Supplement material to Ref. JASMS Ms. No Detection of an amine impurity and quality assessment related to this impurity of the UV MALDI matrix  -cyano-4-hydroxy- cinnamic acid for the analysis of peptides in the attomole range Justyna Rechthaler, Ernst Pittenauer, Tanner M. Schaub and Günter Allmaier

Legends to Figures in the Supplement Figure 1S Positive-ion MALDI mass spectra (curved field reflectron mode) of two CHCA matrix batches: matrix B (a) and matrix E (b). Matrix solvent: acetone. The mass spectrum (a) exhibits a [M+H] + /[M*+H] + ratio > 1, which represents a high quality matrix, and the following spectrum (b) a [M+H] + /[M*+H] + ratio < 1 representing a matrix of lower quality. Figure 2S Comparison of the [M+H] + /[M*+H] + (a) and [2M+H] + /[M*+H] + (b) ratios of five various CHCA matrix batches (A, B, C, D and E, matrix solvent: acetone) obtained on a bench-top (MALDI IV) and floor-standing high resolution TOF instrument (AXIMA-CFR). Figure 3S Positive-ion MALDI FT-ICR mass spectrum of the matrix E (including highest amount of the contaminant) with the region around m/z 102. The spectrum was internally calibrated with following matrix signals: [M-CO 2 +H] +, [M-H 2 O+H] + and [M+H] +. The RMS error on the three point calibration was ppm. The mass spectrometric resolving power observed for the m/z signal was (FWHM). Figure 4S Positive-ion MALDI high energy (E Lab 2 keV) CID (LinTOF/RTOF) mass spectrum of the precursor ion m/z (derived from matrix E in acetone).

%Int Mass/Charge [M-H 2 O+H] + [M+H] + [M+Na] + [M*+H] + [M-CO 2 +Na] + [2M+H] Fig. 1S a

%Int Mass/Charge 102 [M*+H] + [M-CO 2 +Na] + [M+H] + [M+Na] + [2M+H] Fig. 1S b

Fig. 2S a

Fig. 2S b

C 6 H 16 N 1 observed at m/z: Theoretical mass at m/z: Error: –1.2ppm m/z [M*+H] + Fig. 3S

m/z Intensity Precursor ion C 6 H 16 N [M*+H] + H H Fig. 4S