Reproducibility Standard Deviation Research Articles

Simultaneous determination of 13 biogenic amines and their metabolites in liquid fermented food by HPLC-QTRAP-MS without derivatization

Biogenic amines and their metabolites (BAs) are among the most frequently detected compounds in liquid fermented foods, raising significant concerns about the potential risks they pose. To rapidly and selectively determine BAs, this study proposed and validated a method for the simultaneous determination of 13 BAs in liquid fermented foods using high performance liquid chromatography-triple quadrupole/linear ion trap mass spectrometry (HPLC-QTRAP-MS) without derivatization. The simultaneous separation and determination of histamine (HIS), tyramine (TYR), putrescine (PUT), octopamine (OCT), 2-phenylethylamine (2-PHE), dopamine (DOP), spermidine (SPD), epinephrine (EPI), agmatine (AGM), 5-hydroxytryptamine (5-HYD), tryptamine (TRY), L-noradrenaline (L-NOR), cadaverine (CAD) were achieved using a Waters Atlantis Premier BEH Z-HILIC (1.7 μm particle size, 100 mm × 2.1 mm id) column with a mobile phase consisting of water (containing 0.025 % formic acid) and acetonitrile (containing 0.1 % formic acid). The analysis of target compounds was performed with electrospray ionization (ESI) in positive ion mode, multiple reaction monitoring (MRM), information dependent acquisition (IDA), enhanced product ion (EPI), and multi-step mode analysis combined with EPI library searching. To enhance the extraction efficiency of BAs, factors such as extraction solvent, filter membranes, extraction methods, pH, oscillation speed, time and temperature were systematically investigated. The results demonstrated that the method exhibited low limits of detection (LOD) and quantification (LOQ), ranging from 0.05 to 2.00 µg/L and 0.16 to 6.60 µg/L, respectively. The method also showed satisfactory reproducibility, with intra-day and inter-day relative standard deviations ranging from 0.90 % to 3.80 % and 2.65 % to 8.27 %, respectively. Additionally, it had a broad linear range from 0.05 to 200.00 µg/L with excellent linearity (R>0.99) and an average recovery rate between 65.68 % and 115.14 %. Overall, the results demonstrated that the established method was convenient to operate, offered a short analysis time, and achieved high accuracy and sensitivity. It met the qualitative and quantitative requirements for detecting 13 BAs in liquid fermented food, thus providing strong technical support for BAs detection.

Comparison of the repeatability and reproducibility of corneal thickness mapping using optical coherence tomography according to tear film break-up time

BackgroundTo compare the repeatability and reproducibility of corneal and corneal epithelial thickness mapping using anterior segment optical coherence tomography (AS-OCT) according to tear film break-up time (TBUT).MethodsThe included eyes were divided into three subgroups according to TBUT (group 1: TBUT ≤ 5 s, group 2: 5 s < TBUT ≤ 10 s, and group 3: TBUT > 10 s). All eyes were imaged separately thrice by two operators to obtain the thickness maps (TMs) of the cornea and corneal epithelium based on spatial zones encompassing a 9-mm-diameter area. Each TM consisted of 25 areas. Intraoperator (repeatability) and interoperator (reproducibility) standard deviations (Sws), coefficients of variation (CoVs), and intraclass correlation coefficients (ICCs) among the tests were calculated and compared in all the areas.ResultsAltogether, 132 eyes of 67 subjects were included (50, 47, and 35 eyes in groups 1, 2, and 3; respectively). The ICCs of corneal epithelial thickness and corneal thickness were > 0.75 in most of the areas. Pairwise comparisons showed that AS-OCT exhibited lower repeatability in group 1 than in groups 2 and 3 (P < 0.05). However groups 2 and 3 showed similar results. Sws and CoVs of corneal epithelial thickness exhibited no significant interoperator differences. While no significant differences were observed in corneal thickness in most of the areas.ConclusionsTBUT significantly influences the repeatability of corneal and corneal epithelial thickness measurements. Poor tear film stability requires careful evaluation of corneal epithelial thickness.

