Principle of operation
Diaphragm vacuum pump draws the air, and sample is collected onto gold trap. Air flow can be adjusted from 0.1 to 1 LPM, and duration of sampling can be selected by several seconds to tens of minutes by the user.
Second step, zero-air is directed into the gold trap at a low flow rate, the gold trap is heated, mercury desorbs and passes through the measurement optic cell. The height of the UV light absorption peak is determined. Analysis step takes 60 seconds.
Thirst step: gold trap is cooled with fans. 20-40 seconds.
Both gold trap and optic cell and connection in between are provided with heating appliances to keep them above room temperature both during sampling and analysis. Carefully selected temperature profiles helps us to avoid positive interference, minimize collection of VOCs or other interfering compounds within the system, and maximize the lifetime of gold traps.
Classic two-beam absorption photometer with EDL (Electrodeless Discharge Lamp) as a light source is improved in what our lamp by means of a chopper sends the light through two identical and symmetrical optic cells in a quickly alternating way and the light from both beams again are collected on the same photo tube.
So we use only one photo tube instead of two and greatly save with the self-cost.
No, actually this way we get the most from the two-beam AAS photometry, because the phototube and its preamplifier compensate itself for any difference in parameters or thermal drifts.
A servo motor-driven diaphragm physically equilibrates the light in two beams before each measurement, and a zero – shutter is used to check the physical span from zero to full light.
This way we measure the the light and its attenuation in the most sensitive and precise way, avoiding any influence of electronic parameters, offsets, zero-drifts and the like.
The final amplification of a light signal is performed by the phase – sensitive detector.
The dosing device employs a low-emission permeation tube to generate the air stream with a constant Hg vapor concentration, whereas the system of valves precisely “cuts” a bigger or smaller amount of mercury vapor from this stream.
Our trick is a dedicated and miniature oven for mercury permeation source, which is supplied with a precision temperature control, and a finely adjusted system of valves with a nearly zero dead-volume.
Data safety / data handling
For each and single measurement point, the detailed technical information is saved by the analyzer internal logger. This includes concentration, amount, sampled volume, sampled time, injected mercury rom the dosing device (if any), Hg lamp intensity, and the full transcript of mercury evaporation peak. The latter information we find particularly useful, because one can track back for each measurement how mercury evaporated and how this was recorded. Therefore, each and every measurement can be checked in detail, and advanced algorithms of calculation can be applied if desirable.
Data logger capacity is effectively huge, may contain more than 100,000 measurements. The information is available for the operator on the USB memory flash inserted at the analyzer front panel.
In addition to this, all the same is saved on the PC hard disk (in case the PC is coupled), using our proprietary software Gardis Monitor – “Gmonit”. So one gets double safety of data, while using a PC.
Both internal logger and PC disk data format is CSV, easy to import and handle by a bunch of different programs and not only by Gmonit.
Example: mercury desorption peak equivalent to 39 picograms as recorded by analyzer and represented by Gmonit.