[b] 1IntroductionThere is agrowing interest in the impact of agriculture related activitieso ns oil and water quality.P ractices like fertilization, irrigation and application of pesticides are considered potential sources of introduction and deposition of certainh eavy metals and other elements in the environment [1][2][3][4].Phosphate fertilizers are manufactured from rock phosphates and according to their origin they may contain various major and trace elements,n aturally occurring radionuclides and their decay products. Usually,there is apositive correlation between the uraniuma nd the phosphate contenti nr aw material from sedimentary rocks [5,6]. Despite the unquestionablerequirement of phosphate fertilizers,t he application of fertilizers derived from naturally enriched uraniump hosphate rocks configures an anthropogenic source of this analyte [7][8][9][10].S ince an expressiveuranium concentration has been reported in sedimentary phosphate rocks (30-120mgUkg
À1)a nd continuous application of manufacturedp roducts has been performed worldwide in many cultures,t he radionuclide levels are expected to rise over the following years [7,11]. Thus,t he determination of uraniuma nd trace elements such as cadmium and lead in phosphate fertilizersi si mportant, considering that processes like biomagnification and bioaccumulation may occur.Since trace uranium monitoring is significant because of its chemical and radiologic toxicity [ 5,9,[12][13][14][15],e fforts have been devoted for developing sensitive analytical methods applied to uraniumq uantification [16][17][18][19][20][21][22]. Because of their portable character, rapidity,s implicity and sensitivity, voltammetric techniques are especially suitable for this purpose.I np articular,a dsorptive stripping voltammetry (AdSV) has been widely used for trace metal analyses [23][24][25] Thee lectrochemical stripping analysis of tracem etals such as cadmium and lead is widely reported [23,25].A lthough AdSV has been found usefulf or the monitoring of e.g. cadmium concentrations [38],t he anodic stripping voltammetry (ASV) has been commonlye mployed by using the bismuth film electrode (BiFE) [39][40][41][42][43]s ince cadmium and lead signals are ideally placed in the electrode operational potential window [39].With respect to stripping analyses,t here are many published procedures with respect to sequential voltammetric determinations.T he employment of mercury as working electrode is predominant due to the high performance. By using the hangingm ercury drop electrode (HMDE), C. Locatelli has reported the sequential determination of platinum group metals and lead [44,45] and the determiAbstract:Asequential voltammetric procedure for the determination of uranium, cadmium and lead wasi nvestigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)-cupferron complexi nt he differential pulse mode (detection limit of 1.0 mgL À1 ,2 00 sa ccumulation time). Through the manipulation of the same aliquo...
