Variable path length absorption spectrometer with automated continuous gradient measurement

Abstract

The system may comprise a light source for generating a probe signal including incident radiation; an optical probe for directing the incident radiation to pass through a fluid sample; a motor for moving the optical probe along the probe axis to change the path length of the incident radiation passing through the fluid sample; and a detector for receiving the incident radiation as attenuated radiation after passing through the fluid sample. The system may include a control system configured to initiate an absorbance measurement by instructing movement of the optical probe along the probe axis, instruct the light source to emit the incident radiation; and automatically adjust at least one measurement parameter of a set of measurement parameters for the sample measurement based on a gradient parameter m, where m is derived from the ratio of the change in intensity of the attenuated radiation to the change in path length.

Description

Technical Field

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 63 / 343,368, filed on May 18, 2022, entitled "Variable Pathlength Absorption Spectrometer with Automated Continuous Gradient Measurement", the entire disclosure of which is incorporated herein by reference.

[0002] Embodiments of the present disclosure generally relate to spectroscopic analysis, and more particularly, to solution analysis using a light source coupled to a variable pathlength measurement system.

Background Art

[0003] Absorption spectroscopy is used to measure the composition and / or properties of materials in any phase, gas, liquid, or solid. For example, the light absorption spectrum of a liquid substance can be measured to determine the concentration or other properties of the species of interest in the liquid medium. The absorption spectrum can provide a distribution of light attenuation (due to absorbance) as a function of light wavelength. In a known spectrophotometer, the sample substance under study is placed in a transparent container, such that electromagnetic radiation (light) of a known wavelength λ (i.e., ultraviolet, infrared, visible light, etc.) and intensity I can be measured using a suitable detector after passing through the transparent container.

[0004] Known ultraviolet (UV) / visible light spectrophotometers utilize a container such as a standard cuvette. Such a container can have a path length of standard cm, and the incident light is conducted through the liquid containing the substance to be measured over that path length. For a sample consisting of a single homogeneous substance with a concentration C, the light transmitted through the sample follows a relationship known as Beer's law: A = εCL. Here, A is the absorbance (also known as the optical density (OD) of the sample at wavelength λ, where OD is the -log of the ratio of the transmitted light to the incident light), ε is the absorption coefficient or extinction coefficient (usually constant at a given wavelength), C is the concentration of the sample, and L is the path length of the light through the sample. Thus, in principle, information regarding the concentration of a homogeneous substance can be determined based on the recorded light intensity of the signal passing through the sample container. However, in some situations, determination of the concentration in such an apparatus can be difficult. In many cases, the compound of interest in the solution is highly concentrated. For example, certain biological samples such as proteins, DNA, or RNA are often isolated at concentrations that fall outside the linear range of the spectrophotometer when absorbance is measured. Therefore, in order to measure a decrease in absorbance values that fall within the linear range of the instrument, dilution of the sample is often required. Multiple dilutions of the sample are frequently necessary, leading to both dilution errors and the removal of the diluted sample for any downstream applications. Therefore, it would be beneficial to obtain existing samples without knowledge of the possible concentration and to measure the absorption of these samples without dilution. As a common characteristic of one result of these known ultraviolet (UV) / visible light spectrophotometers, a path length L with high accuracy that enables accurate concentration measurement is known.

[0005] To address these issues, techniques based on variable path length spectrophotometers have been developed in recent years. This type of spectroscopy system can generally employ known light sources such as those based on UV / visible light spectrophotometers. The light from the UV / visible light spectrophotometer is then directed to a special probe in an analytical instrument configured to dynamically change the path length L within a special sample chamber during absorbance measurements. Thus, while varying the path length L through a plurality of different positions by movement of the probe, the radiation generated from the light source of the UV / visible light spectrophotometer is detected after passing through the sample chamber. As a result, a series of measurements are made that generate different values of A for each of the different values of L in a manner that does not require knowledge of any particular path length L in order to determine the concentration C.

