Accurate Measurement Procedure Research Articles

Embedding and cross-sectioning as a sample preparation procedure for accurate and representative size and shape measurement of nanopowders

Reliable measurement of the size of polydisperse, complex-shaped commercial nanopowders is a difficult but necessary task, e.g., for regulatory requirements and toxicity risk assessment. Suitable methods exist for the accurate characterization of the size of non-aggregated, stabilized, spherical and monodisperse nanoparticles. In contrast, industrial nanoscale powders usually require dedicated sample preparation procedures developed for the analysis method of choice. These nano-powders tend to agglomerate and/or aggregate, a behavior which in combination with an innate broad particle size distribution and irregular shape often significantly alters the achievable accuracy of the measured size parameters. The present study systematically tests two commercially available nanoscale powders using different sample preparation methods for correlative analysis by scanning electron microscopy, dynamic light scattering, Brunauer–Emmet–Teller method and differential mobility analysis. One focus was set on the sample preparation by embedding nanoparticles in carbon-based hot-mounting resin. Literature on this topic is scarce and the accuracy of the data extracted from cross sections of these particles is unclearly stated. In this paper systematic simulations on the deviation of the size parameters of well-defined series of nanoparticles with different shapes from the nominal value were carried out and the contributing factors are discussed.

FRI485 High Interlaboratory Variability In Free Thyroxine Measurement Indicates Need For Method Standardization

Abstract Disclosure: A. Ribera: None. U. Danilenko: None. O. Sugahara: None. L. Collins: None. T. Buchannan: None. N. Vazquez: None. F. Pokuah: None. D. Wirtz: None. L. Zhang: None. A.N. Lyle: None. H.W. Vesper: None. Thyroid function tests are critical to diagnose diseases of the thyroid. Concerns about the accuracy and reliability of thyroid function tests, especially free thyroxine (FT4), have been stated by the clinical laboratory community for many years. In response to these concerns, the CDC Clinical Standardization Program (CSP) has created a standardization program for FT4 based on the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference system and is partnering with IFCC to standardize FT4 and harmonize TSH testing globally. As part of this program, CDC developed an accurate and sensitive reference measurement procedure (RMP) to assign reference values to individual donor sera. Assay manufacturers and research and clinical laboratories can use these sera to assess the analytical performance of their measurements, and monitor analytical performance over time. To obtain initial information about the analytical performance of FT4 and TSH measurements, an interlaboratory study among commercial assays and laboratory developed test was conducted. A panel of 40 blinded, fresh-frozen single donor patient serum samples with FT4 concentration ranging between 11-32 pmol/L concentrations was measured by participants and compared to the results obtained by CDC RMP for FT4. In addition, commercial assay manufacturers were asked to measure thyroid-stimulating hormone (TSH). Results from sixteen commercial assays and four laboratory developed test (LDT) participated. Preliminary results indicate a negative mean bias for all commercial FT4 assays ranging from -34.46% to -5.08%. Some of the assays agreed more closely to the RMP than others (four assays had mean bias over -25%). An equilibrium dialysis mass spectrometry-based assays had mean biases ranging from -8.86% to - 1.72% agreeing well with RMP. The data suggest that the observed bias can be effectively minimized through recalibration to the RMPs operated by the CDC CSP and the IFCC reference laboratory network. The mean TSH concentrations ranged from 0.34 to 21.56 uIU/mL with mean %CV of 11.42% (95%CI 8.07%-14.76%) suggesting good agreement between various platforms. Findings from this study will be used to customize CDC’s protocols and procedures for standardizing FT4 measurements. Presentation: Friday, June 16, 2023

Methods, Thermodynamic Applications, and Habitat Implications of Physical and Spectral Properties of Hair and Haircoats in Cattle.

