The flow injection system compriseda nASIA analyzer (Ismatec,
Zürich, Switzerland) equipped with avariable speed (1–50 rpm)
four-channel pump (Mode l7610, Rheodyne, USA), Tygons tubing
(2.06and1.42mmi.d.) forpropelling the fluids, and a sample
injection valve (Model 5041, Rheodyne,USA).