[0006] Such variable path length spectroscopy can be adapted for in-line measurement of samples while being conducted in a production system. For example, the instrumentation required for such a measurement scenario can require a great deal of effort to install and an excessive amount of space. For example, a UV / visible light spectrophotometer system used as a light source can occupy several cubic feet of space and can have a weight on the order of tens of kilograms. The present disclosure is provided with respect to these and other considerations. SUMMARY OF THE INVENTION

[0007] In one embodiment, a system is provided. The system may include a light source for generating a probe signal including incident radiation; an optical probe for directing the incident radiation through a fluid sample; a motor for moving the optical probe along a probe axis to change the path length of the incident radiation through the fluid sample; and a detector for receiving the incident radiation as attenuated radiation after passing through the fluid sample. The system starts an absorbance measurement by instructing movement of the optical probe along the probe axis, instructs the light source to emit the incident radiation; and may include a control system configured to automatically adjust at least one measurement parameter of a set of measurement parameters for the sample measurement based on a gradient parameter m, where m is derived from the ratio of the change in the intensity of the attenuated radiation to the change in the path length.

[0008] In another embodiment, a method for determining the concentration of a material in a fluid sample is provided. The method may include starting a sample measurement of the fluid sample to determine the concentration by transmitting a signal to move an optical probe through a sample container containing the fluid sample. The method may also include triggering the light source to emit incident radiation through the optical probe and the fluid sample at a plurality of instances during a measurement period, where the path length L of the incident radiation through the fluid sample varies. The method may further include receiving measurement results of the intensity I of the attenuated radiation derived from the incident radiation after passing through the fluid sample at a plurality of instances during the measurement period. The method may additionally include automatically adjusting at least one measurement parameter of a set of measurement parameters for the sample measurement based on a gradient parameter m, where m is derived from the ratio of the change in I to the change in L during the measurement period.

[0009] In another embodiment, a sample measurement is initiated to determine the concentration of a substance in a fluid sample by transmitting a signal to move an optical probe through a sample container containing the fluid sample; during a measurement period, the light source is triggered to emit incident radiation so as to pass through the optical probe and the fluid sample, where the path length L of the incident radiation passing through the fluid sample varies; during a plurality of instances in the measurement period, measurement results of the intensity I of the attenuated radiation derived from the incident radiation after passing through the fluid sample are received; and at least one measurement parameter of a set of measurement parameters for the sample measurement is automatically adjusted based on a gradient parameter m (where m is derived from the ratio of the change in I to the change in L during the measurement period), and a non-transitory computer-readable storage medium storing computer-readable program code executable by a processor is provided.

Brief Description of the Drawings

[0010] The accompanying drawings illustrate preferred embodiments of the disclosed method devised for practical use of its principle.

[0011]

Figure 1A

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Figure 1B

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Figure 1C

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Figure 2A

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Figure 2B

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Figure 3

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Figure 4

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Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0019] According to an embodiment of the present disclosure, techniques and apparatus are provided for improving absorbance measurements based on a variable path length measurement (VPT) apparatus architecture. In particular, this embodiment provides a rationalized dynamic approach for determining the concentration of a material in a fluid sample. The method of this embodiment employs a plurality of intensity measurements that are dynamically recorded as radiation is transmitted through the fluid sample while varying the path length of the radiation through the fluid sample. As will be described in detail below, in contrast to known absorbance spectroscopy techniques, this embodiment can determine the absorbance or other relevant parameters of the fluid sample during the measurement, such that the measurement parameters can be dynamically adjusted during the measurement as needed, enabling an improvement in the quality of the measurement.

[0020] Figure 1A illustrates an absorption spectrometer shown as system 100 according to an embodiment of the present disclosure. System 100 may include a light source 102, a measuring device 104 coupled to the light source 102, and a detector 112 disposed adjacent to the measuring device 104. The light source 102 may include a light-emitting diode (LED) for generating radiation 114 at a target wavelength, such as in the range of 250 nm to 1000 nm, according to various non-limiting embodiments. Figure 1C shows this variation of system 100 as system 150 with an LED light source 102A, where the other components of system 150 may function in the same manner as those of system 100, and like components have the same labels. In other non-limiting embodiments, the light source 102 may be a known UV / vis absorption spectrophotometer or a UV / vis / IR absorption spectrophotometer. In some examples, the light source 102 may represent a single LED or an array of LEDs that emit radiation at a single wavelength. In other embodiments, multiple LEDs may be provided, where a given LED emits radiation at a wavelength different from that of another LED.

