Determination Of Measurement Uncertainty Research Articles

The promise and peril of comparing fluorescence lifetime in biology revealed by simulations.

Signaling dynamics are crucial in biological systems, and biosensor-based real-time imaging has revolutionized their analysis. Fluorescence lifetime imaging microscopy (FLIM) excels over the widely used fluorescence intensity imaging by allowing the measurement of absolute signal levels, independent of sensor concentration. This capability enables the comparison of signaling dynamics across different animals, body regions, and timeframes. However, FLIM's advantage can be compromised by factors like autofluorescence in biological experiments. To address this, we introduce FLiSimBA, a flexible computational framework for realistic F luorescence Li fetime Sim ulation for B iological A pplications. Through simulations, we analyze the signal-to-noise ratios of fluorescence lifetime data, determining measurement uncertainty and providing necessary error bars for lifetime measurements. Furthermore, we challenge the belief that fluorescence lifetime is unaffected by sensor expression, and establish quantitative limits to this insensitivity in biological applications. Additionally, we propose innovations, notably multiplexed dynamic imaging that combines fluorescence intensity and lifetime measurements. This innovation can transform the number of signals that can be simultaneously monitoring, thereby enabling a systems approach in studying signaling dynamics. Thus, by incorporating diverse factors into our simulation framework, we uncover surprises, identify limitations, and propose advancements for fluorescence lifetime imaging in biology. This quantitative framework supports rigorous experimental design, facilitates accurate data interpretation, and paves the way for technological advancements in fluorescence lifetime imaging.

Experimental uncertainty evaluation by measuring a micro gear standard using focus variation

Abstract Micro gears play an increasingly important role in various industrial applications, and the minimization of their deviations is challenging for metrology and manufacturing. A promising method is the focus variation technology, which enables areal measurements of micro gears. Practice-related standards are used to determine measurement uncertainties by comparison with calibration values. In this work, the external micro gear standard of the Physikalisch-Technische Bundesanstalt (PTB) is used to evaluate experimental measurement uncertainties of a focus variation coordinate measurement system for the first time. The traceable standard with modules between 0.1 and 1 mm is calibrated using micro tactile coordinate measurements. Optical and tactile measurements are then compared. As a result, small expanded measurement uncertainties of less than 4 µm are achieved.

Validation, measurement uncertainty estimation and evaluation of UHPLC greenness for simultaneous determination of metoprolol tartrate and hydrochlorothiazide in binary tablet

A novel green ultra high performance liquid chromatography (UHPLC) method was validated and estimated the measurement uncertainty for simultaneous determination of metoprolol tartrate (MET) and hydrochlorothiazide (HCT) in binary tablet. A Zorbax® SB-C18 column with isocratic elution (flow rate 0.9 mL min−1) at 25°C was used. Analytes and HCT degradation product were separated in approximately 1 min using acetonitrile:water:triethylamine (17:83:0.2, v/v) as mobile phase. Analytical curves were linear with (R 2 > 0.99 for MET and HCT) with detection limits of 2.42 and 1.05 µg mL−1 for MET and HCT, respectively. Precision measurements showed RSD% from 0.39 to 1.2% and method accuracy by recovery tests was 100 ± 2%. Measurement uncertainties using Eurachem procedure were 100.1 ± 2.8% and 100.3 ± 2.4% for MET and HCT, respectively. This UHPLC method was accurate, precise, linear and selective, making it suitable for pharmaceutical quality control. It also proved eco-friendly compared to other reported methods.

Risk Assessment for Linear Regression Models in Metrology

The conformity assessment of products or a measured value with the given standards is carried out based on the global risk of producers and consumers’ calculations. A product may conform to specifications but be falsely rejected as non-conforming. This is about the producer’s risk. If a product does not meet the requirements but is falsely accepted as conforming, that poses a risk to the consumer. The conventional approach to risk assessment, which yields only a single numerical value for the global risk of producers and consumers, is naturally extended and utilized for assessing risk in measurement models with linear regression. The outcomes of the two-dimensional extension, along a moderate scale, are the parabolas with upwards openings. Risk surfaces were obtained through three-dimensional extension over the area limited by the moderate scale and guard band axes. Four models with different ranges of tolerance intervals were used to test this innovative method of risk assessment in linear regression. The corresponding standard measurement uncertainties were determined by applying a simplified measurement model with the use of comprehensive data on the measurement performance and by determining measurement uncertainty derived from consideration of the functional relationship obtained by linear regression analysis. Models that utilize information from linear regression analysis to determine measurement uncertainty are biased towards risks at the edges of the moderate scale. Testing the model’s performances with metrics related to the confusion matrix, such as the F1 score, further substantiated this assertion. The diagnostic odds ratio has been proven to be extremely effective in identifying the curve along the guard band axis, along which the global risks of producers and consumers are at their lowest.

