Mercury , fluorescence

The photooxidation was carried out in a commercial weathero-meter (Q-UV, Q-panel Co., Cleveland, Ohio). This apparatus uses medium pressure mercury fluorescent UV lamps (Sunlamps F5-40, Westinghouse Electric Corp.) which emit UV light in the 273-378 nm range with a maximum intensity at 310 nm. 

Insufficient experimental data is available to demonstrate either the occurrence or lack of selection rules. In Table 15, some of the fastest reactions do correspond to transitions allowed for both atoms. Singlet helium transfers to Ne at a rate consistent with the data in Fig. 26, whereas triplet helium transfers comparatively slowly neither of the He transitions is allowed. However, there appear to be other cases, discussed earlier, where a forbidden transition is preferred to an allowed transition. Stepp and Anderson146 have suggested that there is partial conservation of electronic angular momentum accompanying energy transfer between atoms, and interpreted experiments on mercury fluorescence by means of the steps... 

The quenching of mercury fluorescence was investigated using equipment described previously with a modification that the temperature of the fluorescence cell was kept within 1° at different temperatures, using a heater inserted in an aluminum block surrounding the cell. As before, the temperature of the mercury reservoir was kept within 0.1° using an ethyleneglycol bath. Table I shows an example of experimental data. 

The great advance for AFS in mercury analysis is associated with the CV atomization technique. The sample preparation procedures are the same as for CV-AAS. Most of the methods described below utilize the CV technique for liberation of mercury from the sample solution. Unless othenwise stated, the aeration gas was argon and the mercury fluorescence was measured directly at the outlet of the gas stream carrying the Hg(0) from the reaction vessel into the atmosphere (a "windowless cell"). 

Radiation Procedures The samples were irradiated at 40°C with either a QUV apparatus (Q-Panel Co., Cleveland, Ohio) which uses mercury fluorescent sunlamps (Westlnghouse FS-40) with an emission maximum at 313 nm, or a more Intense (by a factor of about 40) medium pressure mercury lamp (Hanovia) with an emission maximum at 366 nm. All irradiations were pyrex glass filtered. 

Out of the chemical processes of mercury fluorescence quenching, Hg + Hg HgH + H has been studied most extensively. Thus, molecular HgH and HgD generated by the interaction of Hg ( Pi) and also of Hg"( Po) with Hg and Dg have been detected (in absorption spectra) [72]. The cross sections of these processes are of the order of that for process Hg + -> Hg" + H (0.86 A ). 

If the components are colourless, their separation can often be followed by working in a quartz (or special glass) tube which is placed in the light of a mercury lamp. The separate zones are then often revealed by their fluorescence. 

When a question exists about whether the carving is ancient, an examination under uv illumination can be very helpful. For example, an aged marble surface exhibits, under a properly filtered mercury lamp, a mellow, brownish fluorescence, whereas a fresh surface, under the same conditions, appears purple. It is not uncommon that old carvings have been sharpened this is detectable with the microscope and under uv examination. 

Pressure. Standard atmospheric pressure is defined to be the force exerted by a column of mercury 760-mm high at 0°C. This corresponds to 0.101325 MPa (14.695 psi). Reference or fixed points for pressure caUbration exist and are analogous to the temperature standards cited (23). These points are based on phase changes or resistance jumps in selected materials. For the highest pressures, the most rehable technique is the correlation of the wavelength shift, /SX with pressure of the mby, R, fluorescence line and is determined by simultaneous specific volume measurements on cubic metals... 

X-Ray Methods. In x-ray fluorescence the sample containing mercury is exposed to a high iatensity x-ray beam which causes the mercury and other elements ia the sample to emit characteristic x-rays. The iatensity of the emitted beam is directly proportional to the elemental concentration ia the sample (22). Mercury content below 1 ppm can be detected by this method. X-ray diffraction analysis is ordinarily used for the quaUtative but not the quantitative determination of mercury. 

California and Minnesota have placed restrictions on the disposal of fluorescent light tubes, which contain from 40—50 mg of mercury per tube, depending on size. After batteries, fluorescent lamps are the second largest contributor of mercury in soHd waste streams in the United States (3,14). A California law classifies the disposal of 25 or more fluorescent lamp tubes as hazardous waste. In Minnesota, all waste lamps generated from commercial sources are considered hazardous waste. Private homes are, however, exempt from the law (14). Other states have proposed similar regulations. Several companies have developed technologies for recovering mercury from spent lamps (14). 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

As atomic fluorescence spectrometer a mercury analyzer Mercur , (Analytik-Jena, Germany) was used. In the amalgamation mode an increase of sensitivity by a factor of approximately 7-8 is obtained compared with direct introduction, resulting in a detection limit of 0,09 ng/1. This detection limit has been improved further by pre-concentration of larger volumes of samples and optimization of instrumental parameters. Detection limit 0,02 ng/1 was achieved, RSD = 1-6 %. 

DETERMINATION OF MERCURY (Hg) IN NATURAL AND WASTE WATERS BY MEANS OF THE MILLENNIUM MERLIN ATOMIC FLUORESCENCE SPECTROFOTOMETER... 

Mercury generally is found in low and trace concentrations. So there is need to determine Hg in ranges corresponding to various types of water samples. Detection levels of Hg can be improved by the use of vapour generation technique. This technique allows to sepai ate the analyte from the sample matrix and so to overcome the matrix interference. The fluorescence technique, with its high sensitivity and linearity, in combination with vapour generation, provides for a possibility to detect Hg in parts per trillion per liter regions. 

The mercury vapour was detected by atomic fluorescence spectrometer Millennium Merlin PSA 10.025. 

A continuous source has to be employed to record absorption spectra. Fluorescence is usually excited with mercury vapor lamps in the region of their major bands they radiate more powerfully than do xenon lamps (Fig. 14). 

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