Invented by Charles McAlister Marshall, Donald Kuehl, Jeffrey Guasto, Redshift Bioanalytics Inc
Fluid Analyzer For Liquids and Gas With Modulation
Fluid analysis testing is an essential element in guaranteeing your equipment runs optimally. It helps you avoid costly breakdowns or repairs which could significantly disrupt operations and put a strain on finances.
The market for Fluid Analyzers for Liquids and Gas with Modulation is expanding rapidly due to its capacity to detect issues early, saving you money in the long run.
Analytical Methods
Analytical methods are employed in the market for Fluid Analyzers for Liquids and Gas with Modulation to measure analyte concentration or identify its presence. These include spectroscopy, mass spectrometry, separation techniques, analytical chemistry, and titration.
Spectroscopy is an analytical technique that utilizes light and its interaction with molecules to identify the chemical composition of a sample. It’s divided into several subcategories, such as atomic absorption spectroscopy, X-ray spectroscopy, ultraviolet-visible spectroscopy, X-ray fluorescence spectroscopy, and Raman spectroscopy.
In some applications, spectroscopy is performed by combining multiple tunable lasers and scanning over a broad spectral range. This measurement method is more efficient than scanning narrow spectral ranges and minimizes interference with the analyte of interest.
Another approach is to utilize two measurement channels in one system, one containing the analyte and background matrix, the other simply having the background matrix without any analytes. This approach eliminates the need for performing multiple measurements, thus simplifying and reducing instrument complexity and cost.
This method can also help avoid the effects of interfering bands in a wide spectral range by using higher-order derivatives derived from the frequency modulation scheme to determine if the signal is dominated by background spectrum. These derivatives provide an accurate indicator as to whether or not this spectrum is dominant, but they must still be interpreted carefully since they do affect the final results.
Gas chromatography employs a similar technique as liquid chromatography; however, this method works better for liquids and may need more complex equipment and calibration procedures than what GC requires.
Flow modulation is an analytical technique used to improve the precision of liquid-liquid extraction, gas chromatography and other analytical instruments. It involves mixing sample and reference streams with a solution which scatters or reflects light as they pass through a beam. The reflected or scattered light is then detected by an array of detectors (as illustrated in Figure 8 for a single-dimensional system).
Detectors
Detectors are devices that measure gas concentration or composition changes. Different types of detectors exist, such as piezoelectric gas sensors, conductive metal-oxide sensors, conducting polymer composite (CP) sensors and optical gas sensors. These sensor types can be employed for various applications like environmental monitoring.
One of the primary applications for gas sensors is to provide odor information. A variety of odorant compounds can be used as reagents to detect natural gas or other gases, such as tert-butyl mercaptan, tetrahydrothiophene, and methylethyl sulfide.
Natural gas odorants are added to distinguish it from other gases. Their use is important because these compounds possess high sensitivity levels, making them suitable for identifying a wide variety of gases.
Some of the most widely employed odorants include tert-butyl mercaptan, dimethyl sulfide, methylethyl sulfide and n-propyl mercaptan. They find applications such as environmental monitoring and gas-powered vehicles.
However, using these odorants has its drawbacks. For instance, they are highly flammable and potentially hazardous to users; hence their need for close monitoring. Furthermore, these agents cause corrosion and oxidation in pipelines.
To address these problems, researchers have designed a direct thermoelectric gas sensor (DTEG). These devices detect odorants through thermal energy and electrical signals.
These sensors not only detect odorants, but they are also capable of measuring gas concentrations and changes in vapor pressure. Furthermore, they have the capacity to measure gas temperature as well.
DTEGs have many applications in chemical, biological and medical research. They have also been demonstrated to accurately sense soil vapors and volatile compounds. These sensors require minimal manufacturing costs and power consumption for efficient operation; additionally they can be manufactured as arrays so multiple sensors can be connected together to form an analyzer.
Detector Arrays
Detector arrays are employed in a variety of applications from medical imaging to oil and gas exploration. They offer advantages like reduced cost and power consumption. Furthermore, their flexibility allows you to modify your detector layout if needed.