Determination of stearoyl lactylate in starchy products using liquid chromatography method after hydrazine derivation

Sodium stearoyl lactylate (SSL) is an emulsifying agent that significantly enhances&amp;nbsp;dough volume, surface area, and structural integrity while also increasing air retention even&amp;nbsp;with a small amount of yeast added. Its remarkable properties extend to improving&amp;nbsp;preservation quality, facilitating finer slicing, and inhibiting microbial proliferation, thereby&amp;nbsp;reducing shortening. Owing to these benefits, SSL finds extensive application in the production of starch-containing industrial products. In this study, SSL was quantified&amp;nbsp;following the hydrazine derivatization stage using the HPLC-PDA method. The lactate&amp;nbsp;derivative was analyzed on a C18 column with a gradient program comprising 0.1% formic&amp;nbsp;acid and acetonitrile. The method was validated and met the AOAC requirements for good&amp;nbsp;linearity (R2 = 1). The limits of detection (LOD) and limits of quantification (LOQ) were&amp;nbsp;2.00 mg/kg and 6.66 mg/kg SSL for bread samples; 1.45 mg/kg and 4.82 mg/kg for biscuit&amp;nbsp;samples. Precision was performed on spiked bread and biscuit matrices with relative&amp;nbsp;standard deviations of repeatability RSDr = 1.91% and 3.07%, respectively; the relative&amp;nbsp;standard deviation of reproducibility (RSDR) was 4.22% and 3.47%. Recovery values ranged&amp;nbsp;between 95.1% and 105% for bread and 95.4% to 104.7% for biscuits. The validated method&amp;nbsp;was subsequently applied to analyze SSL content in 20 different starchy products purchased in the Hanoi market.

Implementation of ISO 16140-3:2021 for Enumeration of Enterobacteriaceae in Food Products

Method verification is one of the steps required to ensure that all methods used meet the standards required for data reliability and accuracy in a laboratory that implements Good Laboratory Practices (GLP). In accordance with ISO 16140-3:2021, the method verification for microbiology testing implemented by calculating the Intralaboratory Reproducibility Standard Deviation (SIR) for implementation verification and eBias value for food item verification. Method verification for enumeration of Enterobacteriaceae in food products using ISO 16140-3 has never been carried out at the Indonesian Food and Drug Authority (FDA) laboratories. Therefore, verification of this method needs to be performed. This study aimed to verify the ISO 21528-2:2017 as reference method for enumeration of Enterobacteriaceae in food products by colony count technique. The selected food item for implementation verification was pasteurized milk while for food item verification, the selected food items were yogurt, traditional preserved egg (telur pindang), sweet and hard candy, seasoning dry powder, worcester sauce and cassava chips. All of selected foods were artificially contaminated with Escherichia coli WDCM 00012. The SIR value obtained was 0.12 ≤ 2× 0,18 (lowest mean value of SR from ISO 21528-2:2017), indicating that the acceptability limit for the implementation verification was met. While the eBias value for all selected food item were less than 0,5 log10, thus the verification study in the National Quality Contol Laboratory of Drug and Food (NQCLDF), Indonesian FDA, meets the acceptance criteria defined in the standard ISO 16140-3:2021.

Matrix uncertainty in feeding-stuffs according to ISO 19036:2019

Abstract The combined measurement uncertainty of quantitative microbiological methods in the area of food and feed is calculated according to ISO 19036:2019 from the technical (intra-laboratory reproducibility standard deviation), the distributional and the matrix uncertainty (umatrix) of the respective sample type. The matrix uncertainty is a property of a certain sample type and independent of the individual laboratory and analysis, respectively. This study broadens the, so far, comparatively small data base on matrix uncertainties for feeding stuffs by investigating 20 representative feed types in 46 sample series. Thereby, difficulties and limitations arising from sample preparation, the selection of different microbial groups (bacteria and fungi) and the nature of different feed types are highlighted. In addition, the applicability with industrially added feed additives (e.g. probiotics) is discussed. In conclusion, the postulated independence and scope of the matrix uncertainty are limited in these respects.

Collaborative Study for Iodine Monitoring in Mandatory Direct-Iodized Sauce in Thailand.

