Andbovine serum albumin

Luteolin (Lut,
>98%) was from Shanxi Huike Plant Co., Ltd. (Shanxi, China), and
bovine
serum albumin (BSA, ≥98%) was from Sigma Chemical Company (St.
Louis, USA). CuSO₄·5H₂O (>99%) and NaOH
(≥96%) were from Beijing Chemical Plant (Beijing, China). 2,2′-Azobis(2-methylpropionamidine)
dihydrochloride (AAPH, 98%) was from Energy Chemical (Anhui, China).
Warfarin and ibuprofen (≥98%) were from Aladdin Industrial
Co. (Shanghai, China). The 30% H₂O₂ (9.8 M)
aqueous solution (≥99.7%) was from Tianjin Fuchen Chemical
Reagent Factory (Tianjin, China). The buffer solution used in the
experiments was prepared using 3-(N-morpholino)propanesulfonic
acid (MOPS, ≥99.5%, Sigma-Aldrich, St. Louis, MO, USA). All
experiments were performed in a 25 mM MOPS buffer at pH 7.4. NaOH
was used to adjust the pH, and 3% (v/v) ethanol (99.9%, Fine Chemical
Industry Research Institute, Tianjin, China) was used to increase
the solubility of Lut. All experimental sections were repeated three
times in parallel to produce error analyses.

Standard samples of heroin and morphine were granted by CFSL (the Central Forensic Science Laboratory), Chandigarh, India. MAM, M-3-G, and bovine serum albumin (BSA) was acquired from Sigma Aldrich Co., Delhi, India. 3,3′,5,5′-Tetramethylbenzidine (TMB) was procured from Bangalore Genei, India Pvt. Ltd (BGIP). ELISA plates (polystyrene made) were purchased from NUNC (A/S), Denmark. HPLC-grade solvents included acetonitrile A and B (CH₃CN), ethyl acetate (CH₃COOC₂H₅) and methanol (CH₃OH). Buffer preparation (ph 6.0 ± 0.1) was done using a blend of 0.1 mol L⁻¹ sodium acetate (CH₃COONa) and 0.1 mol L⁻¹ acetic acid (CH₃COOH) with 50 g L⁻¹ sodium fluoride (NaF) solution. Thermo Fisher Scientific, phosphate buffered saline (PBS) was also employed as washing buffer for ELISA plates in competitive immunoassay. Sample pad, absorption pad, and dipstick plastic unit was obtained from Advance Microdevices, Ambala, India.
All other reagents, chemicals and solvents availed in the experimental study were of high purity and analytical grade.