[0021] The measuring device 104 is configured to contain a fluid sample that includes the material of the substance to be measured, where details of the variation of the measuring device 104 are discussed below. The detector 112 is configured to detect the intensity I of the radiation transmitted through a given fluid sample contained in the measuring device 104, and that radiation is shown as attenuated radiation 111. According to the Lambert-Beer law shown in Equation 1 below, the concentration C of the material in the sample can be determined as A / eL, where A is the absorbance, e is the molar absorptivity, and L is the path length of the radiation through the fluid sample. Lambert-Beer law: A = εlC (1) where A is determined as log 10 (I 0 / I), and I 0 is the intensity of the incident radiation 103, and I is the intensity of the attenuated radiation 111.

[0022] According to the method of gradient spectrometry, Lambert-Beer's law can be modified as A / L = εC and further extended to dA / dL = εC, where the entity dA / dL is regarded as the gradient parameter m. Therefore, the measurement of the change in absorbance dA with respect to the change in path length L directly leads to the determination of the concentration C if the molar absorption coefficient of a given substance is known.

[0023] It can be easily shown that dA can be determined by a series of measurements of the intensity of the radiation emitted from the light source 102 while varying the path length L. This relationship is shown in detail in Equation (2).

Equation

Equation

Equation

[0024] Based on Equation (3) or Equation (4), system 100 measures the change in the intensity of the radiation from light source 102 while L is varied by measuring device 104. In particular, light source 102 directs incident radiation 103 through fluid sample 115 (see the enlarged view of fluid sample 115 in FIG. 1B) contained in sample container 110 via a light probe 108 coupled to receive the incident radiation 103. Fluid sample 115 attenuates or absorbs a portion of incident radiation 103, such that the attenuated radiation, such as attenuated radiation 111, generally exhibits a lower intensity I 0 than the intensity I.

[0025] Generally, a portion of incident radiation 103 can be measured before passing through fluid sample 115 to record the value of I 0 , and that parameter is used to determine DA according to Equation (2). However, according to Equation (4), in situations where the stability of light source 102 is sufficient, the measurement of the intensity I 0 of incident radiation 103 can be omitted. In this case, only the measurement of the intensity I of the attenuated radiation 111 after passing through fluid sample 115 is recorded to measure the absorbance of fluid sample 115. Thus, to perform the absorbance measurement, measuring device 104 also includes a light probe 108 and a motor assembly 106 configured to move light probe 108 along probe axis 117. Light probe 108 can be an optical fiber, a fiberlet, or a bundle of fibers configured to conduct incident radiation 103 into sample container 110 containing fluid sample 115 that includes the material of interest whose concentration C is to be measured. Incident radiation 103 then appears as attenuated radiation 111, which is recorded by detector 112. Suitable examples of detector 112 include photomultiplier tubes, photodiodes, avalanche photodiodes, charge-coupled devices (CCDs), and intensified CCDs.

[0026] The movement of the optical probe 108 is effective in varying the path length L of the radiation traveling through the fluid sample 115 in the sample container 110, while for each value of L, a measurement of the intensity I of the attenuated radiation 111 is performed simultaneously. In various non-limiting embodiments where the sample container 110 is coupled to an external fluid line of a processing system or apparatus, the volume of the fluid sample 115 within the sample container 110 can range from microliters to several milliliters, while the path length L can be variable between 0 and several centimeters.

[0027] To vary L, the optical probe 108 can be translated incrementally or continuously with respect to the sample container 110, where the increment can range from 0.2 μm to 1 cm, and more specifically, the increment ranges from 1 μm to 50 μm. Thus, L 1 , I 1 , L 2 , and I 2 Using the knowledge of the values of, for any pair of instances during the measurement process, the gradient parameter m can be readily calculated according to Equation (4).