An array detector works by collecting a high number of pixel signals and multiplexing them together to form one spectrum. As such, array detectors are faster than scanners at acquiring the desired spectral region.
Array detectors save time while offering higher resolution than scanning systems due to their larger detection area. This makes them ideal for capturing narrow spectral ranges like human eye radiation sensitivity or measuring minute features like particles in air.
Typically, the sensitivity of an array depends on its pixel pitch p and detector size Np (see below). Generally speaking, higher pixel pitches lead to better resolution.
However, it’s essential to remember that an array’s sensitivity is compromised by both temporal and spatial noise. Furthermore, the spectral region of interest must be large enough to fully cover the array’s sensitivity range.
We therefore suggest an array with a low sensitivity limit and read noise limited design. To do this, select diode arrays with low shot noise and ensure it operates at the square root of the number of particles observed.
Our current work involves the design of a semi-spherical electronic detector array using active matrix connectivity (Fig. 3a). This is an innovative approach for fabricating three-dimensional semi-spherical electronic detectors.
To verify this design, CAT3D generated a test phantom with five 3D conformal intracranial fields and then exposed it to an 6 MV photon beam from a Varian 2100 C/D linac at an isocenter dose of 100 cGy. This allowed us to assess both the performance of AM connectivity and array quality assurance measures.
Detector Modulation
Detector modulation is an indispensable tool in the fluid analyzer market for liquids and gases. It involves using multiple detectors in an interrogation cell to measure a property of the fluid flowing through it, improving sensitivity and robustness when performing online measurements, while also circumventing problems associated with traditional two beam ratio methods.
Modulation can be tailored to fit the requirements of a particular application by altering its frequency or amplitude. This compensates for any variations in fluid properties like diffusion, dispersion and turbulent mixing that may exist. This helps improve certain signal processing algorithms such as those that calculate analyte concentration or reference/sample absorbance values more accurately.
This can be accomplished using a straightforward circuit consisting of a diode, capacitor and resistor. The voltage applied to the diode is reduced by the capacitor and increased by the resistor until it reaches its desired value. Finally, this resistor is swept at various frequencies in order to determine both frequency and amplitude of modulated signal.
One method to accomplish this is by using a nonlinear device with a beat frequency oscillator (BFO) tuned at a different frequency than the original AM signal. This is then mixed with the AM signal at a beat frequency in order to recover both low-frequency modulated audio and any high frequencies not picked up by the AM signal.
Amplitude modulation detectors fall into two main categories: synchronous and asynchronous. The former are ideal for consumer products, AM broadcast radio receivers, and other applications with less stringent performance requirements. Synchronous detectors are more sophisticated and costlier, typically implemented through a digital circuit.
Asynchronous detectors use ring modulators, which are closely related to phase-sensitive detector circuits. These circuits can be constructed using anything from a ring of diodes up to an integrated circuit with a Gilbert cell.
Fluid analyzers for liquids with modulation often employ the use of a Mid-IR laser as one technique. This can be an effective method of detecting trace elements, particularly those highly absorbed in water. Furthermore, this technique works great when measuring gases that are difficult to measure with other methods.
The Redshift Bioanalytics Inc invention works as follows
An optical source and detector are part of a fluid analyzer. They create an optical beam path through the interrogation area of a fluid flow cells. Flow-control devices measure the flow of fluid through the channel and interrogation area, and then manipulate the fluid flow to move the fluid boundary that separates the analyte from the reference fluids. The controller generates control signals that (1) cause the fluid boundary of the interrogation area to move accordingly; (2) sample an output signal of the optical detector at an interval when the interrogation regions contains more analyte than reference fluid; and (3) determine, from samples of this output signal, a measurement value indicative a optically measured characteristic for the analyte liquid.
Background for Fluid analyzer for liquids and gas with modulation
The unique spectroscopic fingerprint in Mid-IR makes it a powerful tool to measure organic materials qualitatively and quantitatively. Mid-IR spectroscopy can be difficult to use for low analyte concentrations. This is due to several factors: (1) high background absorbance from water or other highly polar solvents, which limits the sample pathlength; (2) interferences with the analyte that make it difficult to measure the absorption features of the analyte, and (3) weak, broad spectral characteristics which are difficult to distinguish from low frequency drifts in instrumentation optical source, detector and electronics.
