Electrodes, cleaning

The use of intermittent BD arrangements employing timers and electrical conductivity electrodes has been standard technology for at least 25 years. Nevertheless, problems still occur that may be attributable to the use of electrodes unsuitable for the temperatures involved or inadequate electrode cleaning and maintenance. 

A modified immersion method has been used by Hamm et al.140 to obtain electrochemical cell by a closed-transfer system, and immersed in 0.1 M HCIO4 solution at various . was derived from the charge flowing during the contact with the electrolyte under potential control. For the reconstructed Au(l 11M22 X Vayo.l M HCIO4interface, =0.31 0.04V (SCE) (Table 9). Using the impedance method, = 0.34 V (SCE) for recon-... 

Marken F, Compton RG (1998) Sonoelectrochemically modified electrodes ultrasound assisted electrode cleaning, conditioning, and product trapping in 1-octanol/water emulsion systems. Electrochim Acta 43 2157-2165... 

Platinum is the most popular choice of inert electrode for electroanalysis. It will also be clear from the discussion above that electrodes made of platinum should be cleaned thoroughly and as often as possible. Unfortunately, many analytical laboratories employ automated equipment, so cleaning occurs sporadically at best. Worse still, in many industrial laboratories, where the cost and number of each sample are always a consideration, the frequency of electrode cleaning will be a commercial decision. 

In any setup, it is paramount that the electrodes get cleaned regularly. The minimum frequency, e.g., once a week, should be described in the instrument standard operation procedure (SOP), but for some methods or samples more frequent cleaning is necessary. An example is the determination of the enantiomeric purity of adrenaline in local anesthetic solutions. The samples are isotonic and contain high concentrations of local anesthetics (5—20mg/ml). The determination concerns very low concentrations of adrenaline (typically 5 pg/ml of 1-form and only a few percent of that of the d-form) and the samples are therefore injected undiluted. Furthermore, relatively high concentrations of cyclodextrin are present in the BGE. Eong sequences therefore require electrode cleaning for every sequence and this is thus described in the method procedure. ... 

Is acid added to the system If so, is it added via a dilution sump into an area close to the makeup water addition point Is the pH electrode cleaned and buffered regularly (2 times weekly) ... 

Is there a conductivity controlled, solenoid bleed system installed Does it work Is it accurate Is the electrode cleaned regularly (once per 2 weeks typically) ... 

Flow assemblies are recommended for housing a conductivity cell, pH/ORP probes, or other monitoring devices. However, they should be designed and installed for easy physical access and cell/electrode cleaning. Flow assemblies should also incorporate a sample port. 

Electrode cleaning to ensure repeatable nonlinear dielectric spectra is a complex and empirical task, due to the lack of knowledge of the exact form of the... 

This section summarizes some of the most significant electrochemical results obtained to date for selected electrodes cleaned and characterized under UHV in PEO-lithium-based solutions, and include nonalloy (Ni)- and alloy-forming metals (Ag and Al), a noninteracting substrate (boron-doped diamond, BDD) and a material capable of intercalating Li+ (graphite). It is expected that the information herein contained will serve to illustrate the power of this methodology for the study of highly reactive interfaces. 

Sonovoltammetry mass transport effects - further aspects 80 Electrode cleaning and activation 81 Electrode kinetics 82... 

Wightman and his group have continued with studies of this type and have found that using a variant of normal pulse voltammetry is probably preferable to using cyclic voltammetry because the period at the base potential between pulses helps to prevent film formation on the electrode and thus keeps the electrode clean. In this way, the behaviour of an implanted microelectrode remains reproducible over a long period of time, which is important as it is very difficult to reposition an electrode in exactly the same spot after it has been removed for cleaning. 

A pulsed voltammetric method for carbon electrodes would be advantageous in many respects (electrode cleaning, increases sensitivity, lack of sensitivity to flow rate variations with suffidently fiut pulse time). Present... 

B) SFG spectra of CN adsorbed on a platinum electrode in 0.1 M NaCI04 and 0.025 M KCN. Starting from an electrode cleaned at -1.25 V/SCE, going toward positive potentials. Filled diamonds,... 

Immediately determine the voltage of your galvanic cell by connecting the wires to the proper terminals of the voltmeter as indicated by your starch-potassium iodide test. Continue to read the voltmeter for several minutes to make sure that you observe the maximum voltage of your cell. Record the maximum voltage in TABLE 29.lA. Remove the zinc electrode, clean it, and return it to the reagent shelf. 

Hordenine was detected with a dual-electrode coulometric cell. The potential of the first electrode was set to -I-0.50V [vs. solid palladium reference electrode (Pd)], which was at the base of hordenine s hydro-dynamic voltammogram. This electrode cleaned the sample by removing easily oxidizable impurities. Hordenine and its precursors were subsequently detected by a second electrode at a potential of -I-0.75V. This method of detection is called the screen mode . In addition, the mobile phase was purified by connecting a coulometric cell between the pump and injector as a guard cell. This additional cell operated at +0.80 V. The detection limit of hordenine was at 1.1 ng, which was 25 times better than detection by UV at 275 nm. 

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