Photoacoustic spectroscopy with mica and graphene micro-mechanical levers for multicomponent analysis of acetic acid, acetone and methanol mixture

Multilayer graphene and mica cantilevers as part of an optical microphone in combination with CO2 laser emitting in the range of 9-11 μm were employed in a multicomponent analysis of a mixture of acetone, acetic acid and methanol by photoacoustic spectroscopy. Using these elements, the detection limits of mica circle cantilever were 0.54, 0.80 and 24.8 ppm for acetic acid, methanol and acetone, respectively; these limits were approximately 5 times lower than the detection limit of the highest-class microphone used in this study. The multicomponent analysis was performed using five selected CO2 laser lines and a classical method of least squares. Despite the inaccuracies of our system, very good agreement between the concentration of acetic acid calculated from the photoacoustic signal and from weighing of concentration standards (~3%) was found when measuring the signal in a 10:1:1 mixture of acetone:acetic acid:methanol at five selected laser lines. The absorption coefficient of acetic acid at 10.24 μm was almost 500 times higher than that of acetone, which showed the good ability of this method to detect acetic acid in a high background of acetone, which can be beneficial in the medical analysis of breath.