[0028] Even while the optical probe 108 is in motion, the ability to calculate m essentially instantaneously based on the measurement of I provides several advantages, where, while data is being collected, the measurement results can be adjusted in real time, for example, in an automated manner. To control the operation of the measuring device 104 and the light source 102, the system 100 may further include control elements such as a controller 120 and a computer 130. The controller 120 may include a light source driving component 122, which may be configured to output an LED drive signal to emit incident radiation 103 in an LED light source embodiment. The controller 120 may further include a motor control component 124 coupled to a motor assembly 106 (which may include a motor and / or a sensor (not shown separately)) to direct the movement of the optical probe 108 to vary L and / or to determine L for any given instance and / or to receive probe position information regarding the optical probe 108. The controller 120 may further include a measurement interface 126 for receiving intensity I information from the detector 112. In some examples, the controller 120 may be coupled to the computer 130, for example, via an interface 128. In some examples, the controller 120 may form part of a computer or similar computing device, which may or may not be located remotely from the measuring device 104.

[0029] Thus, the controller 120 may integrate motor control, light source, and data acquisition under the control of a single microcontroller. In particular, the control of the light source 102 and data acquisition, for example, from the detector 112, may be synchronized with the movement of the optical probe 108. In some examples, the measurement of the concentration C may be obtained while the optical probe 108 moves in either of two opposite directions while increasing or decreasing L. By using a single controller to control the various components of the system 100, a very tight synchronization (in the microsecond range) is possible between the movement of the optical probe 108, the generation of the incident radiation 103, and the measurement of the intensity I of the attenuated radiation 111 at the detector 112.

[0030] During operation, the light source 102 can be a trigger LED that is triggered to turn on intermittently when acquiring data, or generally with a very low duty cycle, thereby providing better light source stability as compared to operating in continuous mode. It should be noted that in various non-limiting embodiments, the portion of the time during which the LED is triggered over a given series of periods of turning the LED on and off can cover a wide range for the duty cycle. Since the duty cycle depends on how long the LED is on for one data point and how soon the next data point collection starts, this wide range is applicable. In particular, in non-limiting embodiments, the duty can range between about 0.1% and 2%.

[0031] To perform a given absorbance measurement of the fluid sample 115, the controller 120 and / or the computer 130 can establish a set of measurement parameters, such as the maximum path length of the optical probe 108, the motion profile, and the data collection rate during the measurement. The motion profile can include, for example, periods for motor acceleration, principle, and steady speed. P&I motor control adjustment parameters are also included. In one example, to collect the most accurate or significant absorbance measurement results for a fluid sample containing the substance whose concentration C is being measured, an estimation of the values for these measurement parameters can be made prior to the measurement. During the measurement using the initial values of the measurement parameters, after the initial value of m is calculated, it can be determined that the data collection rate should increase or decrease, or that the maximum path length should increase or decrease. According to embodiments of the present disclosure, the system 100 can employ the controller 120 and / or the computer 130 to automatically adjust the measurement parameters in real time as needed in response to the determination of the gradient parameter m.

[0032] To further illustrate these advantages, FIG. 3 illustrates an exemplary absorbance spectrum according to an embodiment of the present disclosure. In this example, the graph of FIG. 3 illustrates the detected radiation intensity as a function of wavelength in the near-UV range. Four spectra generated from an LED light source are shown using a narrowband filter such that the spectra consist essentially of monochromatic radiation having a single peak in intensity at 272 nm corresponding to the type of LED material used for the light source. Spectrum 302 corresponds to a first instance when the optical probe is arranged to form a first path length L of 272 nm radiation through the fluid sample; the spectrum (curve 304) corresponds to a second instance when the optical probe is arranged to form a second path length L; the spectrum (curve 306) corresponds to a third instance when the optical probe is arranged to form a third path length L; the spectrum (curve 308) corresponds to a fourth instance when the optical probe is arranged to form a fourth path length L, where the path length decreases from L to L. As discussed above, note that the intensity of the 272 nm peak essentially corresponds to intensity I, and the rate of increase of the intensity of the 272 nm peak with respect to the change in the value of L is proportional to the change in absorbance DA / DL or gradient coefficient m. Thus, in one instance, the value of DA / DL or m can be determined by measuring the differences in I (curve 304 - curve 302) and L between the first and second instances. Similarly, the value of m can be determined by measuring the differences in I (curve 306 - curve 304) and L between the second and third instances; by measuring the differences in I (curve 308 - curve 306) and L between the third and fourth instances; by measuring the differences in I (curve 308 - curve 302) and L between the first and fourth instances; and by similar means. 1 corresponds to a first instance when the optical probe is arranged to form a first path length L 2 ; the spectrum (curve 304) corresponds to a second instance when the optical probe is arranged to form a second path length L 3 ; the spectrum (curve 306) corresponds to a third instance when the optical probe is arranged to form a third path length L 4 ; the spectrum (curve 308) corresponds to a fourth instance when the optical probe is arranged to form a fourth path length L, where the path length is L 1 to L 4 decreases. As discussed above, note that the intensity of the 272 nm peak essentially corresponds to intensity I, and the rate of increase of the intensity of the 272 nm peak with respect to the change in the value of L is proportional to the change in absorbance DA / DL or gradient coefficient m. Thus, in one instance, the value of DA / DL or m can be determined by measuring the differences in I (curve 304 - curve 302) and L between the first and second instances. Similarly, the value of m can be determined by measuring the differences in I (curve 306 - curve 304) and L between the second and third instances; by measuring the differences in I (curve 308 - curve 306) and L between the third and fourth instances; by measuring the differences in I (curve 308 - curve 302) and L between the first and fourth instances; and by similar means.

