Reproducibility Standard Deviation Research Articles

Ring trial validation of single and multiplex real-time PCR methods for the detection and quantification of the allergenic food ingredients sesame, almond, lupine and Brazil nut

The inter-laboratory (=ring-trial) validation of 4 food allergen quantification methods using real-time PCR is described. Three single real-time PCR methods for the specific detection and quantification of sesame, almond and Brazil nut were used. Additionally, a multiplex real-time PCR method combining the detection of sesame, almond, Brazil nut and lupine was tested in parallel. Matrix based calibrants (rice cookies) spiked (=incurred) with defined amounts of sesame, almond, lupine and Brazil nut were applied for quantitative evaluation. Cookies based upon wheat and rice flour as well as sauce hollandaise powder each incurred with these allergenic ingredients in the range of 10–123 milligram per kilogram were used as ring-trial samples. The lowest spike level of 10 mg/kg could reproducibly be detected by 6 of 7 PCR systems. In quantitative evaluation of the results, reproducibility standard deviations of approximately 50 % and below were obtained. In addition, the effect of the food matrix on allergen quantification was examined. The range of “recoveries” over all matrices and methods was from 43 to 109 %.

Optimisation of an analytical method and results from the inter-laboratory comparison of the migration of regulated substances from food packaging into the new mandatory European Union simulant for dry foodstuffs

This paper presents the outcome of the development, optimisation and validation at European Union level of an analytical method for using poly(2,6-diphenyl phenylene oxide – PPPO), which is stipulated in Regulation (EU) No. 10/2011, as food simulant E for testing specific migration from plastics into dry foodstuffs. Two methods for fortifying respectively PPPO and a low-density polyethylene (LDPE) film with surrogate substances that are relevant to food contact were developed. A protocol for cleaning the PPPO and an efficient analytical method were developed for the quantification of butylhydroxytoluene (BHT), benzophenone (BP), diisobutylphthalate (DiBP), bis(2-ethylhexyl) adipate (DEHA) and 1,2-cyclohexanedicarboxylic acid, diisononyl ester (DINCH) from PPPO. A protocol for a migration test from plastics using small migration cells was also developed. The method was validated by an inter-laboratory comparison (ILC) with 16 national reference laboratories for food contact materials in the European Union. This allowed for the first time data to be obtained on the precision and laboratory performance of both migration and quantification. The results showed that the validation ILC was successful even when taking into account the complexity of the exercise. The results showed that the method performance was 7–9% repeatability standard deviation (rSD) for most substances (regardless of concentration), with 12% rSD for the high level of BHT and for DiBP at very low levels. The reproducibility standard deviation results for the 16 European Union laboratories were in the range of 20–30% for the quantification from PPPO (for the three levels of concentrations of the five substances) and 15–40% from migration experiments from the fortified plastic at 60°C for 10 days and subsequent quantification. Considering the lack of data previously available in the literature, this work has demonstrated that the validation of a method is possible both for migration from a film and for quantification into a corresponding simulant for specific migration.

Determination of Therapeutic γ-Aminobutyric Acid Analogs in Forensic Whole Blood by Hydrophilic Interaction Liquid Chromatography–Electrospray Tandem Mass Spectrometry

Vigabatrin, pregabalin, gabapentin and baclofen are γ-aminobutyric acid analogs that are used in the treatment of epileptic seizures (vigabatrin, pregabalin and gabapentin) and spasticity (baclofen). The intake of these drugs may induce adverse reactions and impair the ability of an individual to drive a vehicle. There have also been reports of cases of intoxication and fatalities from overdoses. For rapid and accurate quantification of these drugs in forensic cases, an ultraperformance liquid chromatography tandem mass spectrometry method using pneumatically assisted electrospray ionization has been developed. The technique has been validated on both ante- and postmortem human whole blood. The protein in the blood samples was removed by the addition of a mixture of methanol and acetonitrile, and the extract was ultrafiltered and diluted with acetonitrile. The separation was performed by hydrophilic interaction liquid chromatography. Calibration of the system was achieved through use of matrix-matched calibrants combined with isotope dilution. The lower limits of quantification were 0.02-0.04 mg/L, and the relative intra-laboratory reproducibility standard deviations were <4 and 8% at concentrations of 10 and 1 mg/L, respectively. The mean true recoveries were >89%. The trueness expressed as the relative bias of the test results was within ±7% at concentrations of 1-40 mg/L for vigabatrin, pregabalin and gabapentin and of 0.1-4 mg/L for baclofen.

