水中EEM,PARAFAC检测方案(分子荧光光谱)

IntroductionWater travels through the envi-ronment carrying dissolved organic mat-ter (DOM)， made up of various chemicalcompounds， which have entered the wa-ter column from many sources.Theamount of DOM in water and its chemi-cal composition vary in space and time.Light's interaction with DOM is a func-tion of its chemical make-up； thus fluo-rescence spectroscopy can provide in-formation about the amount and type ofDOM in a water sample. Because thechemical composition of DOM is deter-mined by its original source material andthe processing occurring in the envi-ronments through which it travels， DOMcharacterization usingfluorescencespectroscopy can help find the source ofDOM， as well as the pathway the watertransporting it has followed. The amount and type of DOM inlocal water systems is important for ur-ban planning， ecological studies， andunderstanding effects of trace amountsof organic compounds on living organ-isms. Fluorescence spectroscopy， es-pecially the excitation-emission matrix(EEM)， is becoming more popular fordetermining the amount of DOM con-tamination in water. Using EEMs to de-termine polyaromatic hydrocarbon and“humic substances”(soil-derived com-pounds)seems especially effective.Brian Bergamaschi and co-workers atthe U.S. Geological Survey have been ( C o ry， R.M.， a n d McKnight， D.M. ， Environ. Sci. Technol.. 39 (2005)， 8142-8149.doi：10.1021/es0506962. ) Fig. 1. FluoroMax spectrofluorometer. recording EEMs of water sourcesinCalifornia to monitor water quality. Experimental method Water samples were quickly fil-tered in the field through 0.2 pm pre-combusted glass-fiber filters， chilled，and shipped overnight to the U.S.G.S.laboratory in Sacramento， California. After the sample equilibrated to25℃， it was placed in a 1-cm² quartzcuvette inside the sample compartment.An EEM was constructed by measuringa sample’s fluorescence via a Fluoro-Maxespectrofluorometer (Fig. ‘1) atthousands of combinations of excitation(200-400 nm) and emission (220-600nm) wavelengths. An automatic shutter ( Kraus， Tamara E .C.， e t al.， Org. Geochem.，39(9)，2008， p p. 1 302-1318； Bergamaschi，B.A. ， et al.， U.S. Geological S urvey S c ientificInvestigations s F Report2005-5152， 38 pp. (2005). ) protected thee9samplesfromphoto-bleaching.Whilerecordingfluores-cence， the signal was corrected with thereference detector. Results and discussion An example of a typical EEMfrom a water sample originating in anatural tidal wetland is shown in Fig. 2. Fig. 2. EEM recorded from water in a naturaltidal wetland. Such EEMs can be decomposedintoEexcitation-emissionn components，representative of fluorophores， via sta-tistical methodsi.. BBeerragamaschi， et al.used parallel tactor analysis(PARAFAC) to decompose data intoseparate components， and provide val-ues proportional to each component’ssignal.Fig.3Iss：an example0ofPARAFAC decomposing an EEM.With separate components determined，plots of loading (proportional to signal)versus excitation and emission can bedrawn (Fig. 4.). ConclusionsEcological and geological studies HORIBA Fig. 3. PARAFAC analysis on the EEM in Fig.2.Thirteen separate modelled components de-scribe 98% of the variability. Fig. 4. Loading (y-axis) vs. wavelength (x-axis)for the components in Fig. 3. by means of parallel factor analysis ofEEMs has been shown to be a usefulapplication involving】HORIBAJobinYvon spectrofluorometers. Copyright C HORIBA Scientific； version .HORIBAExplore the futureAutomotive Test Systems Process & Environmental Medical Semiconductor Scientific Ecological and geological studies by means of parallel factor analysis of EEMs has been shown to be a useful application involving HORIBA Jobin Yvon spectrofluorometers.