An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of phenobarbital in human serum and plasma.

Phenobarbital serves as an antiepileptic drug (AED) and finds application in the treatment of epilepsy either as monotherapy or adjunctive therapy. This drug exhibits various pharmacodynamic properties that account for its beneficial effects as well as potential side effects. Accurate measurement of its concentration is critical for optimizing AED therapy through appropriate dose adjustments. Therefore, our objective was to develop and validate a new reference measurement procedure (RMP) for the accurate quantification of phenobarbital levels in human serum and plasma. A sample preparation protocol based on protein precipitation followed by a high dilution step was established in combination with a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using a C8 column to separate target analytes from known and unknown interferences. Assay validation and determination of measurement uncertainty were performed based on current guidelines. Selectivity and Specificity were assessed using spiked serum and plasma samples; to investigate possible matrix effects (MEs) a post-column infusion experiment and a comparison of standard line slopes was performed. Precision and accuracy were determined within a multiday precision experiment. The RMP was shown to be highly selective and specific, with no evidence of matrix interferences. It can be used to quantify phenobarbital in the range of 1.92 to 72.0 μg/mL. Intermediate precision was less than 3.2 %, and repeatability coefficient of variation (CV) ranged from 1.3 to 2.0 % across all concentration levels. The relative mean bias ranged from -3.0 to -0.7 % for native serum levels, and from -2.8 to 0.8 % for Li-heparin plasma levels. The measurement uncertainties (k=1) for single measurements and target value assignment were 1.9 to 3.3 % and 0.9 to 1.6 %, respectively. A novel LC-MS/MS-based candidate RMP for the quantification of phenobarbital in human serum and plasma is presented which can be used for the standardization of routine assays and the evaluation of clinically relevant samples.

FUNDAMENTAL ASPECTS OF METROLOGICAL SUPPORT IN IoT

The application of intelligent sensors, network technologies, and machine learning in IoT and industry is increas- ingly widespread as a part of the development and implementation of Industry 4.0, Industry 5.0, and Smart City. It is necessary to review the fundamental principles of metrological support for production. This includes calibration, estimation of measurement uncertainty, traceability, and processing of large data sets to reproduce and compare the results of measurements of physical quan- tities remotely. Modern smart sensors are cost-effective, which makes traditional sensor calibration methods increasingly uneco- nomical. The utilization of advanced networking technologies, along with machine learning, complicates the pre-processing of measured values. Therefore, new solutions are required when it comes to implementing digital metrology. In this article, a metrological framework for the full life cycle of measured data in IoT is presented. It ensures transparency, comparability, consistent quality and reliability of measured data, processing methods and results. The OPC-UA digital data com- munication standard is considered, which provides a single interface for exchanging digital data with devices from different manu- facturers or via different protocols. The syntax of a machine-readable representation of SI units and derived quantities as well as the structure of the sensor network metadata model are also described. Special emphasis is placed on dynamic calibration of sen- sors, determining measurement uncertainty in sensor networks, and implementing digital calibration certificates in IoT and industry.

An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure for the quantification of zonisamide in human serum and plasma.

To describe and validate an isotope dilution-liquid chromatograph-tandem mass spectrometry (ID-LC-MS/MS) based reference measurement procedure (RMP) for zonisamide to accurately measure serum and plasma concentrations. Quantitative nuclear magnetic resonance (qNMR) spectroscopy was employed to determine the absolute content of the reference material used in order to establish traceability to SI units. Separation of zonisamide from known or unknown interferences was performed on a C8 column. For sample preparation a protocol based on protein precipitation in combination with a high dilution step was established. Assay validation and determination of measurement uncertainty were performed based on guidelines from the Clinical and Laboratory Standards Institute, the International Conference on Harmonization, and the Guide to the expression of uncertainty in measurement. The RMP was proven to be highly selective and specific with no evidence of a matrix effect, allowing for quantification of zonisamide within the range of 1.50-60.0 μg/mL. Intermediate precision was <1.4 % and repeatability CV ranged from 0.7 to 1.2 % over all concentration levels. The relative mean bias ranged from 0.0 to 0.8 % for native serum levels and from 0.2 to 2.0 % for Li-heparin plasma levels. The measurement uncertainties for single measurements and target value assignment ranged from 1.1 to 1.4 % and 0.8-1.0 %, respectively. We present a novel LC-MS/MS-based candidate RMP for zonisamide in human serum and plasma which provides a traceable and reliable platform for the standardization of routine assays and evaluation of clinically relevant samples.