Direct iodization in fish sauce, soy sauce, and seasoning sauces plays a crucial role in optimizing the iodine intake of Thailand's people. However, determining the iodine content to ensure that these sauces meet the standard of Thailand's Food and Drug Administration (FDA) is challenging. In this study, all local laboratories equipped with inductively coupled plasma-mass spectrometry (ICP-MS) and with experience in iodine analysis by any analytical method were invited to participate in a hands-on training workshop and two rounds of interlaboratory comparison. The aim was to improve laboratory performance and assess the potential for iodine monitoring for mandatory direct-iodized sauces. All target laboratories participated in this study. The hands-on training workshop harmonized the analytical method and increased the capacity of participating laboratories. Most laboratories (7/8) achieved satisfactory performance for six test samples based on interlaboratory comparison. Samples were extracted by tetramethylammonium hydroxide (TMAH), with the presence of 6% 2-propanol, 0.01% triton X-100, internal standard, and iodine determination in direct-iodized sauces by ICP-MS. The reproducibility standard deviation (SL), after the removal of outlier results for iodine content, was 7-22% iodine at a level of 0.03-4.81 mg/L. Moreover, the Thai FDA's judgment range for official control activities should expand the range of 2-3 mg per 1 L (ppm) by at least 22%.

New Method for Quality Assurance of Asphalt Pavements Using a Low-Activity Nuclear Density Gauge

A method was developed for measuring the density of finished asphalt pavement layers using a low-activity nuclear density gauge (LNDG) that is exempt from licensing and other nuclear regulatory burdens in the United States. The gauge using this method, LNDG/TM, requires operating in transmission mode—inserting the gamma-ray source at 0.5 in. (12.5 mm) into the asphalt layer. This method is fast and less destructive than the industry-accepted core-extraction (CE) method—CE followed by laboratory density measurement. This paper presents the measurement principles, method, and properties of this gauge. For evaluating the method, several laboratory and field studies were conducted in North Carolina, USA. For surface course measurements, the repeatability standard deviation of the measurement was 0.3 lb/ft3 (5 kg/m3), and the reproducibility standard deviation was 0.5 lb/ft3 (8 kg/m3). The measurement sensitivity is similar to that of the CE method. The depth of measurement of the gauge is about 2 in. (50 mm). For layers with mean texture depth from 0.5 to 1 mm, the density error is less than 2 lb/ft3 (32 kg/m3). The LNDG/TM requires a density correlation method to provide accurate measurements. Following this method, LNDG/TM density measurements showed a good correlation (correlation coefficient = 0.9) and agreement (root mean square error = 1.3 lb/ft3 [21 kg/m3]) to that using the CE method. These findings indicate that LNDG/TM is a promising alternative to the CE method and has the advantage of testing more locations for acceptance testing.

Interlaboratory comparison of ISO 23351-1: speech level reduction of furniture ensembles

International standard ISO 23351-1:2020 describes a laboratory method for declaring the speech level reduction DS,A of furniture ensembles (such as partially enclosed pods or workstations) and enclosures (such as phone booths). Such products are increasingly used in lounges, hospitals, education buildings, open-plan offices, and similar places to provide local places of improved speech privacy or concentration. DS,A describes how much the product reduces the A-weighted sound power level of standard speech to the exterior space. The method is based on repeated application of ISO 3741 standard. The purpose of our study was to determine the precision of the ISO 23351-1 method for two extreme kinds of products that the method covers: a workstation and a phone booth. Eight independent laboratories from six countries participated in the accuracy experiment. Two specimens were circulated in these laboratories and tested according to ISO 23351-1. Measured DS,A values varied from 3.7 to 5.5 for the workstation and from 27.2 to 30.3 dB for the booth. The corresponding reproducibility standard deviations were 0.6 and 1.1 dB, respectively. The results have been exploited in the ISO 23351-1 standard.

