Categorisation of biological deposits using matrix assisted laser desorption ionisation mass spectrometry

A method of categorising a human using MALDI MS comprising: a) obtaining a biological deposit from a human; b) analysing the deposit using MALDI MS to obtain sample spectral data in the range 2,000 €“ 30,000 m/z; referencing spectral data in a library; c) comparing characteristics of sample spectral data and reference spectral data; and d) characterising the human. Preferably the biological deposit comprises a fingermark comprising compounds from eccrine, sebaceous glands, or sweat glands. The human may be categorised according to gender, ethnicity, age, health status, dietary habits, smoking, drinking, or pregnancy. A method of preparing reference spectral data comprises: a) categorising a plurality of humans; b) obtaining a biological deposit from each human; c) analysing each deposit by MALDI MS; d) associating characteristics of the obtained spectral data with the personal characteristics of the human. Also claimed is apparatus comprising: a sample holder; a MALDI mass spectrometer, a storage device for storing reference spectral data, a processor, and a user interface.