Mercury-specific detection

Wylie, D.E., L.D. Carlson, R. Carlson, F.W. Wagner, and S.M. Schuster. 1991. Detection of mercuric ions in water by ELISA with a mercury-specific antibody. Anal. Bio chem. 194 381. 

Plasma-AES has been utilized for element-specific detection in the specification of mercury compounds by gas chromatography and liquid chromatography (see organic mercury ). 

Figure 8.96 Simultaneous determination of various mercury species with element-specific detection. Separator column Zorbax Eclipse XDB-C18,5 (im column dimensions 50 mm X 2.1 mm i.d. eluent 60 mmol/L ammonium...

The electrochemical characteristics of a solid electrode can be chemically, electrochem-ically, as well as physically modified in order to increase its stability, sensitivity, or most commonly selectivity. An important example of selectivity modification is the formation of a mercury amalgam on gold electrodes to specifically detect thiols. Other examples are the adsorption of metals, polymers, self-assembled monolayers (SAMs), or enzymes but their applications to HPLC are yet scarce. 

F. 1.1 Specific detectivity-cutoff frequency product versus operating frequency for a mercury cadmium telluride photoconductor (denoted as PC) and a pyroelecttic detector (TD). PC 1 is a photoconductor at 200 K, PC 2 at 250 K, PC 3 at 300 K. TD 1 is the theoretical performance maximum for a pyroelecttic detector, TD 2 are values achieved in laboratory... 

As described previously, although techniques to utilize AFS were developed several decades ago, until recently they were not widely used. However, a new generation of simple AFS instruments have been developed to specifically detect the vapour-forming elements, such as those that form hydrides (As and Se) and mercury, which forms an atomic vapour. All of these analytes have a primary line below 260 nm and, since the analytes may be readily separated from the bulk matrix and concomitant elements, dispersion is not necessary. Instead these basic instruments originally used a simple interference filter, although these have now been superseded by the more efficient multi-reflectance filter. 

These early GC-element-specific detection systems are described in several review articles [18-21]. An excellent summary of the applications of these and other sterns, to be discussed later, to the determination of mercury, lead, selenium, tin and arsenic compounds is provided in the review of this field by C.J. Cappon [9]. The detection limits obtained with these systems reach the low picogram levels under ideal conditions however, detection limits in the nanogram range, are more common. With elemental mercury or organic mercury compounds in a sample, 100 picograms of mercury were detected in a system consisting of a fused silica capillary gas chromatograph and a cold vapor atomic absorption spectrometer [22]. 

The selection of biological indicators shoirld be guided by criteria to ensure that the indicators are relevant, useful, and sufficiently diagnostic to detect a change in the concentration of mercury in whole organisms or specific tissue(s) over multi-year or decadal time scales. We identified 9 criteria for the selection of biological indicators ... 

Heavy metal ions detection with porphyrin in sol-gel is possible, too56. The porphyrin, used for detection of heavy metal ions (Hg2+, Pb2+, Cd2+), was 5,10,15,20-tetra(4-N-methylpyridil)porphyrin (TMPyP) preferred to other porphyrins because it was not leaked out of the matrix. The study of metallation of the porphyrin immobilized in sol-gel emphasized the formation of 1 1 complex for each ion with a constant of complexation depending on the nature of the ions. The strongest effects were observed for mercury due to the specific interaction of this metal with the porphyrin. 

Measurements of particle porosity are a valuable supplement to studies of specific surface area, and such data are particularly useful in the evaluation of materials used in direct compression processes. For example, both micromeritic properties were measured for several different types of cellulosic-type excipients [53]. Surface areas by the B.E.T. method were used to evaluate all types of pore structures, while the method of mercury intrusion porosimetry used could not detect pores smaller than 10 nm. The data permitted a ready differentiation between the intraparticle pore structure of microcrystalline and agglomerated cellulose powders. 

The analytic principles that have been applied to accumulate air quality data are colorimetry, amperometry, chemiluminescence, and ultraviolet absorption. Calorimetric and amperometric continuous analyzers that use wet chemical techniques (reagent solutions) have been in use as ambient-air monitors for many years. Chemiluminescent analyzers, which measure the amount of chemiluminescence produced when ozone reacts with a gas or solid, were developed to provide a specific and sensitive analysis for ozone and have also been field-tested. Ultraviolet-absorption analyzers are based on a physical detection principle, the absorption of ultraviolet radiation by a substance. They do not use chemical reagents, gases, or solids in their operation and have only recently been field-tested. Ultraviolet-absorption analyzers are ideal as transfer standards, but, as discussed earlier, they have limitations as air monitors, because aerosols, mercury vapor, and some hydrocarbons could, interfere with the accuracy of ozone measurements made in polluted air. 

The system provides a very sensitive means of detection levels of 10 picograms absolute are measurable with the continuous (permanent) trapping system. A further advantage is that the software calculates the analytical results directly in concentration in the unit volume of sample introduced. However, it should he stressed that the level of mercury measured is an absolute quantity and while the detection Hmit is of the order of 10 picograms, this quantity can be contained in any volume of gas. In addition, the fact that the mercury both absorbs and fluoresces to provide a measurement which can be measured with a specific retention time provides more positive evidence of the presence of mercury. 

Godden and Stockwell [11] have described a specific fluorescence detection system to provide fully supported analytical systems for routine analysis of mercury at low levels. The fluorescence approach provides a wide linear dynamic range and extremely low detection limits. P.S. Analytical s Merlin Plus System provides a fuUy automated system which will produce results at a rate of around 40 per hour. This is due to the optimization of the optical design of the detector, coupled to the inherent features of the fluorescence technique. 

To extend the levels of detection for mercury stiU lower, several workers, especially in this area of atomic absorption techniques, have chosen to collect the mercury on gold or other noble metal trapping systems prior to revaporizing the mercury into the measurement technique. Figure 7.14 shows the configuration of a specific system to concentrate mercury onto an amalgam preconcentrator prior to analysis. 

The emission and excitation peaks occur at 251 and 347 nm, respectively with a Stokes shift of 10,000 cm It is very close to luminescence and excitation bands detected in natural samples. In order to prove the possible relation of the UV luminescence band at 355 nm to Pb in natural hardystonite, its decay time as a function of temperature has been studied. These decay curves are very specific for mercury-like ions, where the emission at low temperatures is ascribed to the forbidden transition and has a long decay... 

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