Determination of ionophore coccidiostat salinomycine in premixes and poultry feeding stuffs by liquid chromatography after post-column derivatisation

Coccidiosis is a common parasitic disease of broiler chickens caused by single-celled protozoan parasites of the genus Eimeria which are commonly referred to as coccidian. This is an infective disease of the digestive tract which is most frequent with poultry, causing a decrease in daily increment, prolonged fattening, poorer skin pigmentation, slower feed conversion and increased mortality. The disease is caused by Protozoas from the genera of Eimeria, Isospora and Cryptospora, and it is manifested by damaging the intestine epithelial cells, less frequently the bile duct and renal tubuli. Coccidiosis is traditionally controlled by chemotherapy. There are many anticoccidial preparations which are used in the prevention of coccidiosis. We are chose a polyether monocarboxylic acid - salinomycine. Salinomycin is monovalent carboxyl-polyether ionophores. Salinomycin, produced by Streptomyces albus, destroys the cell membranes and causes their lysis. Salinomycin and other ionophoric antibiotics combine with a number of mono and divalent cations and in the form of bi-complexes make it possible to transfer metal ions through lipid hydrophobic membrane, and when they are added to diet, they change bioavailability, gut uptake and absorption and reserves of nutrient tissues. In this paper has been developed and validated process of Liquid chromatography determination of ionophoric coccidiostat salinomycin with UV spectrophotometric detection and post-column derivatisation with dimethylaminobenzaldehyde (DMAB). The method is based on extraction of salinomycin in animal feed samples using mixture acetonitrile-water (80:20, v/v) and purification of extracts obtained by the filter 0,2 ?m Acrodisc? PSF. The relative standard deviation (RSD) for reproducibility and accuracy varied from 2,4 to 8,8% and from 2,6% to 8,8%, respectively and the values for the relative recovery rate ranged from 89 to 98%. The limit of detection (LOD) and limit of quantification (LOQ) were estimated to be below 47 ?g/kg and 71 ?g/kg, respectively. Based on this results, it is concluded that the described method is accurate, precise, selective and reproducible and can be applied for determination of salinomycine in feeds and premixes for poultry.

Odor measurements according to EN 13725: A statistical analysis of variance components

In Europe, dynamic olfactometry, as described by the European standard EN 13725, has become the preferred method for evaluating odor emissions emanating from industrial and agricultural sources. Key elements of this standard are the quality criteria for trueness and precision (repeatability). Both are linked to standard values of n-butanol in nitrogen. It is assumed in this standard that whenever a laboratory complies with the overall sensory quality criteria for n-butanol, the quality level is transferable to other, environmental, odors.Although olfactometry is well established, little has been done to investigate inter laboratory variance (reproducibility). Therefore, the objective of this study was to estimate the reproducibility of odor laboratories complying with EN 13725 as well as to investigate the transferability of n-butanol quality criteria to other odorants.Based upon the statistical analysis of 412 odor measurements on 33 sources, distributed in 10 proficiency tests, it was established that laboratory, panel and panel session are components of variance that significantly differ between n-butanol and other odorants (α = 0.05). This finding does not support the transferability of the quality criteria, as determined on n-butanol, to other odorants and as such is a cause for reconsideration of the present single reference odorant as laid down in EN 13725.In case of non-butanol odorants, repeatability standard deviation (sr) and reproducibility standard deviation (sR) were calculated to be 0.108 and 0.282 respectively (log base-10). The latter implies that the difference between two consecutive single measurements, performed on the same testing material by two or more laboratories under reproducibility conditions, will not be larger than a factor 6.3 in 95% of cases.As far as n-butanol odorants are concerned, it was found that the present repeatability standard deviation (sr = 0.108) compares favorably to that of EN 13725 (sr = 0.172). It is therefore suggested that the repeatability limit (r), as laid down in EN 13725, can be reduced from r ≤ 0.477 to r ≤ 0.31.

Quantitation of Acrylamide in Foods by High-Resolution Mass Spectrometry

Acrylamide detection still represents one of the hottest topics in food chemistry. Solid phase cleanup coupled to liquid chromatography separation and tandem mass spectrometry detection along with GC-MS detection are nowadays the gold standard procedure for acrylamide quantitation thanks to high reproducibility, good recovery, and low relative standard deviation. High-resolution mass spectrometry (HRMS) is particularly suitable for the detection of low molecular weight amides, and it can provide some analytical advantages over other MS techniques. In this paper a liquid chromatography (LC) method for acrylamide determination using HRMS detection was developed and compared to LC coupled to tandem mass spectrometry. The procedure applied a simplified extraction, no cleanup steps, and a 4 min chromatography. It proved to be solid and robust with an acrylamide mass accuracy of 0.7 ppm, a limit of detection of 2.65 ppb, and a limit of quantitation of 5 ppb. The method was tested on four acrylamide-containing foods: cookies, French fries, ground coffee, and brewed coffee. Results were perfectly in line with those obtained by LC-MS/MS.

