Determination of Co(II) in plant tissue by microwave digestion and ion chromatography coupled with luminol/perborate or luminol/percarbonate chemiluminescence detection.
BACKGROUND
The cobalt is an essential element for leguminous plants but may be harmful for other species; for that reason determination of Co(II) is very important for the management of polluted areas and for discover plants with capacity for the hyperaccumulation of heavy metals, which has produced a growing necessity of fast, sensitive and selective analytical techniques.


OBJECTIVE
To develop an analytical procedure for the determination of cobalt in plant tissue by coupling the ionic chromatography to the luminol-based chemiluminescence detection.


METHODS
The sample was digested in a mixture of concentrated nitric acid and hydrogen peroxide, using an microwave oven to dissolve the Co(II). The solution containing Co(II) ions was injected to an ionic chromatograph using oxalic acid as the eluent. The detection was based on the catalytic effect of Co(II) on the luminol chemiluminescence using perborate or percarbonate as oxidants. Experimental variables, such as concentrations, pH, flow rates and acid digestion conditions were optimised.


RESULTS
Well-resolved chromatographic peaks were obtained. The height and area showed linear dependences with the Co(II) concentration, which were used to quantify the heavy metal, with recoveries up to 95%. The microwave irradiation (60  s) was sufficient for the complete mineralisation of 200  mg of sample, employing 2  mL of the acid mixture. The method was free from the interferences, requiring less than 12 minutes to complete the analysis.


CONCLUSIONS
The method was simple and rapid for the determination of cobalt in plant tissue with detection limits comparable to those obtained with more sophisticated and expensive analytical equipment.
Murillo Pulgarín
José A
JA
Department of Analytical Chemistry and Foods Technology, University of Castilla-La Mancha, 13071 Ciudad Real, Spain. joseantonio.murillo@uclm.es
García Bermejo
Luisa F
LF
Carrasquero Durán
Armando
A
D001881:Borates / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D002845:Chromatography / Q000379:methods*; D003035:Cobalt / Q000737:chemistry*; D008165:Luminol / Q000737:chemistry*; D008872:Microwaves; D015203:Reproducibility of Results; D012639:Seeds / Q000737:chemistry / Q000378:metabolism; D027843:Vitis / Q000737:chemistry* / Q000378:metabolism
D001881:Borates; D002254:Carbonates; D003035:Cobalt; D008165:Luminol; C027707:sodium perborate; C034738:sodium percarbonate