Investigating key influencing factors of low wettability of Indigo Naturalis based on component “knockout method” combined with surface property analysis / 中草药

ABSTRACT

Objective: To explore the key factors affecting the low wettability of Indigo Naturalis by using “knockout” method combined with surface element analysis, so as to provide scientific basis for regulating and changing the wettability of Indigo Naturalis. Methods: Using N,N-dimethylformamide as solvent, six Indigo Naturalis powders were prepared by ultrasonic extraction for 0-5 times, 30 min for each time, filtration and drying process. The contents of indigo and indirubin in six kinds of Indigo Naturalis were determined by HPLC. The contact angle, surface free energy and its components, particle size, surface morphology, surface element analysis and infrared spectroscopy were determined. The relationship between the content of organic matter and wettability of Indigo Naturalis was discussed by correlation analysis. Results: With the increase of extraction times, the content of indigo decreased from 3.320% to 0.112%, the content of indirubin decreased from 0.120% to 0.006%, the contact angle in pure water decreased from 53.56 degrees to 34.84 degrees, the polar component of surface free energy increased from 24.880 to 38.701 mJ/m2, the non-polar component changed little, and the total surface free energy increased from 46.523 to 62.240 mJ/m2. Scanning electron microscopy (SEM) showed that the particulate matter on the surface of Indigo Naturalis was gradually disappeared, and the surface became smooth; Mapping scanning by energy spectrometer showed that N element was gradually decreased, Ca and Si element were increased slightly; Particle size distribution and infrared spectrum changed little; Correlation analysis showed that the content of indigo, indigo and indirubin was positively correlated with the contact angle, and the higher the content, the worse the wettability. Conclusion: The contact angle, polar component of surface free energy and total surface free energy of Indigo Natural was significantly increased after knockout, and the wettability was increased. Organic substances adhering to the surface of Indigo Naturalis were the key factors leading to its low wettability. To improve the hydrophilicity of Indigo Naturalis by powder surface modification technology, it is necessary to focus on organic substances.