Candidates For Reference Materials Research Articles

Development of a new reference material for accurate measurements of lithium in Li-clays

Currently, there are no national and international certified reference materials (CRM) in lithium clays that can make reliable and traceable lithium measurements for the International System of Units (SI). Hence, it is necessary to have references to meet the needs in terms of mining and activities that involve the use of lithium to favor the economy derived from its multiple uses and associated benefits in the exploration, exploitation, and handling of lithium ore. In this study, a candidate for reference material (RM) of Li in clays was developed and certified based on the provisions of ISO 17034:2016 and ISO Guide 35:2017. Different mass sizes of the RM (0.05, 0.1, and 0.25 g) were used to evaluate homogeneity. An isochronous study (short-term stability) was carried out in the assessment of stability, influenced by the effects of transport at different temperatures (20, 40, and 50 °C) for a determined time of 6 weeks, in addition to a classic (long-term) study for 19 weeks. The sample was treated using microwave-assisted acid digestion and Li measurements were performed using the analytical technique of Flame Atomic Absorption Spectrometry (FAAS). The CRM is homogeneous for the sample mass sizes of 0.05 and 0.1 g, and the mass fraction of w(Li) was stable in the RM for temperatures of 20, 40, and 50 °C. The determined period of validity was 3 years.

Identification by HSQC and quantification by qHNMR innovate pharmaceutical amino acid analysis

This study introduces a new NMR-based methodology for identification (ID) and quantification (purity, strength) assays of widely used amino acids. A detailed analysis of four amino acids and their available salts was performed with both a high-field (600 MHz) and a benchtop (60 MHz) NMR instrument. To assess sensitivity constraints, samples for 1H NMR analysis were initially prepared using only 10 mg of analyte and 1 mg of maleic acid (MA) as an internal calibrant (IC) and secondary chemical shift reference. The characteristic dispersion of the peak patterns indicating the presence or absence of a counterion (mostly chloride) was conserved at both high and low-field strength instruments, showing that the underlying NMR spectroscopic parameters, i.e., chemical shifts and coupling constants, are independent of the magnetic field strength. However, as the verbal descriptions of 1H NMR spectra are challenging in the context of reference materials and pharmaceutical monographs, an alternative method for the identification (ID) of amino acids is proposed that uses 13C NMR patterns from multiplicity-edited HSQC (ed-HSQC), which are both compound-specific and straightforward to document. For ed-HSQC measurements, the sample amount was increased to 30 mg of the analyte and several acquisition parameters were tested, including t1 increments used in the pulse program, number of scans, and repetition time. Excellent congruence with deviations <0.1 ppm was achieved for the 13C chemical shifts from 1D 13C NMR spectra (150 MHz) vs. those extracted from ed-HSQC (15 MHz traces). Finally, all samples of amino acid candidate reference materials were quantified by 1H qNMR (abs-qHNMR) at both 600 and 60 MHz. At high field, both IC and relative quantitations were performed, however, with the low-field instrument, only the IC method was used. The results showed that the analyzed reference material candidates were generally highly pure compounds. To achieve adequately low levels of uncertainty for such high-purity materials, the sample amounts were increased to 100 mg of analytes and 10 mg of the IC and replicates were analyzed for selected amino acids.

Preparation of Fluorine Certified Reference Material for Fluoroether Rubber

High-pressure free radical emulsion polymerization was used to prepare the fluorine certified reference material candidates for fluoroether rubber. Ion chromatography method and high performance liquid chromatography were adopted for the determination of the certified reference material, and various sources of uncertainty in the determination process were analyzed and calculated to gain the expanded uncertainty by synthesis. The homogeneity of the certified reference material was checked by F test and the stability was investigated by t test. The results show that the prepared fluorine certified reference material for fluoroether rubber has accurate value and good homogeneity and stability.

Air‐based polyethylene fragmentation with high yield to form microplastic particles as reference material candidates

AbstractMicroplastic (MP) particles with sizes between 1 and 1000 µm are widely distributed worldwide. Origin, transport pathways, and fate are poorly known, as sampling, sample preparation, and detection methods are major challenges. In addition, reference materials that mimic environmental particles are lacking. The most challenging is the yield of MP particle production and the need for resource‐intensive grinding with liquid nitrogen. In this paper, a machine is designed to produce aged microplastic particles as reference material candidates with high yield. The machine is based on ultraviolet aging of a thin foil and mechanical fragmentation using clean air. An example of aging and fragmentation of high‐density polyethylene with additional physical and chemical characterization of shape, size, aging state by carbonyl index, and density is presented.

