The invention relates to a determining device for hydrocarbon emissions of a thermal engine, in particular of a motor, having an inspection probe (21), which is designed to remove a sample volume from a liquid, a measurement channel (22), which conducts the sample volume to a measurement apparatus (8) via an ion source apparatus (3), wherein the measurement apparatus (8) is a broadband measurement apparatus, which is designed to determine a spectrum to be measured in one step, wherein the ion source apparatus (3) is designed for soft ionization and the measurement apparatus (8) is designed as a simultaneously measuring "time-of-flight" detector or as a "double focusing sector field mass spectrometer in Mattauch-Herzog geometry," which forms an intensity signal sequence across the mass spectrum. A fast measurement across the entire spectrum range, from short-chained to long-chained molecules, is achieved according to the invention by the combination of a soft ion source with the claimed detectors. An intensity signal sequence thus results which reproduces the occurring molecules over the entire spectrum, and moreover having high dynamics. The total material quantity can be reliably and quickly determined by a simple summation according to the invention in that a separate intensity signal is provided for each individual molecule mass as a result of said detector type.