This communication details our recent developments in the application of electrospray mass spectrometry to the field of arsenic speciation. The experiments detailed demonstrate that recognition of individual arsenic-containing compounds can be achieved in electrospray mass spectra of biological extracts containing at least fifty different compounds. The excellent mass accuracy and resolution obtainable with modern mass spectrometers makes this process possible. This work demonstrates the first application, as far as the authors are aware, of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR) to the analysis of organoarsenic compounds. The excellent mass accuracy of FT-ICR is exploited to assign elemental compositions and thus identify ions generated from arsenic-containing compounds. This extends to the tandem mass spectral data, where product ions could be assigned as arsenic-containing or non-arsenic-containing. As FT-ICR instrumentation is expensive and not readily available to most arsenic-chemists the approach developed for use with FT-ICR was also evaluated using a hybrid quadrupole–time-of-flight (Q-ToF) instrument. It is shown that the low parts per million (ppm) mass accuracies obtained using these instruments, although not as great as those obtainable with FT-ICR technology, still enable the characterisation of arsenic-containing compounds in a crudely fractionated kelp extract. These results offer new perspectives for the rapid recognition, and subsequent identification, of unknown arsenic species in crude extracts, without the need for extensive purification or previously characterised standards.