The importance of metrological tools to implementation of alternative method OECD TG 428

Usually, if percutaneous absorption tests are conducted in accordance with OECD Guideline 428, in vitro determination is accepted by mainly regulatory agencies. In this paper, we focus on the lack of comparability of the results regarding the permeation parameter/flow rate, although it is widely discussed in the literature. This work sought to evaluate the absorption of caffeine using Franz-type diffusion cell with porcine ear skin samples, varying the storage duration and the way to handle them. Metrological tools were used for caffeine quantification such as certified reference material candidate, calibrated instruments, and validated methodology. Our results corroborate with the recommendation that membranes should be freshly prepared or frozen for short periods. Samples frozen for approximately one year should not be used because they present high cutaneous absorption. The results obtained for the absorption rate (J) are comparable to the results obtained by previous studies using similar experimental conditions. The evidence of the barrier characteristic promoted by the stratum corneum and the effect promoted by the storage time is shown through J = 6.25 ± 0.48 μg/cm2/h. We demonstrated the importance of metrological tools to guarantee reproducibility and comparability of the results between different laboratories.

Assessing the Variability of Cell-Associated HIV DNA Quantification through a Multicenter Collaborative Study.

ABSTRACTReliable and accurate quantification of cell-associated HIV DNA (CA HIV DNA) is critical for early infant diagnosis, clinical management of patients under therapy, and to inform new therapeutics efficacy. The present study assessed the variability of CA HIV DNA quantification obtained from various assays and the value of using reference materials to help harmonize the measurements. Using a common set of reagents, our multicenter collaborative study highlights significant variability of CA HIV DNA quantification and lower limit of quantification across assays. The quantification of CA HIV DNA from a panel of infected PBMCs can be harmonized through cross-subtype normalization but assay calibration with the commonly used 8E5 cell line failed to reduce quantification variability between assays, demonstrating the requirement to thoroughly evaluate reference material candidates to help improve the comparability of CA HIV DNA diagnostic assay performance.IMPORTANCE Despite a global effort, HIV remains a major public health burden with an estimated 1.5 million new infections occurring in 2020. HIV DNA is an important viral marker, and its monitoring plays a critical role in the fight against HIV: supporting diagnosis in infants and underpinning clinical management of patients under therapy. Our study demonstrates that HIV DNA measurement of the same samples can vary significantly from one laboratory to another, due to heterogeneity in the assay, protocol, and reagents used. We show that when carefully selected, reference materials can reduce measurement variability and harmonize HIV DNA quantification across laboratories, which will help contribute to improved diagnosis and clinical management of patients living with HIV.

The use of ANOVA-PCA and DD-SIMCA in the development of corn flour laboratory reference materials

The development of a collaborative study as a requirement for the preparation of a laboratory reference material candidate is reported in this paper. The evaluation was performed by 13 laboratories invited to quantify the calcium, potassium, magnesium, phosphorus, copper, iron, manganese and zinc; 8 of them presented results for all the analytes under investigation. The data were statistically analyzed by applying the z-score robust technique as recommended by ISO Guide 35. For the potassium element, laboratories 4 and 13 presented questionable results. Laboratory 5 proved to be unsatisfactory for calcium and zinc. ANOVA-PCA and DD-SIMCA were also applied to evaluate stability and interlaboratory studies results, respectively. It has been demonstrated that multivariate data analysis can be successfully applied as an alternative method to the recommendations made by ISO 13528 and ISO Guide 35 with defined confidence intervals.

Feasibility of Reference Material Certification for Speed of Sound and Attenuation Coefficient Based on Standard Tissue-Mimicking Material

Speed of sound and attenuation are essential for characterizing reference materials such as biological tissue-mimicking materials (TMMs) used in ultrasonic applications. There are many publications on the manufacture of TMMs and the measurement of their properties. However, no studies in the literature have applied the metrological approach of International Organization for Standardization (ISO) Guide 35 to certify biological ultrasound TMMs as candidates for reference materials (RMs). The work described here was aimed at studying the process for manufacturing fat, muscle and aorta artery TMMs, including the study of the homogeneity, stability, trend and characterization of TMMs. The properties of interest were the speed of sound (SoS) and attenuation coefficient (AttC) at 7.5 MHz, with target expanded uncertainty of 40 m/s and 0.3 dB/cm, respectively. The short-term stability study was 2 mo at 4°C and 40°C (simulating possible transportation conditions). The long-term stability study lasted an additional 4 mo with the TMM at 22°C (simulating possible storage conditions). Homogeneity was evaluated before the stability study. Uncertainties associated with homogeneity, stability, characterization and trend were duly calculated. No trend was observed in this study, but the AttC spread widely during the stability test, substantially enlarging the final uncertainty. Therefore, this property could not be used to certify TMM candidates as RMs. However, the SoSs for most TMMs lay within the target uncertainty, disclosing viability to certify TMMs as RMs for this property. Assigned values for SoS were 1560 m/s for aorta TMM with an average expanded uncertainty for certificate validity of 12 mo (Ue;12=20 m/s), 1552 m/s for muscle TMM (Ue;12=20 m/s) and 1494 m/s for fat TMM (Ue;12=11 m/s). Thus, TMMs were proved suitable to be certified as RMs for SoS.