International interlaboratory study for sizing and quantification of Ag nanoparticles in food simulants by single-particle ICPMS

This publication describes the first international intercomparison of particle-size determination by single-particle inductively coupled plasma mass spectrometry (sp-ICPMS). Concentrated monodisperse silver nanoparticle suspensions with particle diameters of 20, 40 and 100 nm and a blank solution were sent to 23 laboratories in Europe, the USA and Canada. Laboratories prepared eight nanoparticle preparations in two food simulants (distilled water; 10% ethanol) and reported median particle size, Ag particle mass concentration and Ag particle number concentrations. Average repeatability and reproducibility standard deviation (sr and sR) for the median particle diameter were 1 and 14 nm, respectively. Relative precision was worse for Ag particle number concentrations (RSD r = 11%; RSD R = 78%). While further improvements of the method, especially with respect to software tools for evaluation, hardware options for shorter dwell times, calibration standards for determining nebuliser efficiency and further experience by laboratories are certainly desirable, the results of this study demonstrate the suitability of sp-ICPMS for the detection and quantification of certain kinds of nanoparticles.

Geological materials testing and uncertainty calculations: a simple GUM-based algorithm

We have applied a simple GUM-based procedure to estimate the uncertainties of physical and mechanical properties in geological materials. First, we define the quantity to measure and decide whether we want to work with units or relative quantities. Subsequently, we calculate the repeatability standard deviation (sr) and the standard uncertainty. If we have proficiency test data or use certified reference materials, we use them to estimate the laboratory bias, the reproducibility standard deviation (sR) and the reproducibility standard uncertainty. We also make sure that we know or have estimated the standard uncertainty of the instruments that we use in the measurements. The latter is typically taken from the instrument calibration or precision statement. We estimate the standard uncertainty of the reference materials and the standard uncertainty of the laboratory bias. The final two steps include the calculation of (1) the laboratory standard uncertainty uncorrected for bias and corrected for bias, and (2) the laboratory expanded uncertainty at the 95% confidence limit.

Simultaneous determination of β-hydroxybutyrate and β-hydroxy-β-methylbutyrate in human whole blood using hydrophilic interaction liquid chromatography electrospray tandem mass spectrometry

ObjectivesFor the quantification of β-hydroxybutyrate (BHB) and β-hydroxy-β-methylbutyrate (HMB) in human whole blood, a method using hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC–MS/MS) was developed, which does not require chemical modification of the analytes. Design and methodsSamples were deproteinised by a mixture of methanol and acetonitrile, and the extracts were cleaned-up using both polymeric strong cation exchange and strong anion exchange sorbents. The analytes and their structural isomers were separated using a column with a zwitterionic stationary phase. Isotope dilution of both analytes was used for quantitative analysis. ResultsSeparation of BHB from isobaric interferences was achieved through chromatography. The relative intra-laboratory reproducibility standard deviations were better than 10% for blood samples at concentration levels of 10–20μM BHB and 1μM HMB and better than 5% at concentration levels 10 times higher. The mean true extraction recoveries were close to 100%. The trueness expressed as the relative bias of test results was within ±5% at concentration levels of 10–1000μM BHB and 1–20μM HMB. The lower limits of quantification were estimated to be 3μM for BHB and 0.4μM for HMB. ConclusionsA simple and highly sensitive and selective HILIC–MS/MS method was developed that is suitable for the quantification of BHB and HMB in whole blood.

