Matrix Reference Materials Research Articles

Development of two reference materials for all trans-retinol, retinyl palmitate, α- and γ-tocopherol in milk powder and infant formula

Vitamins are important food constituents that can be present in almost every foodstuff. Food quality and safety depends on food surveillance by reliable quantitative analysis enabled by appropriate quality control. Certified matrix reference materials are versatile tools to support quality assurance and control. However, in the case of vitamins, which are important in various foods, there is a lack of matrix reference materials. Two certified reference materials for the determination of all–trans-retinol, retinyl palmitate, and α- and γ-tocopherol in milk powder and infant formula have been developed by the National Institute of Standards, Egypt. This article presents the preparation, characterization, homogeneity, and stability testing as well as statistical treatment of data and certified value assignment. The assignment of the certified values and associated uncertainties in the prepared natural-matrix reference materials were based on the widely used approach of combining data from independent and reliable analytical methods.

Novel application of high pressure processing for the production of shellfish toxin matrix reference materials

The production of homogeneous and stable matrix reference materials for marine biotoxins is important for the validation and implementation of instrumental methods of analysis. High pressure processing was investigated to ascertain potential advantages this technique may have in stabilising paralytic shellfish poisoning toxins in shellfish tissues compared to untreated materials. Oyster tissues were subjected to a range of different temperatures and pressures, with results showing a significant reduction in biological activity in comparison to control samples, without significantly altering toxin profiles. Tissue subjected to pressures >600 MPa at 50 °C was assessed for homogeneity and stability. The sample homogeneity was determined using a pre-column oxidation LC-FLD method and shown to be within accepted levels of within batch repeatability. Short and long-term stability studies were conducted over a range of temperatures, with analysis by pre and post column oxidation LC-FLD demonstrating improved stability of toxins compared to the untreated materials and with epimerisation of toxins also notably reduced in treated materials. This study confirmed the technique of high pressure processing to improve the stability of PSP toxins compared to untreated wet tissues and highlighted its applicability in reference material preparation where removal of biological activity is of importance.

Interlaboratory comparison of two AOAC liquid chromatographic fluorescence detection methods for paralytic shellfish toxin analysis through characterization of an oyster reference material.

An interlaboratory ring trial was designed and conducted by the Centre for Environment, Fisheries, and Aquaculture Science to investigate a range of issues affecting the analysis of a candidate Pacific oyster paralytic shellfish toxin reference material. A total of 21 laboratories participated in the study and supplied results using one or more of three instrumental methods, specifically precolumn oxidation (Pre-COX) LC with fluorescence detection (FLD; AOAC Official Method 2005.06), postcolumn oxidation (PCOX) LC-FLD (AOAC Official Method 2011.02), and hydrophilic interaction LC/MS/MS. Each participant analyzed nine replicate samples of the oyster tissue in three separate batches of three samples over a period of time longer than 1 week. Results were reported in a standardized format, reporting both individual toxin concentrations and total sample toxicity. Data were assessed to determine the equivalency of the two AOAC LC methods and the LC/MS/MS method as well as an assessment of intrabatch and interbatch repeatability and interlaboratory reproducibility of each method. Differences among the results reported using the three methods were shown to be statistically significant, although visual comparisons showed an overlap between results generated by the majority of tests, the exception being the Pre-COX quantitation of N-hydroxylated toxins in post ion-exchange fractions. Intralaboratory repeatability and interlaboratory reproducibility were acceptable for most of the results, with the exception of results generated from fractions. The results provided good evidence for the acceptable performance of the PCOX method for the quantitation of C toxins. Overall the study showed the usefulness of interlaboratory analysis for the characterization of paralytic shellfish poisoning matrix reference materials, highlighting some issues that may need to be addressed with further method assessment at individual participant laboratories.

Certification of Three Reference Materials for α- and γ-Tocopherol in Edible Oils

Tocopherols are important vegetable oil constituents, and their reliable quantitative analysis depends largely on the existence and quality of certified reference materials (CRMs) which provides traceability of the measurement results to the SI units. Since there is a lack of suitable CRMs in case of tocopherols analysis, three matrix reference materials from corn, peanut and soybean oils were certified for the content of α and γ-tocopherols. Homogeneity and stability of the prepared reference materials were studied and certification was done by two independent chromatographic analytical methods. The measurement results were statistically treated and the certified values of α and γ-tocopherol in corn, peanut and soybean oils were assigned and their associated expanded uncertainties were estimated as: 322.04 ± 8.62, 771.48 ± 15.31, 106.23 ± 5.19, 108.94 ± 9.72, 140.66 ± 5.93, 418.00 ± 14.36 mg/kg, respectively. These values were found useful for many food testing laboratories in validation of analytical methods and analytical quality control.

