Measures for optimizing pulsed EC-QC laser spectroscopy of liquids and application to multi-analyte blood analysis

Brandstetter, Markus; Koch, Cosima; Genner, Andreas; Lendl, Bernhard

doi:10.1117/12.2038585

Cited by 10 publications

(19 citation statements)

References 7 publications

(5 reference statements)

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“…Despite this limitation, the recent successful utilisation of such instrumentation has been reported for several clinical chemistry applications. [19][20][21][22][23] By using multivariate infrared spectroscopy, the application of acetate or mannitol containing perfusates has been investigated for microdialysate measurements. The latter marker substance is suggested especially for application with single external cavity tuneable quantum cascade lasers, rendering only a limited wavenumber interval compared with FTIR-devices, but can be much smaller in device size.…”

Section: Introductionmentioning

confidence: 99%

Ex-vivo glucose sensors using micro-dialysis: importance of on-line recovery rate determination by multi-analyte infrared spectrometry

et al. 2015

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Micro-dialysis has been established in the clinical environment for continuously harvesting body fluids, but a drawback of this process are variable recovery rates, which can be observed especially for subcutaneously implanted catheters. Perfusates with either acetate or mannitol have been investigated as recovery markers. The latter substance is suggested for application with external cavity tuneable quantum cascade lasers, rendering a limited wavenumber interval in contrast to FTIR-spectrometers. Despite the overlap of mannitol and glucose spectra, their simultaneous quantification was successful. By investigating the depletion of the marker substances from the perfusates using different micro-dialysis devices, the theoretical nonlinear relationship between the relative dialysate marker concentration and glucose recovery rate was confirmed for the marker substance-analyte pair of acetate and glucose, rendering a basis for reliable blood glucose measurements. For the pair of mannitol and glucose an almost linear dependency was expected for the microdialysate catheters and experimentally verified, which provides a straightforward correction of any dialysis recovery rate variation during patient monitoring.

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Section: Introductionmentioning

confidence: 99%

Ex-vivo glucose sensors using micro-dialysis: importance of on-line recovery rate determination by multi-analyte infrared spectrometry

et al. 2015

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“…High-intensity laser light sources however contribute to the overall noise level, especially when operated in pulsed mode, because of pulse-to-pulse intensity fluctuations. 24 , 25 …”

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confidence: 99%

The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection

et al. 2020

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We report a mid-IR transmission setup for the analysis of the protein amide I and amide II band in aqueous solutions that achieves a limit of detection as low as 0.0025 mg mL –1 (outperforming our previous results and other state-of-the-art mid-IR-based techniques by almost an order of magnitude). This large improvement is made possible by combining the latest-generation external cavity-quantum cascade laser (EC-QCL) operated at room temperature with an optimized double-beam optical setup that adjusts the path length (26 μm) to ensure robust sample handling. For minimizing the noise introduced by the high-intensity laser light source, a thermoelectrically cooled mercury cadmium telluride balanced detection module was employed. In this way, noise levels better by a factor of up to 20 were achieved compared with single-channel measurements. Characteristic spectral features of proteins with different secondary structures were successfully identified at concentrations as low as 0.1 mg mL –1 . Furthermore, a highly linear response was demonstrated for concentrations between 0.05 and 10 mg mL –1 . The total acquisition time of the setup can be adapted to fulfill the required sensitivity of the protein measurements and to ensure maximum flexibility for future applications. The presented setup combines high sensitivity, large optical path lengths, and short measurement times and thus outperforms previous research type EC-QCL setups as well as commercially available instruments. This opens a wide range of future applications including protein–ligand interaction studies as well as qualitative and quantitative analyses of proteins in complex matrices such as those found in up- and downstream bioprocess monitoring and similar challenging applications which can not be readily met by conventional FT-IR spectroscopy.

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“…The IR beam path passes through the center of the hollow rods. The advantage of an adjustable path length was established previously as the maximum increase in the QCL path length is a function of the absorption coefficient . Previous work on variable path length transmission IR flow cells provided a starting point for the current design, but were further modified to meet the needs of SEC, specifically to minimize flow disturbances and too long residence distribution times .…”

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confidence: 99%

A New Quantum Cascade IR‐Laser Online Detector: Chemical‐Sensitive Size‐Exclusion Chromatography Measurement at Unprecedented Low Levels

Kübel

Botha

Bucka

et al. 2019

Macromol. Rapid Commun.

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enables new applications in fields such as sensor development. [1][2][3] Practical considerations such as their robustness, (relatively) low price, low weight, and compact size (for distributed feedback QCLs, where the wavelength selection is built into the QCL source itself, instead of external to the source) also allow for field sensing applications not possible with an FTIR instrument including reaction monitoring, [4] environmental monitoring of H 2 S, [5] clinical diagnostics (breath analysis, biofluid analysis), [6][7][8] and greenhouse gas detection in the atmosphere [9] measured over distances up to 50 m or even in flight. [10,11] We previously published work on an online setup combining size exclusion chromatography (SEC) and FTIR (SEC-FTIR) [12,13] and with a first prototype QCL spectrometer from Bruker Optik GmbH (Ettlingen, Germany, abbreviated as QCLS-B) used as an online chemically sensitive detector for SEC. The measured limit of detection (LOD) was compared with results from a high-end research IR spectrometer (Vertex 70 FTIR spectrometer from Bruker Optik GmbH). [14] These measurements were performed in series and allowed for a direct comparison between the two instruments. Both the Vertex 70 and the QCLS-B spectrometer face the challenge that SEC requires dilute injection concentrations of about 0.2 wt% to achieve good analyte separation with respect to hydrodynamic volume, while IR absorption is proportional to the sample concentration. As this is an online coupled technique, the time for the IR measurements is also limited (e.g., 15 s) to retain the resolution in the SEC size separation. Comparable method development work was done by Lendl and co-workers where they coupled liquid adsoption chromatography, LAC, to a QCL setup to measure sugars in beverages [15] and later standalone QCL setups were used to measure biological applications such as proteins in aqueous solutions, [16,17] glucose levels, [6] and multianalyte blood analysis. [18] Analog correlation between chemical composition and molecular weight are currently conducted via SEC-NMR indicating the needs for the acquisition of correlated information. [19][20][21][22] Previous results [14] showed that the LOD measured for the QCLS-B was about a factor of four better than the Bruker Vertex 70 FTIR, even though a liquid nitrogen Size Exclusion Chromatography Online chemically sensitive detectors for size exclusion chromatography (SEC) through coupled setups based on infrared (IR) (or NMR) spectrometers present new possibilities through unprecedented levels of polymer detail with respect to molecular weight and chemical composition.Herein, a new external cavity quantum cascade laser (EC-QCL) mid-IR spectrometer as a chemically sensitive online detector for SEC is customdesigned, built, and tested. This unique spectrometer features multiple broadly tunable EC-QCL sources, which can be operated in continuous wave and pulsed mode, accompanied with balanced liquid nitrogen cooled mercury cadmium telluride (MCT) detectors and a new custombuilt ...

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Measures for optimizing pulsed EC-QC laser spectroscopy of liquids and application to multi-analyte blood analysis

Cited by 10 publications

References 7 publications

Ex-vivo glucose sensors using micro-dialysis: importance of on-line recovery rate determination by multi-analyte infrared spectrometry

Ex-vivo glucose sensors using micro-dialysis: importance of on-line recovery rate determination by multi-analyte infrared spectrometry

The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection

A New Quantum Cascade IR‐Laser Online Detector: Chemical‐Sensitive Size‐Exclusion Chromatography Measurement at Unprecedented Low Levels

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