Mercury, determination with

Jian, L., Goessler, W, and Irgolic, K. J. (2000). Mercury determination with ICP-MS Signal suppression by acids. Fresenius J.Anal. Chem. 366(1), 48. 

Beckmann thermometer A very sensitive mercury thermometer with a small temperature range which can be changed by transferring mercury between the capillary and a bulb reservoir. Used for accurate temperature measurements in the determination of molecular weights by freezing point depression or boiling point elevation. 

Ultrapure (triple distilled) mercury is commonly tested by evaporation or spectrographic analysis. In the former, a composite sample is evaporated and the residue weighed. In spectrographic analysis, a sample is dissolved and evaporated, the residue mixed with graphite [7782-42-5] and the emission spectmm determined with a spectrograph. 

The Nernst equation shows that the glass electrode potential for a given pH value will be dependent upon the temperature of the solution. A pH meter, therefore, includes a biasing control so that the scale of the meter can be adjusted to correspond to the temperature of the solution under test. This may take the form of a manual control, calibrated in 0 C, and which is set to the temperature of the solution as determined with an ordinary mercury thermometer. In some instruments, arrangements are made for automatic temperature compensation by inserting a temperature probe (a resistance thermometer) into the solution, and the output from this is fed into the pH meter circuit. 

Mercury in various cement products was determined with a special mercury oven for solid samples. Calibration was performed with four BCR CRMs and one NIST SRM with different Hg content as well as with a reference solution and excellent agreement found (Bachmann and Rechenberg 1991). 

Bettmer, J., Cammann, K., and Robecke, M., Determination of organic ionic lead and mercury species with high-performance liquid chromatography using sulphur reagents, /. Chromatogr., 654, 177, 1993. 

Samples for mercury analysis should preferably be taken in pre-cleaned flasks. If, as required for the other ecotoxic heavy metals, polyethylene flasks are commonly used for sampling, then an aliquot of the collected water sample for the mercury determination has to be transferred as soon as possible into glass bottles, because mercury losses with time are to be expected in polyethylene bottles. 

In animal studies [9], up to 8% of isotopically labelled mercuric chloride applied to the skin was absorbed within 5 h. The state of the skin is one factor which determines the rate of absorption [10]. Passive diffusion cannot be the only process involved, since the absolute absorption rate of mercury increases with increasing concentration up to a plateau value. In addition, skin absorption probably occurs transepidermally rather than via the follicular pathway [11]. 

Figure 6.9 Polarogram showing a time-averaged current, i.e. redrawn without the sawtoothed effect caused by the cyclic nature of the mercury drops the half-wave potential, 1/2, and the residual current are also indicated. The magnitude of the diffusion current, 7a, is determined with respect to the residual current.

Elements such as As, Se and Te can be determined by AFS with hydride sample introduction into a flame or heated cell followed by atomization of the hydride. Mercury has been determined by cold-vapour AFS. A non-dispersive system for the determination of Hg in liquid and gas samples using AFS has been developed commercially (Fig. 6.4). Mercury ions in an aqueous solution are reduced to mercury using tin(II) chloride solution. The mercury vapour is continuously swept out of the solution by a carrier gas and fed to the fluorescence detector, where the fluorescence radiation is measured at 253.7 nm after excitation of the mercury vapour with a high-intensity mercury lamp (detection limit 0.9 ng I l). Gaseous mercury in gas samples (e.g. air) can be measured directly or after preconcentration on an absorber consisting of, for example, gold-coated sand. By heating the absorber, mercury is desorbed and transferred to the fluorescence detector. 

Typical cold vapour generation AAS system used for mercury determination. The same system can be used with a flame in place of the Pyrex tube to allow the determination of hydride -forming elements. 

R. Rodil, A. M. Carro, R. A. Lorenzo, M. Abuin and R. Cela, Methyl-mercury determination in biological samples by derivatisation, solid-phase microextraction and gas chromatography with microwave-induced plasma atomic emission spectrometry, J. Chromatogr. A, 963(1-2), 2002, 313-323. 

The determination of the temperatures of crystallization of the mixtures was carried out in a closed glass apparatus with a manual stirrer. This entered the vessel through a hole of tight bore in the rubber stopper, which was greased with vaseline, so that the accession of atmospheric moisture was reduced to a minimum. Temperatures above 0°C were measured with a mercury thermometer with scale divisions of 0-1°, which was calibrated by the ice-water mixture at 0° and by the Na2S04 0H2O transition point at 32 38°. For temperatures below 0° an alcohol thermometer with 0 2° scale divisions was used. It was calibrated also at 0° with the ice-water mixture. Since the thermometer capillary was at room temperature in the course of the determinations, a correction for its expansion was applied. The low temperatures were obtained by means of dry ice-acetone mixtures. 

Instead of making a direct volumetric determination of the hydrosulphite it is possible to modify the process by estimating volumetrically the product of a primary reaction. For example the hydrosulphite solution may be submitted to atmospheric oxidation and the resulting acidity determined with standard alkali,2 or a mercuric salt may be reduced, the mercury produced being estimated subsequently by the addition of standard iodine solution and titration of the excess of iodine one molecule of hydrosulphite is equivalent to an atom of mercury and therefore to two atoms of iodine.4 Similarly, instead of the gravimetric estimation of silver as described above, the latter may be redissolved in nitric acid and determined volumetrically.5... 

The following data show how the density D of mercury vanes with the Kelvin temperature T Plot these data From the resulting graph, determine the mathematical equation that shows how D vanes with T... 

There are mercury compounds with mercury oxidation numbers lower than +1, e.g. +0.5,16,21 +0.6713,15,27 or +0.35.18,20 Yellow crystals of Hg3(AsF6)2 have been formed by the reaction of metallic mercury with AsFs in liquid S02.13 X-Ray structure determination showed a linear polycation Hg+—Hg—Hg+ with Hg—Hg distances of 255 pm.15 Metallic mercury and SbF5 react in liquid S02 to form Hg3(Sb2Fu)2.15,23 The Hg—Hg distances in the complex Hg3(AlCU)2 are 256 pm 14 the Hg—Cl distances are 251 and 256 pm the Hg—Hg—Hg angle is 174°. Dark red crystals of Hg4(AsF6)2 were obtained in liquid S02. This coordination compound contains centrosymmetric Hg4+ ions, which are connected to chains (see l).21... 

It remains to be determined to what extent the dye adsorption technique is applicable to other substrates. No evidence was obtained for Pseudocyanine adsorption to Mn02, Fe2Os or to pure silver surfaces, although this dye can be bound to mica, lead halides, and mercury salts with formation of a /-band (61). Not only cyanines but other dye classes can yield surface spectra which may be similarly analyzed. This is specifically the case with the phthalein and azine dyes which were recommended by Fajans and by Kolthoff as adsorption indicators in potentio-metric titrations (15, 30). The techniques described are also convenient for determining rates and heats of adsorption and surface concentrations of dyes they have already found application in studies of luminescence (18) and electrophoresis (68) of silver halides as a function of dye coverage. 

In the last two decades, mercury film electrodes (MFEs) have been used frequently in electroanalytical practice. Using such electrodes, metal ions present in the solution in trace amounts may be determined with satisfactory accuracy by their reduction on the surface of MFEs, formation of relatively concentrated amalgam, and anodic oxidation from MFEs of the preconcentrated metal in a final step (see Chap. 24). 

Porous materials are often analyzed with a mercury porosimeter. With a mercury porosi-meter we can measure the pore distribution of a solid. Thus, we can determine the specific surface area. Mercury is used because of its high surface tension (0.48 N/m) it does not wet... 

---