[0033] Note that the absorbance measurement to generate the spectrum of FIG. 3 can be performed using a set of parameters whose values are first input to the control system, as discussed above. These parameters can include the maximum path length, data collection rate, and the like. For a given fluid sample, since the rate of change of absorbance with respect to the change in path length, i.e., the value of m, is generally not known in advance, during the absorbance measurement, the initially determined value of m can be greater than or less than the expected value of m that can be used at least in part to set the initial values of the measurement parameters. Thus, according to an embodiment of the present disclosure, the gradient information obtained from the analysis of the spectrum, such as that of FIG. 3, can be used to dynamically adjust the measurement parameters during the measurement period.

[0034] FIG. 4 shows a series of ideal curves plotting absorbance versus path length for a wide range of values of m. The shallower curves represent smaller values of m, while the steeper curves represent larger values of m. For purposes of illustration, the examples of FIGS. 3 and 4 below are for L 1 、L 2 、L 3 and L 4 with exemplary values. In this example, for the initial measurement parameters, it can be assumed that the maximum path length is set to 0.1 mm, and the gradient parameter m for the fluid sample to be measured is expected to be within the range of 5.0 shown by curve 402. Under these conditions, the maximum absorbance at path length L 1 (0.1 mm) can be expected to fall within the range of 0.5, which is well below the maximum absorbance limit set to 1.0. However, the recorded values of I in the different absorbance spectra in FIG. 3 can correspond to absorbance values that more closely match the gradient parameter of 10 corresponding to curve 404 (the different absorbance curves in FIG. 3 are shown in FIG. 4 at the corresponding L and A values). According to an embodiment of the present disclosure, using these results, the values of one or more measurement parameters can be automatically adjusted during the measurement. For example, the path length increment used to generate the data in FIG. 3 can correspond to 0.025 mm. If the gradient parameter m is higher than expected and L 1Since it results in a very small transmission in [reference to something not specified in the text], for the same amount of measurement, the maximum path length can be reset to 0.05 mm, resulting in a small increment in the path length L, and a more reliable spectrum is obtained over the entire measurement range. Alternatively, the number of measurements made over the range between 0 mm and 0.1 mm can be increased, increasing the data reliability. In another example, the speed of the movement of the optical probe can be automatically increased or decreased based on the calculation of m from the initial settings of the measurement of I.

[0035] It should be noted that according to this embodiment, the change of the measurement parameters can be executed by the controller in an automatic manner based on a pre-set algorithm. Therefore, during the measurement period initially set so that two dozen intensity I measurements at corresponding different path lengths are performed, after the first set of measurements such as two measurements, three measurements, or four measurements are performed, when the calculated gradient parameter m, which is the result from the first set of measurements, meets any suitable criterion, the target measurement parameters can be adjusted. In one embodiment, the absorbance measurement procedure can be set to measure the intensity at multiple instances during the continuous movement of the optical probe to decrease the path length during the first period and then increase the path length during the second period. The initial setting of the measurement parameters can include the first data collection rate applied during the continuous movement of the optical probe to decrease the path length L. Based on the calculated value of m derived from the I data collected during the first period, the data collection rate can be adjusted to the second data collection rate during the second period.

