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Ion chromatography determination of formic acid, acetic acid and oxalic acid

Determination of formic acid, acetic acid and oxalic acid in ambient air particles by ion chromatography with self-produced chromatographic column

There are two main aspects of fine particulate matter produced by human activities in the ambient air:
① The first is the direct release of fine particles into the air from various pollution sources, including smoke, dust, fugitive dust, oil fume, etc.;
② The second is the fine particulate matter generated after some chemically active gaseous pollutants (precursor pollutants) react in the air. These precursor pollutants include sulfur oxides, nitrogen oxides, volatile organic compounds, and ammonia.

As a component of PM2.5, organic acids play a very important role in photochemical reactions. However, there is currently no international limit on the content of organic acids in ambient air particles. Domestically, the "Comprehensive Emission Standard of Air Pollutants" (GB16297-1996) did not see the limit statement on the concentration of organic acid pollutants in particulate matter, and the "Ambient Air Quality Standard" (GB3095-2012) only covers The requirements are made as a whole, and no limit is specified for organic acids. At present, the determination methods of organic acid content mainly include potentiometric titration, spectrophotometry, enzymatic analysis, capillary electrophoresis, gas chromatography, liquid chromatography, mass spectrometry and ion chromatography.

In order to implement the Environmental Protection Law of the People’s Republic of China and the Air Pollution Prevention and Control Law of the People’s Republic of China, prevent and control environmental pollution, improve the quality of the ecological environment, and standardize the determination methods of formic acid, acetic acid and oxalic acid in ambient air particles, the Ministry of Ecology and Environment organizes The draft of the National Ecological Environment Standard "Ion Chromatography for the Determination of Formic Acid, Acetic Acid and Oxalic Acid in Ambient Air Particles" for comments was compiled.

1 Chromatography equipment

Ion chromatograph: IC6200, equipped with conductivity detector

Eluent generator: EG6100, OH-type

Autosampler: AS3100



Chromatographic conditions

Column Wayeal HS-5A-P2 4.6x250mm
Eluent KOH Gradient elution
Flow rate 1.2mL/min
Column temperature 40℃ Pond temperature 40℃
Current 150mA Injection volume 200μL

3 Interference test

Chromatograms of mixed standard test of 7 kinds of anions with formic acid, acetic acid and oxalic acid

Injection information:

No. Compound name Retention time Peak height Peak area Signal-to-noise ratio Degree of separation
1 F 9.535 7.379 123.064 11164.922 4.111
2 Acetic acid 11.512 1.779 34.867 2691.65 4.987
3 Formic acid 13.817 2.067 31.889 3,127,584 11.267
4 CI 18.354 5.148 78.898 7789.201 8.728
5 NO2 22.189 2.638 48.030 3991.557 7.718
6 Br 26.062 1.323 25.788 2001.121 5.043
7 NO3 29.019 1.986 52.182 3004.555 7.001
8 SO4 32.749 3.927 62.709 5941.778 8.397
9 Oxalic acid 36.536 2.368 43.925 3582.716 15.927
10 PO4 44.808 1.448 30.772 2190.442
Note: It can be seen from the test chromatogram and injection information that there is no interference between the target ion and the conventional 7 kinds of anions, and the resolution meets the test requirements, and the chromatographic conditions are available.

4 Standard curve test

Standard curve series concentration gradient table (μg/L)
Formic acid25501002505001000
Acetic acid5010020050010002000
Oxalic acid5010020050010002000
Overlapping chromatograms for standard curve determination

5 Repeatability test

Standard curve 6 continuous 6 needle overlapping chromatogram

Repetitive information:

No. Acetic acid Formic acid Oxalic acid
Retention time Peak area Retention time Peak area Retention time Peak area
1 10.992 104.504 13.429 142.432 36.894 192.451
2 11.004 104.748 13.439 142.631 36.869 192.483
3 10.987 104.562 13.416 142.537 36.874 192.121
4 10.997 104.382 13.428 142.515 36.842 192.456
5 10.987 104.568 13.41 142.594 36.828 192.141
6 10.876 104.471 13.349 141.578 36.567 191.029
Average 10.974 104.539 13.412 142.381 36.812 192.115
RSD(%) 0.441 0.118 0.242 0.281 0.333 0.290

Note: In this test, the qualitative repeatability and quantitative repeatability of formic acid, acetic acid, and oxalic acid are all less than 1%.

6 Detection limit test

The test results are as follows:
(Formic acid—8.64μg/L, acetic acid—28.8μg/L, oxalic acid—28.8μg/L, low-concentration standard solutions for this test (formic acid—5μg/L, acetic acid—10μg/L, oxalic acid—10μg/L ), the detection limit is calculated by the signal-to-noise ratio.

Formic acid-5ppb+acetic acid-10ppb+oxalic acid-10ppb test chromatogram



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