Lc ms methanol

Solid-phase
extraction (SPE) was carried out for river and ocean waters. This
extraction methodology allows the capturing of a myriad of natural
and anthropogenic organic molecules composing the dissolved organic
matter (DOM).^{54 (link),55 (link)} The SPE resins were activated
with a 3× cartridge volume of 100% methanol (LC/MS grade, Fisher
Scientific) and conditioned with a 1× cartridge volume of the
3% methanol (LC/MS methanol diluted in LC/MS H2O, Fisher Scientific).
The resins did not run dry between the washes. Subsequently, 500 mL
of each sample type was loaded into each resin type via vacuum-assisted
flow at a rate of 20 mL/min with the help of a vacuum SPE station
(Agilent). Following loading, the resins were flushed with 1×
cartridge volume of 3% methanol and eluted using 2 mL 80% methanol
into glass LC vials. The sample extracts were then transferred to
preweighed glass vials and dried down using a speedvac at room temperature.
Each vial was weighed a second time to quantify the extract and stored
at −80 °C until further analysis. The extracts were resuspended
to a concentration of ∼10 mg/mL in 50% methanol/water (LC/MS
grade). Samples were analyzed immediately following resuspension.

The drug substance sulconazole nitrate was obtained from the USP Reference Standard. Commercial samples of sulconazole nitrate were purchased from Sigma-Aldrich (St. Louis, MI, USA), Spectrum Chemical (New Brunswick, NJ, USA), Glentham Life Sciences (Corsham, UK), and Erregierre (Sovere, Italy). Hydrochloric acid (37%), glacial acetic acid (≥ 99.7%), sodium hydroxide solution (10 N, J.T.Baker), trifluoroacetic acid (TFA, 99.5%, Acros Organics), ammonium acetate (LC/MS), methanol (LC/MS), and acetonitrile (HPLC and LC/MS) were purchased from Fisher Scientific (Waltham, MA, USA). Hydrogen peroxide (~30%) was obtained from Sigma-Aldrich. Water was purified with a Milli-Q plus system from Millipore (Bedford, MA, USA).