A method for the detection of analytes using resonant 
mass sensors or sensor arrays comprises 
frequency encoding each sensor element, acquiring a time-domain 
resonance signal from the sensor or 
sensor array as it is exposed to 
analyte, detecting change in the frequency or resonant properties of each sensor element using a 
Fourier transform or other 
spectral analysis method, and classifying, identifying, and / or quantifying 
analyte using an appropriate 
data analysis procedure. Frequency encoded sensors or sensor arrays comprise sensor elements with 
frequency domain resonance signals that can be uniquely identified under a defined range of operating conditions. 
Frequency encoding can be realized either by fabricating individual sensor elements with unique resonant frequencies or by tuning or modifying identical resonant devices to unique frequencies by adding or removing 
mass from individual sensor elements. The array of sensor elements comprises multiple resonant structures that may have identical or unique sensing 
layers. The sensing 
layers influence the sensor elements' response to 
analyte. Time-domain 
signal is acquired, typically in a single 
data acquisition channel, and typically using either (1) a pulsed excitation followed by acquisition of the free oscillatory decay of the entire array or (2) a 
rapid scan acquisition of 
signal from the entire array in a direct or 
heterodyne configuration. 
Spectrum analysis of the 
time domain data is typically accomplished with 
Fourier transform analysis. The methods and sensor arrays of the invention enable rapid and sensitive analyte detection, classification and / or identification of complex mixtures and unknown compounds, and quantification of known analytes, using sensor element design and signal detection hardware that are robust, simple and low cost.