The harmonisation of growth hormone measurements: Taking the next steps

For over 20years differences in results of growth hormone (GH) measurement have been recognised as being significant enough to lead to misdiagnosis and inappropriate management of patients with GH-related disorders. Whilst issues of method standardisation, variable antibody specificity, use of different reporting units with different conversion factors, and interference from GH binding protein have been acknowledged as contributing to the discrepancies, inconsistent approaches to method harmonisation have hampered opportunities to enhance the evidence base for GH measurements. Amongst the first steps to be taken, international collaboratives recommended the universal adoption of the International Standard 98/547 and the reporting of results in mass units. Whilst inter-method variability may have improved over the last 10years, clinically significant differences remain. A more recently recognised issue contributing to the discrepancies may be the differences in the matrix materials used by kit manufacturers to assign values to their calibrants. The establishment of an international harmonisation oversight group is recommended: its key roles to include identification of a commutable matrix reference material, assessing the clinical significance of assay interferents, the evaluation of liquid chromatography–mass spectrometry as a reference measurement procedure and the provision of acceptance criteria for the clinical application of GH methods.

Application of LA-ICP-MS as a rapid tool for analysis of elemental impurities in active pharmaceutical ingredients

The control of inorganic contaminants in active pharmaceutical ingredients has a significant role in the quality control of drug products. The concentration limits for metal residues in drug products have been defined by various regulatory guidelines. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful and fast analytical technique for multi-elemental analysis. A disadvantage in using LA-ICP-MS method is the lack of matrix reference materials for validation and calibration purposes. This article focuses on the handling strategy of laboratory-made matrix calibration standards for the quantification of elemental impurities in an active pharmaceutical ingredient by LA-ICP-MS.

Determination of nivalenol in food and feed: an update

Based on the recent scientific opinion published by the EFSA CONTAM panel on the risks to human and animal health related to the presence of nivalenol in food and feed, this article provides an update on the determination of thisFusarium mycotoxin. After a brief introduction into the chemistry of nivalenol, chromatographic methods as well as other approaches are being discussed. Methods for the determination of nivalenol are well established and can be applied for the analysis of cereals, food, feed and biological samples. Accurate quantification of nivalenol is mostly carried out by liquid chromatography coupled with (multi-stage) mass spectrometry (MS) often within a multi-analyte approach. Some novel techniques, such as direct analysis in real time (DART) MS and electrochemical methods, have shown potential to determine nivalenol, but applications for routine measurements are not yet available. None of the currently available analytical methods has been formally validated in interlaboratory validation studies. While a certified calibrant for nivalenol is available, no matrix reference materials have been developed. Due to the scarcity of appropriate antibodies also no rapid immunochemical methods specific for nivalenol have become available.

Activity concentration measurements of 137Cs, 90Sr and 40K in a wild food matrix reference material (Wild Berries) CCRI(II)-S8

In 2009, the CCRI approved a supplementary comparison to be organized by the IRMM as pilot laboratory for the activity concentrations of 137Cs, 90Sr and 40K in a matrix material of dried bilberries. The organization of this comparison and the material and measurement methods used are described. The supplementary comparison reference values (SCRV) for each of the three radionuclides are given together with the degrees of equivalence of each participating laboratory with the SCRV for the specific radionuclide. The results of this supplementary comparison allow the participating NMIs/designated institutes to declare calibration and measurement capabilities (CMCs) for the given radionuclides in a similar type of food matrix, an important aspect given the relatively few supplementary comparisons for activity in matrix materials organized so far.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A feasibility study into the production of a freeze-dried oyster reference material for paralytic shellfish poisoning toxins

Matrix reference materials are an essential component for the validation and quality control of analytical methodologies for the quantitation of marine biotoxins in shellfish. Given the potential advantages of reference materials in powder form, a study was conducted to assess the feasibility for the production of a freeze-dried oyster tissue reference material containing a range of important paralytic shellfish poisoning toxins. One bulk sample of a wet oyster tissue homogenate was generated following mass culturing of toxic Alexandrium and oyster feeding experiments. The bulk tissue was used to prepare untreated wet frozen aliquots with the remainder being freeze-dried and processed into appropriately-sized powder samples. A pre-column oxidation LC-FLD analysis was used to confirm the absence of any chromatographic artefacts resulting from the processing and to confirm acceptable homogeneity of the tissues. Excellent stability over both the short-term (1 month) and long-term (1 year) of the freeze-dried material was demonstrated as compared with the stability of the untreated wet tissue. A post-column oxidation LC-FLD method was used to confirm the absence of toxin epimerisation in freeze-dried tissues which were observed in the wet tissues. Overall the work showed the feasibility of an approach to produce a homogenous freeze-dried oyster matrix material with enhanced stability in comparison to the untreated wet tissue. The potential for use of the process for preparation of large scale production batches of a freeze-dried CRM for paralytic shellfish poisoning toxins has therefore been demonstrated.

