Analytical systems and methods that use a modular interface structure for providing an interface between a sample substrate and an analytical unit, where the analytical unit typically has a particular interface arrangement for implementing various analytical and control functions. Using a number of variants for each module of the modular interface structure advantageously provides cost effective and efficient ways to perform numerous tests using a particular substrate or class of substrates with a particular analytical and control systems interface arrangement. Improved optical illumination and detection system for simultaneously analyzing reactions or conditions in multiple parallel microchannels are also provided. Increased throughput and improved emissions detection is provided by the present invention by simultaneously illuminating multiple parallel microchannels at a non-normal incidence using an excitation beam including multiple excitation frequencies, and simultaneously detecting emissions from the substances in the microchannels in a direction normal to the substrate using a detection module with multiple detectors.