The mercury analyzer is a highly sensitive instrument for atomic absorption spectroscopy for mercury measurement. Mercury anomalies in the air in some metal deposits are often as low as a few tens of nanograms per cubic meter. The original methods of mercury measurement could not find such weak anomalies. In recent years, successful mercury analyzers have a sensitivity of up to 1 ng/m3. It is designed using mercury vapor to strongly absorb the 253.7 nm line. The instrument mainly includes mercury lamps emitting 253.7 nm lines, gas absorption chambers and devices for photoelectric amplification and measurement. A sample of gas entering the absorption chamber, such as mercury containing micro-tracks, will be attenuated by the absorption of mercury by the absorption chamber. The amount of mercury in the gas can be measured based on the degree of light attenuation. Since sulfur dioxide and many rare gases have significant absorption of the line around 253.7 nm, serious interference occurs. According to the method of eliminating interference, it is divided into various types of mercury analyzers, for example: 1 using a precious metal trap to trap mercury, causing the interference gas to escape; 2 splitting the sample airflow into two strands, and pre-empting the mercury in one strand Remove and then compare the output of the same light source through the two absorption chambers; 3 use the pressure-induced broadening effect to split the light passing through the absorption chamber into two, one through the saturated mercury vapor chamber, and then measure the two rays The ratio of the intensity; 4 uses the "the Zeeman effect" to compare the ratio of the intensity of the light passing through the absorption chamber when a magnetic field is applied to the source and when no magnetic field is applied. According to the practical requirements, an instrument for continuously measuring mercury in automobiles and airplanes, and a portable backpack-type mercury measuring instrument capable of measuring in situ have been prepared.
working principle
The mercury atomic vapor selectively absorbs ultraviolet light of 253.7 nm. In a certain concentration range, the absorbed light is proportional to the concentration of mercury. After the water sample is digested, the various forms of mercury are converted into divalent mercury, and then the stannous chloride is used to reduce the divalent mercury to elemental mercury. The mercury vapor generated by the carrier gas is taken into the absorption tank of the mercury analyzer to determine the absorbance. , quantitative comparison with the absorbance of mercury standard solution.
Scope of application
It is suitable for environmental monitoring, sanitation and epidemic prevention, tap water, chemical industry, etc. It is used to measure the content of mercury in water, air, soil, food, cosmetics, chemical raw materials.
advantage
Fast measurement, simple operation, digital direct reading, ideal for measuring mercury in the laboratory
Precautions
l, the choice of flow: generally set at 1.2L / min, but the user can change within 1-2.5L / min. For the instrument, the flow is reduced, which can increase the response peak and increase the sensitivity, otherwise it is the opposite.
2. During the measurement process, when the conventional button is kept in the hold state, after measuring a sample, press the reset button to return the display to the initial state, and then measure the next sample.
3. Number of corrections: In principle, each calibration is performed once, but if the ambient temperature does not change much (within 5 °C), the calibration curve can be omitted directly.
4. Addition of mercury standard solution: When the instrument is calibrated, only one mercury standard solution (0.1ug/ml) is prepared below. Other concentrations of mercury standards are achieved by changing the amount of standard added to the vial. To obtain a 3 ng/ml mercury standard, simply add 0.3 ml of the standard (containing 30 ng of mercury) to the vial. In the bottle, 8 ml of distilled water and 2 ml of stannous chloride are added, and the final concentration of mercury in the bottle is about 30 ng 8 ml + 2 ml = 3 ng / ml.
5, desiccant:
During the operation, the desiccant should be used as much as possible. The use of the desiccant will cause errors in the measurement. When the blank liquid appears to interfere with the water peak, a small amount of desiccant is added.
6. High-concentration samples: Samples with a concentration exceeding 10 ng/ml should be diluted, and the measured concentration should be within the range of 0-5 ng/ml.
7. Make a low concentration standard curve. For example, when 0.1 ng/ml-O.5 ng/ml, the displayed value is adjusted by the display knob, and the value is also adjusted within the range of 020-100.
8. Pretreatment of samples: Refer to the relevant analytical procedures.
9, the processing of glassware, refer to the relevant analytical procedures.
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