RA-915+ Mercury Analyzer

Description - Direct detection of mercury without its preliminary accumulation on a gold sorbent - Extremely low mercury detection limit and high selectivity - Field operation from a built-in battery for mercury detection in atmospheric air and industrial gases - Totally automated unattended stand-alone mode of operation for continuous monitoring of the environment for mercury pollution - Ultra low mercury detection limit in water - Streamlined design configured to a small-size and lightweight single portable unit - Built-in microprocessor, LC display and computer interface for optional customized report output and storage in a stand-alone computer - Optional attachments using the «cold vapor» technique for assaying water solutions and the pyrolysis with afterburning for assaying solid samples of complex composition

The RA-915+ mercury analyzer employs differential atomic absorption spectrometry technique, which is implemented using the direct Zeeman effect (Zeeman Atomic Absorption Spectrometry using High Frequency Modulation of Light Polarization ZAAS-HFM). A glow discharge mercury lamp is placed in a permanent magnetic field, whereby the 254-nm mercury resonance line is split into three polarized components, only two of those, ó+ and ó-, which are circularly polarized in the opposite directions, being detected for analysis. After passing through a polarization modulator, which modulates the polarization at a frequency of 50 kHz and thus triggers the line components in turn, the radiation then passes through a multi-path cell, whose equivalent optical length is about 10 m. Being equipped with narrow-band high reflectivity mirrors, the cell isolates solely the 254-nm resonance line and suppresses all the nonresonance and stray radiation. A logarithm of the intensity ratio of ó+ and ó-, which is proportional to the mercury atom concentration in the cell, is determined upon detecting the radiation by a photodetector and subsequent analog-digital conversion of its electric signal by a built-in microprocessor. The measurement results are read out from a built-in LC display, or are transmitted to a computer for further processing or data storage. In this measurement technique, the analytical signal depends only on mercury concentration and is independent of the presence of dust, aerosols, and other foreign contaminants in the analytical cell.

An RP-91 attachment is used for the mercury determination in water by the «cold vapor» technique. A reducing agent, SnCl2, is added to a sample, and the atomic mercury thereby released is conveyed to the analytical cell by a carrier gas. The ultimate mercury detection limit in water solutions is 0.6 ppt (ng/l), the sample volume being 10 ml and the analysis time being no more than 90 sec.

An analysis is carried out using an RP-91C attachment, wherein mercury is converted from a bound state to the atomic state by thermal decomposition in a two-section atomizer. The sample is vaporized in the first section, and the mercury compounds are partly decomposed. In the second section, which is heated to 800° C, the mercury compounds become fully decomposed, organic compounds and carbon particles are catalytically after burnt, to carbon dioxide and water. This technique is used to determine mercury in soils, food products, biological samples, and crude hydrocarbon products, no preliminary sample mineralization being needed and the analysis itself taking 1-2 minutes.

• RA-915+ portable Zeeman mercury analyzer with RA-915P software
• RA-915+DL portable Zeeman mercury analyzer with Data Logger and RA-915P software
• RP-91 attachment for liquid samples
• RP-91C attachment for solid samples
• PYRO-915+ attachment for liquid and solid samples

For software installation a PC is necessary. Minimal system requirements: Windows®-98, Pentium 120 MHz, 20 Mb RAM, Serial COM port.