Uncertainty estimation in the analysis of pesticide residues in olive oil using data from proficiency tests

In this work we report the results for estimating the measurement uncertainty (MU) following up the application of two different approaches, relatively the top-down procedure, by using proficiency test data. We have focused the estimation on the olive oil matrix. We used the analytical data obtained from five selected editions of the Proficiency Tests (PTs, from 2007 to 2011) on pesticide residues in olive oil to estimate the MU. These PTs have been organized by Istituto Superiore di Sanità annually in cooperation with International Olive Council (IOC) since 1997. The number of participants in each trial ranged from 10 to 43. We used a total of 34 pesticide results. The expanded uncertainty U (c) was calculated using a covering factor k = 2 for a confidence interval of 95%. In the approach 1, the within–laboratory reproducibility standard deviation is combined with estimates of the method and laboratory bias using PTs data. In the approach 2, the way of estimating the MU is based only on the bias that the laboratory has obtained participating in a sufficient number of the IOC proficiency tests. Comparing the relative expanded uncertainty based on these different approaches we notice values quite constant and close, from 42% to 48%. Moreover, these calculated expanded uncertainties are less than the default value of 50% (corresponding to a 95% confidence level), adopted from European guidance document SANCO based on the fit-for-purpose relative standard deviation (FFP-RSD).

Uncertainty analysis by a Round Robin Test of field measurements of sound insulation in buildings: Single numbers and low frequency bands evaluation - Airborne sound insulation

The uncertainty of field measurements of a lightweight wall and a heavy floor was analysed by Round Robin Test (RRT), conducted in a full-scale experimental building at ITC-CNR. Each of the 9 teams involved in the I-RRT replicates the tests 5 times, for a total of 45 measurements, while the repetitions of reverberation time were 110. Both for sound insulation and reverberation time the main variations are in the low frequency range. The differences between D, R', Dn and DnT and their reproducibility and repeatability standard deviations values were also analysed. The study is also focused on the single numbers evaluation: true value and uncertainty. Single numbers were evaluated in both narrow and extended range. The extension to low frequencies implies a variation in single number values that reaches its maximum in the case of X +Ctr in the extended range. This is because this index is the most influenced by low frequencies. Thus the measurement uncertainty at low frequencies has to be more deeply investigated, before including the low frequency range in the on-field measurements

Fresh broad (Vicia faba) tissue homogenate-based biosensor for determination of phenolic compounds

In this study, a novel fresh broad (Vicia faba) tissue homogenate-based biosensor for determination of phenolic compounds was developed. The biosensor was constructed by immobilizing tissue homogenate of fresh broad (Vicia faba) on to glassy carbon electrode. For the stability of the biosensor, general immobilization techniques were used to secure the fresh broad tissue homogenate in gelatin-glutaraldehyde cross-linking matrix. In the optimization and characterization studies, the amount of fresh broad tissue homogenate and gelatin, glutaraldehyde percentage, optimum pH, optimum temperature and optimum buffer concentration, thermal stability, interference effects, linear range, storage stability, repeatability and sample applications (Wine, beer, fruit juices) were also investigated. Besides, the detection ranges of thirteen phenolic compounds were obtained with the help of the calibration graphs. A typical calibration curve for the sensor revealed a linear range of 5–60 μM catechol. In reproducibility studies, variation coefficient (CV) and standard deviation (SD) were calculated as 1.59%, 0.64 × 10−3 μM, respectively.

The BIOREMA project—part 3: International interlaboratory comparison for bio-ethanol test methods

The main objective of the reference materials for biofuel specifications (BIOREMA) project is the development of two test materials (one bio-ethanol material and one biodiesel material) with well-established reference values. Of a series of three papers, this part describes the material preparation, homogeneity study, stability study, and characterisation of the bio-ethanol material. The test material thus obtained was used in an interlaboratory comparison (ILC) to assess current practices and comparability amongst laboratories providing bio-ethanol testing services. Only 13 participants provided data, resulting in a small dataset for evaluation. Further, it appeared that for a number of laboratories, there was not sufficient material for the determination of all requested parameters. In most cases, as far as the data permit, it can be concluded that the consensus values (based on participant’s results) are in good agreement with the reference or the BIOREMA values (obtained by NMIs participating in the project). For three parameters, namely ethanol content, water content, and density, there is good agreement between the reference and consensus values. For these parameters, the reproducibility standard deviation is close to, or even smaller than, the expanded uncertainty associated with the reference value. A number of parameters show very poor reproducibility, for example, pHe, electrolytic conductivity, and acidity. The same applies to sodium and copper content, which are very low and therefore challenging parameters to measure accurately. The results of the ILC underpin the need for certified reference materials and demonstrate the requirement for more robust quality control to improve the precision and trueness of the results from testing laboratories.

