4. Method Summary

The sample was extracted with a mixture of acetonitrile, N, N-dimethylformamide (DMF), and the extract was purified using a cation exchange column. It was then determined by liquid chromatography with a UV detector and quantified using an external standard method.

5. Reagents

Unless otherwise specified, all reagents used are analytical grade, and the water is first grade water as specified in GB/T6682.

5.1 Acetonitrile HPLC grade.

5.2 Methanol HPLC grade.

5.3N, N-dimethylformamide (DMF).

5.4 Phosphoric acid.

5.5 Hydrochloric acid.

5.6 n-hexane.

5.7 Ammonia solution, 25%.

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6. Instruments

Liquid chromatograph, oscillator, solid phase extraction device with vacuum pump, centrifuge speed ≥ 4000r/min, nitrogen blowing concentration device, rotary evaporator, my preferred mixer, stainless steel sieve with 1mm aperture.