A device for detecting a class of target species containing quadrupolar nuclei in a specimen by nuclear quadrupole resonance, comprising pulse generating means for generating a three-pulse-composite-pulse to refocus signals that were excited by another pulse, irradiating means for irradiating a specimen with the three-pulse-composite-pulse, detecting means for detecting an NQR signal in response to irradiating the specimen, coupling means for transmitting the three-pulse-composite-pulse to the irradiating means, coupling means for receiving the NQR signal from the detecting means and transform means for converting the free induction decay signal into a frequency domain signal. A method for detecting a class of target species containing quadrupolar nuclei in a specimen by nuclear quadrupole resonance, comprising generating a three-pulse-composite-pulse, irradiating said specimen with said three-pulse-composite-pulse, detecting an NQR signal in response to irradiating said specimen and converting said free induction decay signal into a frequency domain signal.