Mercury Vapor Analysis Using Portable Atomic Fluorescence Spectroscopy

Although products containing mercury are generally safe, they can pose a risk to people during accidental exposure. For that reason, stringent regulations and guidelines have been developed to limit the level of mercury exposure, and special techniques are required to remove mercury in case of accidental exposures.

The time weighted average limit for mercury differs with each regulating agency. The time weighted average limit for mercury is 0.1mg/m3 for OSHA, 0.05mg/m3 for NIOSH, and 0.025mg/m3 for ACGIH.

J505 Atomic Fluorescence Analyzer

The J505 Atomic Fluorescence Analyzer (Figure 1) from Arizona Instrument is a handheld atomic fluorescence spectrophotometer capable of measuring mercury concentration in air. The higher and lower detection limits of this device are 0.5mg/m3 and 0.000050mg/m3 respectively, exceeding the current industrial exposure limits as well as clean-up levels for public facilities.

Arizona Instrument’s J505 Atomic Fluorescence Analyzer.

Figure 1. Arizona Instrument’s J505 Atomic Fluorescence Analyzer.

Atomic Fluorescence Spectroscopy (AFS)

In AFS, the excitation of an atom by an input of energy causes one of its electrons to move from a stable ground state to a higher energy, unstable excited state. The electron reaches its ground state again subsequent to the removal of the energy source, releasing the absorbed energy as a photon (light). This phenomenon is known as fluorescence.

Often the amount of energy released is not the same as the amount of energy absorbed. However, in the case of mercury, the amount of energy absorbed by an electron to reach the unstable excited state is the same as that of the photon released as the electron returns to its ground state. This phenomenon is known as resonance fluorescence, which can be detected easily with AFS.

The J505 instrument excites the mercury atoms using a mercury lamp at a wavelength of 254nm and measures the emission of photons using a detector at the same wavelength. The ability to measure the photon emission makes the AFS technique free from interferences, such as ammonia, hydrogen sulfide, hydrocarbons, which often influence the results of conventional detection techniques.

Difference Between AFS and Atomic Absorption Spectroscopy (AAS)

AAS involves exposing the sample of interest to a light source of known wavelength and intensity. The sample absorbs some amount of the energy of the source light, causing its electrons to transition from the ground state to an excited state. A detector positioned at the end of the pathway determines the amount of energy passed through.

The difference between the energy of the source light and the energy of the light reaching the detector varies in direct proportion to the analyte concentration in the sample. One of the shortcomings of AAS however is the possibility of energy absorption by a number of other common molecules at the same wavelength as mercury.

Manufacturers use different filtering techniques to limit background interference in order to negate these unwanted absorptions. This results in a more complex and bulkier instrument. Additionally, physical limitations of AAS may affect its low level sensitivity. Detection at very low concentrations is a challenge with AAS due to the difficulty in differentiating the amount of absorbed light from electronic noise, when compared to the intensity of the incident light source.

Specifications for J505 Atomic Fluorescence Analyzer

The following table summarizes the specifications of the J505 Atomic Fluorescence Analyzer:

Table 1. Specifications for J505 Atomic Fluorescence Analyzer.

Test Mode         Units: ng/m3 µg/m3 mg/m3
Standard Range

Resolution
50 to 500,000 .05 to 500 0.00005 to 0.50000
(0.05 µg/m3 ± 0.033 µg/m3 to 500 µg/m3 ± 40 µg/m3)
10 0.01 0.00001
Quick Range
Resolution
100 to 500,000 0.1 to 500 0.0001 to 0.500
100 0.1 0.0001
Search Range
Resolution
100 to 500,000 0.1 to 500 0.0001 to 0.500
100 0.1 0.0001
Typical Test Time Standard
Quick
Search
28 seconds
16 seconds
8 seconds for first reading then continuous 1 second updates
Power requirements Internal battery (NiMH) with 10+ hours of operation
12VDC power adapter runs on 100-240VAC, 0.8A, 50-60Hz
Battery charges in 3 hours or less
(Note: Battery will not charge if battery temperature > 40 °C)
Operating environment
Dimensions
5 to 45 °C, non-condensing, non-explosive
12in L x 6.2in W x 8.4in H
(30.5cm L x 15.7cm W x 21.3cm H)
Weight 6.5 pounds (3.0 kilograms)
Display 3.5 inch (9 cm) color LCD display.
High brightness backlight
Unattended Autosample Available in intervals of 1, 2, 5, 10, 15, 20, 30, 45, 60, 90 or 120 minutes
Data storage capacity Up to 10,000 test results
100 test sites
USB USB port located on rear of instrument
Test results and calculations saved to USB flash drive
Menu navigation, text entry, and softkey operation with optional USB Keyboard
Certifications Power adapter marked with UL and TUV

The following table describes the accuracy and precision of the J505 Atomic Fluorescence Analyzer in standard mode:

Table 2. Accuracy and Precision (Standard mode).

Gas Level Accuracy Precision (RSD)
0.3 µg/m3 ± 15% 15%
1 µg/m3 ± 10% 7%
25 µg/m3 ± 10% 5%
100 µg/m3 ± 10% 3%

Arizona Instrument

This information has been sourced, reviewed and adapted from materials provided by AMETEK Brookfield Arizona

For more information on this source, please visit AMETEK Brookfield Arizona

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