Tools for Assuring Data Quality in Natural Products Studies: The NIH/ODS Analytical Methods and Reference Materials Program (AMRM)

Assessing the quality of natural products can be a challenge. Most definitions of quality start with assurance that biomass has been properly identified and ranges through proper sanitation and absence of deleterious substances such as pesticides, toxic elements, natural toxins, and non-target plant material. Some quality systems set minimum and maximum content standards for desirable phytochemicals. Evaluation of the accuracy, precision and reproducibility of chemical measurements in natural products and biological specimens can be difficult. In 2002, the NIH Office of Dietary Supplements created a new program, the Analytical Methods and Reference Materials Program, to provide tools to address challenges inherent to analysis of natural products. The program is stakeholder driven, with participation by government agencies, non-governmental organizations, academic researchers, and the private sector. It provides tools for demonstrating the integrity of analytical data: 1) published methods that have undergone formal validation studies (useful for analysts just entering the field and for dispute resolution); 2) certified matrix reference materials for use as method development and method evaluation tools; 3) certified calibration standard solutions for use in compound identification and instrument calibration; 4) laboratory quality assurance programs to assist laboratories in evaluating and improving method, analyst, and laboratory performance. The poster describes the AMRM, provides an overview of accomplishments and resources made available by the program, and reviews suggestions for future program directions made by an external expert review panel charged with program evaluation.

Feasibility studies into the production of gamma-irradiated oyster tissue reference materials for paralytic shellfish poisoning toxins

A study was conducted to assess the feasibility for the production of sterile, stable and homogenous shellfish reference materials containing known concentrations of paralytic shellfish poisoning (PSP) toxins. Pacific oysters were contaminated with toxins following mass culturing of toxic algae and shellfish feeding experiments. Live oysters were shucked and tissues homogenised, before measuring into multiple aliquots, with one batch subjected to gamma irradiation treatment and the other remaining untreated. The homogeneity of both batches of samples was assessed using a pre-column oxidation liquid chromatography with fluorescence detection (Pre-COX LC-FLD) method and shown to be within the limits of normal within-batch repeatability. A twelve-month stability experiment was conducted for both untreated and gamma irradiated batches, specifically examining the effects of long term storage at −20 °C, +4 °C and +40 °C. Results indicated mostly good stability of PSP toxins in both materials when stored frozen at −20 °C, but with the instability of GTX2&3 concentrations in the untreated tissues eliminated in the irradiated tissues. Analysis using a post-column oxidation (PCOX) LC-FLD method also showed epimerisation in both GTX1&4 and GTX2&3 epimeric pairs in untreated samples after only 6 months frozen storage. This issue was not present in the tissues irradiated before long term storage. Biological activity testing confirmed the absence of bacteria in the irradiated samples throughout the 12 month study period. With such results there was clear evidence for the potential of increasing the scale of the mass culturing and shellfish feeding for the production of large batches of tissue suitable for the preparation of a certified matrix reference material. Overall results demonstrated the feasibility for production of oyster reference materials for PSTs, with evidence for prolonged stability following gamma irradiation treatment and storage at −20 °C.

NIH/ODS Analytical Methods and Reference Materials (AMRM) Program: Accomplishments and Future Directions

Assuring the quality of natural products is a challenge to manufacturers, researchers, regulators, and consumers. Because biological materials contain complex mixtures of metabolites, they pose unique analytical challenges. Evaluation of the accuracy, precision and reproducibility of chemical measurements made in these complex matrices is vital. The AMRM Program provides tools to help scientists in the dietary supplement and nutrition communities address these challenges. Program elements include: 1) publicly available methods that have undergone formal validation studies (useful for facilitating method selection and for dispute resolution); 2) suites of certified matrix reference materials for use as method development and method evaluation tools; 3) certified calibration standard solutions for use in analyte identification and instrument calibration; 4) fee‐free laboratory quality assurance programs to assist laboratories in evaluating and improving method, analyst, and laboratory performance. The poster will provide an overview of accomplishments and resources made available by the program, and include future program directions.

