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Blood Chemistry Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Most blood chemistry analysis measurements are derived from one of two methods: electrochemical and optical. There are other specific measurement techniques, such as gas chromatography, but they are more of a specialized measurement and will not be addressed. Electrochemical measurements are based on the Clark electrode with the blood component or electrolyte of interest using a different ion-specific electrode. The Clark electrode consists of an electrode in a medium. The first electrode for oxygen tension measurements was a platinum electrode and a silver anode. The current or voltage generated at the electrode is measured and is proportional to the amount of that component. The relationship is usually a calculated concentration derived from empirical data. For optical measurements, there are many approaches, but all are based on absorption, reflection, scattering, and fluorescence techniques. One optical probe has been called an optode. The optode is a cross measurement of optical fluorescence and electrochemical measurement. Figure 68.2 shows a diagram of one configuration for an optode arrangement. In an optode, an ion-selective membrane is used to diffuse an ion or compound into the fluorescent dye measurement chamber. The ion is associated with a fluorescent dye, excited with a light source, and the emitted fluorescent light is measured. Many measurements can be obtained, such as oxygen tension, carbon dioxide tension, pH, potassium concentration, calcium concentration, and chloride concentration.
O
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
optode a fiber optic sensor used to determine the concentration of a particular chemical species present in the sensor's environment by utilizing spectroscopic changes in a sensing element placed at the end of the optical fiber.
Prior brain endurance training improves endurance exercise performance
Published in European Journal of Sport Science, 2023
Neil Dallaway, Sam Lucas, Joseph Marks, Christopher Ring
Prefrontal cortical haemodynamics were assessed using near infra-red spectroscopy (NIRS; NIRO-200NX, Hamamatsu Photonics KK, Japan). The NIRO-200NX device measures changes in chromophore concentrations of oxyhaemoglobin and deoxyhaemoglobin (ΔO2Hb and ΔHHb) via the modified Beer–Lambert law and provides depth-resolved measures of tissue O2 saturation [total oxygenation index (TOI)] and tissue Hb content (i.e. relative value of the total haemoglobin normalised to the initial value, nTHI) using the spatially resolved spectroscopy (SRS) method. The SRS-derived NIRS parameters limit contamination from superficial tissue via depth-resolved algorithmic methods, providing an index of targeted local tissue saturation (TOI) and perfusion (nTHI), see Davies et al. (Davies et al., 2015) for a recent review. Probes were enclosed in light-shielding rubber housing that maintained emitter-to-detector optode spacing (4 cm), positioned over the right pre-frontal electrode site (Fp2 in 10–20 system). Before each task, participants were instructed to sit still, relax, clear their mind, and look at a fixation cross for 2 min (Gusnard & Raichle, 2001). Measures of TOI, nTHI, O2Hb and HHb were averaged over 30-s calculated relative to the last 30 s of the prior baseline. To examine changes as a function of time, the value during first 30-s interval was subtracted from the value during final 30-s interval, for each measure during the physical tasks.
Highly selective sol-gel derived optical sensor using 2,6-dichlorophenolindophenol for the sensitive determination of aqueous iron(III)
Published in Instrumentation Science & Technology, 2023
Abdollah Yari, A. Shiravandi, S. Moradi
A 1 cm quartz cell with a volume of 4 ml was employed for spectrophotometric measurements. A glass slide (1 cm) was placed inside the optical cell. The 0.1 M iron (III) nitrate stock solution was prepared in distilled water, standardized with EDTA, and serially diluted to obtain working standards. The solutions were added to the quartz cuvette using 10 μl and 100 μl Hamilton syringes. The measurements were recorded at 610 nm at room temperature. The limiting absorption values, Ac and A0, were measured for the optode in the absence or presence of 1.0 × 10−2 M Fe3+. A calibration relationship was obtained by plotting the absorbance versus the negative logarithmic of the iron concentration (pFe) at room temperature and used to determine the iron (III) concentrations in the samples.
Recent applications of fluorescent nanodiamonds containing nitrogen-vacancy centers in biosensing
Published in Functional Diamond, 2022
Yuchen Feng, Qi Zhao, Yuxi Shi, Guanyue Gao, Jinfang Zhi
Raabova and her fellows also developed a pH nanosensor based on the dependence of NV center spectroscopy on surface charge changes [66]. Unlike measuring T1 relaxation time, the authors analyzed ratio of NV-/NV0 which was modulated by charged molecules on the surface of FND surface. In this strategy, the FND was coated by a stimuli-responsive polymer called polyacrylic acid. The charge of the polymer shell varied with surrounding pH with physiologically relevant ranges, then alter the ratio of NV-/NV0 states in FND. The fluorescence spectra (ratio of intensity in spectral maximum to the intensity of NV0 ZPL) of the nano-optode showed a monotonous increase in the pH range of 5–8(∼). This work provides an inspiring readout modality of NV center in FND, which can be further used in (bio)sensing applications together with recent improvements in optical measurements of the charge of NV centers and preparative schemes for FND.