Description
Aqualog for water CDOM research
- A Faster and better spectrometer for coloured dissolved organic matter (CDOM)
Not just a slow scanning PMT fluorometer for EEMs, Aqualog simultaneously acquires absorbance and fluorescence EEM’s with its patented A-TEEM design and ultra-fast CCD detector, acquiring complete A-TEEM fingerprints in seconds.
- Two-In-one spectrometer captures more information simultaneously
Simultaneously acquiring absorbance and fluorescence EEMs, Aqualog captures information about fluorescent molecules, such as proteins, algae and BTEX, but it also acquires information about non-fluorescing absorbing parameters, such as specific UV absorbance (SUVA).
- Aqualog A-TEEM fingerprints provide better chemometric analysis
With absorbance-corrected fluorescence EEM fingerprints, the Aqualog provides A-TEEM fingerprints that are independent of fluorophore concentration over a wider dynamic range, thus lending themselves to more reliable chemometric component analysis than a traditional scanning fluorescence EEM.
- NIST-traceable validation
The Aqualog spectrometer is fully traceable with National Institutes of Standards and Technology (NIST) standard reference materials (SRMs) for both fluorescence and absorbance.
Aqualog A-TEEM compared to traditional scanning PMT fluorometers
Traditional scanning spectrofluorometers have been used to collect a molecular fingerprint, in the form of a fluorescence excitation emission matrix, or EEM. Sometimes also referred to as 3D Fluorescence, an EEM is a three-dimensional data set of fluorescence excitation wavelength versus fluorescence emission wavelength versus fluorescence intensity. With a scanning spectrofluorometer, this data set is acquired by sequentially scanning a series of emission spectra, at varying excitation wavelengths, and then reconstructing the resultant data set three dimensionally. This three-dimensional data set can be used with third party multivariate analysis software for component analysis, as is done with other analytical techniques such as FTIR, HPLC and MS. There are, in fact, many scientific papers published citing the use of scanning spectrofluorometers for fluorescence EEM component analysis in many disciplines including food sciences, water research and pharmaceuticals.
There are, however, two fundamental limitations of using a traditional scanning PMT fluorometer for EEM component studies. The first is that it takes a very long time to collect a single EEM with a scanning fluorometer. Depending on the brightness of the signal, and the wavelength range and resolution that is required, a single EEM experiment can take a scanning spectrofluorometer up to an hour to collect!
Another important limitation of scanning fluorometers is that the shape of the fluorescence EEM fingerprint itself can change with even subtle variations in sample concentration. If an instrument measures different EEM fingerprints for the same molecule at different concentrations, it really can’t be used for component analysis. For an EEM to be used as a true analytical technique, the shape of the spectra must be independent of concentration.
These two inherent limitations of a scanning spectrofluorometer have impacted the usability of the fluorescence EEM technique, and this has lead to the development by HORIBA of the A-TEEM technique.
HORIBA’s unique A-TEEM technique overcomes these two limitations. With CCD detection technology, HORIBA solves the serious speed limitations of scanning spectrofluorometers because with HORIBA technology, an entire fluorescence EEM can be acquired in mere seconds to minutes depending on the sample.
HORIBA has also solved the problems associated with the fluorescence inner filter effect by taking advantage of the fact that the A-TEEM technique also collects absorbance of the same sample at the same time as the fluorescence, and uses the absorbance to correct EEMs for the inner filter effect (IFE).
HORIBA calls this technique A-TEEMTM, for Absorbance-Transmission Excitation Emission Matrix. By correcting for inner filter effects, the A-TEEM molecular fingerprint is a much more absolute representation of the true molecular fingerprint. Therefore when using third party multivariate chemometrics analysis software, the A-TEEM data provides much more robust component analysis than can be achieved with just a simple EEM from a scanning fluorometer.
Fluorescence Hardware
Light source
Extended-UV: 150W vertically mounted xenon arc lamp
Excitation range
200 nm to upper limit of emission detector
Excitation bandpass
5 nm
Excitation monochromator
Subtractive double monochromator
Excitation gratings
1200 gr/mm, 250 nm blaze
Excitation wavelength accuracy
±1 nm
Choice of Detector
Red-extended
Emission range
250-800 nm
Emission grating
285 gr/mm; 350 nm blaze
Hardware pixel binning
0.58, 1.16, 2.32, 4.64 nm/pixel
Emission bandpass
5 nm
Emission spectrograph
Fixed, aberration-corrected 140 mm focal length
Emission detector
TE-cooled back-illuminated CCD
Emission integration time
5 ms minimum
CCD gain options
2.25 e-/cts in high gain, 4.5 e-/cts in medium gain, 9 e-/cts in low gain
Sensitivity
Water-Raman SNR > 20,000:1 (RMS method) (350 nm excitation, 30s integration)
Weight
32.72 kg (72 lbs)
Dimensions
LWH (618 x 435 x 336 mm); (24″ x 17″ x 13″)
