Acetonitrile hplc supra gradient grade

Acetonitrile HPLC supragradient grade and acetonitrile LiChrosolv were purchased from Scharlab (Sentmenat, Spain) and Merck (Billerica, MA, USA), respectively. Solutions and solvent mixtures were made up of water purified by the Milli-Q ® plus system from Millipore (Bedford, MA, USA) with a resistivity of 18.2 m cm. Readymade 0.5M solutions of potassium hydroxide and hydrochloric acid were obtained from Merck and Sigma, respectively. 1-octanol ACS reagent and potassium bromide were purchased from Sigma (Saint Louis, Missouri, USA). Deuterated chloroform-d and methanol-d4 were obtained from Sigma Aldrich (Steinheim, Germany).
The chemicals used for buffer preparation were obtained from Merck (Darmstadt, Germany), Fluka (Steinheim, Germany), Sigma-Aldrich (Steinheim, Germany), Baker (Deventer, Netherlands), Riedel de Haën (Seelze, Germany) and Carlo Erba (Milano, Italy) . Some of the drugs were purchased from Sigma-Aldrich (Steinheim, Germany), Alfa-Aesar (Ward Hill, USA), Prestwick Chemical (Illkirch, France) in high purity grade. Other drugs were synthesized in ESTEVE (Barcelona, Spain).