The stability study of electrolytic conductivity synthetic wastewater

The accurate and traceable measurement of electrochemical parameters, such as electrolytic conductivity, in water environment is crucial for water quality monitoring. This can be achieved by the use of metrological traceable certified reference material produced according to ISO 17034. It requires stability test of the reference material candidate as part of the certification for a new reference material. This study is focused on monitoring of the stability of electrolytic conductivity synthetic wastewater, as an example of complex solution containing high concentration of ions. The stability study is focused on the material of the packaging bottle, the shelf-life duration and the high temperature representing a shipping condition. The results demonstrate that the electrolytic conductivity synthetic wastewater is stable for all the conditions tested, but the synthetic wastewater packaged in glass bottle has longer shelf-life. The results confirmed that the synthetic wastewater has potential to be developed as a certified reference material.

ELEMENTAL CHARACTERIZATION OF COAL FLY ASH BY NEUTRON ACTIVATION ANALYSIS TOWARDS REFERENCE MATERIAL CERTIFICATION

&lt;p&gt;Coal combustion by-products, such as coal fly ash, has known as a significant source of potentially toxic elements that may affect the environment since the increase of coal utilization as power fuel in Indonesia. Issuing the policies to protect the environment and public health is often based on analytical results. The quality of data analysis is very important since many crucial policies related to public health and environmental protections are based on the analytical results. Considering the need for reference material in ensuring the validity and reliability of the analytical results, reference material candidate of coal fly ash is being developed. Elemental characterization as one of the important parts in certifying the reference material is carried out using Neutron Activation Analysis (NAA) since it considered as high accuracy analytical method and commonly used to certified many reference materials throughout the world. Our NAA facility performance was assessed through optimizing analytical conditions by varying samples weight, method validation, and comparison test with other techniques as well. As much as 25, 100, and 250 mg of sample weight were assessed for its homogeneity effect. Method validation using SRM NIST 1633b had shown good results with bias not more than 10% compared to its certificate values. A comparison test with other results also showed a great agreement.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

Potency of Catfish (Clarias sp.) Protein Hydrolysates as Candidates Matrices for Microbiology Reference Material

Fish protein hydrolysate (FPH) is a derivative product of fish proteins containing smaller peptides and amino acids. FPH products have high water solubility, good emulsion capacity, and large expanding ability. With its functional properties, it allows FPH to be used as a raw material in the manufacturing of secondary microbiological reference materials. This study was intended to characterize catfish (Clarias sp.) FPH as a candidate for the matrix of microbial secondary reference. The FPH was prepared through enzymatic hydrolysis, freeze-drying and milling. The hydrolysis processes were carried out using 5% (w/w) papain, 55 °C for 5 hours, then the papain activity was stopped by increasing the temperature to 80 °C for 20 minutes.The FPH was combined with gelatine, sodium glutamate, glucose solution, and was spiked with Salmonella enteritica sv Enteritidis and freeze-dried. Results showed that catfish FPH was yellowish-white powder with a FPH yield of 11.05%. The proximate analysis of FPH revealed the moisture content of 3.77 ± 0.12%, ash content of 7.26 ± 0.03%, protein content of 86.09 ± 0.17%, and fat content of 1.38 ± 0.07%. The protein content of the FPH was greater than skim milk (33.42%). Carbohydrate levels of catfish FPH and skim milk were 1.56% and 57.46%, respectively. The best concentration of catfish FPH to perform as a microbiological reference material was 14%, obtained from highest viability of Salmonella bacteria and homogeny. The candidate for reference material were stable at storage temperatures of -20 oC.

