PAN online automatic analyzer

NegotiableUpdate on 01/06

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Overview

PAN online automatic analyzer

Product Details

Background introduction:

PAN (peroxyacetic anhydride, commonly known as peroxyacetyl nitrate) in the environment is generated by the reaction of some volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere, and its formation process is similar to ozone formation. Therefore, PAN and O3 are both VOC-NO X-ray chemical indicators.

The concentration of PAN ranges from a few ppts of oceanic background points to over 10 ppb in urban polluted air. Known for its tear gas effect and phytotoxicity. Due to the low-temperature stability of PAN, it is also an important reservoir for atmospheric reactive nitrogen. Therefore, it can serve as a migration form for active nitrogen compounds such as NO2, ultimately affecting the production of tropospheric ozone.

Instrument Introduction:

In 1992, under the support of the German Ministry of Environmental ProtectionBased on the technology and research of Max Planck Institute in Germany, Metcon has developed a PAN online automatic analyzer. Since then, the system has undergone multiple upgrades, with the calibration process undergoing in-depth testing by the research institute. The instrument is also operating stably in many countries around the world.

The automated PAN analyzer is suitable for 19 "rack mounted installation. It integrates computer-controlled fully automatic analytical instruments and a simple and reliable calibration method. The detection limit of PAN is less than 50ppt. The dynamic linear range exceeds 10 ppb. The dynamic calibration unit is based on the photochemical synthesis of PAN using NO calibration airflow.

PAN is separated by gas chromatography using a capillary column below room temperature and detected by an electron capture device. The chromatographic column is installed in a compact column box controlled by Peltier semiconductor refrigeration chips. Temperature fluctuations below 1K (1 degree). Backblowing the pre column can prevent species with high retention time from entering the analysis main column and detector, prevent contamination, and reduce analysis time. The sampling, injection, and switching of chromatographic columns are completed by a pneumatic 10 way valve (VALCO brand). The bypass design for sample sampling can reduce the dwell time of the sampling pipeline.

Chromatography software:

For the convenience of controlling the chromatography system and data acquisition and integration, we have designed a new computer software (based on Windows 7 system). The software utilizes an I/O control board (USB-DA or PCMCIA/PC Card) produced by Measurement Computing Inc., USA. The following modules are some of the main components of the software:

*Control the chromatography and its continuous operation to receive control parameters for remote control.

*Data acquisition of ECD signals and automatic integration of peak data.

*In offline mode, view the raw data and re integrate the peak area.

*Evaluate the time series of integral peaks, such as CCl4 and PAN.

The identification of peaks is automatic, and users first need to determine the approximate position and peak width of the corresponding peak on the test chromatogram. In the subsequent automated chromatography, accurate peak positions and integrals will be fitted and automatically optimized using the least squares method. The peak area of PAN and the concentration data generated by calibration factors are stored simultaneously.

Calibration unit:

The calibration unit is capable of generating sustained and stable PAN gas of known concentration. Based on the photochemical synthesis of PAN from NO calibration gas (ppm level), it is dynamically diluted to 0.1-30ppb with a total flow rate of 1-10L/min. The use of NO instead of NO2 is due to the better stability of NO calibration gas. The PAN calibration unit and PAN analysis unit are connected through a pneumatic PFA valve. In calibration mode, the sample comes from the overcurrent component of the calibration module. The peroxyacetyl radicals required for the calibration unit are generated by the photolysis of acetone. These peroxyacetyl radicals first oxidize NO to NO2 and then generate PAN.
The calibration unit was evaluated by the quality assurance program of German Tropospheric Research Focus (TFS) using two independent techniques, and the yield of PAN was determined to be 92% ± 3%. At the same time, it was found that this parameter is stably applicable under a wide range of operating conditions, such as 0.1~30ppb PAN at a flow rate of 10L/min.
Because the concentration of CCl4 in the background station is quite stable, its peak can be used as an internal standard to evaluate the response of ECD.

Zero gas for dilution:

High purity air, composed of 21% O2 and the rest N2, is purified through a purification tube.

Technical parameters:

analysis unit

Method: Gas chromatography;

Pre column and main column: wide pore capillary column;

Detector: ECD detector;

Chromatography oven: Peltier refrigeration and Pt100 temperature control;

Sample injection/chromatographic column switching: Pneumatic VALCO 10 way valve, equipped with external quantitative tube;

Carrier gas and tail blowing gas: 99.999% nitrogen, total flow rate<50ml/min;

Detection limit:<50ppt;

Measurement frequency: 6 times/hour;

Calibration: once a week;

Working temperature: 15-30 ℃;

Control/Data Collection: Dual USB interface data collection device;

Software: Based on the Windows 7 operating system, complete data collection, integration, and control;

Data format: PAN concentration data is in. gc file format and can be opened in Excel; The chromatographic raw data is an. adc file, which can be opened and processed using adam32 software;

Size: 19 "cabinet 3U (45 × 45 × 13.5cm);

Weight: Approximately 15kg;

Calibration unit:

Method: Synthesis by continuous photochemical reaction using NO standard gas; Conversion efficiency of 92% ± 3%;

Gas and reagent: NO, 10ppm/99.999% nitrogen (approximately 2mL/min);

Zero air (<50ml/min);

Acetone (analytical grade);

Dilution gas: Zero air purified by oxidant and activated carbon (5L/min);

Maximum ambient temperature: 30 ℃ (optional to withstand higher temperatures);

Size: 19 '' cabinet 2U (45 × 45 × 9 cm);

Weight: Approximately 12kg;

Main power supply of the instrument: 220VAC, 300W.