The challenges and benefits of implementing the requirements of ISO/IEC 17043 by PT/EQA providers

ISO/IEC 17043 Conformity assessment??general requirements for proficiency testing is intended to replace previous international guides used to assess the competence of proficiency testing (PT) providers. It expands on the requirements of previous guides and is intended to accommodate PT providers of calibration laboratories and testing laboratories handling both qualitative and quantitative data. QMP-LS is an office-based external quality assessment provider for medical laboratories in Ontario, Canada and operates 46 different PT schemes for approximately 250 diagnostic tests. In 2010, these schemes were accredited to ISO/IEC 17043. Schemes included tests from the following disciplines: chemistry, hematology, microbiology, transfusion medicine, cytology, histology and genetics. Thirty of the schemes were qualitative. The challenges and benefits of implementing ISO/IEC 17043 are discussed, with particular emphasis on clauses addressing the following requirements: statistical design, determination of assigned value, homogeneity and stability testing, packaging, labeling and distribution, performance evaluation and subcontracting services.     

Development of botanical and fish oil standard reference materials for fatty acids

As part of a collaboration with the National Institutes of Health’s Office of Dietary Supplements and the Food and Drug Administration’s Center for Drug Evaluation and Research, the National Institute of Standards and Technology has developed Standard Reference Material (SRM) 3274 Botanical Oils Containing Omega-3 and Omega-6 Fatty Acids and SRM 3275 Omega-3 and Omega-6 Fatty Acids in Fish Oil. SRM 3274 consists of one ampoule of each of four seed oils (3274-1 Borage (Borago officinalis), 3274-2 Evening Primrose (Oenothera biennis), 3274-3 Flax (Linium usitatissimum), and 3274-4 Perilla (Perilla frutescens)), and SRM 3275 consists of two ampoules of each of three fish oils (3275-1 a concentrate high in docosahexaenoic acid, 3275-2 an anchovy oil high in docosahexaenoic acid and eicosapentaenoic acid, and 3275-3 a concentrate containing 60 % long-chain omega-3 fatty acids). Each oil has certified and reference mass fraction values for up to 20 fatty acids. The fatty acid mass fraction values are based on results from analyses using gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). These SRMs will complement other reference materials currently available with mass fractions for similar analytes and are part of a series of SRMs being developed for dietary supplements.

Determination of perfluorinated alkyl acid concentrations in biological standard reference materials

Standard reference materials (SRMs) are homogeneous, well-characterized materials used to validate measurements and improve the quality of analytical data. The National Institute of Standards and Technology (NIST) has a wide range of SRMs that have mass fraction values assigned for legacy pollutants. These SRMs can also serve as test materials for method development, method validation, and measurement for contaminants of emerging concern. Because inter-laboratory comparison studies have revealed substantial variability of measurements of perfluoroalkyl acids (PFAAs), future analytical measurements will benefit from determination of consensus values for PFAAs in SRMs to provide a means to demonstrate method-specific performance. To that end, NIST, in collaboration with other groups, has been measuring concentrations of PFAAs in a variety of SRMs. Here we report levels of PFAAs and perfluorooctane sulfonamide (PFOSA) determined in four biological SRMs: fish tissue (SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue), bovine liver (SRM 1577c), and mussel tissue (SRM 2974a). We also report concentrations for three in-house quality-control materials: beluga whale liver, pygmy sperm whale liver, and white-sided dolphin liver. Measurements in SRMs show an array of PFAAs, with perfluorooctane sulfonate (PFOS) being the most frequently detected. Reference and information values are reported for PFAAs measured in these biological SRMs.

Milk and serum standard reference materials for monitoring organic contaminants in human samples

Four new Standard Reference Materials (SRMs) have been developed to assist in the quality assurance of chemical contaminant measurements required for human biomonitoring studies, SRM 1953 Organic Contaminants in Non-Fortified Human Milk, SRM 1954 Organic Contaminants in Fortified Human Milk, SRM 1957 Organic Contaminants in Non-Fortified Human Serum, and SRM 1958 Organic Contaminants in Fortified Human Serum. These materials were developed as part of a collaboration between the National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC) with both agencies contributing data used in the certification of mass fraction values for a wide range of organic contaminants including polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, polybrominated diphenyl ether (PBDE) congeners, and polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners. The certified mass fractions of the organic contaminants in unfortified samples, SRM 1953 and SRM 1957, ranged from 12 ng/kg to 2200 ng/kg with the exception of 4,4′-DDE in SRM 1953 at 7400 ng/kg with expanded uncertainties generally <14 %. This agreement suggests that there were no significant biases existing among the multiple methods used for analysis.