Homogeneity and stability of a secondary microbiological reference material candidate for Salmonella in fish matrix

Reference material (RM) is defined as a material, sufficiently homogeneous and stable with respect to one or more specified properties which has been established to be fit for its intended use in a measurement process. RM is one of the tools used to assess laboratory performance on an ongoing basis, as quality control in conducting testing and can be used to calibrate an equipment and to validate or verify the testing method. Currently microbiological reference materials with fish matrices are not much available so that there is a need for RM with fisheries matrices specification. Comprehensive studies of homogeneity and stability are need to be able to develop of any reference material. Initially, a feasibility study revealed a suitable processing procedure for fish matrix, the fish protein hydrolysate (FPH) was prepared by enzymatic hydrolysis, freeze-drying, and milling. Microbiological reference material with fish matrix were shown to be sufficiently homogeneous, and storage at temperatures of -20°C for 4 weeks statistically showed the effect of storage time (P value that was significant at 5% significance level). These results provide the basis for the development of a RM for Salmonella in fish matrix.

Particle induced X-ray emission and Rutherford backscattering spectrometry for testing homogeneity of environmental certified reference material candidates

ABSTRACT Taking advantages of non-destructive techniques, between-bottles homogeneity tests were carried out in term of elemental composition of seven certified reference materials (CRMs) candidates using particle-induced X-ray emission technique (PIXE). A combination of PIXE and RBS techniques (Rutherford backscattering spectrometry) was also used for CRMs candidates having biological matrices. The CRMs candidates have the matrices of soil, sediment, dust, fish muscle, leaves and fruit, which will be certified for some major, minor and trace elements. One batch was produced for each CRM candidate, which included 80 bottles. Between-bottles homogeneity tests were performed for each CRM candidate using seven representative bottles. The repeatability of measurements by PIXE and RBS was examined. The relative standard deviations (RSD) and relative average deviation (RAD) of the elements contents were considered for variability assessment for both repeatability and between-bottles homogeneity. Al, Si and Fe showed good repeatability with RSD and RAD of <4%, while Mg, S, Cl, K, Ca, Mn and Sr showed RSD and RAD in the range of 4–10%. A content of one element in the examined CRMs candidates, with the exception of the date fruit, showed RSD and RAD of <5% indicating good between-bottles homogeneity. For date fruit, the relative error of all elements was <10%, with the exception of Si and Zn, while RAD of S, Cl and K were <10%.

Long-term stability test of elemental content in new environmental certified reference material candidates using ICP OES and ICP-SFMS

The need of certified reference materials (CRMs) is consistently growing due to various aspects in the environment and communities. A research project on the production of seven environmental CRMs with international collaboration has been proposed as a pilot study. The CRMs are intended to be applied for quality assurance of toxicological, environmental, and food analyses of matrices of soil, sediment, dust, leaves, date fruit, and edible fish muscle for some elements at macro-, micro-, and trace-levels. This article demonstrates stability tests, as an essential parameter for CRMs, of element content in CRMs using ICP OES and ICP-SFMS. Useful and simple approaches were proposed for stability assessment. Cluster analysis of stability revealed that Cu, Fe, Mn, and Al in CRMs of soil matrices were the most similar elements in term of stability; and likewise for Cu, Fe, and Mn in CRMs of biological matrices. An overall stability of all elements in each CRM was also assessed by paired samples t-test at confidence interval of 95%. The p values of all CRMs are all >.05 indicating no significant variation on elements contents before and after underwent storage, besides limited transport conditions. Despite this study presents a simple way for assessment of stability of elements concentrations in CRMs, further stability studies are required concerning several intervals to study the effect of conditions on stability.

Natural Titanite Reference Materials forIn SituU‐Pb and Sm‐Nd Isotopic Measurements byLA‐(MC)‐ICP‐MS

Titanite is a common accessory mineral that preferentially incorporates considerable amounts of U and light rare earth elements in its structure, making it a versatile mineral forin situU‐Pb dating and Sm‐Nd isotopic measurement. Here, we presentin situU‐Pb ages and Sm‐Nd isotope measurement results for four well‐known titanite reference materials (Khan,BLR‐1,OLT1 andMKED1) and eight titanite crystals that could be considered potential reference material candidates (Ontario,YQ‐82, T3, T4,TLS‐36,NW‐IOA, Pakistan and C253), with ages ranging from ~ 20 Ma to ~ 1840 Ma. Results indicate thatBLR‐1,OLT1, Ontario,MKED1 and T3 titanite have relatively homogeneous Sm‐Nd isotopes and low common Pb and thus can serve as primary reference materials for U‐Pb and Sm‐Nd microanalysis.YQ‐82 and T4 titanite can be used as secondary reference materials forin situU‐Pb analysis because of their low common Pb. However, internal structures and mineral inclusions inYQ‐82 will require careful selection of suitable target domains. Pakistan titanite is almost concordant with an age of 21 Ma and can be used as a reference material when dating Cenozoic titanite samples.

