An analysis system for analysing samples that comprises: - a reflective substrate; - a hollow elongate structure having two ends; - two polymer supports coupled to the ends of the hollow elongate structure and joined to the reflective substrate; - at least one piezoelectric device coupled to the reflective substrate and in contact with the hollow elongate structure, and designed to produce vibrations in the hollow elongate structure; - at least one laser configured for emitting a laser beam, - at least one photodetector designed to absorb the laser beam which passes through the hollow elongate structure before reaching the photodetector, and produce an electrical signal associated with the modulation intensity and frequency of the received laser beam, wherein the analysis system additionally comprises: - at least one amplification module coupled to the piezoelectric device and to the photodetector and configured for amplifying and filtering the electrical signal provided by the photodetector, and for separating the modulated component and an unmodulated component of the signal; and - a processor coupled to the amplification module and configured for processing the amplified and filtered electrical signal and obtaining, based on the modulated component of the signal, a measurement of the resonance frequency of the hollow elongate structure at each instant of time, which varies depending on the variation in the buoyant mass of the sample, and based on the unmodulated component of the signal, the reflectivity inside the hollow elongate structure at each instant of time; wherein the processor is further configured to provide the piezoelectric device, through the amplification module, with an excitation signal at the resonance frequency, for said piezoelectric device to produce vibrations in the hollow elongate structure at the resonance frequency at each instant of time. - a reflective substrate; - a hollow elongate structure having two ends; - two polymer supports coupled to the ends of the hollow elongate structure and joined to the reflective substrate; - at least one piezoelectric device coupled to the reflective substrate and in contact with the hollow elongate structure, and designed to produce vibrations in the hollow elongate structure; - at least one laser configured for emitting a laser beam, - at least one photodetector designed to absorb the laser beam which passes through the hollow elongate structure before reaching the photodetector, and produce an electrical signal associated with the modulation intensity and frequency of the received laser beam, wherein the analysis system additionally comprises: - at least one amplification module coupled to the piezoelectric device and to the photodetector and configured for amplifying and filtering the electrical signal provided by the photodetector, and for separating the modulated component and an unmodulated component of the signal; and - a processor coupled to the amplification module and configured for processing the amplified and filtered electrical signal and obtaining, based on the modulated component of the signal, a measurement of the resonance frequency of the hollow elongate structure at each instant of time, which varies depending on the variation in the buoyant mass of the sample, and based on the unmodulated component of the signal, the reflectivity inside the hollow elongate structure at each instant of time; wherein the processor is further configured to provide the piezoelectric device, through the amplification module, with an excitation signal at the resonance frequency, for said piezoelectric device to produce vibrations in the hollow elongate structure at the resonance frequency at each instant of time. - at least one amplification module coupled to the piezoelectric device and to the photodetector and configured for amplifying and filtering the electrical signal provided by the photodetector, and for separating the modulated component and an unmodulated component of the signal; and - a processor coupled to the amplification module and configured for processing the amplified and filtered electrical signal and obtaining, based on the modulated component of the signal, a measurement of the resonance frequency of the hollow elongate structure at each instant of time, which varies depending on the variation in the buoyant mass of the sample, and based on the unmodulated component of the signal, the reflectivity inside the hollow elongate structure at each instant of time;