An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure for the quantification of carbamazepine in human serum and plasma.

An isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) was developed and validated to accurately measure serum and plasma concentrations of carbamazepine. Quantitative nuclear magnetic resonance (qNMR) spectroscopy was used to determine the absolute content of the reference material, ensuring its traceability to SI units. The separation of carbamazepine from potential interferences, whether known or unknown, was achieved using a C18 column. A protein precipitation protocol followed by a high dilution step was established for sample preparation. Assay validation and determination of measurement uncertainty were performed in accordance with the guidelines of the Clinical and Laboratory Standards Institute, the International Conference on Harmonization (ICH), and the Guide to the Expression of Uncertainty in Measurement (GUM). In order to demonstrate equivalence to the already existing RMP a method comparison study was performed. The RMP was proven to be highly selective and specific with no evidence of a matrix effect, allowing for quantification of carbamazepine within the range of 0.800-18.0 μg/mL. Intermediate precision and repeatability (n=60 measurements) was found to be <1.6 % and <1.3 % over all concentration levels and independent from the matrix. The relative mean bias ranged from-0.1 to 0.6 % for native serum and from-0.3 to-0.1 % for Li-heparin plasma levels. The measurement uncertainties for single measurements and target value assignment were found to be <1.8 % and <1.3 %, respectively. Method comparison showed a good agreement between the Joint Committee of Traceability in Laboratory Medicine (JCTLM) listed RMP and the candidate RMP resulting in a Passing-Bablok regression equation with a slope of 1.01 and an intercept of-0.01. The bias in the patient cohort was found to be 0.9 %. We present a novel LC-MS/MS-based candidate RMP for carbamazepine in human serum and plasma which provides a traceable and reliable platform for the standardization of routine assays and evaluation of clinically relevant samples.

Comprehensive and sensitive validation of the method and determination of measurement uncertainty for simultaneous specification of aflatoxin B1, B2, G1 and G2 in nuts

In this study, a comprehensive and sensitive validation study of the legally used method was conducted to simultaneously determine the levels of aflatoxin B1, B2, G1, and G2 in nuts. The applied method has been extensively evaluated in terms of in-laboratory detection limit and quantification limit, linearity, selectivity, precision, recovery, accuracy, adequacy, and measurement uncertainty. Levels of aflatoxins were examined by a validated immunoaffinity column-high performance liquid chromatography-post column derivatization-fluorescence detection (IAC-HPLC-PCA-FLD) analytical method. Detection limits (LOD) for aflatoxin G2, G1, B2, and B1 were found to be 0.05 μg/kg, 0.13 μg/kg, 0.06 μg/kg, and 0.15 μg/kg, respectively. The regression coefficient (R2) was greater than 0.999 according to constructed calibration curves for all aflatoxin components. Thus, the curves exhibited satisfactory linearity within the analyzed range. The combined standard uncertainty values for precision (RSD%) studies were below 10%. It showed a robust and reliable sensitivity with <10% RSD with the test procedure. Average recovery values were detected as 67-84% for hazelnut and 60-89% pistachio. All aflatoxin components in hazelnut paste, which is the proficiency test material, were determined within an appropriate |Z|-score range (≤ 2). The relative expanded uncertainty of measurement was 0.80 μg/kg for AFB1 and AFG1, 0.83 μg/kg for AFB2 and AFG2, and 0.78 μg/kg for total AFs. The results showed that the approved method for the investigation and monitoring of aflatoxins in hazelnuts and pistachios is highly sensitive, robust, reliable, selective, and reproducible. Validation parameters can be successfully used in routine analysis to monitor aflatoxins in nuts for compliance with current regulations.