Coffea arabica and C. canephora discrimination in roasted and ground coffee from reference material candidates by real-time PCR

To produce specific desirable coffee blends, Coffea arabica and C. canephora are mixed each other, in some cases to suit consumer preference, but in others to reduce production costs. In this scenario, the aim of this work was to evaluate standard candidate reference materials (RMc) for analysis of different blends of roasted and ground coffee. For this purpose, we analyzed different percentages of C. arabica and C. canephora (100:0; 50:50; 25:75; and 0:100, respectively). These RMc samples were developed in a previous study with green coffee beans submitted to medium roasting. In this work, coffee species differentiation (C. arabica and C. canephora) was analyzed by real-time PCR, using specific primers previously developed, called ARA primers. The RMc material with 100% C. canephora did not present amplification, in contrast with the samples containing C. arabica, which all presented amplification. These results indicate the specificity of ARA primers for C. arabica and that the detection system assay can be used as a promising molecular tool to identify and quantify percentages of C. arabica in different coffee blends.

Homogeneity study of candidate reference material (contaminated soil) based on determination of selected metals, PCBs and PAHs

Reference materials (RMs) are an indispensable part of QA/QC system and have played a critical role in the continual expansion of analytical capabilities of the analytical laboratories. The homogeneity study of the candidate for reference material is essential for the quality of reference material (certified reference material) used in quality assurance activities. The homogeneity study of candidate for reference materials of contaminated soil collected from a plot situated near the chemical factory “Rokita” in Brzeg Dolny (Silesian Region of Poland) for total metal content of Mg, Fe, Zn, Hg and analytes from a group of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) was carried out. The experimental design and study by using one way ANOVA showed no significant difference within and between bottle homogeneity and the material was found homogeneous. Total expanded uncertainty (k = 2) due to heterogeneity for all four metals and analytes from a group of PCBs and PAHs was determined within the range of 5–15%. The candidate for reference material of fortified soil was found to be homogeneous up to the minimum sample size of 100 mg for total Hg, 500 mg for Mg, Fe, Zn and 1 g from a group of PCBs and PAHs, and thus is suitable for certification.

Stability assessment of a bovine kidney reference-material candidate

Reference materials are used worldwide and necessary for quality control purposes during analytical determinations. The present study describes the stability evaluation of a bovine kidney reference-material candidate. An isochronous layout was performed, in which the flasks involved are exposed at different temperatures for different time periods and then are analyzed at the same time at the end of the study. The mass fractions of ten inorganic constituents were determined using instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Statistical analysis, univariate and multivariate, showed no significant differences in composition between units exposed to the different temperatures and times. The reference material may be transported under normal transportation conditions and the certified values and uncertainties will continue to be valid for a period of 2 years.

SAXS analysis of single- and multi-core iron oxide magnetic nanoparticles.

This article reports on the characterization of four superparamagnetic iron oxide nanoparticles stabilized with dimercaptosuccinic acid, which are suitable candidates for reference materials for magnetic properties. Particles p1 and p2 are single-core particles, while p3 and p4 are multi-core particles. Small-angle X-ray scattering analysis reveals a lognormal type of size distribution for the iron oxide cores of the particles. Their mean radii are 6.9 nm (p1), 10.6 nm (p2), 5.5 nm (p3) and 4.1 nm (p4), with narrow relative distribution widths of 0.08, 0.13, 0.08 and 0.12. The cores are arranged as a clustered network in the form of dense mass fractals with a fractal dimension of 2.9 in the multi-core particles p3 and p4, but the cores are well separated from each other by a protecting organic shell. The radii of gyration of the mass fractals are 48 and 44 nm, and each network contains 117 and 186 primary particles, respectively. The radius distributions of the primary particle were confirmed with transmission electron microscopy. All particles contain purely maghemite, as shown by X-ray absorption fine structure spectroscopy.

Investigation of the effects of food processing and matrix components on the analytical results of ELISA using an incurred gliadin reference material candidate

Disorders induced by cereal proteins (e.g. wheat allergy, celiac disease) are widespread in human population. Since their only effective treatment is the avoidance of the problematic proteins, patients have to be familiar with the composition of food products. For checking special foods produced for them, proper analytical methods are necessary. At the moment, in gluten analysis there are no reference methods and reference materials which model real food matrices. During the production and experimental utilisation of our previously developed reference material candidate, numerous questions emerged. As our model product is a real food matrix, interactions can be present between gluten proteins and other macro and micro components. Fat content of the baked cookies is almost 20%, which might affect the results of ELISA measurements. The detectable gluten content is significantly increasing after the defatting procedure, as a pre-treatment of samples. Moreover, baking is a common food processing step that mig...