CHROMATOGRAPHIC SEPARATIONS OF METAL-CHELATES PRESENT IN COMMERCIAL FERTILIZERS .1. DEVELOPMENT OF A GEL-PERMEATION CHROMATOGRAPHIC-SEPARATION METHOD FOR THE IDENTIFICATION OF METAL-CHELATES IN COMMERCIAL FERTILIZERS

The separation of iron(III) chelates of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxy-2-ethylenediaminetriacetic acid (HEEDTA), ethylenediaminedi(o-hydroxyphenyl)acetic acid (EDDHA) and ethylenediaminedi(o-hydroxy-p-methylphenyl)ac acid (EDDHMA) and the Cu(II), Zn(II) and Mn(II) chelates of EDTA by gel permeation chromatography on Bio-Gel P2 and Fractogel HW-40(S) was investigated. The chelates FeDTPA, FeHEEDTA, FeEDDHA and FeEDDHMA were separated on a 35 x 1 cm I.D. Fractogel column using 0.05 M NaCl-0.005 M KH2PO4 (pH 8.0) with a total analysis time of 3 h. FeEDTA was not completely resolved from FeDTPA, and FeHEEDTA, CuEDTA, ZnEDTA and MnEDTA were found to co-elute with FeDTPA. The method is applicable to the qualitative analysis of fertilizers containing a single trace element in combination with a single chelating agent. Positive identification of a chelate is achieved by comparison of retention time data and identification of the metal present by atomic absorption spectrometry or inductively coupled plasma mass spectrometry. Quantification can be achieved by comparison of peak height or area with that of standards.