all the soil sampled (5 orders) including three samples (3 orders) where Pg was not detected, and the content ranged from 0.07 to 1.66 g kg(-1) (dry soil). Therefore, the method for estimating the CEGF content in soils developed in the present study was found to be suitable for various soil orders and it was assumed that CEGF occurred in various soil orders.
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