Methyl orange

Commercial samples of COS used in this study were obtained from Qingdao (Shangdong, China) and had average molecular weights of 1000 Da and 3000 Da, respectively. The DD of the commercial COS were >90% in glucosamine hydrochloride. The N-acetylglucosamine used in this study was purchased from Sigma Aldrich (St. Louis, MO, USA) and had a purity greater than 99%. The deuterium oxide used had an isotopic purity of 99.8%, and was obtained from Shanghai Macklin Biochemical Co., Ltd. (Tianjin, China). Bromocresol green and methyl orange were purchased from Tianjin Damao Chemical Reagent Factory (Tianjin, China) and methyl orange from Tianjin Zhiyuan Chemical Reagent Co., Ltd. (Tianjin, China), respectively. Sodium hydroxide pellets (NaOH), hydrochloric acid (HCl), and potassium hydroxide pellets were obtained from Tianjin Kermel Chemical Reagent Co., Ltd. (Tianjin, China). All other reagents and solvents were of analytical grade and used without further purification. All water used in the extraction and analysis was distilled and deionized.

Dichloromethane, ethanol, FeCl₃∙6H₂O, FeSO₄·7H₂O, HCl, H₂O₂, MB, methanol, rhodamine B (RhB), methyl orange (MO), crystal violet (CV), NaOH, and tetrahydrofuran (THF) were obtained from Tianjin Damao Chemical Reagent Factory (Tianjin, China). Aqueous ammonia (25%) was purchased from Tianjin Kermel Chemical Reagent Co. (Tianjin, China). Pyrrole (J&K Scientific, Beijing, China) was distilled before use. Poly(sodium-p-styrene sulfonate) (PSS), polyvinyl chloride (PVC), polyvinyl pyrrolidone (PVP), SDBS, and sodium dodecyl sulfate (SDS) were obtained from Aladdin Industrial Co. (Shanghai, China). All reagents and solvents were of analytical grade. The ultrapure water (18.2 MΩ·cm) used in the experiments was prepared using a Purifier water purification system.