Change of fucosylated IgG2 Fc-glycoforms in pancreatitis and pancreatic adenocarcinoma: a promising disease-classification model

The fixed constant (Fc) region of IgG is subject to changes in glycosylation state in response to diseases. On the basis of sera from 75 healthy controls, 75 pancreatitis (PT) patients, and 75 pancreatic adenocarcinoma (PAC) patients, we analyzed six fucosylated glycoforms of IgG₂ (G0F, G1F, G2F, G0FN, G1FN, and G2FN), by matrix-assisted laser desorption/ionization–Fourier-transform ion cyclotron resonance mass spectrometry (MALDI–FTICR MS), to evaluate their use as biomarkers for pancreatic diseases. Compared with healthy controls, significant increases in agalactosylated glycoforms and decreases in galactosylated glycoforms were observed for PT and PAC patients. Logistic regression analysis suggested that truncation of the sugar chain was prone to occur in PT and, especially, PAC patients. After participants were stratified by sex and age, receiver operating characteristic curve analysis revealed good overall sensitivity and specificity for discrimination of PAC and PT patients from healthy controls. A combination of G0F and galactosylation also had acceptable power for differentiating PAC patients from PT patients.

Comparison of multianalyte proficiency test results by sum of ranking differences, principal component analysis, and hierarchical cluster analysis

Sum of ranking differences (SRD) was applied for comparing multianalyte results obtained by several analytical methods used in one or in different laboratories, i.e., for ranking the overall performances of the methods (or laboratories) in simultaneous determination of the same set of analytes. The data sets for testing of the SRD applicability contained the results reported during one of the proficiency tests (PTs) organized by EU Reference Laboratory for Polycyclic Aromatic Hydrocarbons (EU-RL-PAH). In this way, the SRD was also tested as a discriminant method alternative to existing average performance scores used to compare mutlianalyte PT results. SRD should be used along with the z scores—the most commonly used PT performance statistics. SRD was further developed to handle the same rankings (ties) among laboratories. Two benchmark concentration series were selected as reference: (a) the assigned PAH concentrations (determined precisely beforehand by the EU-RL-PAH) and (b) the averages of all individual PAH concentrations determined by each laboratory. Ranking relative to the assigned values and also to the average (or median) values pointed to the laboratories with the most extreme results, as well as revealed groups of laboratories with similar overall performances. SRD reveals differences between methods or laboratories even if classical test(s) cannot. The ranking was validated using comparison of ranks by random numbers (a randomization test) and using seven folds cross-validation, which highlighted the similarities among the (methods used in) laboratories. Principal component analysis and hierarchical cluster analysis justified the findings based on SRD ranking/grouping. If the PAH-concentrations are row-scaled, (i.e., z scores are analyzed as input for ranking) SRD can still be used for checking the normality of errors. Moreover, cross-validation of SRD on z scores groups the laboratories similarly. The SRD technique is general in nature, i.e., it can be applied to any experimental problem in which multianalyte results obtained either by several analytical procedures, analysts, instruments, or laboratories need to be compared.

A multiresidual method based on ion-exchange chromatography with conductivity detection for the determination of biogenic amines in food and beverages

In the present work a sensitive and accurate method by ion chromatography and conductimetric detection has been developed for the determination of biogenic amines in food samples at microgram per kilogram levels. The optimized extraction procedure of trimethylamine, triethylamine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine from real samples, as well as the separation conditions based on a multilinear gradient elution with methanesulfonic acid and the use of a weak ionic exchange column, have provided excellent results in terms of resolution and separation efficiency. Extended calibration curves (up to 200 mg/kg, r?>?0.9995) were obtained for all the analyzed compounds. The method gave detection limits in the range 23–65 μg/kg and quantification limits in spiked blank real samples in the range 65–198 μg/kg. Recovery values ranged from 82 to 103 %, and for all amines, a good repeatability was obtained with precision levels in the range 0.03–0.32 % (n?=?4). The feasibility and potential of the method were tested by the analysis of real samples, such as tinned tuna fish, anchovies, cheese, wine, olives, and salami.

