Determination of synthetic ferric chelates used as fertilizers by liquid chromatography-electrospray/mass spectrometry in agricultural matrices.
A high-performance liquid chromatography-electrospray ionization/mass spectrometry (time of flight) method has been developed for the simultaneous determination of synthetic Fe(III)-chelates used as fertilizers. Analytes included the seven major Fe(III)-chelates used in agriculture, Fe(III)-EDTA, Fe(III)-DTPA, Fe(III)-HEDTA, Fe(III)-CDTA, Fe(III)-o,oEDDHA, Fe(III)-o,pEDDHA, and Fe(III)-EDDHMA, and the method was validated using isotope labeled (57)Fe(III)-chelates as internal standards. Calibration curves had R values in the range 0.9962-0.9997. Limits of detection and quantification were in the ranges 3-164 and 14-945 pmol, respectively. Analyte concentrations could be determined between the limits of quantification and 25 muM (racemic and meso Fe(III)-o,oEDDHA and Fe(III)-EDDHMA) or 50 muM (Fe(III)-EDTA, Fe(III)-HEDTA, Fe(III)-DTPA, Fe(III)-CDTA and Fe(III)-o,pEDDHA). The average intraday repeatability values were approximately 0.5 and 5% for retention time and peak area, respectively, whereas the interday repeatability values were approximately 0.7 and 8% for retention time and peak area, respectively. The method was validated using four different agricultural matrices, including nutrient solution, irrigation water, soil solution, and plant xylem exudates, spiked with Fe(III)-chelate standards and their stable isotope-labeled corresponding chelates. Analyte recoveries found were in the ranges 92-101% (nutrient solution), 89-102% (irrigation water), 82-100% (soil solution), and 70-111% (plant xylem exudates). Recoveries depended on the analyte, with Fe(III)-EDTA and Fe(III)-DTPA showing the lowest recoveries (average values of 87 and 88%, respectively, for all agricultural matrices used), whereas for other analytes recoveries were between 91 and 101%. The method was also used to determine the real concentrations of Fe(III)-chelates in commercial fertilizers. Furthermore, the method is also capable of resolving two more synthetic Fe(III)-chelates, Fe(III)-EDDHSA and Fe(III)-EDDCHA, whose exact quantification is not currently possible because of lack of commercial standards.
Alvarez-Fernández
Ana
A
Plant Nutrition Department, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain. ana.alvarez@eead.csic.es
Orera
Irene
I
Abadía
Javier
J
Abadía
Anunciación
A
D000383:Agriculture; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry; D005029:Ethylenediamines / Q000032:analysis / Q000737:chemistry; D005290:Ferric Compounds / Q000032:analysis* / Q000737:chemistry; D005308:Fertilizers / Q000032:analysis*; D007502:Iron Chelating Agents / Q000032:analysis*; D004369:Pentetic Acid / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*
D005029:Ethylenediamines; D005290:Ferric Compounds; D005308:Fertilizers; D007502:Iron Chelating Agents; C443343:ethylenediaminedi-(o-hydroxy-p-methylphenylacetic)acid; C011813:ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid); C061309:DTPA ferric chelate; C005390:CDTA; D004369:Pentetic Acid; D004492:Edetic Acid; C019179:Fe(III)-EDTA; C026060:N-(hydroxyethyl)ethylenediaminetriacetic acid