Potentiometric measurements stripping analysis

Potentiometric stripping analysis has been applied by Sheffrin and Williams [320] to the measurement of copper in seawater at environmental pH. The advantage of this technique is that it can be used to specifically measure the biologically active labile copper species in seawater samples at desired pH values. The method was applied to seawater samples that had passed a 0.45 pm Millipore filter. Samples were studied both at high and at low pH values. 

Electrochemical measurements have been developed by using different electrochemical techniques (differential pulse voltammetry (DPV), cyclic voltametry (CV), potentiometric stripping analysis (PSA), square wave voltammetry (SWV), adsorptive stripping transfer voltammetry (ASTV), etc.). The abbreviations given in covalent attachment of DNA onto different transducers are water soluble carbodimide l-(3-dimethyaminopropyl)-3-ethyl-carbodimide (EDC), IV-hydroxysuccimide (NHS), mercaptohexanol (MCH), aminoethanethiol (AET), mercaptosilane (MSi), and N-cyclohexyl-lV -[2-(N-methylmorpholino)-ethyl]carbodimide-4-tolune sulfonate (CDS). 

Town, R.M. (1997) Potentiometric stripping analysis and anodic stripping voltammetry for measurement of Cu(II) and Pb(II) complexation by fulvic acid a comparative study. Electroanalysis, 9, 407-415. 

Wang, J. Cai, X. Wang, J. Johnsson, C. Palecek, E. Trace measurements of RNA by potentiometric stripping analysis at carbon paste electrodes. Anal. Chem. 1995, 67, 4065-4075. 

Besides these potentiometric-based methods, a series of electrochemical techniques can be applied to the detection of biomolecular interactions. Depending on the desired dynamic detection range and the specific properties of the system under study, techniques such as electrochemical impedance spectroscopy, voltage step capacitance measurements, amperometry, differential pulse voltammetry, square wave voltammetry, AC voltammetry, and chronopotentiomet-ric stripping analysis can be used for label-free detection of DNA, proteins, and peptides [1]. Often these techniques require the use of redox mediators. Electrochemical impedance spectroscopy (EIS), in particular, is a very promising technique for DNA biosensing [2,3]. 

Three broad classifications of electrochemical methods are used in this chapter. Po-tentiometric methods include zero-current potentiometry and methods in which current of controlled magnitude is apphed to the working electrode, such as in potentiometric stripping analysis (PSA). Amperometric methods consider all techniques in which current is measured these include constant-potential amper-ometry and amperometric measurements made in response to a variety of applied potential waveforms in voltammetric methods. Impedimetric methods comprise a final classification in these methods, faradaic currents are generally absent, and impedance, conductance, or capacitance is the measured property. 

Potentiometric stripping analysis (PSA) is another commonly used technique in water analysis. This technique can usually be applied directly to the analysis of water samples without previous treatment, and it is virtually free from interferences of dissolved oxygen. Both, PSA and ASV techniques are based on the same principle the anal) e is first deposited on the electrode surface while the solution is stirred, and then stripped back to the solution in the measurement step [14,22,196]. The ASV technique works on a film electrode (electrochemically deposited mercury or gold on a glassy carbon support). One advantage of PSA is that it requires simpler equipment than ASV, and can compete with nonelectroanalytical techniques in terms of price, and possibility of automation [247-249]. This method has been applied to determine metals in tap water and rainwater samples [250-253], coupled with FIA to determine copper in natural waters [254,255], etc. In addition, portable PSA instruments have also been developed, and demonstrated to be useful for metals determination in aquatic samples [256-259]. 

By changing the deposition time, the oxidant concentration, or the electrode size, the method can be adjusted to the different analytical tasks. Most often, the trace levels of Cu, Pb, Bi, Sn, and Cd ion concentrations are measured with potentiometric stripping analysis. 

---