What Is So Intriguing About NVP-BKM120?

Fluorescence spectroscopy [10] is suitable to measure at least three of the most important indicators of the ecological status of natural waters: chlorophyll-a (Chl-a), oil, and protein-like materials. In fact, light-induced fluorescence (LIF) was widely used to detect both dissolved and particulate components of waters coming from aquifers, rivers and lakes [11,12,13,14,15,16,17,18,19,20,21,22,23]. Usually, for this kind of measurement, water undergoes a coarse filtration (30 ��m), that eliminates unwanted materials, and the sample containing both dissolved and particulate components is pumped into a cuvette, where it is irradiated by one or more wavelengths. If only dissolved matter has to be analyzed, a fine filtration (0.22 ��m) has to be carried out. Fluorescence spectra give information about the chemical composition BIBW2992 chemical structure of the sample (i.e., carotenoids, phycoeritrin, phycocyanin, chlorophyll) [24]. Thus, each component has absorption and emission peaks allowing for its identification. Spectrofluorometers are good candidates for a field campaign because, in general, they are battery-operated, fully controlled by a portable computer, and one measurement NVP-BKM120 takes less than one minute. Once calibrated with known samples, they reach remarkable accuracies at absolute concentrations. Many submersible spectrofluorometers are available on the market [25,26,27,28,29], but they measure some selected wavelengths and not the full spectrum. This choice is probably dictated by economic reasons, but, from the scientific point of view, the availability of the full spectrum provides the instrument with unrivalled flexibility in different application scenarios and accuracy for many water components. In a recent publication, MacIntyre et al. [17] indicated that the sensitivity for Chl-a of LED based commercial instruments is SWAP70 in a laser than in an LED. Based on these considerations, we focused on developing a low-cost submersible sensor for non-invasive, real-time sensing of water quality (patent pending) able to measure fluorescence in a wide spectral interval (200 nm�C1100 nm) and to detect at least 0.2 ?g/L of Chl-a by using LEDs instead of lasers. The achieved sensitivity lies in between LED-based commercial instruments and laser systems, as can be explained by the detection of the full spectrum (compared to commercial instruments) and the lower optical power (compared to laser systems). In the following sections, a thorough presentation of the instrument components, calibrations, laboratory tests and results of field campaigns will be reported.