The easiest way is to carry a biological sensor with you in the form of a mouse or a rat. Unfortunately, if they try to poison you, the sensor will die, saving your life
I remember the news that a group of scientists had created a nail polish that changes color when in contact with drugs, which are usually poured on girls to get them into bed.
For a mass spectrometer, "compact" means "about the size of a desktop computer system unit." If we check a drink a little more complicated than vodka, the mass spectrometer should not be by itself, but combined with a chromatograph, otherwise there will be one big porridge. Plus, after each carrying all these pieces of iron, you should do a good calibration from scratch.