A high-throughput multi-class liquid chromatography tandem mass spectrometry method for quantitative determination of licit and illicit drugs in whole blood

An ultra-high-performance liquid chromatography tandem mass spectrometry confirmatory method using pneumatically assisted electrospray ionisation (UPLC-ESI-MS/MS) was developed for the simultaneous quantification of licit and illicit drugs in whole blood across multiple drug classes. The method was validated on 51 frequently detected drugs and metabolites in human ante-mortem and post-mortem whole blood. The generic sample treatment procedure was based on deproteinisation by a mixture of methanol and acetonitrile followed by ultrafiltration of the extract. Matrix-matched calibrants combined with isotope dilution of almost all substances were used for quantitative analysis. A high sample throughput was obtained by using a 96-well format. The total instrumental run-time between injections was 16 min. The relative intra-laboratory reproducibility standard deviations were generally below 8% and 15% at concentrations of 250 μg L−1 and 5 μg L−1, respectively. The mean true recoveries were in most cases greater than 90% for ante-mortem samples and greater than 80% for post-mortem samples. For most substances, the limits of detection and quantification were less than 1 μg L−1 and 3 μg L−1, respectively.

Anatomically reproducible assessment of volumetric bone mineral density — Based on clinical computed tomography

Local distribution and quality of bone mineral density (BMD) in the proximal humerus are important for rotator cuff repair, internal fixations, and arthroplasty. The current study aimed to develop a volumetric BMD (vBMD) measurement technique that can specify the volumetric region of interest in an anatomically reproducible manner and ensures fair comparison of vBMD among intrasubjective or intersubjective measurements. Computed toed into three-dimensional (3D) polygon models. A standardized volumetric block was asmographic images of 10 intact shoulders (from six women and four men, age range 46–69 years) were reconstruct signed, and it included whole insertion areas of the supraspinatus and infraspinatus tendons on the greater tuberosity. For standardizing a bone block, a mathematical method for reproducible landmark assignment and reproducible local coordinate system was developed. After converting the polygonal standardized volumetric block into 3D tetrahedron finite element models, its vBMD was calculated. The repeatability and reproducibility standard deviations of the vBMD measurement method were found to be less than 2%. The current study developed a vBMD measurement technique that can specify the vROI in an anatomically reproducible manner and ensures fair comparison of BMD among intrasubjective or intersubjective measurements, with less than 2% reproducibility error.

Estimation of the uncertainties of extraction and clean-up steps in pesticide residue analysis of plant commodities

Extraction and clean-up constitute important steps in pesticide residue analysis. For the correct interpretation of analytical results, uncertainties of extraction and clean-up steps should be taken into account when the combined uncertainty of the analytical result is estimated. In the scope of this study, uncertainties of extraction and clean-up steps were investigated by spiking 14C-labelled chlorpyrifos to analytical portions of tomato, orange, apple, green bean, cucumber, jackfruit, papaya and starfruit. After each step, replicate measurements were carried out with a liquid scintillation counter. Uncertainties in extraction and clean-up steps were estimated separately for every matrix and method combination by using within-laboratory reproducibility standard deviation and were characterised with the CV of recoveries. It was observed that the uncertainty of the ethyl acetate extraction step varied between 0.8% and 5.9%. The relative standard uncertainty of the clean-up step with dispersive SPE used in the method known as QuEChERS was estimated to be around 1.5% for tomato, apple and green beans. The highest variation of 4.8% was observed in cucumber. The uncertainty of the clean-up step with gel permeation chromatography ranged between 5.3% and 13.1%, and it was relatively higher than that obtained with the dispersive SPE method.

Performance of the AOAC Use-Dilution Method with Targeted Modifications: Collaborative Study

The U.S. Environmental Protection Agency (EPA), in collaboration with an industry work group, spearheaded a collaborative study designed to further enhance the AOAC use-dilution method (UDM). Based on feedback from laboratories that routinely conduct the UDM, improvements to the test culture preparation steps were prioritized. A set of modifications, largely based on culturing the test microbes on agar as specified in the AOAC hard surface carrier test method, were evaluated in a five-laboratory trial. The modifications targeted the preparation of the Pseudomonas aeruginosa test culture due to the difficulty in separating the pellicle from the broth in the current UDM. The proposed modifications (i.e., the modified UDM) were compared to the current UDM methodology for P. aeruginosa and Staphylococcus aureus. Salmonella choleraesuis was not included in the study. The goal was to determine if the modifications reduced method variability. Three efficacy response variables were statistically analyzed: the number of positive carriers, the log reduction, and the pass/fail outcome. The scope of the collaborative study was limited to testing one liquid disinfectant (an EPA-registered quaternary ammonium product) at two levels of presumed product efficacies, high and low. Test conditions included use of 400 ppm hard water as the product diluent and a 5% organic soil load (horse serum) added to the inoculum. Unfortunately, the study failed to support the adoption of the major modification (use of an agar-based approach to grow the test cultures) based on an analysis of method's variability. The repeatability and reproducibility standard deviations for the modified method were equal to or greater than those for the current method across the various test variables. However, the authors propose retaining the frozen stock preparation step of the modified method, and based on the statistical equivalency of the control log densities, support its adoption as a procedural change to the current UDM. The current UDM displayed acceptable responsiveness to changes in product efficacy; acceptable repeatability across multiple tests in each laboratory for the control counts and log reductions; and acceptable reproducibility across multiple laboratories for the control log density values and log reductions. Although the data do not support the adoption of all modifications, the UDM collaborative study data are valuable for assessing sources of method variability and a reassessment of the performance standard for the UDM.

