Extractive spectrophotometric and fluorimetric determination of boron with 2,2,4-trimethyl-1,3-pentanediaol and carminic acid.
Boric acid at mug ml or ng ml level can be extracted from 1-6M hydrochloric acid into 2,2,4-trimethyl-1,3-pentanediol solution in chloroform and thus separated from many ions which interfere in the usual spectrophotometric methods. The boron is determined directly in the organic phase without back-extraction into water, by adding a solution of carminic acid in a mixture of sulphuric and glacial acetic acids (1+2 v v ) and measuring the absorbance at 549 nm. The molar absorptivity is 2.58 x 10(4) l.mole(-1).cm(-1) and Beer's law is valid for the 0.05-0.4 mug ml boron range. In the fluorimetric method, 509 or 547 nm can be used as the excitation wavelength and 567 nm for emission measurement, giving a linear response in the 8-120 ng ml boron range. Both methods have been applied to determination of boron in plants and natural waters with good precision and accuracy.
Aznarez
J
J
Department of Analytical Chemistry, Faculty of Sciences, University of Zaragoza, Spain.
Ferrer
A
A
Rabadan
J M
JM
Marco
L
L