The physical properties (hair diameter, hair length, haircoat depth and haircoat density) and spectral properties (absorptivity, reflectivity, transmissivity) of the hair and haircoat of cattle are inputs to heat and moisture exchange between the skin surface and the surrounding environment, and thus play a critical role in body temperature regulation. Physical and spectral properties of haircoats also play an important role in protecting the skin against penetration of ultraviolet radiation. The focus of this review is to identify accurate and consistent measurement procedures of these properties. Additionally, the paper shows the utilization of the properties on heat exchange models and their implications on voluntary thermoregulation of cattle. To highlight the effects and benefits of haircoat color vis-à-vis solar radiation and its implication on ecological habitation, a brief explanation is provided using polar bears (white haircoat in a cold environment) and black goats in a hot desert environment.

Development of an equilibrium dialysis ID-UPLC-MS/MS candidate reference measurement procedure for free thyroxine in human serum

BackgroundAccurate and reliable measurement of human serum free thyroxine (FT4) is critical for the diagnosis and treatment of thyroid diseases. However, concerns have been raised regarding the performance of FT4 measurements in patient care. Centers for Disease Control and Prevention Clinical Standardization Programs (CDC-CSP) address these concerns by creating a FT4 standardization program to standardize FT4 measurements. The study aims to develop a highly accurate and precise candidate Reference Measurement Procedure (cRMP), as one key component of CDC-CSP, for standardization of FT4 measurements. MethodsSerum FT4 was separated from protein-bound thyroxine with equilibrium dialysis (ED) following the recommended conditions in the Clinical and Laboratory Standards Institute C45-A guideline and the published RMP [20,21,23]. FT4 in dialysate was directly quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS) without derivatization. Gravimetric measurements of specimens and calibrator solutions, calibrator bracketing, isotope dilution, enhanced chromatographic resolution, and T4 specific mass transitions were used to ensure the accuracy, precision, and specificity of the cRMP. ResultsThe described cRMP agreed well with the established RMP and two other cRMPs in an interlaboratory comparison study. The mean biases of each method to the overall laboratory mean were within ±2.5%. The intra-day, inter-day, and total imprecision for the cRMP were within 4.4%. The limit of detection was 0.90 pmol/L, which was sufficiently sensitive to determine FT4 for patients with hypothyroidism. The structural analogs of T4 and endogenous components in dialysate did not interfere with the measurements. ConclusionOur ED-LC-MS/MS cRMP provides high accuracy, precision, specificity, and sensitivity for FT4 measurement. The cRMP can serve as a higher-order standard for establishing measurement traceability and provide an accuracy base for the standardization of FT4 assays.

ODP467 CDC Clinical Standardization Programs (CSP) for Free Thyroxine (FT4) to improve the accuracy and reliability of FT4 measurements in patient care and clinical research

Abstract Concerns about the accuracy and reliability of thyroid function tests, especially free thyroxine (FT4), have been stated by the clinical laboratory community for many years. Thyroid function tests are the most used tests in the U. S. and are the only means to detect and treat diseases of the thyroid. The consequences of inadequate thyroid hormone levels can be severe and are easily preventable and treatable with early detection. In response to these concerns, the CDC CSP has partnered with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and created a standardization program for FT4 based on the IFCC reference system. The CDC program aims to improve the accuracy, reliability, and comparability of current methods and, thus, improve the diagnosis, treatment, and prevention of thyroidal illnesses. There were no commutable, certified serum-based FT4 reference materials (RMs) available to assess the accuracy and reliability of FT4 assays. CDC has developed an accurate and sensitive reference measurement procedure (RMP) to assign reference values to individual donor sera. Assay manufacturers and research and clinical laboratories can use these sera to assess the analytical performance of their measurements, and monitor performance over time. In addition, the CDC's FT4 RMP is used to assign reference values to materials used in EQA/PT programs to verify that standardization efforts at the developer level translate to the end-user level. The CDC FT4 RMP uses equilibrium dialysis (ED), based on an internationally recognized ED procedure, followed by solid-phase and solvent extractions before analysis by LC-MS/MS. Certified primary RM IRMM468 is used as calibrators. The intra- and inter-day imprecision of the CDC RMP are 3. 0% and 1.1%, respectively. The CDC RMP measurement range is 3. 02–258 pmol/L, which is suitable for analysis of hypo- and hyperthyroid patients. Based on an IFCC comparison study between four FT4 RMPs, the CDC RMP's bias was within 2.5% of the all-labs mean. CDC CSP is currently conducting a comparison to further define the differences among various types of commercially available FT4 assays. A set of 40 serum RMs value assigned with the FT4 RMP are now available via the Phase 1 of the Hormone Standardization (HoSt) Program. These materials can be used for calibration and verification by assay developers. CDC CSP is currently working to develop a Phase 2 of the HoSt Program for FT4 to assist developers with certification of FT4 assays. Based on the needs and requests from the clinical community, programs for new biomarkers, such as thyroid-stimulating hormone, are also being developed. Presentation: No date and time listed

