Gaseous Mercury Detector UT3000 | mercury instruments (2023)

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Mercury Monitoring App

The UT-3000 Mercury UltraTracer provides a compact and reliable tool for measuring mercury in gases at ultra-trace levels. Utilizing the high-performance GoldTrap aggregation module and an optimized state-of-the-art AA mercury vapor detector, the UT-3000 UltraTracer offers detection limits at levels below ng/m³ (ppq parts per quadrillion).

Applications include:

• Air quality studies
• Indoor Air Pollution Monitoring
• Monitoring of sources of environmental contamination
• plume profile
• Studies of mercury dispersion in the atmosphere
• Studies of interaction between atmosphere and surfaces.
• Contamination prevention
• Natural gas and derivatives
• Hydrogen and other gases
• Soil studies and soil degassing

Hg Measuring principle

Sample gas is fed into an optical cell by a maintenance-free diaphragm pump. A beam of ultraviolet light is passed through the optical cell, part of it is absorbed by the mercury atoms in the sample. This method is called atomic absorption spectroscopy; or shortly after AAS. It is extremely selective and sensitive. For the determination of mercury, the AAS method has retained its importance, although second
Methods have been worked out from the earliest beginnings. The AAS method has low interference and does not require an aggregation step or expensive carrier gases.

Mercury monitoring in natural gas and LNG

Mercury is a common component of natural gas. It can be found in concentrations from a few µg/m³ up to 10,000 µg/m³. An important application for the UT-3000 is the measurement of mercury in
natural gas and liquefied natural gas (LNG). A special version of the UT-3000 analyzer is dedicated to measuring mercury in natural gas. Both a manual system using the Tedlar® bag technique and an automatic system for in-line installations are available.

Click here to download more information on the natural gas application (8 pages)

Automated Mercury Detector Operation

The UT-3000 works automatically. All functions are controlled by a built-in microprocessor. Once the analysis starts, measurements are taken and data is collected by the built-in data logger. With the standard configuration, the data logger has a logging capacity of 4 weeks.

Urban air quality measurement Tedlar® Bag air sample measurement

GoldTrap aggregation system

For use in the UT-3000, a new trap system has been developed: Mercury GoldTrap, which is one of the key components of the system. It consists of a thin ceramic tube that is carefully designed to achieve minimal thermal inertia. The tube is filled with ultra-pure gold and supports a heating coil on the outside. Mercury GoldTrap reveals sharp, high peaks and excellent long-term stability. Since air is used to purge the trap during the heating step, potential contaminants are oxidized and swept away, preventing passivation.

atomic absorption detector

The mercury vapor detector used in the UT-3000 provides the highest sensitivity, accuracy, and stability. A hill
The frequency-driven electrodeless mercury low-pressure lamp is used as the ultraviolet light source. It generates an emission line of 253.7 nm with an extremely narrow bandwidth, which is consistent with the absorption line of the measured Hg atoms. The reference beam method is used to achieve extremely high stability of the UV source. Mercury concentration is measured in an optical cell made entirely of fused silica (Suprasil). Thanks to GoldTrap's increased sensitivity, there is no need for a long-range cell, which always has a greater surface effect. Newer solid-state UV detectors with subsequent digital signal processing are used for absorption measurement.

mercury sampling

It is important that the trap is free of mercury before sampling. This is ensured by a cleaning step that is carried out automatically. To keep particulates out of the system and protect the trap from passivation, a filter is installed upstream of the sample inlet. The filter is made of low interaction material; the filter membrane has a porosity of 0.45 µm and is made of PTFE. The complete filter unit is easy to replace.

Mercury in natural gas Video UT

Mercury sample flow control

The sample flow is measured with a high precision electronic mass flowmeter. The flow rate integrated over time gives the total volume of the sample. The flow is automatically changed to a lower value during the desorption step to achieve maximum sensitivity.

UT-3000: Flowchart

How does the UT-3000 Mercury Analyzer work?

Mercury Instruments GoldTrap is used to capture total gaseous mercury (TGM) directly from
atmosphere. GoldTraps work because mercury adheres to gold at room temperature. A gas containing gaseous mercury is drawn through the trap; the gas continues to flow through the trap, but the mercury remains, trapped in the gold. After trapping the mercury, the GoldTrap heats up very quickly; this releases the mercury as a gas (thermal desorption). The gaseous mercury is then swept by the mercury-free stream of purified air into the detector's optical cell. Here, mercury is measured by atomic absorption spectrometry.

Mercury gas detector calibration

There are two methods for checking and calibrating the instrument: One way is to trap the mercury in the GoldTrap by bubbling air through a liquid mercury standard to which a tin chloride solution has been added. Another fast, accurate and precise way is static calibration with mercury saturated air. Gaseous mercury is injected directly into the GoldTrap. In this case, the built-in calibration port is used, which is internally connected to the sample gas line leading to the GoldTrap. The calibration port is equipped with a partition through which gaseous mercury is injected with a syringe. The type of syringe used for this purpose is specifically designed to measure and dispense gases. The mercury is then automatically extracted into the GoldTrap. Calibration gas sources are available as accessories. The calibration check procedure can be automated as an option.

Inject calibration gas into the analyzer calibration port

Display and output of mercury measurements

Measurement results are displayed on a graphical LCD screen as a bar graph and numerically. It is possible to view previous readings with a paging feature. Calibrations are stored in non-volatile memory. The device has a serial interface for data transfer to a PC and a 0-20 mA output.

Advantages of the AA detection method for mercury

The latest AA detection technique used in the UT-3000 offers some clear advantages over other methods. Detection of trace amounts of mercury by fluorescence requires a carrier gas and sometimes an envelope gas and suffers from the quenching effect that can never be completely removed. The UT-3000 does not require expensive gases to operate and there is no negative interference caused by the quenching effect. The sensitivity and detection limits are much higher than those of those instruments based on the measurement of the electrical resistivity of a thin gold film.