One way to overcome these limitations is to introduce two measurement channel in the system. One with the analyte and the background matrix (e.g. The?Sample Channel’ contains the analyte and the background matrix (e.g., solvent in a liquid sample), while the other channel contains the reference matrix without analyte. Each channel is then measured separately or simultaneously, and the ratios are calculated to get the desired?transmission?. spectrum. Low analyte concentrations will cause the reference channel and the sample matrix to be essentially identical. This cancels out the background matrix, which makes it easier to extract the small absorption characteristics of the analyte. There are many ways to accomplish this method.
One technique is ?pseudo? Dual beam in time (as with FTIR). This case, there is only one measurement channel. The sample and reference cells are placed alternately in the measurement channels. To calculate the transmission spectrum, the (computer-stored) Sample and Reference measurements must be compared. As any slight drift in the measurement will cause noise, this method requires stability of source, electronics and detector. This requires matching identical sampling cells or flushing and refilling one cell.
Another approach is to switch between two optical paths. This can speed up the process, but it’s not as fast. It is also difficult to match both channels precisely, because it is optically complicated. The sampling cells must match too closely.
Dual beam optical subtraction is the measurement of optical difference from two output beams of an optical interferometer that are 180 degrees apart in phase. It is still difficult to match channels and is optically complicated. Therefore, two matched cells will be required.
Another approach is dual beam with two channels and detectors. Both beams can be measured simultaneously. However, it is important to match the optical channels and the detectors, making the measurement more challenging.
Conventional grating-based scanning instruments or with tunable Lasers can use a dual beam system in which a mechanical cutter rapidly alternates between two optical paths while the system scans across a spectrum. Although this rapid modulation increases the signal-to-noise ratio, it still has the disadvantage of not matching the sampling cells and optical paths.
These methods require stability, detectors, electronics, precise optical matching between the two optical channels, sampling cells, and electronics. They all add complexity to the measurement.
Modulation spectroscopy is a very efficient method to minimize these limitations. Modulation spectroscopy places one or more modulations on the measuring device or the sample. This allows one to detect only the frequency of the modulation and/or its higher frequencies overtones. This eliminates noise sources that are not related to modulation frequencies. This eliminates the low frequency drift problem that is inherent in the two-beam ratio method.
Modulation spectroscopy can be seen in the measurement narrow gas lines using laser spectroscopy. This includes frequency modulation (FMS), and wavelength modulation (WMS). WMS modulates the laser wavelength in a wavelength range that is smaller than the gas line being measured. The signal to noise ratio will be significantly improved by scanning over the line of interest using a lock-in amplifier at either the modulation frequency or at higher order frequencies. Although this does not completely eliminate the effects from low frequency drift in the source and detector, electronics, scanning over the line of interest with a lock-in amplifier at the modulation frequency, or at the higher order frequencies, will limit the signal to noise bandwidth. However, it is possible to scan the narrow spectral area fast enough so that the noise source can be minimized. There are also other methods for modulating the measuring device, such as amplitude modulation and mechanical modulation with a mechanical cutter or optical modulation like with a photo elastic modulator. Interferometers work by simultaneously modulating different wavelengths at different frequencies. However, it is still susceptible to long-term drift.
Frequency modulation will help minimize background interferences. This is provided that the background is not significantly larger than the measured line. The modulation scheme provides higher-order derivatives that can be used to accomplish this.
The frequency modulation technique is not suitable for broad spectral features. This is due to the difficulties in modulating quickly with repeatable power over large frequency ranges and the added challenge of interfering band over a wider spectral range. A broad spectrum of scans is less efficient because the measurement must be extended to include baseline points well beyond the peak absorbance. This means that less time is spent measuring maximum signal of the analyte.