Detection and Quantification of SARS-CoV-2 Receptor Binding Domain Neutralization by a Sensitive Competitive ELISA Assay.

This protocol describes an ELISA-based procedure for accurate measurement of SARS-CoV-2 spike protein-receptor binding domain (RBD) neutralization efficacy by murine immune serum. The procedure requires a small amount of S-protein/RBD and angiotensin converting enzyme-2 (ACE2). A high-throughput, simple ELISA technique is employed. Plate-coated-RBDs are allowed to interact with the serum, then soluble ACE2 is added, followed by secondary antibodies and substrate. The key steps in this procedure include (1) serum heat treatment to prevent non-specific interactions, (2) proper use of blank controls to detect side reactions and eliminate secondary antibody cross-reactivity, (3) the addition of an optimal amount of saturating ACE2 to maximize sensitivity and prevent non-competitive co-occurrence of RBD-ACE2 binding and neutralization, and (4) mechanistically derived neutralization calculation using a calibration curve. Even manually, the protocol can be completed in 16 h for >30 serum samples; this includes the 7.5 h of incubation time. This automatable, high-throughput, competitive ELISA assay can screen a large number of sera, and does not require sterile conditions or special containment measures, as live viruses are not employed. In comparison to the ‘gold standard’ assays (virus neutralization titers (VNT) or plaque reduction neutralization titers (PRNT)), which are laborious and time consuming and require special containment measures due to their use of live viruses. This simple, alternative neutralization efficacy assay can be a great asset for initial vaccine development stages. The assay successfully passed conventional validation parameters (sensitivity, specificity, precision, and accuracy) and results with moderately neutralizing murine sera correlated with VNT assay results (R2 = 0.975, n = 25), demonstrating high sensitivity.

Indoor noise A-level assessment related to the environmental noise spectrum on the building facade

There is a growing body of research reporting that unwanted indoor noise can negatively affect the well-being of the occupants. According to the World Health Organisation (WHO), indoor guideline values in dwellings are 30 dBA (LAeq,night,indoor), which in turn should also include appropriate airborne and impact sound insulation of façades. Such low noise values in dwellings are difficult to measure, which is why indirect methods of indoor noise assessment (including the accurate calculation and measurement procedures for sound insulation of dwelling façades) are an important issue worth investigating. Therefore, in this paper, a new methodology of how indoor noise A-level may be assessed by applying the outdoor noise monitoring and standardized sound insulation measurement of the façade is proposed. It also provides an overview of the existing difficulties in performing accurate calculations of the sound insulation on the façades. The proposed calculation procedure for indoor equivalent noise A-level estimation is also evaluated. The highest accuracy was achieved by adding to the calculation a specific spectrum adaptation term Cspec,100-3150 for the noise emitted façade in-situ instead of a standard spectrum adaptation term Ctr,100-3150, defined by the unified spectra corresponding to road traffic, and suggested by the ISO 717–1 for the calculations. The specific spectrum adaptation term was calculated based on the averaged spectrum of the specific noise events (different from road traffic noise) that contribute to the outdoor environment at the locations where measurements were carried out. When assessed in such a way, the equivalent sound levels of indoor noise, which are produced by different types of outdoor noise sources, show a good agreement with the directly measured levels indoors.