The NIH/ODS Analytical Methods and Reference Materials Program: Accomplishments and Future Directions

Assuring the quality of natural products is a challenge to manufacturers, researchers, regulators, and consumers. There are numerous ways to describe quality, often starting with botanical identity and sanitation and expanding to include specifications for pesticides, toxic elements, non-target plant material, and content of desirable and undesirable natural chemicals. Because plants contain complex mixtures of secondary metabolites, they pose unique analytical challenges. Evaluation of the accuracy, precision and reproducibility of chemical measurements made in these complex matrices is difficult. In 2002, the NIH Office of Dietary Supplements created a new program, the Analytical Methods and Reference Materials Program (AMRM), to provide tools to help members of the supplement community address these challenges. The program is stakeholder driven, with participation by government agencies, non-governmental organizations, academic researchers, and the private sector. The program provides the user community with several tools for demonstrating the integrity of analytical data: 1) published, publicly available methods that have undergone formal validation studies (useful for analysts just entering the field and for dispute resolution); 2) suites of certified matrix reference materials for use as method development and method evaluation tools; 3) certified calibration standard solutions for use in compound identification and instrument calibration; 4) no-cost laboratory quality assurance programs to assist laboratories in evaluating and improving method, analyst, and laboratory performance. The presentation will describe the structure and evolution of the NIH AMRM, provide an overview of accomplishments and resources made available by the program, and review suggestions for future program directions made by an external expert review panel charged with program evaluation.

Development of certified matrix reference materials for quality assurance of screening 134Cs and 137Cs in food

A certified reference material using activated alumina powder certified for activity of 134Cs and 137Cs was developed. The results of the verification and the certification are described. The certified reference material can be used for quality assurance of screening activity measurements of 134Cs and 137Cs in food/foodstuffs. Commercially available equipments were experimentally tested using the CRM and another CRM including 40K. The results of these tests are also shown.

Food safety measurement issues: way forward

Ensuring food safety (FS) is a persistent concern frequently faced by many countries. Safeguarding the quality of food that is fit for human consumption is the primary responsibility of the governmental regulatory agencies. For most part, agro-industries and food processors assume voluntary leadership for producing safe food. However, in the event of FS breach, the regulatory responsibility kicks into identify and rectify the situation. Notwithstanding whether it is the regulator or the industry that institutes the remedial action (e.g. improved hygiene and refined agricultural and manufacturing practices), the role of laboratory measurements is central in safeguarding the integrity of a functioning FS system. There are many analytical tools available to implement this task, such as validated analytical methods, natural matrix reference materials, field tested monitoring systems (proactive assessment) and effective surveillance systems (constant vigilance to prevent repeat safety violations). Way forward: existing FS tools are insufficient and should be strengthened with innovative approaches. Examples are: assembling swift intervention logistics to face FS breaches; rapid response systems including communication; robust metrology based measurement systems located at strategic locations in the country; and inter-disciplinary human resource to match the need for capacity development. These issues are discussed.

Need and use of reference materials in a comprehensive countrywide monitoring of radionuclides

The reliability of measurement results is essential for forming a common database of a laboratory network, because a well-maintained and consistent database is the crucial point of countrywide monitoring. Reference materials are important tools in realizing some aspects of quality assurance; they are especially useful in harmonizing work within the network. Among usual types of reference materials in radio analytics solutions, matrix reference materials and some special reference objects are used. All classes of reference materials should be used depending on the purpose of the demonstration of quality, even in-house reference materials. Interlaboratory measurement comparison and performance evaluation programs play important quality assurance role in radio analytical laboratories. Fortunately, nowadays, the main task is to determine a very low radioactivity concentration in the environment; therefore, pre-concentration is necessary. Generally, the radionuclide bearing natural materials collected from sites where there had been sufficient time for natural processes to redistribute various chemically different species of radionuclides are more reliable reference materials than spiked materials—the main difference is the chemical bounding which is crucial from the point of view of the bioavailability. The need of reference material is summarized according to the intended use, like quality control, measurement validation, and instrument calibration.

The need for new isotope reference materials

Isotope reference materials are needed to calibrate and validate analytical procedures used for the determination of isotope amount ratios, procedurally defined isotope ratios or so-called δ values. In contrast to the huge analytical progress in isotope ratio analytics, the production of isotope reference materials has not kept pace with the increasing needs of isotope analysts. Three representative isotope systems are used to explain the technical and non-technical difficulties and drawbacks, on one hand, and to demonstrate what can be achieved at its best, on the other hand. A clear statement is given that new isotope reference materials are needed to obtain traceable and thus comparable data, which is essential for all kinds of isotope research. The range of available isotope reference materials and δ reference materials should be increased and matrix reference materials certified for isotope compositions or δ values, which do not exist yet, should be provided.

