One of the advantages of the external ion source method is that the operating parameters for generating ions in the MALDI source can be optimized independently from the parameters for detecting the ions in the FTMS analyzer cell. With this method, the detection limits for peptides and small proteins like insulin are in the low femtomole range, and the mass measurement accuracy under high resolution conditions is in the low ppm range. The ProMALDI is offered with a 96 or 384 sample plate and an optional EI source. No other MALDI mass spectrometer can match its mass measurement accuracy, mass resolving power, and powerful MS/MS capabilities. IonSpec FTMS are also offered with an AP MALDI source that attaches to the front of the ESI source.