A Simple Chamber Design for Calibrating Weiss Saturometers and Recommendations for Measuring and Reporting Total Dissolved Gases

AbstractTotal dissolved gas (TDG) supersaturation downstream of features such as hydroelectric dams can cause harmful bubbles to grow in the tissues of aquatic animals. TDG supersaturation is often measured using Weiss saturometers, but information on the calibration and use of these instruments is scarce in the literature. Regular calibration, accurate measurement procedures, and standardized TDG reporting are important for generating reliable measurements that are easily interpreted. We provide a description of low‐cost calibration equipment that practitioners can build themselves and recommend a specific two‐point calibration protocol. We also recommend methods for the more accurate measurement and reporting of TDG.

CDC Clinical Standardization Programs (CSP) for Free Thyroxine (FT4) to Improve the Accuracy and Reliability of FT4 Measurements in Patient Care and Clinical Research

Reliable FT4 measurement is critical to assess thyroid function and diagnose and treat thyroid disorders. The Partnership for the Accurate Testing of Hormones (PATH) categorizes FT4 as a biomarker in high need for standardization, and currently high inter-assay variability restricts the interpretation of FT4 results in patient care to assay-specific reference intervals. The CDC CSP has partnered with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and PATH to create a standardization program for FT4 to improve accuracy, reliability, and comparability of current methods and thus to improve diagnosis, treatment and prevention of thyroidal illnesses. Currently, there are no serum FT4 reference materials available to assess the accuracy and reliability of FT4 assays. CDC has developed an accurate and sensitive reference measurement procedure (RMP) to create commutable serum reference materials with FT4 target values. Assay manufacturers, research and clinical laboratories can use these reference materials to assess their calibration, certify the analytical performance of their measurements, and monitor performance over time by collaborating with CDC CSP. The CDC FT4 RMP uses equilibrium dialysis (ED) with LC-MS/MS based on an internationally recognized ED procedure[1] followed by solid-phase and solvent extractions. Certified primary reference material IRMM468 was used to prepare calibrators. Chromatographic separation is achieved with a gradient of methanol and water with 0.1% formic acid. FT4 is quantified using positive electrospray ionization in positive mode. The intra- and inter-day imprecision of the CDC RMP are 3.0% and 1.1%. A comparison among FT4 RMPs resulted in a +2.5% bias for the CDC RMP to the mean for all labs. The CDC RMP measurement range was 3.02-258 pmol/L and thus suitable for analysis of hypo- and hyperthyroid patients. The CDC FT4 RMP demonstrates good accuracy and precision, and can be used as a viable accuracy base to which routine methods can be compared. An initial comparison study of a commercially available FT4 immunoassay (IA) and the CDC RMP with 24 samples (7.98-109 pmol/L) indicated a mean bias of -37.7%, further indicating a need for standardization. Findings from an IFCC study suggest that alignment of IA measurements to a FT4 RMP can improve comparability and would allow for a uniform reference interval for FT4.[2] CDC CSP established a new standardization program for FT4 to address the needs of the community and assist with improving test comparability and reliability.1. Clin. Chem. Lab. Med. 2011, 49: 1275-81. 2. Clin. Chem. 2017, 63: 1642-52.

Long-Term Longitudinal Stability of Kidney Filtration Marker Measurements: Implications for Epidemiological Studies and Clinical Care.

Establishment and improvement of glomerular filtration rate estimating equations requires accurate and precise laboratory measurement procedures (MPs) for filtration markers. The Advanced Research and Diagnostic Laboratory (ARDL) at the University of Minnesota, which has served as the central laboratory for the Chronic Kidney Disease Epidemiology Collaboration since 2009, has implemented several quality assurance measures to monitor the accuracy and stability of filtration marker assays over time. To assess longitudinal stability for filtration marker assays, a 40-sample calibration panel was created using pooled serum, divided into multiple frozen aliquots stored at -80 °C. ARDL monitored 4 markers-creatinine, cystatin C, beta-2-microglobulin (B2M) and beta-trace protein-measuring 15 calibration panel aliquots from 2009 to 2019. Initial target values were established using the mean of the first 3 measurements performed in 2009-10, and differences from target were monitored over time. New MPs for cystatin C and B2M were added in 2012, with target values established using the first measurement. The mean percentage difference from mean target values across time was <2% for all original MPs (-0.59% for creatinine; -0.94% for cystatin C; -0.82% for B2M; 1.24% for beta-trace protein). Close monitoring of filtration marker trends with a calibration panel at ARDL demonstrates remarkable long-term stability of the MPs. Routine use of a calibration panel for both research studies and clinical care is recommended for filtration markers where longitudinal monitoring is important to detect analytical biases, which can mask or confound true clinical trends in patients.