Formation of an N-formylkynurenine-derived fluorophore and its use for measuring indoleamine 2,3-dioxygenase 1 activity

Indoleamine 2,3-dioxygenase 1 (IDO1) is a tryptophan-catabolizing enzyme whose expression by a broad range of clinical tumors is associated with immunosuppression and poor patient outcome. Here we describe a new fluorescence assay for measuring IDO1 activity suitable for high-throughput screening of compound libraries for novel IDO1 inhibitors. This assay is easy to perform, requiring the addition of only one reagent prior to readout. In place of measuring kynurenine, it uses the in situ formation of an N-formylkynurenine-derived fluorophore (NFKPIP) measured at an excitation wavelength of 400 nm and an emission wavelength of 500 nm. The fluorescence intensity of the NFKPIP formed is directly related to the amount of enzyme activity, and the signal is stable over 8 h. This assay has a lower limit of detection, equating to 153 nM N-formylkynurenine, which is over 30-fold lower than the limits of detection of existing assays for IDO1 activity. When we compared the performance of the new assay with that of the published colorimetric absorbance assay in screening the National Cancer Institute Diversity Set III of 1,597 compounds for IDO1 inhibitors, we obtained an identical list of the 25 most active compounds in the two assays. Although 93 compounds (aldehydes, ketones, and aromatic amines) in the library interfered with the absorbance readout, only 18 compounds (conjugated systems and fused cycles) interfered with the readout of the new fluorescence assay. IC₅₀ values determined using the new assay for three known IDO1 inhibitors—1,4-naphthoquinone, 4-amino-N-(3-chloro-4-fluorophenyl)-N’-hydroxy-1,2,5-oxadiazole-3-carboximidamide and 4-phenyl-1H-imidazole—were consistent with their literature values, further validating the new assay for measuring IDO1 activity.

Evaluation of the performance of 57 Japanese participating laboratories by two types of z-scores in proficiency test for the quantification of pesticide residues in brown rice

A proficiency test for the analysis of pesticide residues in brown rice was carried out to support upgrading in analytical skills of participant laboratories. Brown rice containing three target pesticides (etofenprox, fenitrothion, and isoprothiolane) was used as the test samples. The test samples were distributed to the 57 participants and analyzed by appropriate analytical methods chosen by each participant. It was shown that there was no significant difference among the reported values obtained by different types of analytical method. The analytical results obtained by National Metrology Institute of Japan (NMIJ) were 3 % to 10 % greater than those obtained by participants. The results reported by the participant were evaluated by using two types of z-scores, that is, one was the score based on the consensus values calculated from the analytical results of participants, and the other one was the score based on the reference values obtained by NMIJ with high reliability. Acceptable z-scores based on the consensus values and NMIJ reference values were achieved by 87 % to 89 % and 79 % to 94 % of the participants, respectively. Graphical Abstract

Distribution of z and z_NMIJ-scores for isoprothiolane     

An efficient electrochemical disinfection of E. coli and S. aureus in drinking water using ferrocene–PAMAM–multiwalled carbon nanotubes–chitosan nanocomposite modified pyrolytic graphite electrode

This work reported an efficient electrochemical treatment for drinking water disinfection using a pyrolytic graphite electrode modified with ferrocenyl tethered poly(amidoamine) dendrimers–multiwalled carbon nanotubes–chitosan nanocomposite. The influence parameters of electrochemical disinfection of Escherichia coli and Staphylococcus aureus, such as applied potential and sterilization time, were investigated. Further investigation indicated that almost all (99.99 %) of the initial bacteria were killed after applying a low potential of 0.4 V for 10 min. During the electrochemical disinfection process, the oxidized form of ferrocene was formed on electrode, which played a key role in the disinfection towards E. coli and S. aureus. Hence, the proposed method may provide potential application for the disinfection of drinking water.

