In practice mercury analysis sample matrices very often show different and variable compositions. Depending on the chemical process the forms of mercury differ: elementary, ionic, dissolved as a salt, as an organic compound or as insoluble sulfide.

The PA-1 offers a variety of sample pretreatment procedures to allow highly precise determination of total mercury in all these samples, with the results from the PA-1 showing very good correlations with standard laboratory analyses.

High flexibility is achieved by the modular structure of the sample pretreatment module. This allows the user to choose from the following digestion methods:

• Sample preoxidation with hydrochloric acid + potassium permanganate
• Sample preoxidation with sulphuric acid + potassium permanganate
• Sample preoxidation with hydrochloric acid + sodiumchlorate
• Sample preoxidation with Fenton´s reagent

The integrated heated reaction module allows accelerated sample digestion at higher temperatures. The installation of a UV sample pretreatment unit not requiring reagents is also possible. The duration of reactions can be adapted to the need of your application by employing reaction coils of different lengths.

The detection of mercury contained in the sample occurs in an optical cell made of fused silica (Suprasil). In a first step mercury is reduced to the elementary state by means of tin(II)chloride or NaBH4. Subsequently mercury is stripped from the aqueous phase with an air stream and carried into the optical cell. Here the UV absorption measurement is conducted at a wavelength of 253,7 nm.

This analytical technique called "cold vapor atomic absorption spectroscopy (CVAAS)" shows extreme sensitivity and selectivity. It has been reliable and proven for many years. In contrast to the occasionally recommended atomic fluorescence method the analytical technique utilized by the PA-1 is extremely low in interference and does not require an amalgamation step nor expensive noble gas as a carrier.

The PA-1 is equipped with sensors to detect malfunctions of the system and triggers an alarm for the operator. The following functions/malfunctions are checked and indicated:

• Reagent flow
• Sample flow
• Stripping air flow
• Leakage of fluids
• Photometer lamp
• Calibration

These features permit reliable unattended operation. Malfunctions are reported to the user both optically and via a status signal.

The following data is available at the serial RS 232 interface:
Actual mercury concentration Status (Ready - Maintenance - Malfunction)

Thanks to the bidirectional interface, operational functions like
"Zero Adjustment", "Calibration Check" and "Start Measurement" can be triggered externally