2D fluorescence

The formal approach of 2D correlation analysis to time-dependent spectral intensity fluctuations has been extended to UV, Raman [1010], and near-IR spectroscopy [1011-1014] 2D fluorescence is upcoming. 

An on-line monitoring of an industrial chromatographic process was realized by using the Bio View sensor. 2D-fluorescence spectroscopy allows automatic real time measurements directly at the outlet of the chromatographic columns. The fluorescence technique for separating different amino acids is faster and more accurate than conventional methods. The appHcation of the Bio View sensor will reduce costs and will increased the productivity of further chromatographic separations [92,93]. 

Fluorescence sensors have been used since 1957 to measure cell internal NAD(P)H at 450 nm. Later on they were applied for in situ determination of the cell concentration. However, the culture fluorescence intensity is not only influenced by the cell concentration, but also by the physiological state of the cells [56] and, in addition to that, there are several other compounds that participate in the fluorescence emission besides NAD(P)H. To identify the fluorophores in the cells and cultivation medium, the excitation and the emission wave lengths are varied in a broad range [57,58]. Two instruments were applied for the 2D-fluorescence spectroscopy Model F-4500 (Hitachi) and the BioView Sensor (Delta light Optics). Each of them uses an excitation range of 250-560 nm,an emission range of 260/300-600 nm and the measuring time of 1 min [59,60]. The application of this technique for CPC production was performed by Lindemann [61]. 

The evaluation of the measurements, the correlation between the medium components and the various ranges of the 2D-fluorescence spectrum was performed by Principal Component Analysis (PCA), Self Organized Map (SOM) and Discrete Wavelet Transformation (DWT), respectively. Back Propagation Network (BPN) was used for the estimation of the process variables [62]. By means of the SOM the courses of several process variables and the CPC concentration were determined. 

To present our methodology, we describe the time-gated excitation-emission spectroscopic system in Section 32.3. 2D fluorescence spectroscopy acquiring excitation and fluorescence spectra has been widely used at research and diagnostic levels because of the high selectivity and simple configuration of the measurement system [12-16]. Here, we extended it to the 3D (Ex, Em, and x) system with a time-resolution of200 ps, by a combination of a spatially dispersed super continuum as the... 

Solle D, Geissler D, Stark E, Scheper T, Hitzmann B (2003). Chemometric modeling based on 2D-fluorescence spectra without a calibration measurement. Bioinformatics 19 173-177. 

Li Z, Lu J, Li S, Qin S, Qin Y. Orderly ultra-thin films based on perylene/poly(V-vinyl carbazole) assembled with layered double hydroxide nanosheets 2D fluorescence resonance energy transfer and reversible fluorescence response for volatile orgaiuc compounds. Adv Mater 2012 24(45) 6053-7. 

Figure 7c shows 2D fluorescence intensity profiles at various times after the start of pulsatile release. The profile was governed by diffusion from a point source and reached steady state after 10 min. The measured fluorescence intensity profiles after 10 and 30 min fit well with the diffusion profile predicted by simulation. The concentration gradient produced by repetitive ejection of the solution was calculated by summing the concentration profiles from each pulse. The concentration profile after n injections was expressed as... 

In a broad sense, spectroscopic methods applied in process analytics comprise widely used techniques like UVA IS, mid-IR, NIR, NMR and XRF, and less frequently used ones, such as Raman spectroscopy, fluorescence, chemiluminescence, acoustic emission and dielectric specfloscopy. Upcoming in-process analysis techniques are 2D-fluorescence, and laser absorption specfloscopy (LAS) with tuneable lasers and ppm level sensitivity. The availability of mini-spectrometers (e.g. UVA IS/NIR) is not highly relevant in plant environments where safety is of primary concern. 

This chapter introduces and discusses different fluorescence techniques that do not require the use of external labeling steady-state fluorescence (including 2D fluorescence), fluorescence anisotropy and time-resolved fluorescence and it provides illustrative examples showing how these techniques may be used for the monitoring of membrane processes. 

The second major challenge involves the development of 2D fluorescence probing devices that may allow for in situ, online and non-invasive monitoring of... 

Figure 12.6 Optical fiber bundle applied in online and in situ 2D fluorescence measurements for monitoring (a) the biofilm growth at the membrane surface and (b) the performance of membrane bioreactor for water treatment processes.

Figure 12.8 2D fluorescence applied for monitoring of membrane bioreactor in wastewater treatment. 3D fluorescence maps were acquired for (a) feedwater stream,... 

The use of 2D fluorescence techniques for the monitoring of membrane processes, namely the ones involving water treatment and biological systems such cell culture/membrane bioreactors, may be adopted soon. The applications envisaged (some of them under study for which results were not shown) involve ... 

Figure 3 In situ 2D fluorescence. 1 liquid CO2 tank, 2 cooled high pressure pump, 3 quartz-window equipped reaction vessel, 4 2d fluorescence spectrometer, 5 light guide.

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