Semi-Automated Enzymatic Determination of Ethanol in Beverages: Collaborative Study for RIDA&amp;#174;CUBE Ethanol

Easy and quick methods to quantify ethanol reliably in beverages are always important. In 2022, the EnzytecTM Liquid Ethanol test kit was approved as AOAC Official MethodSM 2017.07 Final Action after a collaborative study was conducted with different beverages such as kombucha, juices, and beer. During set-up of this collaborative test, small sized companies asked to include the RIDA®CUBE Ethanol/RIDA®CUBE SCAN device since it is easy to use, suitable for a few samples only and contains the identical reagents as the EnzytecTM Liquid system. It is applicable to quantify ethanol in diluted kombucha, fruit juices, and alcohol-free beer samples around 0.5% alcohol-by-volume within 12 min. The overall relative reproducibility standard deviation across a wide concentration range for kombucha, was calculated to be 6.29%. Analysis of juices and beer showed an overall higher variation with an estimated overall RSD(R) value by regression of 14.4%. The data obtained by this collaborative study show that the RIDA®CUBE Ethanol in combination with the RIDA®CUBE SCAN device is suitable to quantify ethanol from matrices representing important alcohol-free liquid food categories.

Determination of Ethanol in Food by Enzymatic Method Enzytec™ Liquid Ethanol, Collaborative Study: Final Action 2017.07.

Enzytec™ Liquid Ethanol was approved as AOAC Official MethodSM2017.07 First Action in September 2017 and is now further characterized by a collaborative study using the manual and automated version of the test. It is applicable to quantify ethanol in diluted or undiluted kombucha, fruit juices, vegetable juices, and alcohol-free beer samples around 0.5% ABV within 20 min using two ready-to-use reagents and measurement of absorbance at 340 nm. The overall relative reproducibility standard deviation across a wide concentration range for kombucha was calculated to be 6.99% by modeling the reproducibility standard deviation by the mean concentration for each of the six kombucha pairs by a linear regression. Analysis of juices and beer showed an overall higher variation with an estimated overall RSD(R) value by regression of 10.1%. Mean recovery of aqueous ethanol reference solutions tested by each participant was between 100 and 103%. The data obtained by this collaborative study show that the EnzytecTMLiquid Ethanol is suitable to quantify ethanol from matrices representing important alcohol-free liquid food categories. The EnzytecTMLiquid Ethanol was approved as AOAC Method 2017.07 Final Action.

International ring trial to validate a new method for testing the antimicrobial efficacy of domestic laundry products.

Due to greater environmental awareness, domestic laundry habits are changing, and antimicrobial control by chemical methods has become an essential factor to compensate for the use of lower temperatures during washing machine cycles. Disinfectants added to laundry detergents are a preventive strategy to reduce the transmission of bacteria, fungi, and viruses in the home, correct aesthetic damage (e.g., spotting, discolouration, and staining), and control the microbial contamination that leads to malodour. In Europe, disinfectants are regulated by the EU Biocidal Products Regulation (No. 528/2012), which stipulates that antimicrobial efficacy must be evaluated according to standardized methods. Current European standards for laundry sanitization only apply to clinical settings (EN 16616: 2015) and are restricted to the main wash cycle. Therefore, there is a gap in the EU standards regarding the testing of product efficacy in household laundering. With the aim of addressing this gap, an international ring trial was organized to evaluate the robustness of a new method (prEN 17658) designed to test the efficacy of antimicrobial laundry products in a domestic setting. The seven participating laboratories were equipped with 5 different laboratory-scale devices to simulate the washing process, and they evaluated 7 microbial parameters for 2 experimental conditions and 3 levels of active substance. The analysis of data according to ISO 5725–2 and ISO 13528 demonstrated that the method was robust. All reproducibility standard deviation values were between 0.00 and 1.40 and the relative standard deviation indicates satisfactory reproducibility. Values of logarithmic reduction ranged from less than 2 log10 for tests with water to more than 5 log10 when disinfectants were added. The evidence generated by the ring trial was presented in a proposal for a standardized method under CEN/TC 216, in which the SOP used in the ring trial is referred to as the prEN 17658 phase 2 step 2 test method covering chemothermal textile disinfection in domestic settings.

