Metoprolol tartrate

Standards of (±)-atenolol, (±)-acebutolol, (±)-labetalol and (±)-bisoprolol were purchased from Sigma-Aldrich (St. Louis, MO, USA) and (±)-metoprolol tartrate was purchased from Tokyo Chemical Industry (Tokyo, Japan). All standards were of high-purity grade (>98 %). High-purity grade (99 %) triethylamine (TEA) was purchased from Tokyo Chemical Industry, and glacial acetic acid (HAc) from Alkaloid AD Skopje (Skopje, North Macedonia). HPLC-purity grade methanol (MeOH) was purchased from J. T. Baker (Gliwice, Poland). Sodium hydroxide was of p.a. grade and purchased from Kemika (Zagreb, Croatia). Ultrapure water was obtained from a Milli-Q Advantage A10 purification system (Merck, Kenilworth, NJ, USA).

(R)-(+)-atenolol (ATE), metoprolol tartrate (MET) and propranolol hydrochloride (PRO) were purchased from Tokyo Chemical Industry. ITA, ethylene glycol dimethacrylate (EGDMA), benzoyl peroxide (BPO), triethylamine (TEA) and trifluoroacetic acid (TFA) were purchased from Sigma Aldrich. HPLC grade acetonitrile and methanol were purchased from Fischer Scientific. Acetone, potassium bromide and acetic acid were purchased from Merck. Blood samples were provided by the Indonesian Red Cross. If not otherwise specified, all chemicals are analytical grade. The morphological evaluation analysis was carried out by JSM-6610LV JEOL Ltd. A UV-visible spectrophotometer (Analytic Jena, Specord 200) was used to detect the UV absorbance for constant association determination. Analyses of blood after extraction with the MI-SPE were performed using HPLC (Dionex Ultimate 3000 with UV detector) by isocratic elution, using a mixture of methanol/water containing 0.01% TEA (15:85) as the mobile phase and a column Merck C18G 125A (250 × 4.6 mm i.d.). The flow rate was 1 mL min^−1, and the detection wavelength was set at 229 nm. The column was passed through with mobile phase until the baseline was obtained before detecting the samples.