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Citric Acid by ANP
Low Molecular Weight Organic Acids
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printable Application Sheet
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Notes: ANP Chromatography with MS Detection (ANP-LCMS) has become more and more popular for analysis of certain mixtures of
organic acids because of the simplicity, rapidity and stability of the method. The statutory methods for the determination of
low molecular mass organic acids are turbidimetric and colorimetric methods and ion-exchange chromatography. “Turbidimetry by
means of calcium oxalate precipitation and colorimetry by means of zinc ferricyanide color development are time-consuming and
only achieve limited rather than exact results”.
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Citric, Maleic and Trans Aconitic Acids Retained and Separated
Method Conditions
| Column |
Cogent Diamond Hydride™, 4µm, 100A |
| Catalog No. |
70000-15P-2 |
| Dimensions |
2.1 x 150 mm |
| Solvents |
A: DI water + 0.1% ammonium formate
B: acetonitrile + 0.1% ammonium formate |
| Mobile Phase |
Gradient:
| Time |
%B |
Time |
%B |
| 0.0 |
90 |
6.1 |
30 |
| 2.0 |
90 |
7.0 |
30 |
| 5.0 |
70 |
7.1 |
30 |
| 6.0 |
70 |
10.0 |
90 |
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| Flow Rate |
400 µL/min. |
Peaks
(Compounds) |
1. Maleic acid 115.0031 m/z (M-H)-
2. trans- Aconitic acid 173.0086 m/z (M-H)-
3. Citric acid 191.0192 m/z (M-H)-
Sample mixture was prepared in 50% DI water/50% acetonitrile. |
| Detection |
ESI – neg - Agilent 6210 MSD TOF mass spectrometer |
Discussion
Low molecular mass acids were retained and separated using a Cogent Diamond Hydride™ column in the Aqueous Normal Phase mode of
HPLC LC-MS chromatography (ANP-LC-MSHPLC). The method described above was able to resolve three acids in 10 minutes.
Limits of detection (LOD) for the 3 acids ranged from 0.05 to 24 microM. The disadvantages of current ion-exchange chromatography
methods are the use of a strongly acidic cation exchanger which has low exchange capacity, the long time required for equilibrium,
separation and re-equilibrium.
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