The pH value control in air plasma–liquid system by sodium bicarbonate Bangbang He, Xinning Gong, Yupengxue Ma, Xin Wang, Junshuai Li, Qing Xiong and Qiang Chen Eur. Phys. J. D, 73 2 (2019) 40 Published online: 19 February 2019 DOI: 10.1140/epjd/e2019-90221-3