Single and multi-laboratory validation of a droplet digital PCR method

The authorisation of genetically modified food and feed in the EU is subject to the provision of evidence of safety and of the availability of reliable analytical methods. These methods represent an essential tool for official laboratories to enforce a harmonised market control.Here the validation of droplet digital PCR (dPCR) methods has been performed for studying if the performance and acceptance parameters set by EU and other international guidelines for the analysis of genetically modified organisms (GMO) in food and feed are suitable and achievable also with such methods. The single-laboratory validation study showed that performance requirements set for GMO analysis by real time PCR can also be used to assess dPCR-based methods. Moreover, trueness and precision were assessed for both simplex and duplex formats in a multi-laboratory validation study organised according to international standards. Overall, the data on trueness, repeatability and reproducibility precision resulting from the collaborative study are satisfying the acceptance criteria for the respective parameters as stipulated in the EU and other international guidance such as the Codex Committee on Methods of Analysis and Sampling (CCMAS). For instance, the duplex droplet dPCR method for MON810 showed relative repeatability standard deviations from 1.8% to 15.7%, while the relative reproducibility standard deviation was found to be between 2.1% and 16.5% over the dynamic range studied. Moreover, the relative bias of the dPCR methods was well below 25% across the entire dynamic range.In addition, other aspects supporting the application of digital PCR for the control of GMOs on the market were experimentally assessed such as the conversion of the measurement results from copy number ratio to mass fraction, the influence of the DNA extraction step and of the ingredient content. It was found that the DNA extraction step added only a limited contribution to the variability of the measurement results under the studied conditions. The decreasing amount of the target ingredient content may decrease the level of precision of the method, although within the acceptance range of GMO performance parameters.

Interlaboratory Reproducibility of Contour Method Data in a High Strength Aluminum Alloy

BackgroundThe contour method for residual stress measurement has seen significant development, but an experimental reproducibility study utilizing physical samples has not been published.ObjectiveA double-blind reproducibly study is reported, having scope beginning with EDM cutting and ending with residual stress calculation.MethodsA reinforced I-beam sample geometry is identified for its unique residual stress profile when extracted from residual stress bearing quenched aluminum bar (7050-T74). Contour measurements are prescribed on a midplane of symmetry with dimensions 24.0 mm by 50.0 mm. Fourteen identically prepared samples are fabricated from a single long bar with well characterized and uniform residual stress. Five samples throughout the bar are identified for planning measurements to validate sample uniformity and overall suitability of the residual stress field. The planning measurements employ a range of techniques: contour method, neutron diffraction, and hole-drilling. Eight samples are distributed to an international group of participants to execute their standard measurement practice. A double-blind process is followed to provide anonymity.ResultsResults are provided by eight participants: six being self-similar and two being quite different, the latter set aside as outliers. An average residual stress field is established from non-outlying results and the spatial distribution of reproducibility standard deviation is determined. The average stress field ranges from -60 to 70 MPa and the reproducibility standard deviation averages 8.1 MPa on the measurement plane. The average reproducibility standard deviation is about 3 × larger for points within 1.0 mm of plane boundaries (17.6 MPa) than for the remaining points (6.1 MPa).ConclusionsReproducibility standard deviation (among different labs) for contour method residual stress measurement is found to be very similar to repeatability standard deviation (in a single lab) reported in prior work. The reproducibility observed here, for the entire measurement process, is also similar to that found in a prior reproducibility study limited to contour method data analysis.