Determination of measurement uncertainty by a Monte Carlo method for an RF power sensor calibration system using a VNA

This work proposes a systematic assessment of measuring type A uncertainty (caused by random errors) used in RF power sensor calibration. To reduce A type uncertainty, several successive measurements are repeated. The uncertainty arises from repeatability errors in connectors caused by changes in their electrical properties during repeated mating. The suitability of the METAS UncLib software was analysed and we concluded that software should be developed to take into account the shape of probability density function (PDF) using a Monte Carlo method (MCM), which was lacking in METAS UncLib. The self-developed software was then tested on an example taken from the literature and the superiority of the MCM over the analytical method (GUM) was confirmed. During the calibration of the RF sensor using a vector network analyzer (VNA), a series of repeated measurements were performed and, after applying our MCM software, it was found that the measurement uncertainties calculated by the MCM method were several times larger than those by the GUM. The reason for this was that the correlation between the measured input quantities was not taken into account. When this was done using a covariance matrix and assuming a normal PDF of the input quantities, the results obtained with the GUM and the MCM converged. Our main objective was to investigate the influence of the PDF shape of the input measurement samples on the measurement uncertainty. Taking more than a dozen measurements is too costly, on the other hand, the small sample size prevents a reliable determination of the PDF shape. Finally, to overcome this inconvenience, we have developed a special method that uses the histograms of standardized input data taken at all measurement frequencies under fixed conditions without disconnecting the connectors, to increasing the total number of results which were needed to create the PDF histograms of input quantities.

Approaches to assess reliability in visual inspection

Non-destructive testing (NDT) plays an important role in quality assurance and ensuring reliable ongoing operations in many industries. Thus, the importance of reliability assessment of inspection results is increasing. Current standards and regulations provide several approaches for this purpose. For example, DIN EN ISO/IEC 17025:2018-03 provides general requirements to determine measurement uncertainty. In contrast, method-related standards such as DIN ISO 19828:2021-03 specify detailed requirements for visual inspection (VT), considering environmental conditions and other factors (for example experience of the inspection personnel). In contrast, VDA Volume 5 defines visual inspection as an attributive method, making measurement uncertainty determinations unnecessary. Instead, the reliability of the inspection process is evaluated by proficiency tests. This paper examines approaches of regulations, based on previous experiments, for their applicability and suitability for considering the reliability of visual inspections. It is shown that individual measurement values (for example illuminance) are not suitable for this purpose. Furthermore, it is shown that human factors (HFs) (for example training or experience of the inspector), considered in isolation, are also not sufficiently suitable. Hence, the combination of the qualification of inspection methods, by means of proficiency tests on reference objects, and the application of Cohen's kappa for evaluating human factors appeared to be more suitable for the investigated issue.

Development and validation of a multianalyte method for quantification of isoxazolines in animal-derived matrix samples using SPE-HPLC–MS/MS

Isoxazoline drugs, including afoxolaner, fluralaner, lotilaner, and sarolaner, are widely used in veterinary medicine. However, the lack of available analytical methods has made regulatory monitoring of these drugs difficult. Therefore, in this study, we developed an optimized solid phase extraction process using hydrophilic–lipophilic cartridges, and subsequently analyzed the extracts using liquid chromatography–tandem mass spectrometry under optimized conditions. The detection limits for the four isoxazolines were 5.0 μg/kg, while the recoveries in six animal-derived matrices were 71.1–109.2 %, with intra-day and inter-day relative standard deviations below 11.9 % and 11.7 % respectively. Furthermore, an inter-laboratory comparison demonstrated that this method had good recovery (60.3–112.9 %) and acceptable precision (< 11.3 %). Additionally, the developed method exhibited excellent linearity, accuracy, precision, sensitivity, measurement uncertainty and robustness for isoxazoline residue determination in animal-derived samples. It was also successfully applied to determine incurred isoxazoline residues in medicated hens.

Experiences with accreditation for radon measurement laboratories.

The adoption of the Council Directive 2013/59/EURATOM into Austrian national law generated new challenges for businesses, authorities and measurement services. The law defines radon priority regions in which all employers are obliged to hire an authorised radon-monitoring service to determine radon activity concentration at workplaces in basements and on ground floors. In this paper, an overview of our experiences with the process of becoming an accredited and authorised radon-monitoring body using integrating and time-resolved radon measurement equipment is given. The main challenges to overcome, such as determination of measurement uncertainty, conducting metrologically traceable calibration of the track-etch detector system, information not covered by ISO 11665-1, ISO 11665-4 and ISO 11665-5, availability of proficiency tests, etc., are described. This paper aims to be a guideline for laboratories seeking accreditation in the field of radon activity concentration measurements.