A General and Accurate Measurement Procedure for the Detection of Power Losses Variations in Permanent Magnet Synchronous Motor Drives

The research of innovative solutions to improve the efficiency of electric drives is of considerable interest to challenges related to energy savings and sustainable development. In order to successfully validate the adoption of new and innovative software or hardware solutions in the field of electric drives, accurate measurement procedures for either efficiency or power losses are needed. Moreover, high accuracy and expensive measurement equipment are required to satisfy international standard prescriptions. In this scenario, this paper describes an accurate measurement procedure, which is independent of the accuracy of the adopted instrumentation, for the power losses variations involved in electrical drives, namely ΔΔP, useful to detect the efficiency enhancement (or power losses reduction) due to the real-time modification of the related control algorithm. The goal is to define a valuable measurement procedure capable of comparing the impact of different control algorithms on electric drive performance. This procedure is carried out by experimentally verifying the action of different control algorithms by the use of a Field Oriented Control (FOC) with different values of the direct-axis current component (i.e., Id = 0 A and Id = −1 A) applied for fixed working conditions in terms of speed and load torque. Two different measurement systems of power losses, each one characterized by different accuracy and cost, are taken into account for the validation of the proposed method. An investigation is, then, carried out, based on the comparison between the measurements acquired by both instrumentations, for different working conditions in terms of load and speed, highlighting that the uncertainty generated by systematic errors does not affect the ΔΔP measurements. The results reported in this work demonstrate how the ΔΔP parameter can be used as a valuable index for the characterization of the power drive system, which can also be evaluated even with low-accuracy instrumentation.

MON-130 Improving the Accuracy and Reliability of Free Thyroxine (FT4) Measurements Through the CDC Clinical Standardization Programs (CSP)

Reliable free thyroxine (FT4) measurements are essential for assessing thyroid function and for correctly diagnosing and treating thyroid disorders. Thyroid hormones play an important role in normal brain development of the fetus, and abnormal FT4 during pregnancy is associated with adverse pregnancy outcomes. Standardization of FT4 measurements, is critical to improving the accuracy and reliability of current methods and thus to improve diagnosis, treatment and prevention of thyroidal illnesses. Currently, there are no serum-based reference materials available for FT4 to assess the accuracy and reliability of FT4 assays. CDC CSP is collaborating with the International Federation of Clinical Chemistry and Laboratory Medicine, and the Partnership for the Accurate Testing for Hormones to address these issues through development of an accurate and sensitive higher-order Reference Measurement Procedure (RMP) for FT4 that will be used to assign target value to serum-based materials. The CDC CSP FT4 reference method is using equilibrium dialysis in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS). FT4 in serum is isolated from the binding proteins in 1 mL equilibrium dialysis cells for 4 hours at 37oC. FT4 is further isolated by extractions prior to LC-MS/MS analysis. To determine the concentration of FT4 in serum, certified primary reference materials are used to prepare calibration materials. Chromatographic separation is achieved using a C18 reverse phase column with a gradient of methanol and water with 0.1% formic acid. Quantification by selective reaction monitoring is performed in the positive mode using electrospray ionization. Two transitions are monitored for each analyte and internal standard, and triplicate injections are used to minimize instrument instability. The within- and between-day imprecision for the CDC RMP are 2.2–3.9% and 1.8–2.6%, respectively. By comparisons with the RMPs at Ghent University in Belgium, Radboud University Medical Center in the Netherlands, and the Reference Material Institute for Clinical Chemistry Standards in Japan, the CDC RMP reported a bias within +2.5% of the mean for all labs. Factors affecting measurement accuracy were investigated, to maximize recovery for optimum performance of the method. FT4 was detectable in all samples, and thus, suitable for analysis of hypo-, eu-, and hyperthyroid patients. A comparison among hypo-, eu-, and hyperthyroid patients of a commercially available immunoassay and the CDC RMP indicated a mean bias of -37.7%. The CDC CSP has also evaluated the RMP for accurate measurement of FT4 in pregnant individuals. This candidate reference method for FT4 in serum demonstrates good accuracy and precision, and can be used as a viable base for accuracy to which routine methods for FT4 can be compared. 1. Van Houcke, S.K., et. al. Clin. Chem. Lab. Med. 2011, 49, 1275–1281.

