scholarly journals A First Step towards Determining the Ionic Content in Water with an Integrated Optofluidic Chip Based on Near-Infrared Absorption Spectroscopy

Optics ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 175-190
Author(s):  
Gerwin W. Steen ◽  
Adam D. Wexler ◽  
Elmar C. Fuchs ◽  
Herman L. Offerhaus
Keyword(s):  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Early Stage ◽  
Ion Concentration ◽  
Differential Absorption ◽  
Ionic Content ◽  
Stretch Vibration ◽  
Dissolved Ions ◽  
Optofluidic Chip

In this work, we present a feasibility study of integrated optofluidic chips to measure the ionic content in water using differential absorption spectroscopy. The second overtone of the OH-stretch vibration of water is used as indicator for both the type and concentration of the dissolved ions. The optofluidic chips are based on silicon nitride (TripleX) containing Mach–Zehnder interferometers (MZI) with two 5 cm sensing paths for the sample and reference arms, respectively. Simulations show that, theoretically, the determination of both the type and concentration of a mixture of four electrolytes is possible with the techniques presented. However, the performance of the chips deviated from the expected results due to the insufficient reproducibility and precision in the fabrication process. Therefore, at this early stage, the chips presented here could only determine the ion concentration, but not differentiate between the different ion types. Still, this work represents the first steps towards the realization of an online and real-time sensor of ionic content in water.

Noninvasive determination of exercise-induced hydrodgen ion threshold through direct optical measurement

2008 ◽  
Vol 104 (3) ◽  
pp. 837-844 ◽  
Author(s):  
Babs R. Soller ◽  
Ye Yang ◽  
Stuart M. C. Lee ◽  
Cassie Wilson ◽  
R. Donald Hagan
Keyword(s):  
Gas Exchange ◽  
Blood Lactate ◽  
Near Infrared ◽  
Optical Measurement ◽  
Vastus Lateralis ◽  
Ion Concentration ◽  
Flexor Digitorum Profundus ◽  
Hydrogen Ion Concentration ◽  
Gas Exchange Threshold

The intensity of exercise above which oxygen uptake (V̇o2) does not account for all of the required energy to perform work has been associated with lactate accumulation in the blood (lactate threshold, LT) and elevated carbon dioxide output (gas exchange threshold). An increase in hydrogen ion concentration ([H+]) is approximately concurrent with elevation of blood lactate and CO2 output during exercise. Near-infrared spectra (NIRS) and invasive interstitial fluid pH (pHm) were measured in the flexor digitorum profundus during handgrip exercise to produce a mathematical model relating the two measures with an estimated error of 0.035 pH units. This NIRS pHm model was subsequently applied to spectra collected from the vastus lateralis of 10 subjects performing an incremental-intensity cycle protocol. Muscle oxygen saturation (SmO2) was also calculated from spectra. We hypothesized that a H+ threshold could be identified for these subjects and that it would be different from but correlated with the LT. Lactate, gas exchange, SmO2, and H+ thresholds were determined as a function of V̇o2 using bilinear regression. LT was significantly different from both the gas exchange threshold (Δ = 0.27 ± 0.29 l/min) and H+ threshold (Δ = 0.29 ± 0.23 l/min), but the gas exchange threshold was not significantly different from the H+ threshold (Δ = 0.00 ± 0.38 l/min). The H+ threshold was strongly correlated with LT ( R2 = 0.95) and the gas exchange threshold ( R2 = 0.85). This initial study demonstrates the feasibility of noninvasive pHm estimations, the determination of H+ threshold, and the relationship between H+ and classical metabolic thresholds during incremental exercise.

scholarly journals First retrieval of global water vapour column amounts from SCIAMACHY measurements

2004 ◽  
Vol 4 (1) ◽  
pp. 111-125 ◽  
Author(s):  
S. Noël ◽  
M. Buchwitz ◽  
J. P. Burrows
Keyword(s):  
Water Vapour ◽  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Weighting Function ◽  
Global Scale ◽  
Visible Spectral Region ◽  
Mean Deviation ◽  
Differential Absorption ◽  
Scanning Imaging ◽  
Global Water

Abstract. Global water vapour column amounts have been derived for the first time from measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the European environmental satellite ENVISAT. For this purpose, two different existing retrieval algorithms have been adapted, namely the Air Mass Corrected Differential Absorption Spectroscopy (AMC-DOAS) which was originally designed for GOME and the Weighting Function Modified Differential Absorption Spectroscopy (WFM-DOAS) which was mainly designed for the retrieval of CH4, CO2 and CO from SCIAMACHY near-infrared spectra. Here, both methods have been applied to SCIAMACHY's nadir measurements in the near-visible spectral region around 700 nm. Taking into account a systematic offset of 10%, the results of these two methods agree within a scatter of about ±0.5 g/cm2 with corresponding SSM/I and ECMWF water vapour data. This deviation includes contributions from the temporal and spatial variability of water vapour. In fact, the mean deviation between the SCIAMACHY and the correlative data sets is much smaller: the SCIAMACHY total water vapour columns are typically about 0.15 g/cm2 lower than the SSM/I values and less than 0.1 g/cm2 lower than corresponding ECMWF data. The SCIAMACHY water vapour results agree well with correlative data not only over ocean but also over land, thus showing the capability of SCIAMACHY to derive water vapour concentrations on the global scale.

scholarly journals Design Considerations to Realize Differential Absorption-Based Optofluidic Sensors for Determination of Ionic Content in Water

2018 ◽  
Vol 18 (15) ◽  
pp. 6051-6058 ◽  
Author(s):  
Gerrit W. Steen ◽  
Elmar C. Fuchs ◽  
Adam D. Wexler ◽  
Herman L. Offerhaus
Keyword(s):  
Differential Absorption ◽  
Ionic Content ◽  
Design Considerations

scholarly journals First retrieval of global water vapour column amounts from SCIAMACHY measurements

2003 ◽  
Vol 3 (6) ◽  
pp. 5659-5688
Author(s):  
S. Noël ◽  
M. Buchwitz ◽  
J. P. Burrows
Keyword(s):  
Water Vapour ◽  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Weighting Function ◽  
Global Scale ◽  
Visible Spectral Region ◽  
Mean Deviation ◽  
Differential Absorption ◽  
Scanning Imaging ◽  
Global Water

Abstract. Global water vapour column amounts have been derived for the first time from measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the European environmental satellite ENVISAT. For this purpose, two different existing retrieval algorithms have been adapted, namely the Air Mass Corrected Differential Absorption Spectroscopy (AMC-DOAS) which was originally designed for GOME and the Weighting Function Modified Differential Absorption Spectroscopy (WFM-DOAS) which was mainly designed for the retrieval of CH4, CO2 and CO from SCIAMACHY near-infrared spectra. Here, both methods have been applied to SCIAMACHY's nadir measurements in the near-visible spectral region around 700 nm. The results of these two methods agree within a scatter of ±0.5 g/cm2 with corresponding SSM/I and ECMWF water vapour data. This deviation includes contributions from the temporal and spatial variability of water vapour. In fact, the mean deviation between the SCIAMACHY and the correlative data sets is much smaller: the SCIAMACHY total water vapour columns are typically about 0.2 g/cm2 lower than the SSM/I values and less than 0.1 g/cm2 lower than corresponding ECMWF data. The SCIAMACHY water vapour results agree well with correlative data not only over ocean but also over land, thus showing the capability of SCIAMACHY to derive water vapour concentrations on the global scale.

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