Estimation of Activation Energy from the Survival Yields: Fragmentation Study of Leucine Enkephalin and Polyethers by Tandem Mass Spectrometry

A simple collision model for multiple collisions occurring in quadrupole type mass spectrometers was derived and tested with leucine enkaphalin a common mass spectrometric standard with well-characterized properties. Implementation of the collision model and Rice-Ramsperger-Kassel-Marcus (RRKM) algorithm into a spreadsheet software allowed a good fitting of the calculated data to the experimental survival yield (SY) versus collision energy curve. In addition, fitting also ensured to estimate the efficiencies of the kinetic to internal energy conversion for Leucine enkephalin in quadrupole-time-of-flight and triple quadrupole instruments. It was observed that the experimental SY versus collision energy curves for the leucine enkephalin can be described by the Rice-Ramsperger-Kassel (RRK) formalism by reducing the total degrees of freedom (DOF) to about one-fifth. Furthermore, this collision model with the RRK formalism was used to estimate the critical energy (E _o ) of lithiated polyethers, including polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofurane (PTHF) with degrees of freedom similar to that of leucine enkephalin. Applying polyethers with similar DOF provided the elimination of the effect of DOF on the unimolecular reaction rate constant. The estimated value of E _o for PEG showed a relatively good agreement with the value calculated by high-level quantum chemical calculations reported in the literature. Interestingly, it was also found that the E _o values for the studied polyethers were similar.

Mass Spectrometric Study of the Gas-Phase Difluorocarbene Expulsion of Polyfluorophenyl Cations via F-Atom Migration

An increasing number of fluorinated drugs, pesticides, and fine chemicals are now produced and applied, especially those containing polyfluorinated aromatic moieties. However, at present, the extent of literature covering the special mass spectrometric behaviors of these compounds remains limited. Herein, we report an unexpected but also general gas-phase dissociation mode of polyfluorinated aromatics in mass spectrometry: expulsion of difluorocarbene (50-Da neutral loss). Results from accurate mass measurements, tandem mass spectrometric experiments, and density functional theory (DFT) calculations support an intramolecular F-atom “ring-walk” migration mechanism for gas-phase CF₂ loss. Based on an assessment of the electron ionization-mass spectrometry (EI-MS) data of more than 40 polyfluorinated aromatic compounds from the National Institute of Standards and Technology data bank, we generalized on the substitution group effects on the difluorocarbene dissociation process of polyfluorinated aromatic compounds in EI-MS. These studies have enriched our knowledge of the special gas-phase reactivity of polyfluorinated aromatics and will provide valuable information in further analytical research of these compounds by mass spectrometry.

Lanthanoid complexes with thenoyltrifluoroacetone and 4-tert-butylcalix[4]arene-tetraacetic acid tetraethyl ester: synergistic extraction and separation

The solvent extraction of fourteen lanthanoid ions with thenoyltrifluoroacetone (HTTA) in combination with tetraethyl 4-tert-butylcalix[4]arene-tetraacetic acid tetraethyl ester (S) from a perchlorate medium at constant ionic strength was investigated. The extracted species were identified as the Ln(TTA)₃·S complexes by slope analysis. Equilibrium constants, parameters for extraction, and the synergistic and separation factors between two adjacent Ln(III) ions were determined.

Capillary liquid chromatographic fingerprint used for discrimination of Zingiber montanum from related species

Fingerprint analysis using capillary liquid chromatography (CLC) has been developed for discrimination of Zingiber montanum (ZM) from related species, for example Z. americans (ZA) and Z. zerumbet (ZZ). By comparing the fingerprint chromatograms of ZM, ZA, and ZZ we could identify ZM samples and discriminate them from ZA and ZZ by using their marker peaks. We also combined CLC fingerprint with multivariate analysis, including principal-component analysis (PCA) and canonical variate analysis (CVA); all three species were discriminated successfully. This result indicates that CLC fingerprint analysis in combination with PCA and CVA can be used for discrimination of ZM samples from samples of related species.

