Fully electrochemical hyphenated flow system for preconcentration, cleanup, stripping, capillary electrophoresis with stacking and contactless conductivity detection of trace heavy metals

Automated two‐dimensional separation flow system with electrochemical preconcentration, stripping, capillary electrophoresis and contactless conductivity detection for trace metal ion analysis

“…Four orifices were drilled in the upper block (35 Â 35 Â 10 mm 3 ) for flow inlet, flow outlet, capillary fitting and a silver electrode fixing. In applications different from that described here, where products formed at the auxiliary electrode could interfere, the inlet of the cell can be reversed with the outlet (as in [1]). The Ag wire (1 mm diameter) was inserted closely adjacent to the capillary, above the WE, to act as a pseudo-reference electrode and presenting a potential of À230730 mV against an Ag/AgCl reference electrode.…”

“…Before stripping, this medium was replaced by a solution containing 6 mmol/L MES and 6 mmol/L His or a synthetic sample matrix constituted by Ba 21 , Na 1 , Mg 21 and Li 1 5 mg/L in 6 mmol/ L MES/His. As demonstrated elsewhere [1], this diluted buffer is a compromise between the needs of the EPC and CE procedures. Its conductivity is sufficient to allow potential control of the electrode/buffer interface, thus avoiding any loss of metals due to oxidation by dissolved oxygen as well lengthening of the stripping of all metals, while not being too high to hinder preconcentration by field-enhanced sample stacking during the CE separation.…”

“…But ASV and CSV are not free of shortcomings such as unresolved peaks when multiple metals are being determined, or peak broadening and splitting due to the (quite common) formation of intermetallic compounds [6,7]. EPC is, however, not limited to determinations by voltammetry: examples of combinations with other techniques include chromatography, optical spectroscopy, mass spectroscopy, potentiometry [8][9][10][11][12][13] and, in the recent precursor communication of this work, CE [1].…”

“…As already mentioned, the first description of a coupling of EPC with CE coupled with contactless conductivity detection (CE-C 4 D) [1] takes advantage of the perhaps unsurpassed number of electrochemical phenomena in the stages of electrodeposition for metal accumulation and matrix exchange, electrodissolution, field-enhanced sample stacking, electro-osmotic flow pumping, electrophoretic separation and conductance detection, not to mention electrolysis at the cathodic and anodic semi-cells to which the CE high voltage is applied. Manual operation of the components of this EPC-CE-C 4 D prototype is not a simple matter due to the large number of parameters to be controlled and synchronized.…”

“…The conception, design and demonstration of the first interface for coupling electrochemical preconcentration (EPC) with CE was recently communicated [1], unveiling a new range of research opportunities. To speed up advancement in this field, a fully automated EPC-CE flow system is presented and characterized here.…”