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36 PCB007 MAGAZINE I JULY 2018 mass spectrometry. The resulting high-resolu- tion mass spectra were used for the calcula- tion of sum formula, which allows a prediction of structures which can be com- pared with reference substances. Hence, it is possible to identify additives like photoinitiators, cross-linkers, flame retardants and other plastic additives. Fig- ures 6 and 7 show the compari- son of the signals of the photoini- tiators. For a better comparison, the ex- tracted ion chromatograms are used. Therefore, the desired mass was extracted from the whole mass spectrometric data. In com- parison the samples show dif- ferences in their signal intensi- ties of photoinitiators. It should be noted that the identified pho- to-initiators contain sulphur. Ta- ble 2 demonstrates the correla- tion between sulphur in the el- emental analysis and the re- sponse of the mass signals. In general, samples with a high sul- phur content show intense sig- nals of leaching products. This is especially true for the sul- phur-containing photoinitia- tors and is demonstrated in Figures 6 and 7. Figures 6 and 7 along with Ta- ble 2 show the correlation be- tween sulphur in the elemental analysis and the response of the extracted ion chromatogram. Table 2: Elemental analysis of critical customer samples A, B, C and D. Figure 6: Extracted ion chromatogram of photoinitiator 1. Figure 7: Extracted ion chromatogram of photoinitiator 2. the same wavenumbers. This method has the potential to be a performance indicator. Leaching Experiments This is a simulation of the potential of a sol- der mask to leach into the plating chemis- try. Acetonitrile, (ACN), is used as a solvent. The samples are exposed to the solvent to ex- tract the potential leachants. The resulting ex- tracts were analyzed by GC-MS and HPLC- ESI-TOF MS. In this work, only the results of the HPLC-ESI-TOF MS are shown. Therefore, the compounds of the extracts were separat- ed by liquid chromatography and analyzed by