To a 1.5 mL test tube, 25 [micro]L sample was added along with 1.25 [micro]L of the internal standard solution (1 [micro]g/mL final concentration) and 6.25 [micro]L of the extraction solution (acetonitrile:10mM ammonium formate
[pH 3.86] = 90: 10).
GR grade ammonium formate
and ammonium acetate reagents were procured from Merck Specialities Pvt.
Addition of anionic ion-pairing reagents, for example, sodium dodecyl sulphate or salts (e.g., ammonium acetate, ammonium formate
, and sodium phosphate) is also used to improve the chromatographic separation [5, 13, 17, 22].
Lu, Highly Efficient N-formylation of Amines with Ammonium Formate
Catalyzed by Nano-Fe3O4 in PEG-400, RSC Adv., 4, 1234 (2014).
Formic acid, ammonium formate
, and ammonium phosphate were obtained from Sigma Aldrich; LC-MS-grade methanol and acetonitrile from Burdick & Jackson; Strata-X-CW weak cation exchange (WCX) solid-phase extraction (SPE) cartridges (3 mL) from Phenomenex; and Oasis WCX [mu]Elution 96-well SPE plates from Waters.
Bio-ultragrade ammonium formate
and LC-MS grade formic acid were purchased from Sigma-Aldrich (St.
Mass spectrometry-grade reagents (formic acid and ammonium formate
) and analytical-grade reagents (sodium chloride and Tween 60) were purchased from Fluka (Buchs, Germany), Sigma (St.
Ten ppb spiked river samples are simply filtered, 10 mM of ammonium formate
is added and then pipetted onto a mesh.
Denoxium is a solution of ammonium formate
and urea and it has a freezing point of -30oC.
All the reagents used (acetonitrile, ammonium formate
, formic acid, sodium hydroxide, hydrochloric acid, and hydrogen peroxide) were analytical grade, purchased from Merck (Darmstadt, Germany).
HPLC grade ammonium formate
and formic acid were purchased from Sigma (St.
(LC-MS grade) was purchased from Sigma-Aldrich Chemie GmbH.