a
Department of Analytical Chemistry and Computer Chemistry, University of Plovdiv, 24 Tzar Assen Str, 4000 Plovdiv, Bulgaria
E-mail: georgieva@uni-plovdiv.bg
;
Tel: +359 32 261 467
b
Department of Analytical Chemistry and Food Science, University Materials Institute, University of Alicante, PO Box 99, 03080 Alicante, Spain