Complex sentence: Direct examination of biological tissue by mass spectrometry (MS) has been raised in the 1970s, but then the next available technical conditions, the method did not provide any useful information on the chemical composition of the samples tested.
Split into simpler sentences: Direct examination of biological tissue by mass spectrometry (MS) began in the 1970s, but at that time the next advance in technical conditions did not exist. The method did not provide any useful information on the chemical composition of the samples tested.