Hadamard transform time-of-flight mass spectrometry: more signal, more of the time.

Hadamard transform time-of-flight mass spectrometry (HT-TOF MS) is a type of mass analysis that was developed to couple continuous ion sources to the inherently pulsed nature of time-of-flight measurements. Unlike conventional TOF MS, the Hadamard transform method offers a duty cycle of 50%, with the possibility of extending it to 100%. Because it is a multiplexing technique, the attainable signal-to-noise ratio (SNR) is also significantly higher than that of conventional TOF MS. This review covers the basic principles behind HT-TOF MS. We illustrate, through examples, the source of the high-duty cycle and the increase in SNR. These features translate to a mass spectral storage rate that is the fastest among similar instruments, which enables its use as a detector for high-speed separations.