MON-602 Improving The Accuracy And Reliability Of Free Thyroxine Measurements Through The CDC Clinical Standardization Programs

Reliable free thyroxine (FT4) measurements are essential for assessing thyroid function and properly diagnosing and treating thyroid disorders. Although FT4 measurements are used extensively in research and clinical practice, the accuracy and reliability of current methods prevent correct detection, treatment, and prevention of thyroid disorders in patient care, making standardization of FT4 measurements a priority. Currently, there are no serum-based reference materials commercially available for FT4. CDC Clinical Standardization Programs (CDC CSP) is working with the Committee for Standardization of Thyroid Function Tests (C-STFT) of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the Partnership for the Accurate Testing for Hormones (PATH) to address these issues through development of an accurate and sensitive higher-order Reference Measurement Procedure (RMP) for FT4. The CDC Clinical Reference Laboratory has developed a FT4 method using a modified equilibrium dialysis procedure. 1 FT4 in serum was isolated from the binding proteins in 1 mL equilibrium dialysis cells for 4 hours at 37oC. Dialysates were spiked with internal standard (thyroxine-13C6) and further isolated with extractions prior to injection on a liquid chromatography tandem mass spectrometry (LC-MS/MS) instrument. Bracketed calibration and primary reference materials were used to determine the concentration of FT4 in serum. Chromatographic separation was achieved using a C18 reverse phase column with a gradient of water and acetonitrile with addition of 0.1% formic acid. Quantification by selective reaction monitoring (SRM) analysis was performed in the positive ion mode using electrospray ionization (ESI). Two transitions were monitored for each analyte and internal standard, and triplicate injections were used to minimize any instrument instability. The proposed RMP has been evaluated and optimized for precision, accuracy, and sensitivity. The within-day and between-day imprecision are 2.5-2.9% and 0.9-1.3%, respectively. By comparisons with the Reference Laboratory at the University of Ghent, the proposed CDC RMP reported a bias within +1.0%. Factors affecting measurement accuracy were investigated and steps were taken to maximize recovery for optimum performance of the method. FT4 was detectable in all samples and thus suitable for analysis of hypo-, eu-, and hyperthyroid patients. To ensure accurate values are reported for FT4, careful consideration is needed for all steps of sample preparation and analysis. This candidate reference method for FT4 in serum demonstrates good accuracy and precision, and as such this method can be used as a viable base for accuracy to which routine methods for FT4 can be compared. 1. Van Houcke, S.K., et. al. Clin. Chem. Lab. Med. 2011, 49, 1275-1281.

Development and validation of a simple isotope dilution-liquid chromatography-tandem mass spectrometry method for detecting vitamins A and E in serum and amniotic fluid

