Mercury analysis automatic

Stripping analysis with inherent pre-concentration seems attractive to CFA, but until recently such a procedure appeared rather exceptional. It has been used in the automatic determination of heavy metals in water by anodic stripping voltammetry (ASV12S) in a continuous flow cell with a mercury-covered graphite electrode, having the advantage that one can distinguish... 

Part—III exclusively treats Electrochemical Methods invariably and extensively used in the analysis of pharmaceutical substances in the Official Compendia. Two important methods, namely potentiometric methods (Chapter 16) deal with various types of reference electrodes and indicator electrodes, automatic titrator besides typical examples of nitrazepam, allopurinol and clonidine hydrochloride. Amperometric methods (Chapter 17) comprise of titrations involving dropping-mercury electrode, rotating—platinum electrode and twin-polarized microelectrodes (i.e., dead-stop-end-point method). 

Marquez M, Silva M, Perez-Bendito D. 1988. Semi-automatic analysis of mercury in pharmaceuticals by catalytic titration. J Pharm Biomed Anal 6(3) 307-312. 

For the determination of tin(ll) in kits an EG 8c G polarographic analyzer (model 384) with a static mercury drop electrode (model 303) and a cabinet reference electrode was used. Model 384 is a microprocessor-based polarographic analyzer with built-in floppy disk memory to store and recall analytical curves. By controlling each step of the analysis, the microprocessor automates polarographic and voltammetric measurements. All experimental parameters may be chosen by the operator. Concentrations are computed automatically aud recorded iu the rauge from 0.001 ppb to 9999 ppm. 

An automatic analysis system has been used regularly over the past three years for the determination of mercury in natural waters. Some results will be presented to show the possible applications of this system to determine directly, without the use of sample vessels, the concentration of mercury and its species in natural waters. In this way, contamination - mainly due to sampling procedure - can be considerably reduced. 

In our laboratory, prior to the use of the automatic analysis system for the determination of total mercury in water, acid washed polyethylene vessels were used as storage vessels and 1% v/v cone, sulfuric acid was used as a preservative. At that time, the manual method used for the determination of total mercury in water had a detection limit of 100-200 ng/liter. In the rivers of the region of interest. Northwestern Quebec, the reported concentrations of mercury in the water were highly variable with a mean value of 500 ng/liter. 

The automatic analysis system discussed above is used for the direct determination of mercury in water without using sampling vessels. In remote areas, this requires the use of an electrical generator with a voltage stabilizer and, if the air temperature is low, some insulation of the absorption cell of the mercury monitor. The system can be run on a normal 30 sec sampling-150 sec distilled... 

Some recent advances in methodology have been made by Goulden, one of the originators of the automated analytical technique for the determination of total mercury in water (16), using an automatic analysis manifold similar to that already used in the standard technique. The method, which enables speciation, is a more sophisticated automated modification of the selective reduction method devised by Magos (10,26). A detection limit of 1 ng/liter can be obtained readily, using this method. 

FIA analyzers or FIA components. One company produces a series of instruments that are flow injection systems with atomic absorption spectrometric detection dedicated to determination of mercury. Some companies produce flow injection analyzers for a large number of ions. One supplier has an analyzer that comprises three separate units a basic analytical module, an automatic sample module, and a data capture module, all these units being completely automated. The instrument is capable of analyzing nutrients, ions, and metals. It offers a wide analytical choice using ion-selective electrodes (ISEs), chemiluminescence, or fluorescence. With analysis speeds up to 120 samples per hour and detection limits down to parts per billion levels, this flow injection analyzer performs determinations well compared with other techniques. 

Under these experimental conditions, if the concentration of OCP exceeds 5 X 10 M, its adsorption on the mercury electrode will reach a state of saturation, i.e., a complete coverage of the electrode occurs, which inhibits the reduction of the complex. Therefore the appropriate concentration of OCP to be used in the analysis should be considerably lower than 5 x 10 " M, but about one order of magnitude greater than the estimated concentration of the rare earth ions. The pH value of the solution exerts a great influence on the shape of the wave only at pH 9 does Pj have a sufficient height even at very low of rare earth ions concentration. Under the conditions shown in fig. 5, the linear relationship holds between the heights of P2 and the concentrations of La(III) or Pr(IlI) in the range of 5 x 10" to 1 x 10". When the automatic subtraction technique is applied, the limit of detection is 1 X10" M. 

Vacuum is carefully applied to remove physically adsorbed gases. Degassing times vary decoding on the sample and can be greatly reduced if the samples are oven dried before testing. Triple distilled mercury is slowly introduced until it completely covers the sample and fills the sample chamber any excess is drained off. Air is introduced to raise the pressure to O.S psia from which point the analysis begins. The pressure is raised manually or automatically in steps of about 1 psia to atmospheric pressure. As the pressure on the filled penetrometer is increased, mercury intrudes into tlK sample container and recedes in the capillary. After each increment the pressure is monitored, and may be maintained by the addition of additional pressure until the system... 

Generally, the hanging mercury drop electrode (HMDE) is the most suitable electrode for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) analyses because such electrode allows fast and reproducible surface renewal and provides high adsorptivity for organic compounds. Nevertheless, even HMDE has some drawbacks that limited its use particularly for automatic or on-site voltammetry analysis as well as analysis in flow conditions since it requires a mercury reservoir and regular maintenance of the capillary and... 

---