[0036] Another advantage of this embodiment is the ability to adjust the measurement parameters to account for dynamic changes in the fluid sample being measured. FIG. 2A illustrates another system, shown as system 200, according to a further embodiment of the present disclosure. System 200 may be configured similarly to system 100 described previously, where like components have the same labels and may function similarly to each other. FIG. 2B shows a variation of system 200 having an LED light source 102A as system 250, where the other components of system 250 may function similarly to those of system 200 and like components have the same labels. Referring particularly to FIG. 2A, system 200 is shown as being coupled to an external processing system represented as processing system 210. Thus, processing system 210 may represent any suitable system that generates a fluid sample to be measured, such as a chromatographic system, a protein purification system, a filtration system, or other fluid processing system, as described previously.

[0037] In the scenario of FIG. 2A, the processing system 210 is shown to generate a fluid sample 212 that is conducted through the fluid sample container 211 of the measuring device 204 to measure the concentration C of the material in the fluid sample 212. During operation, the light source 102, the measuring device 204, the controller 120, and the computer 130 can operate in the same manner as the similar components of the system 100 to measure C by determining DA / DL as described in detail above. Similarly, the system 200 can automatically adjust the measurement parameters based on the determination of the gradient parameter m during measurement, generally as described in detail above. The adjustment of the measurement parameters can be performed dynamically, such as during the movement of the probe, or can be performed in an iterative manner to perform continuous measurements using different measurement parameters that are adapted in accordance with the consideration of calculated entities such as m. In the scenario of FIG. 2A, since the fluid sample 212 is provided from an external system and can move through the fluid sample container 211, a change in the value of C can be assumed. Since the change in C is reflected in the change in the gradient parameter m, the system 200 provides a useful means for dynamically adjusting the measurement parameters in consideration of the change in the gradient parameter m during measurement, which may be more likely to be within the flowing fluid sample provided from the external system. In particular, the system 200 can result in a series of more accurate measurement periods during a given sample measurement procedure for the fluid sample, where during a given measurement period, measurement parameters such as the data acquisition rate and the maximum path length are more preferably matched to the most recent value of C such that they are dynamically determined during measurement.

[0038] Figure 5 presents process flow 500 according to an embodiment of the present disclosure. At block 502, initial absorbance measurement parameters are set in the absorbance measurement system. The absorbance measurement device can be configured to measure the substance concentration in a fluid sample using the principle of gradient spectroscopy, as described in detail with respect to the embodiments of FIGS. 1A - 2B, for example. The absorbance measurement parameters can include a motion profile for the optical probe used to change the transmission intensity of radiation by moving through the fluid sample; non - limiting examples include the data collection rate for collecting transmission intensity data; and can include the maximum path length of the radiation through the fluid sample.

[0039] At block 504, the measurement procedure is initiated in the absorbance measurement device. When a fluid sample is included in the measurement device of the absorbance measurement system, the measurement procedure can be initiated by sending a signal to a motor or other drive mechanism in an initial instance to start the movement of the optical probe along the probe axis through the fluid sample.

[0040] At block 506, during a measurement period referred to as the current measurement period, as the probe moves through the fluid sample, the probe radiation is directed to pass through the optical probe. In some examples, the probe radiation can be generated intermittently, such as during a given period corresponding to different path lengths of the probe radiation through the fluid sample. In some examples, the probe radiation can be directed during the continuous movement of the optical probe.

[0041] At block 508, during the current measurement period, the intensity (I 1 、I 2 、I 3 、...) of the attenuated radiation, which means the probe radiation after passing through the fluid sample, is measured at a plurality of instances corresponding to a plurality of different path lengths (L 1 、L 2 、L 3 、...) of the probe radiation through the fluid sample.

[0042] In block 510, the initial gradient parameter DA / DL or m is determined based on at least one pair of path length values from the current measurement period, and a corresponding pair of transmission intensity values L 1 , I 1 , L 2 , and I 2 .