Transformation of paralytic shellfish poisoning toxins in Crassostrea gigas and Pecten maximus reference materials

Matrix reference materials are an important requirement for the assessment of method performance characteristics and for routine quality control. In the field of marine toxin testing where biological assays have been used and where modern analytical testing methods are now becoming available, this requirement has become an urgent one. Various approaches are utilised for preparation of such materials in the absence of available naturally occurring toxic shellfish samples. Toxin-free shellfish may be artificially fortified through the addition of cultured toxic phytoplankton or shellfish may be incurred through natural feeding on toxic algae in a laboratory environment. Both of these approaches may be potentially affected by issues relating to the degradation or transformation of toxin analytes, so studies were conducted to assess these effects within our laboratory. A range of PSP-toxic shellfish tissues were prepared using the two approaches, in both Pacific oyster (Crassostrea gigas) and king scallops (Pecten maximus). Additionally, sub-samples of incurred Pacific oyster tissue were further treated, through addition of artificial chemical stabilisers and gamma irradiation. Two separate month-long stability trials were conducted at +4 °C on each material. Results highlighted clear evidence for improved stability of materials following shellfish feeding experiments in comparison with the tissues which had been spiked with plankton. In addition, there were clear differences in stability of toxins between the two shellfish species studied. There was evidence for good stability of C1&2 toxins in both the incurred tissues and improved stability of some toxins in tissues which had been subjected to either gamma irradiation or treatment with chemical additives. The results therefore highlighted the benefits of conducting shellfish feeding if suitable stable reference materials are to be prepared containing a full range of PSP toxin analytes. The study also highlighted the benefits of post-production treatment to prolong the stability of the materials. Work is ongoing to assess the full characteristics of candidate reference materials prepared with these approaches with the aim of producing a homogenous and stable PSP reference material in Pacific oysters.

Feasibility study for producing a carrot/potato matrix reference material for 11 selected pesticides at EU MRL level: Material processing, homogeneity and stability assessment

The feasibility for producing a matrix reference material for selected pesticides in a carrot/potato matrix was investigated. A commercially available baby food (carrot/potato-based mash) was spiked with 11 pesticides at the respective EU maximum residue limits (MRLs), and further processed by either freezing or freeze-drying. Batches of some 150units were produced per material type. First, the materials were assessed for the relative amount of pesticide recovered after processing (ratio of pesticide concentration in the processed material to the initially spiked pesticide concentration). In addition, the materials’ homogeneity (bottle-to-bottle variation), and the short-term (1month) and mid-term (5months) stability at different temperatures were assessed. For this, an in-house validated GC–EI-MS method operated in the SIM mode with a sample preparation procedure based on the QuEChERS (“quick, easy, cheap, effective, rugged, and safe”) principle was applied. Measurements on the frozen material provided the most promising results (smallest analyte losses during production), and also freeze-drying proved to be a suitable alternative processing technique for most of the investigated pesticides. Both the frozen and the freeze-dried material showed to be sufficiently homogeneous for the intended use, and storage at −20°C for 5months did not reveal any detectable material degradation. The results constitute an important step towards the development of a pesticide matrix reference material.

A new monitor set for the determination of neutron flux parameters in short-time k0-NAA

Multipurpose research reactors such as LVR-15 in Řež require monitoring of the neutron flux parameters (f, α) in each batch of samples analyzed when k0 standardization in NAA is to be used. The above parameters may change quite unpredictably, because experiments in channels adjacent to those used for NAA require an adjustment of the reactor operation parameters and/or active core configuration. For frequent monitoring of the neutron flux parameters the bare multi-monitor method is very convenient. The well-known Au–Zr tri-isotopic monitor set that provides a good tool for determining f and α after long-time irradiation is not optimal in case of short-time irradiation because only a low activity of the 95Zr radionuclide is formed. Therefore, several elements forming radionuclides with suitable half-lives and Q0 and Ēr parameters in a wide range of values were tested, namely 198Au, 56Mn, 88Rb, 128I, 139Ba, and 239U. As a result, an optimal mixture was selected consisting of Au, Mn, and Rb to form a well suited monitor set for irradiation at a thermal neutron fluence rate of 3×1017 m−2 s−1. The procedure of short-time INAA with the new monitor set for k0 standardization was successfully validated using the synthetic reference material SMELS 1 and several matrix reference materials (RMs) representing matrices of sample types frequently analyzed in our laboratory. The results were obtained using the Kayzero for Windows program.