Accurate and simple measurements of vitamins A(all-trans retinol) and E(α-tocopherol) are essential for ensuring the appropriate supplementation and diagnosis of diseases related to vitamin A or E deficiency. High-performance liquid chromatography is a widely used method; however, few studies have reported an isotope dilution-liquid chromatography tandem mass spectrometry method(ID-LC–MS/MS) for detecting vitamins A and E in serum, let alone amniotic fluid. Here, we developed and validated an accurate and precise measurement procedure based on ID-LC–MS/MS for detecting vitamins A and E in serum and amniotic fluid. In this method, only 50 μL of serum/amniotic fluid was used. After simple protein precipitation and extraction, all-trans retinol and α-tocopherol were analyzed by ID-LC–MS/MS using positive electrospray ionization in multiple reaction monitoring mode. Vitamins A and E status was evaluated using the validated method in 65 apparently healthy volunteers and 58 pregnant women in the second trimester. The within-run and total coefficients of variation(CVs) of all-trans retinol were 2.8%–3.9% and 4.7%–6.0%, respectively, in serum; and 5.0%–7.3% and 5.4%–7.4%, respectively, in amniotic fluid ; and the values for α-tocopherol were 3.2%∼4.3% and 3.3% ∼ 4.9% in serum and 6.2%–7.1% and 8.0%–9.1% in amniotic fluid. The accuracy bias of the ID-LC–MS/MS method was less than 5.0% for both all-trans retinol and α-tocopherol. Mean levels of all-trans retinol and α-tocopherol in the 65 apparently healthy volunteers were 0.504±0.126 mg/L and 12.038±2.501 mg/L, respectively. A significant positive correlation was observed between serum and amniotic fluid all-trans retinol (r=0.277, P=0.035) in the pregnant women in the second trimester, while no correlation with α-tocopherol (P=0.290). None of the volunteers developed vitamin A or E deficiency. In conclusion, an ID-LC–MS/MS method for measuring both serum and amniotic fluid all-trans retinol and α-tocopherol levels was developed. This method is accurate and simple, and can be used clinically to monitor vitamins A and E status.

Assessment of a colorimetric method for the measurement of low concentrations of peracetic acid and hydrogen peroxide in water

The recent growing interest in peracetic acid (PAA) as disinfectant for wastewater treatment demands reliable and readily-available methods for its measurement. In detail, the monitoring of PAA in wastewater treatment plants requires a simple, accurate, rapid and inexpensive measurement procedure. In the present work, a method for analyzing low concentrations of PAA, adapted from the US EPA colorimetric method for total chlorine, is assessed. This method employs N,N-diethyl-p-phenylelnediamine (DPD) in the presence of an excess of iodide in a phosphate buffer system. Pink colored species are produced proportionally to the concentration of PAA in the sample. Considering that PAA is available commercially as an equilibrium solution of PAA and hydrogen peroxide (H2O2), a measurement method for H2O2 is also investigated. This method, as the one for the determination of PAA, is also based on the oxidation of iodide to iodine, with the difference that ammonium molybdate Mo(VI) is added to catalyze the oxidation reaction between H2O2 and iodide, quantifying the total peroxides (PAA+ H2O2). The two methods are suitable for concentration ranges from about 0.1–1.65 mg L−1 and from about 0.3–3.3 mg L−1, respectively for PAA and H2O2. Moreover, the work elucidates some relevant aspects related to the operational conditions, kinetics and the possible interference of H2O2 on PAA measurement.

A Simple and Accurate Measurement Procedure for Serum Chloride by Ion Chromatography and Bias Evaluation of Six Ion Selective Electrode Measurements in China.

Chloride is the main anion in human body. A simple and accurate method for serum chloride measurement was developed using ion chromatography (IC) in China. In the measurement, serum samples were diluted 500 times with water, filtered and injected into ion chromatography column. A mixed eluent (2 mmol/L CO32- + 12 mmol/L OH-) was used and peak area signal was collected. Five calibrators made from Standard Reference Material (SRM) 919b were used in the bracketing method. The IC method was applied as the comparative method and six ion selective electrode (ISE) measurement systems were evaluated using 60 individual patient serums. The IC method was proven to be accurate. The precision was 0.18% - 0.30%, the recovery was 99.66% - 100.60%, the bias was 0.19% to -0.06%, and the related expanded uncertainty was 0.775% (k = 2). The precisions of the ISE systems were smaller than the 0.9% tolerable CV except for the Beckman DXC (0.91% - 1.16%). In comparison, the results of linear regression analysis showed that the correlation coefficients were 0.9876 to 0.9979. For all systems, the range of mean biases was -5.96 - 1.48 mmol/L (-5.57% - 1.36%); the expected biases at the medical decision levels were -4.97% - 0.84% at 90 mmol/L and -6.02% - 1.76% at 120 mmol/L. All biases of the Beckman AU met the requirement of within ± 1.5%. The IC measurement method is proven to be of high precision and trueness, and the quality of routine ISE measurement of serum chloride still needs significant improvement. The establishment of the IC method can improve the measurement quality and promote its standardization process in China.

