38 Measurement and Testing
QuantaRed Laser Technology Revolutionises Oil in Water Measurement
L. K. Hoffmann, T. Furch, W. Ritter & B. Lendl, QuantaRed Technologies GmbH Phorusgasse 8, A-1040 Vienna, Austria • Email:
office@quantared.com • Website:
www.quantared.com
CFC-free measurements on site: the ERACHECK goes below 1 ppm The advent of Quantum Cascade Lasers (QCLs) as a new, powerful mid-IR light source has opened the possibility to develop a fast and ecologically friendly method for quantifying oil in production water and wastewater. After extracting the hydrocarbons with cyclohexane or cyclopentane instead of ozone depleting freon, precise concentrations can be determined by means of mid-IR laser spectroscopy. The ERACHECK oil in water analyser was developed by QuantaRed Technologies GmbH, Austria (
www.quantared.com), in cooperation with EralyticsTM GmbH, Austria (
www.eralytics.com). The benchtop instrument is easy to use (touch screen operation) and allows CFC free measurements with high precision and sensitivity (sub-ppm concentrations). Due to its portability and a measurement time of only 2 minutes the ERACHECK may be used on-site as well as in mobile or stationary laboratories.
The obstacles of standard methods
In the petrochemical industry there is a need for a portable analyser capable of rapid and accurate analysis of hydrocarbons in water in the low ppm range. Information on the hydrocarbon content is needed for process control as well as to comply with regulatory issues. Former well established methods for this parameter (DIN 38409-H18, ASTM 3921) were based on mid-IR spectroscopy. These methods required a liquid- liquid extraction step using fully halogenated solvents, in most cases 1,1,2 trichloro-1,2,2 trifluoro-ethane (CFC) prior to analysis by mid-IR spectroscopy. This method was well accepted in routine laboratories due to its simplicity and ease of use. However, due to environmental concerns, especially with regard to the ozone depleting effect of CFCs, alternative methods have been developed in recent years. In this context ISO 9377-2 needs to be mentioned as it is the new European standard method for measuring hydrocarbons in water. As DIN 38409-H18, ISO 9377-2 is based on a liquid-liquid extraction step which ensures complete recovery of the hydrocarbons from water as well as from the surfaces of sample containers. Extraction solvent hydrocarbons with a low boiling point, such as hexane or cyclopentane should be used. In contrast to DIN 38409-H18, ISO 9377-2 uses gas chromatography for quantifying the extracted hydrocarbons. This chromatographic step allows separation of the analytes from the extraction solvent and thus enables quantification of hydrocarbons present in the extraction solvent. Quantitative results are obtained from integration of the chromatogram between the retention times of decane (C10) and tetracontane (C40). Due to the nature of this analysis procedure a fully equipped laboratory is required to carry out ISO 9377-2. Therefore ISO 9377-2 cannot easily be implemented in portable analysers.
QCLs make the difference
Quantum Cascade Lasers (QCLs) are new, powerful mid- IR light sources which enable combining the advantages of DIN 38409-H18 with those of ISO 9377-2. The new method for determining hydrocarbons in water was developed by QuantaRed Technologies GmbH in close cooperation with the Vienna University of Technology and with Eralytics GmbH. It is based on extracting the sample with a cyclic hydrocarbon, preferably cyclohe- xane or cyclopentane and measurement of the extracted hydrocarbons in the cyclic extraction solvent by mid-IR laser spectroscopy. This is made possible by the fact that non-cyclic hydrocarbons show IR absorptions slightly different from those of cyclic aliphatic hydro- carbons. Using QCLs it becomes possible to exploit these small differences for accurate determination of
Figure 1: Calibration curve using hexadecane hydrocarbons in the low ppm and even sub-ppm range.
With state of the art FTIR instrumentations it is not possible to measure hydrocarbons extracted into cyc- lohexane or cyclopentane at the desired concentration levels. However, when the FTIR instrument is replaced with a QCL, reliable measurements become possible, even at path lengths of several millimetres. This is due to the spectral power densities of QCLs, which are several orders of magnitude higher than those of thermal light sources employed in FTIR spectrometers.
Never change a winning team
Whereas novel quantum cascade laser technology has practical benefits in terms of measurement quality and environmental issues, the procedure for extracting the hydrocarbons from water stays unchanged. When using cyclohexane or cyclopentane as the extraction solvent, complete recovery of the hydrocarbons in an aqueous sample can be achieved. Similar to DIN 38409 H18 and ISO 9377-2 the obtained extract can be dried with Na2SO4 and filtered over solid phase materials like Florisil®
to remove polar components. Eracheck - Total oil and grease in water by QCL-IR technology ERACHECK – calibration and operation
The ERACHECK can be calibrated using standards containing the target hydrocarbon source or hexadecane standards, respectively, both dissolved in
Annual Buyers’ Guide 2010
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