Mercury Process Analyzer PA2

Flexibility in Sample Digestion

In practice mercury analysis sample matrices 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-2 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-2 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 pre-oxidation with hydrochloric acid + potassium permanganate
• Sample pre-oxidation with sulfuric acid + potassium permanganate
• Sample pre-oxidation with hydrochloric acid + sodiumchlorate
• Sample pre-oxidation with Fenton´s reagent
• The integrated heated reaction module allows accelerated sample digestion at increased temperatures. The duration of reactions can be adapted to the need of your application by employing reaction coils of different lengths.

Proven Mercury Measurement Principle

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-2 is extremely low in interference and does not require an amalgamation step nor expensive noble gas as a carrier.

Industrial Grade Design

To provide optimum protection against corrosive environments all parts of the PA-2 Mercury Analyzer are enclosed in an industrial-grade cabinet made of fiber glass, reinforced polyester (protection class IP 66; NEMA 4X; etc.). The electronic circuitry is shielded from the wet chemical section by a chemically resistant wall.

Continuous and Interval Operation

The PA-2 analyzer is controlled by a built-in computer and operates fully automatic. The continuous measuring mode can be switched over to a periodic measuring mode (for example 10 minutes of measurement every hour). Auto-Cal. Check: periodically the instrument switches from the sample stream to a calibration solution to check any deviation from the reference value. A status signal is generated if the value measured is out of range. Auto-Zero: the zero line of the analyzer is adjusted automatically after a preset period of time. Self-Cleaning: Precipitations like manganese dioxide are dissolved by an automatic rinse step which makes manual cleaning superfluous.

This online mercury analyzer is Easy to Operate

The PA-2 is operated via a waterproof membrane keypad. All inputs required are selected in a readily understandable menu shown on the graphical display. It is also possible to initiate some functions like Auto Zero from an external computer via the RS 232 interface.

Output and Display of Mercury Measurements

The analytical results are continuously displayed on an LCD in micrograms per liter and as absorption units. A linear electrical signal (4 ... 20 mA) is also output and can be connected to a recorder or to the analog input of a data acquisition system.

Automatic Self Diagnosis System

The PA-2 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.

Communication with External Computers

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