A spectroscopy device for inline monitoring of fluid analytes, the device comprising: - a cassette suitable for holding a fluid analyte and having a laser entry wall part and a detector wall part, the laser entry wall part arranged to be optically transparent to laser radiation of predetermined a wavelength and the detector wall part arranged to be optically transparent for spectral parts of interest; - a laser transmission optic for transmitting a laser beam of the predetermined wavelength from a laser system, via the laser transmission optic into the cassette, the laser transmission optic arranged to focussing the laser beam through the laser entry wall in an excitation spot within the cassette in order to create a laser induced breakdown plasma within the fluid analyte, which emits optical radiation; - a photodetector formed by an array of photosensors provided on a substrate, the photodetector substrate being conformal to at least the detector wall part of the cassette; each sensor in the array arranged with a bandpass filter for detection of emission radiation of the plasma in a spectral part of interest; - a placement provision; arranged for removable placement of the cassette with its laser entry wall part facing the laser transmission part; and - a control mechanism arranged to impinge the laser beam on the excitation spot within the fluid analyte, in order to create the laser induced plasma emission radiation; and detect the emission radiation of the plasma via the detector wall part by the array of photosensors in the spectral parts of interest; wherein - a notch filter is provided for blocking the predetermined wavelength of the laser beam radiation for each sensor, wherein the detector wall part is arranged so that the excitation spot within the cassette projects emission radiation centrally relative to the array of photosensors; and wherein the laser entry wall part is provided with a dichroic cold mirror coating that is arranged to reflect emission radiation towards the detector wall part. - a cassette suitable for holding a fluid analyte and having a laser entry wall part and a detector wall part, the laser entry wall part arranged to be optically transparent to laser radiation of predetermined a wavelength and the detector wall part arranged to be optically transparent for spectral parts of interest; - a laser transmission optic for transmitting a laser beam of the predetermined wavelength from a laser system, via the laser transmission optic into the cassette, the laser transmission optic arranged to focussing the laser beam through the laser entry wall in an excitation spot within the cassette in order to create a laser induced breakdown plasma within the fluid analyte, which emits optical radiation; - a photodetector formed by an array of photosensors provided on a substrate, the photodetector substrate being conformal to at least the detector wall part of the cassette; each sensor in the array arranged with a bandpass filter for detection of emission radiation of the plasma in a spectral part of interest; - a placement provision; arranged for removable placement of the cassette with its laser entry wall part facing the laser transmission part; and - a control mechanism arranged to impinge the laser beam on the excitation spot within the fluid analyte, in order to create the laser induced plasma emission radiation; and detect the emission radiation of the plasma via the detector wall part by the array of photosensors in the spectral parts of interest; wherein - a notch filter is provided for blocking the predetermined wavelength of the laser beam radiation for each sensor, wherein the detector wall part is arranged so that the excitation spot within the cassette projects emission radiation centrally relative to the array of photosensors; and wherein the laser entry wall part is provided with a dichroic cold mirror coating that is arranged to reflect emission radiation towards the detector wall part.