Improving the dimensional accuracy of 3D x-ray microscopy data

X-ray microscopy instruments have the unique ability to achieve nondestructive imaging with higher spatial resolutions than traditional x-ray computed tomography (CT) systems. This unique ability is of interest to industrial quality control entities, as they deal with small features in precision manufactured parts (with tolerances in the order of ±25 µm or better). Since many of today’s technology and manufacturing companies demand increasingly higher levels of precision, accuracy, and reliability for dimensional measurements on feature sizes that are much smaller than 5 mm, it would be ideal to further expand the imaging capabilities of x-ray microscopy to the field of precision metrology. To address such demand, this paper describes the development of a measurement workflow, through a package consisting of hardware and software, to improve the accuracy of dimensional data obtained with 3D x-ray microscopes (XRMs)—also known as sub-micrometer CT systems. The measurement workflow, called Metrology Extension (MTX), was designed to adjust and configure the XRM instrument work-zone to perform dimensional measurement tasks. The main adjustments of an XRM instrument through the MTX workflow, which must be implemented before scanning parts of interest for dimensional evaluation, include applying a distortion map correction on the image projections produced by the x-ray detector and a voxel scale correction. The main purpose of this article is to present, evaluate, and analyze the experimental results of various measurement tests to verify the metrological performance of several XRM systems operating with the MTX workflow. The main results show that these systems can produce repeatable and reproducible measurements, with repeatability standard deviations of the order of 0.1 μm and reproducibility standard deviations of less than 0.5 μm. In addition, coordinate-based 3D XRM measurements produce dimensional accuracies comparable to those offered by high-precision tactile coordinate measurement machines (with deviations within the range of ±0.95 µm). Therefore, once the MTX workflow is executed, XRM instruments can be used to measure small volumes, in the order of (5 mm)3 or less, with improved dimensional accuracy.

Fast DNA biosensing based on isothermal amplification, unmodified gold nanoparticles, and smartphone detection

The protection of the consumer against foodborne illnesses and fraudulent practices requires methods capable of detecting critical components. Classical instrumental and DNA-based technologies have assay time, portability, and cost limitations. Thus, food control needs alternative methodologies for massive and cost-effective screening. Herein, we report an instrument-free method based on detecting genes that encode proteins related to food allergies and ingredients associated with illegal practices. Tailed recombinase polymerase amplification (tailed-RPA) provided the selective isothermal amplification of target regions. A reproducible and fast optical detection was developed based on the salt-induced aggregation of 15 nm gold nanoparticles (AuNPs). The target presence was directly observed (naked-eye detection) and quantified using a smartphone and RGB image decomposition. The advantages arise from the effective formation of a hybrid complex between non-functionalized nanoparticles and amplification products with a single-strand tail, featuring short incubation time, simplicity, and low sample and reagent volumes. As proof of concept, two targets were determined: trnL gene and ITS region. The first sequence is located in the chloroplast genome of cereals and is valuable to control the adulteration of meat products. The second is a fragment common to the three main gluten-containing cereals, applicable to the indirect detection of this allergen. The novelty also is the integration of a low-cost assay platform and a straightforward interpretation system to foster its implementation in the industry. The RPA-AuNP assay offered a good sensitivity (genomic DNA 0.8 ng), selectivity (absence of unspecific response), reproducibility (standard deviation 2–11%), and accuracy in marketed food products (100%). Therefore, a competitive biosensing system enables better control according to food industry/consumers demands from Farm to Fork strategy.

High resolution mass spectrometry method for the determination of 13 antibiotic groups in bovine, swine, poultry and fish meat: An effective screening and confirmation analysis approach for routine laboratories

A screening and confirmatory method for the determination of 13 antibiotic groups including 91 substances was developed for muscle samples and validated using ultra-performance liquid chromatography (UPLC) coupled to time-of-flight mass spectrometry. Optimisation of the parameters was performed for every analyte and personal compound database library was created, comprising the mass spectra for following collision energies; 0, 10, 20 and 40 eV. Validation plan scheming and calculation of the parameters was performed using validation software, which included following performance characteristics; selectivity, trueness, precision, decision limit (CCα), detection capability (CCβ) and relative matrix effect. High resolution mass spectrometry operated in a narrow mass window and resolving power of 50,000 FWHM (2 GHz). Accurate mass measurements with mass accuracy below 10 ppm for all analytes were obtained in spiked muscle samples. The validation experiments showed good selectivity and specificity. The method was validated in the measurement range from 0.5 to 1000 μg/kg, where a specific analyte mixed standard solution was prepared depending on the defined maximum residue limit (MRL) or lowest calibration level (LCL). For screening analysis, detection capabilities (CCβ) below the set MRL values or at LCL concentration levels were defined. CCβ, as the concentration above which the sample can be considered suspect, ranged from 0.63 to 207.8 μg/kg. For confirmation of the analyte, CCα was calculated at LCL or at the MRL, where it ranged from 0.38 to 14.3 μg/kg for unauthorised substances and from 13.8 to 1492.6 μg/kg for authorised substances. Relative within-laboratory reproducibility standard deviation ranged from 5.1 to 34.2%. Satisfactory z-score values in the range from −0.87 to 1.88 were obtained as a result of participating in four proficiency tests organized by European Union Reference Laboratories. • Screening and confirmatory HRMS method for 91 antibiotics. • Wide validation range around the established residue limits. • CCβ and CCα as parameters for screening and confirmatory analysis. • Satisfactory proficiency results as confirmation of good method performance.

