[Ingredients changes in Rehmanniae Radix processing based by HPLC-ELSD specific chromatogram]

To establish the HPLC-ELSD specific chromatogram analysis method of Rehmanniae Radix and Rehmanniae Radix Prae-parata, and analyze and compare their chemical compositions, so as to reveal the change regularity of compositions during the proces-sing. By HPLC-ELSD method, the chromatographic column for Prevail Carbohydrate ES(4.6 mm ×250 mm, 5 μm) was adopted, with acetonitrile(A)-water(B) as mobile phase for gradient elution, and the evaporative light-scattering detector was used. A total of 23 batches of Rehmannia Radix samples, and 25 batches of Rehmanniae Radix Praeparata samples and processing dynamic samples were compared. The established method had a great repeatability, precision and stability. Eight common chromatographic peaks were extracted from 23 batches of Rehmanniae Radix samples, 8 common peaks were extracted from 25 Rehmanniae Radix Praeparata, and 7 chromatographic peaks were identified. The composition ratio of Rehmannia Radix was changed greatly during the processing. When the simila-rity≥0.95 and the fructose peak area was more than 2 times of stachyose tetrahydrate or more than 20 times of raffinose, the processing degree conformed to the requirements of empirical identification. The three main oligosaccharides of Rehmanniae Radix were sucrose that was heated to generate fructose and glucose, stachyose tetrahydrate that was heated to generate melibiose, sucrose and fructose, and stachyose tetrahydrate that was heated to generate manninotriose. The change in the index of proportion between monosaccharides and oligosaccharides can be used as the quantitative criterion for the processing quality of Rehmanniae Radix Praeparata.