This study was realized under the support of the bilateral international collaboration between the Czech Academy of Sciences and CONCYTEC (Peru) 2013-2014. We thank Dr. Gertrud Cronberg, Institute of Limnology, Lund, Sweden, for offering us her unpublished data about the composition of phytoplankton of the Atitlan and Amatitlan lakes from the year 1983. We are indebted to our referees both for comments on the text and helpful cultivation of our English.

Anodic-stripping voltammetry, like as other electro-analytical techniques of chemical analysis can be very valuable as complements for neutron activation analysis (NAA), for rapid, accurate and simultaneous determination of some trace elements in water and in digested biological samples at the ppb(g/L) range. Commercial voltammetric analyzers may have a cost in the range of US$ 20,000.00 and the limited budget of our NAA laboratory not allow us to buy this kind of complementary instrumentation. In this paper we describe a PC- based voltammetric analyzer, designed and built in our laboratories at a relatively low cost.