A Framework for ExacTrac Dynamic Commissioning for Stereotactic Radiosurgery and Stereotactic Ablative Radiotherapy.

This paper aims to provide guidance and a framework for commissioning tests and tolerances for the ExacTrac Dynamic image-guided and surface-guided radiotherapy (SGRT) system. ExacTrac Dynamic includes a stereoscopic X-ray system, a structured light projector, stereoscopic cameras, thermal camera for SGRT, and has the capability to track breath holds and internal markers. The system provides fast and accurate image guidance and intrafraction guidance for stereotactic radiosurgery and stereotactic ablative radiotherapy. ExacTrac Dynamic was commissioned on a recently installed Elekta Versa HD. Commissioning tests are described including safety, isocenter calibration, dosimetry, image quality, data transfer, SGRT stability, SGRT localization, gating, fusion, implanted markers, breath hold, and end-to-end testing. Custom phantom designs have been implemented for assessment of the deep inspiration breath-hold workflow, the implanted markers workflow, and for gating tests where remote-controlled movement of a phantom is required. Commissioning tests were all found to be in tolerance, with maximum translational and rotational deviations in SGRT of 0.3 mm and 0.4°, respectively, and X-ray image fusion reproducibility standard deviation of 0.08 mm. Tolerances were based on published documents and upon the performance characteristics of the system as specified by the vendor. The unique configuration of ExacTrac Dynamic requires the end user to design commissioning tests that validate the system for use in the clinical implementation adopted in the department. As there are multiple customizable workflows available, tests should be designed around these workflows, and can be ongoing as workflows are progressively introduced into departmental procedures.

Summarising the precision statistics from collaborative trials.

A collaborative trial (an interlaboratory study) is reputed to be the most reliable way of validating an analytical procedure applied to a defined class of test material. The most important outcome of a trial is the collection of reproducibility standard deviations estimated at various mass fractions of the analyte. These standard deviations are good estimates of standard uncertainties to be expected when the procedure is used in proficient laboratories. However, collaborative trials are expensive to conduct, as much as ₤50k-100k per trial, depending on the number of test materials under study and the number of laboratories involved. As an outcome, the popularity of trials is declining while the need for information from them is escalating.

A more precise method to evaluate kinetic leakage of anion exchange resin used in condensate polishing of power plant

Sulfate mass transfer coefficient (MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant. However, a sufficiently precise determination method has not been well established. In this paper, the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries’ model, which is widely acknowledged in this field. In the determining system we constructed, in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined. The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained. The repeatability and reproducibility standard deviation are 0.05 × 10−4 m·s−1 and 0.07 × 10−4 m·s−1 respectively, which are lower than previous works. By controlling test condition accurately, this study has developed a more precise sulfate MTC determining method. This method provides a basis for further research.

Towards an explanation of the Horwitz function.

Analytical chemists in the food sector are well acquainted with the empirically observed Horwitz function. It relates reproducibility (interlaboratory) standard deviations estimated by collaborative trial with the mass fraction of the analyte. No compelling theory accounts for the power-law form of the function or its parameters. The equation of Zitter and God, ostensibly covering the same ground, is less well known but, in spite of its secure foundation in theory and practice, seems at first sight to be incompatible with the Horwitz function. In this paper, we see that because of the limited range of mass fractions in which a single collaborative trial is usually conducted, collections of statistics from collaborative trials exhibit the Horwitz function over the mass fraction range from about 10-7 (100ppb) to about 10-1 (10%).