QCLs are Mid-IR lasers that can be tuned to produce a brighter Mid-IR source than the traditional MidIR thermal sources found in scanning spectrometers and FTIR. The laser linewidth can also be narrowed if it is operated in continuous wavelength mode (CW), which is much narrower than that of most small molecule gas rotations. These devices are ideal for measuring such gases because of a variety of reasons. The first is that the brightness of the instrument allows for long pathlengths, which will increase the sample volume and thus increase the sensitivity according to the Beer-Lambert law. The second is that the measured amplitude of a line is more accurate than its measured linewidth because the resolution of the measurement exceeds the sample linewidth. This makes it easier to detect than a lower resolution measurement, which, for instance, has a lower spectrometer resolution and the sample linewidth. In this case, the measured magnitude is smaller. This explains why a typical FTIR instrument measuring 0.1 cm wide gas absorption lines is significantly less efficient than one with a linewidth 8 cm?1.
Mid-IR light sources are not better for measuring broad lines that are typical of condensed phases or high molecular weight gas phases. The increased brightness can allow for enhanced sensitivity in trace samples in highly absorbing matrices such as water or solvents with high concentrations of strong absorbers. Due to the high absorbance of the matrix, condensed phase measurements in a water cell may have pathlengths between 5-20 um for both conventional FTIR or scanning IR using thermal-infrared sources.
The brightness of the MidIR laser allows for longer pathlength transmission cells, which means that optical pathlength cells can be used to measure samples in liquids like water. This will increase both measurement sensitivity and make the system more resistant to clogging and higher back pressure when it is used for online measurement. For systems with a strong absorbent background, like methane in natural gases, you can use longer pathlengths to increase detection of trace constituents, such as H2O and H2S.
ATR cells are an alternative to the short-pathlength transmission cells used for aqueous phase measurements. They are susceptible to high back pressure and clogging. ATR can be used to increase flow and provide the shorter pathlengths required for conventional IR spectroscopy. They are however more complicated optics and more costly, have a higher cell volume, are not always good for laminar flow, and are harder to clean.
However, it is not recommended to use Mid-IR lasers for wide linewidth measurements. It would be ideal to measure the broad line at its peak ampltude for such measurements. However, a baseline point must be measured. This involves scanning back and forth from the peak to the baseline. To accurately measure low concentrations, it is necessary to know the power of the laser at each point of measurement when scanning between the peak amplitude and baseline. The laser, detector, electronics and even the sample may drift between the peak-baseline measurements. This error can be difficult to distinguish from changes in peak amplitude and can cause noise. The difficulty of modulating the laser at high frequencies over large lines limits frequency modulation techniques like frequency modulation. 100 Hz).
A fluid analyzer” is described. It includes an optical source, an optical detector and a path that defines an optical beam path through the interrogation area of a fluid flow cells. Flow-control devices are able to conduct analyte or reference fluids through a channel, the interrogation area, and manipulate fluid flow to respond to control signals. This allows them to move a fluid border that separates the analyte from the reference fluids across this interrogation zone. The controller generates control signals that (1) cause the fluid boundary of the interrogation area to move accordingly; (2) sample an output signal of the optical detector at an interval when the interrogation regions contains more analyte than reference fluid; (3) determine an optically measured characteristic for the analyte liquid from the output signal samples.
This description uses certain terminology. The following general descriptions are provided below, but each term can be further described or modified within a specific embodiment.
The optical source is a source that emits mid-infrared quantum cascade lasers (QCL) in this description. The source doesn’t have to be a MidIR source or a laser. The example uses a Mid-IR Laser, but the method can also be used for other types of spectroscopy, including UV-Visible and Near Infrared Raman. You can use a tunable source such as a laser, high-intensity source or a conventional instrument such as a scanning system, filter-based system or FTIR with a conventional source.
It should be noted that this technique can also be applied to non-optical methods of measuring where it might be beneficial to compare a reference and a sample. Conductivity measurements can be made using inductive loops, electrodes, calorimetry, pH, or inductive loops. This example shows that the interrogation is not optical and instead depends on the interaction of the detection mechanism with the solutions. For example, conductivity measurements using electrodes or inductive loops, calorimetry, pH, and magnetic paths.
