Chromafil xtra polyethersulfone pes

LC–MS grade methanol and formic acid (98% purity) were procured from Fisher Chemicals (Hampton, NH, USA). Deionized water (18.2 MΩ) was obtained from the Bamstead^TMMicroPure water purification system (ThermoScientific^TM). Syringe filters, labeled, CHROMAFIL Xtra polyethersulfone(PES), 25 mm, 0.20 µm, polytetrafluoroethylene(PTFE), 25 mm, 0.45 µm and nylon, 25 mm, 0.45 µm were purchased from Macherey-Nagel (Düren, Germany).
The reference standards of colistin sulfate (colistin was 753 µg mg⁻¹, and colistin B was 53.6%, according to the certificate of analysis) were procured from Sigma-Aldrich, Bangalore, India. The stock solution (1000 µg mL⁻¹) of analyte was prepared in methanol/1% formic acid in water (1/1, v/v) by correcting the sulfate mass, and kept at −20 °C. The working standards were prepared via serial dilution with methanol/1% formic acid in water (1/1, v/v). These working standard solutions were then used for preparing linearity and spiking studies.
A refrigerated centrifuge Sorvall™ ST8 ventilated benchtop (ThermoScientific, San Jose, CA, USA), analytical balance (Aczet, CY2202) and precision balance (Aczet, CY205C, San Diego, CA, USA), vortex mixer (Thermo Scientific, USA), 2, 15 and 50 mL extraction/conical centrifuge tubes (Thermo Scientific) and Thermo Scientific variable volume Finnpipette (100–1000 µL; 10–100 µL; and 0.5 to 5 mL) were also used.

2,2-Diphenyl-1-picrylhydrazyl (DPPH), Folin-Ciocalteu phenol reagent, L-ascorbic acid, di-sodium hydrogen phosphate de-hydrate, and sodium dihydrogen phosphate dehydrate were purchased from HiMedia Laboratories Pvt. Ltd. (India). HPLC grade water, sodium carbonate, and hydrogen peroxide were procured from Loba Chemie Pvt. Ltd. (India). Gallic acid, quercetin, ellagic acid, vanillic acid, catechin, epigallocatechin gallate (EGCG), and DCM were procured from Sigma-Aldrich (USA). LC–MS grade acetonitrile, methanol, and formic acid (of 98% purity) were procured from Fisher Chemicals (Hampton, NH, USA). Colistin was procured from HiMedia Laboratories Pvt. Ltd. (India). Labeled, CHROMAFIL Xtra poly ether sulfone (PES), 25 mm, and 0.20 μm syringe filters were purchased from Macherey-Nagel (Düren, Germany). UV-vis spectrophotometer (Evolution 201) was procured from Thermo Fisher Scientific- Shanghai (China). ORBITEK shaker was purchased from Scigenics Biotech Pvt. Ltd. (India). Refrigerated centrifuge C-24 Plus was from REMI Sales and Engineering Ltd. (India). Analytical balance Aczet, CY2202 was purchased from Mettler-Toledo Pvt. Ltd. (India). Rotary vacuum evaporator-RE-52 was purchased from SONAR (India). Micropipette (20-200, 100-1000, and 0.5-10 μL) of variable volume purchased from HiMedia Laboratories Pvt. Ltd. (India).