[0043] The flow then proceeds to decision block 512, where it is determined whether the measurement operation is complete. If it is complete, the process ends. If it is not complete, the flow moves to decision block 514.

[0044] In decision block 514, it is determined whether the gradient parameter value m is acceptable. According to different embodiments, this determination can be made in different ways. For example, the predetermined criterion for acceptance can be determined by whether the currently calculated value of m is less than a threshold, greater than a threshold, within a predetermined range, and the like. If so, the flow proceeds to block 516.

[0045] In block 516, the system decides to proceed through an additional measurement period without changing the measurement parameters. The flow then proceeds to block 506.

[0046] In decision block 514, if the gradient parameter value m is not acceptable, the flow proceeds to block 518. In block 518, at least one absorbance measurement parameter including at least one of the maximum path length of the optical probe, the motion profile for the optical probe, and the data collection rate while the optical probe is moving is adjusted. The flow then proceeds to block 506.

[0047] This configuration has been disclosed with reference to specific embodiments, but many modifications, alterations, and changes to the described embodiments are possible without departing from the spirit and scope of the disclosed configuration as defined in the appended claims. Accordingly, this configuration is not intended to be limited to the described embodiments, but is intended to have the full scope defined by the language of the following claims and their equivalents.

Claims

1. A light source for generating a probe signal including incident radiation; An optical probe configured to direct the incident radiation to pass through a fluid sample; A motor configured to move the optical probe along a probe axis to change a path length of the incident radiation passing through the fluid sample; A detector arranged to receive the incident radiation as attenuated radiation after passing through the fluid sample; and Start an absorbance measurement of the fluid sample by instructing movement of the optical probe along the probe axis; Instruct the light source to emit the incident radiation; and Automatically adjust at least one measurement parameter of a set of measurement parameters for the absorbance measurement based on a gradient parameter m, where m is derived from a ratio of a change in intensity of the attenuated radiation to a change in the path length, A control system configured as An absorbance measurement system comprising.

2. The light source includes a light emitting diode (LED) configured to receive a trigger signal from the control system and to generate the incident radiation at a characteristic wavelength upon receipt of the trigger signal, The detector is configured to detect the intensity of the attenuated radiation over a wavelength range spanning the characteristic wavelength and over a detection period of 10 microseconds or less, The absorbance measurement system according to claim 1.

3. The control system according to claim 2, configured to synchronize the trigger signal for generation of the incident radiation by the LED and receipt of the intensity of the attenuated radiation to be less than 10 microseconds.

4. The control system is configured to instruct the motor to move the optical probe in a pair of opposite directions along the probe axis, where the intensity of the attenuated radiation is recorded while the motor moves the optical probe along a first direction of the pair of opposite directions and while the motor moves the optical probe along a second direction of the pair of opposite directions. The absorbance measurement system according to claim 2.

5. The control system: Receives a set of probe position information during continuous movement of the optical probe at a plurality of instances during a measurement period; Determine the change in the path length over the measurement period based on the set of probe position information; Receive, in the plurality of instances, a set of intensity information of the attenuated radiation; and Automatically change at least one measurement parameter for a subsequent measurement period of the absorbance measurement based on the change in the path length over the measurement period and the value of the gradient parameter m determined from the change in the intensity of the attenuated radiation over the measurement period The absorbance measurement system according to any one of claims 1 to 4, configured as described above.

6. The absorbance measurement system according to claim 5, wherein the at least one measurement parameter includes a maximum path length of the optical probe, a motion profile of the optical probe, and a data collection rate of the set of probe position information and the set of intensity information.

7. The absorbance measurement system according to any one of claims 1 to 4, wherein the control system determines a concentration C of a material in the fluid sample, where C = m / e, and where e is the molar extinction coefficient of the material.