Comparison of electrical equivalent circuits of human tooth used for measuring the root canal length

An accurate determination of the root canal length, which is the most critical procedure in the endodontic treatment of a tooth, is commonly performed nowadays by electronic apex locators which are based on electrical impedance measurements. In this paper tooth impedances were measured in vitro on extracted tooth in alginate material using HP 4284A LCR meter and a specially designed stalk with a micrometer for precise file positioning. In order to develop a more accurate measurement procedure human tooth was modeled by electrical equivalent circuit. Four new equivalent circuits comprising of resistors, capacitors and constant-phase elements were proposed in this paper and compared with four previously suggested circuits. Elements of equivalent circuits were determined by complex nonlinear least squares fitting using LEVM software. Different quality factors were defined to describe the fit quality of a certain equivalent circuit at each file position. The overall fitting efficiency in the region of file positions of interest was calculated as well. A detailed discussion was given on equivalent circuit parameters that can be used to measure the root canal length. Upon these results the most appropriate equivalent circuit was selected and a new measurement procedure was proposed.

Relationships between marbling measures across principal muscles

As marbling is a principal input into many grading systems it is important to have an accurate and reliable measurement procedure. This paper compares three approaches to measuring marbling: trained personnel, near infrared spectroscopy (NIR) and image analysis. One 25mm slice of meat was utilised from up to 12 cuts from 48 carcasses processed in Poland and France. Each slice was frozen to enable a consistent post-slaughter period then thawed for image analysis. The images were appraised by experienced beef graders and the sample used to determine fat content by NIR. We find that image analysis based marbling measures are capturing something different to trained personnel and that there is a strong relationship between near infrared spectroscopy and trained personnel. Finally, we demonstrate that marbling measures taken on one muscle can be predictive of marbling in other muscles in the same carcase. This is particularly important for cut based models such as the Meat Standards Australia system.

Flow development behind a swirl generator in a hot-water standard measuring facility for large volume rates

The flow development behind a swirl generator according to EN 14154 of a gravimetric cold- and hot-water standard measuring facility is shown at different positions by measurements carried out using Stereoscopic Particle Image Velocimetry (SPIV). Hereby, the effects of the swirl generator downstream are shown, and the prevailing flow condition is evaluated by means of characteristic values.SPIV is suited as a fast and accurate measurement procedure for the high-resolution determination – temporally and spatially – of 3C velocity profiles in piping.

Detection of true IgE-expressing mouse B lineage cells.

B lymphocyte immunoglobulin heavy chain (IgH) class switch recombination (CSR) is a process wherein initially expressed IgM switches to other IgH isotypes, such as IgA, IgE and IgG. Measurement of IgH CSR in vitro is a key method for the study of a number of biologic processes ranging from DNA recombination and repair to aspects of molecular and cellular immunology. In vitro CSR assay involves the flow cytometric measurement surface Ig expression on activated B cells. While measurement of IgA and IgG subclasses is straightforward, measurement of IgE by this method is problematic due to soluble IgE binding to FcεRII/CD23 expressed on the surface of activated B cells. Here we describe a unique procedure for accurate measurement of IgE-producing mouse B cells that have undergone CSR in culture. The method is based on trypsin-mediated cleavage of IgE-CD23 complexes on cell surfaces, allowing for detection of IgE-producing B lineage cells by cytoplasmic staining. This procedure offers a convenient solution for flow cytometric analysis of CSR to IgE.