BD Falcon roundbottom polypropylene test tubes (O.D. L. 12 75 mm), Falcon sterile polyethylene snap caps, Fisherbrand 12 75 mm polystyrene test tubes, Fisherbrand premium microcentrifuge tubes (amber, 1.5 mL), hydrochloric acid (37%, certified A.C.S.), chloroform (HPLC grade) and water (LC–MS grade) were obtained from Fisher Scientific (Fair Lawn, NJ)