8. A method for determining the concentration of a material in a fluid sample, comprising: Initiating a sample measurement of the fluid sample to determine the concentration by transmitting a signal to move an optical probe through a sample container containing the fluid sample; Triggering a light source to emit incident radiation through the optical probe and the fluid sample at a plurality of instances during a measurement period, wherein a path length L of the incident radiation through the fluid sample varies; Receiving, at the plurality of instances during the measurement period, measurement results of an intensity I of attenuated radiation derived from the incident radiation after passing through the fluid sample; and Automatically adjusting at least one measurement parameter of a set of measurement parameters for the sample measurement based on a gradient parameter m, where m is derived from a ratio of the change in I to the change in L during the measurement period A method comprising the above steps.

9. m = DA / DL, where DA = [Number 4] where I １ represents the strength I in the first instance, and I ２ represents the strength I in the second instance, and DL represents the change in the path length L between the first instance and the second instance. The method according to claim 8.

10. Receiving a set of probe position information corresponding to a first probe position in a first instance and a second probe position in a second instance; Determining a first path length L of the incident radiation from the first probe position １ and; The second path length L of the incident radiation from the second probe position ２ is determined, where DL = L ２ - L １ is, The method according to claim 8, further comprising the above step.

11. The step of automatically adjusting is as follows: Adjusting the maximum path length of the optical probe, the motion profile of the optical probe, the data collection rate of the intensity I, or a combination thereof to form a modified set of measurement parameters, the method according to claim 8. **Claim 12** The light source includes a light emitting diode (LED), and the method further comprises the step of synchronizing the triggering of the light source and the reception of the sample measurement in less than 10 microseconds, the method according to claim 8. **Claim 13** Transmitting the signal for moving the optical probe includes instructing a motor to move the optical probe along the probe axis, the method according to any one of claims 8 to 12. **Claim 14** Comprising the step of sending a signal to the motor to move the optical probe in a pair of opposite directions along the probe axis, wherein the step of receiving the measurement result of the intensity is: Receiving a first set of detected intensity measurements while the optical probe moves along a first direction of the pair of opposite directions; and Receiving a second set of detected intensity measurements while the optical probe moves along a second direction of the pair of opposite directions The method according to claim 13. **Claim 15** The step of automatically adjusting is as follows: Determining whether the gradient parameter m is acceptable according to a predetermined criterion; When m is not acceptable, adjusting the at least one measurement parameter; and When m is acceptable, continuing the sample measurement over a second measurement period using the set of measurement parameters without adjustment The method according to any one of claims 8 to 12. **Claim 16** A procedure for starting a sample measurement to determine the concentration of a substance in the fluid sample by transmitting a signal for moving an optical probe through a sample container containing the fluid sample; A procedure for triggering a light source to emit incident radiation through the optical probe and the fluid sample at a plurality of instances during a measurement period, wherein the path length L of the incident radiation through the fluid sample varies; A procedure for receiving a measurement result of the intensity I of the attenuated radiation derived from the incident radiation after passing through the fluid sample at a plurality of instances during the measurement period; and A procedure for automatically adjusting at least one measurement parameter out of a set of measurement parameters for the sample measurement based on a gradient parameter m, where m is derived from the ratio of the change in I to the change in L during the measurement period, A computer program comprising computer-readable program code for causing a processor to execute. **Claim 17** m = DA / DL, where DA = 【Number 5】 where I １ represents the strength I in the first instance, and I ２ represents the strength I in the second instance, and DL represents the change in the path length L between the first instance and the second instance. The computer program according to claim 16. **Claim 18** The computer-readable program code A procedure for receiving a set of probe position information corresponding to a first probe position in a first instance and a second probe position in a second instance; The first path length L of the incident radiation １ A procedure for determining from the first probe position; and The second path length L of the incident radiation ２ A procedure for determining from the second probe position, where DL = L ２ - L １ is The computer program according to claim 16, which causes the processor to execute. **Claim 19** The computer-readable program code A procedure for adjusting the maximum path length of the optical probe, the motion profile of the optical probe, the data collection rate of the intensity I, or a combination thereof to form a modified set of measurement parameters The computer program according to claim 16, which causes the processor to execute. **Claim 20** The computer-readable program code Determine whether the gradient parameter m is acceptable according to a predetermined criterion; When m is not acceptable, adjust the at least one measurement parameter; and When m is acceptable, continue the sample measurement over a second measurement period using the set of measurement parameters without adjustment The computer program according to any one of claims 16 to 19, which causes the processor to execute.

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