Comprehensive estimation of measurement uncertainty in determination of antioxidant activity in natural product by 2,2ʹ-diphenil-1-picrylhydrazyl (DPPH) radical scavenging assay

Comprehensive estimation of measurement uncertainty in determination of antioxidant activity in natural product by 2,2ʹ-diphenil-1-picrylhydrazyl (DPPH) radical scavenging assay

Traceable efficiency determination of a 2.75 MW nacelle on a test bench

In this paper, the efficiency of a 2.75 MW nacelle drivetrain on a test bench was determined traceably at various load points. For this purpose, so-called transfer standards for mechanical and electrical power measurement were additionally installed and integrated into the nacelle drivetrain. As torque measurement contributes greatly to the overall uncertainty, the static torque calibration was expanded to include additional influences present under rotation. An overall system efficiency of 89% was measured in the high torque and high speed range. The relative expanded measurement uncertainty for efficiency determination was between 0.30% and 0.72% over the entire operating range. Both the efficiency and the relative expanded measurement uncertainty were calculated for each operating point.

Similarity assessment and model migration for measurement processes

PurposeThe determination of the measurement uncertainty is relevant for all measurement processes. In production engineering, the measurement uncertainty needs to be known to avoid erroneous decisions. However, its determination is associated to high effort due to the expertise and expenditure that is needed for modelling measurement processes. Once a measurement model is developed, it cannot necessarily be used for any other measurement process. In order to make an existing model useable for other measurement processes and thus to reduce the effort for the determination of the measurement uncertainty, a procedure for the migration of measurement models has to be developed.Design/methodology/approachThis paper presents an approach to migrate measurement models from an old process to a new “similar” process. In this approach, the authors first define “similarity” of two processes mathematically and then use it to give a first estimate of the measurement uncertainty of the similar measurement process and develop different learning strategies. A trained machine-learning model is then migrated to a similar measurement process without having to perform an equal size of experiments.Similarity assessment and model migrationFindingsThe authors’ findings show that the proposed similarity assessment and model migration strategy can be used for reducing the effort for measurement uncertainty determination. They show that their method can be applied to a real pair of similar measurement processes, i.e. two computed tomography scans. It can be shown that, when applying the proposed method, a valid estimation of uncertainty and valid model even when using less data, i.e. less effort, can be built.Originality/valueThe proposed strategy can be applied to any two measurement processes showing a particular “similarity” and thus reduces the effort in estimating measurement uncertainties and finding valid measurement models.

Scientific approach and implementation of a measurement uncertainty in mass balance determination

Scientific approach and implementation of a measurement uncertainty in mass balance determination

Virtual task-specific measurement uncertainty determination for laser scanning

The framework of the Geometrical Product Specification defines the nominal geometry of the components and the characteristic tolerances. Various ISO standards describe the nine defined geometrical properties per characteristic of a workpiece. To prove conformance to the task specific tolerances according ISO 14253–1, the uncertainty budget needs to be determined. This paper presents a digital twin of an optical measurement system as a holistic concept to perform the task specific uncertainty determination. Different measurement strategies are applied to illustrate their effect on the measurement uncertainty of geometrical properties. Not all geometrical properties are relevant for an optical measurement system. Therefore, the discussed properties as a function of the optical measurement strategy in this paper are: size, distance, form and orientation.

Total Analytical Error and Measurement Uncertainty for Analytical Performance Evaluation and Determination of Gray Zones of Glucose Critical Value Limits.

Total analytical error (TAE) and measurement uncertainty (MU) are important approaches to evaluating and improving the quality of measurement procedures. This study evaluates glucose analytical performance (AP) according to TAE and MU and calculates gray zones of glucose critical value limits. Using TAE and MU values, AP was evaluated according to 5 different analytical performance specifications (APS) and the gray zones of critical value limits were calculated. The number of patients in these zones was compared. TAE was higher than MU at all 3 levels. The AP for the low glucose level was poor. The number of patients in the gray zones was statistically higher in the TAE groups than in the MU groups (P < .05). TAE and MU values can be used to evaluate the AP of glucose measurement as well as to evaluate the compliance of patient results with decision limits by creating gray zones.

Towards efficient application-dependent dimensional measurements with computed tomography: optimized reduction of measurement duration using continuous scan mode: experimental investigations

Abstract. Due to the complex physical and technical relationships in dimensional X-ray computed tomography measurement technology, the precise influences on the measurement result are still not fully understood. A deeper understanding of these influences is essential in order to improve the measurement accuracy and economy of computed tomographic measurement systems. In addition, this enables better numerical determination of measurement uncertainties, which is also a topic of current research. Two factors that have a significant influence on the lead times are the scan mode and the number of projections per measurement. In this article, these factors are investigated experimentally using a calibrated workpiece, and the influence of the workpiece position on the measurement result is also examined. It can be shown that the workpiece position has a considerable influence on the quality of the measurement, especially in the case of a continuous scan. The results show a vast potential for application-dependent reduction of lead times.