Ionic liquid‐based microwave‐assisted extraction for the determination of flavonoid glycosides in pigeon pea leaves by high‐performance liquid chromatography‐diode array detector with pentafluorophenyl column

In this study, an ionic liquid-based microwave-assisted extraction (ILMAE) followed by high-performance liquid chromatography-diode array detector with a pentafluorophenyl column for the extraction and quantification of eight flavonoid glycosides in pigeon pea leaves is described. Compared with conventional extraction methods, ILMAE is a more effective and environment friendly method for the extraction of nature compounds from herbal plants. Nine different types of ionic liquids with different cations and anions were investigated. The results suggested that varying the anion and cation had significant effects on the extraction of flavonoid glycosides, and 1.0 M 1-butyl-3-methylimidazolium bromide ([C4MIM]Br) solution was selected as solvent. In addition, the extraction procedures were also optimized using a series of single-factor experiments. The optimum parameters were obtained as follows: extraction temperature 60°C, liquid-solid ratio 20:1 mL/g and extraction time 13 min. Moreover, an HPLC method using pentafluorophenyl column was established and validated. Good linearity was observed with the regression coefficients (r(2)) more than 0.999. The limit of detection (LODs) (S/N = 3) and limit of quantification (LOQs) (S/N = 10) for the components were less than 0.41 and 1.47 μg/mL, respectively. The inter- and intraday precisions that were used to evaluate the reproducibility and relative standard deviation (RSD) values were less than 4.57%. The recoveries were between 97.26 and 102.69%. The method was successfully used for the analysis of samples of pigeon pea leaves. In conclusion, the developed ILMAE-HPLC-diode array detector using pentafluorophenyl column method can be applied for quality control of pigeon pea leaves and related medicinal products.

AACCI Approved Methods Technical Committee Report: Collaborative Study on a Method for Determining Firmness of Cooked Pulses (AACCI Method 56-36.01)

A method based on compression through a Kramer shear cell was developed for determining the firmness of cooked pulses. Ten laboratories analyzed twenty-six blind duplicates of thirteen different samples in a collaborative study to evaluate the repeatability and reproducibility of the method. Statistical analysis of the collaborative data indicated that within-laboratory repeatability standard deviation (sr) was in the range of 0.53 to 1.43, and among-laboratory reproducibility standard deviation (sR) varied from 0.74 to 1.94. The within-laboratory relative standard deviation (RSDr) of samples ranged from 2.45 to 7.24%, and the among-laboratory relative standard deviation (RSDR) ranged from 4.23 to 8.80%.

Inter‐laboratory Study of Particle Size Distribution Measurements by Laser Diffraction

AbstractPresented are results of an inter‐laboratory study (ILS) for measurements of the particle size distribution of fine powders in wet dispersion by laser diffraction. In this proficiency test 32 participants from four countries took part. They utilized 13 different devices from 7 manufacturers.Three commercial powders (glass spheres and two silicon carbide powders) showing a median diameter of about 30, 10 and 1 μm (volume distribution), respectively, were chosen for the procedure. A homogeneity study was carried out after the units had been separated and bottled.All participants received their test samples including a description of the standard operating procedures based on ISO 13320:2009 – to ensure that experiments were performed in a consistent manner. Results were calculated using the Mie Theory. The general means and the precision of the results were estimated in accordance with ISO 5725‐2:2002.The evaluation showed excellent values of repeatability standard deviation. Values of 4 to 21 % of the reproducibility standard deviation of the results were found in the particle size range above 1 μm. Much larger deviation between the labs was detected in the case of smaller particles. Differences in the design of the analyzers were unambiguously identified as the main reason for the large deviations.