Tetralkylammonium salts

Sample preparation and experimental details have been reported previously for 3-ring and 4-ring MDA ESI studies^{2 (link)} and 2-ring MDA ESI and MALDI studies^{1 (link),3 (link)}, but a few details will be mentioned here. Methylenedianiline (MDA) 3-ring and 4-ring samples were provided by Dr. Stefan Wershofen (Bayer MaterialScience AG, 47812 Uerdingen, Germany). Optima grade methanol and water with 0.1% formic acid were obtained from Fisher Scientific (Waltham, MA, USA). Tetralkylammonium salts, α-cy-ano-4-hydroxycinnamic acid (CHCA) and alkali salts were obtained from Sigma-Aldrich (St. Louis, MO, USA). Samples were dissolved at a concentration of 1 mg/mL in 9:1 methanol/water containing 0.1% formic acid (v/v). Each MDA isomer was combined in a 10:1 CHCA matrix-to-analyte ratio and two or three layers of 0.5 µL of samples were spotted on a 100-well MALDI plate.

Sample preparation and experimental parameters have been previously described in detail for ESI studies, but a few details will be mentioned here.^{1 (link)} Methylenedianiline (MDA) 2-ring isomers (2,2′-MDA, 2,4′-MDA, and 4,4′-MDA) were provided by Dr. Stefan Wershofen (Bayer MaterialScience AG, 47812 Krefeld, Germany). Methanol and water with 0.1% formic acid were obtained from Fisher Scientific (Waltham, MA). Tetralkylammonium salts, α-cyano-4-hydroxycinnamic acid (CHCA), alkali salts, and 2,7-diaminofluorene (2,7-DAF) were obtained from Sigma-Aldrich (St. Louis, MO). Samples were dissolved at a concentration of 1 mg/mL in 9:1 methanol/water containing 0.1% formic acid (v/v). Each MDA isomer was combined in a 10:1 matrix-to-analyte ratio and 2 to 3 layers of 0.5 μL of sample were spotted on a 100-well MALDI plate.