Application of cyclic biamperometry to viability and cytotoxicity assessment in human corneal epithelial cells

The application of cyclic biamperometry to viability and cytotoxicity assessments of human corneal epithelial cells has been investigated. Electrochemical measurements have been compared in PBS containing 5.0 mM glucose and minimal essential growth medium. Three different lipophilic mediators including dichlorophenol indophenol, 2-methyl-1,4-naphthoquinone (also called menadione or vitamin K₃) and N,N,N′,N′-tetramethyl-p-phenylenediamine have been evaluated for shuttling electrons across the cell membrane to the external medium. Transfer of these electrons to ferricyanide in the extra cellular medium results in the accumulation of ferrocyanide. The amount of ferrocyanide is then determined using cyclic biamperometry and is related to the extent of cell metabolic activity and therefore cell viability. To illustrate cytotoxicity assessment of chemicals, hydrogen peroxide, benzalkonium chloride and sodium dodecyl sulfate have been chosen as sample toxins, the cytotoxicities of which have been evaluated and compared to values reported in the literature. Similar values have been reported using colorimetric assays; however, the simplicity of this electrochemical assay can, in principle, open the way to miniaturization onto lab-on-chip devices and its incorporation into tiered-testing approaches for cytotoxicity assessment.

Microfluidic robotic device coupled with electrochemical sensor field for handling of paramagnetic micro-particles as a tool for determination of plant mRNA

The expression of genes responsible for the biosynthesis of stress proteins corresponds to the exposition of an organism to abiotic and/or biotic stress. We utilize two types of paramagnetic particles for isolation of total mRNA from early somatic embryos of Norway Spruce (Picea abies /L./ Karst.) and maize plants (Zea mays L.) treated with cadmium(II) ions. The paramagnetic particles were evaluated for analysis of real samples, and poly-adenine was used as a model mRNA. Various approaches (from non-automatic to fully automatic) were tested in terms of handling the particles.

Evaluation of proficiency tests in microbiological analysis: enumeration of aerobic microorganisms

South Korea’s Ministry of Food and Drug Safety (MFDS) has been developing programs for the inspection and accreditation of food sanitation inspection institutions. Food sanitation inspection institutions such as MFDS regional offices, the Research Institute of Public Health and Environment and authorized private service providers in South Korea must participate in proficiency testing (PT) programs to comply with the Food Sanitation Act and MFDS Notification No. 2012-112. As the PT provider, the MFDS annually plans various microbiological and chemical PT programs for foods, cosmetics, and pharmaceutical products in accordance with ISO/IEC 17043. The aim of this project was to evaluate the performance of microbiological PT programs to ensure the quality of their routine test results. The test materials used were freeze-dried BioBalls from BTF Pty Ltd. Homogeneity and stability were investigated to assess the adequacy of the selected test materials. This project also contains data from inter-laboratory comparisons organized by MFDS in 2011 and 2012. More than 50 laboratories attended the PT program and submitted their results. Laboratory results were rated with z-scores according to the international standard ISO 13528. The results from 2011 and 2012 revealed that all participating laboratories had similar levels of proficiency. Most of the participants received a rating of “Satisfactory.” Moreover, the percentage of participants who received a rating of “Unsatisfactory” decreased from 3.5 % in 2011 to 2.0 % in 2012.     

Protein-mediated synthesis of antibacterial silver nanoparticles deposited on titanium dioxide nanotube arrays

We report on an effective route to decorate titanium nanotube arrays (TiNT) with silver nanoparticles (AgNPs). In this method, surface-adsorbed antibody molecules serve as templates to bind silver ions by electrostatic interaction. The photocatalytic activity of the TiNT under UV irradiation causes the photoreduction of AgNPs to occur, and the biological template is decomposed simultaneously. This route also was successfuly applied to gold nanoparticles (starting from negatively charged metallic precursor ions). Compared to undecorated samples, the AgNPs/TiNT samples under visible light display a much higher antibacterial activity against Escherichia coli.

Efficient Production of (S)-Naproxen with (R)-Substrate Recycling Using an Overexpressed Carboxylesterase BsE-NP01

An (S)-enantioselective esterase from Bacillus subtilis ECU0554, named BsE-NP01, has been cloned and over-expressed in a heterologous host Escherichia coli BL21. BsE-NP01 was shown to be a carboxylesterase with a molecular mass of about 32 kDa, and temperature and pH optima at 50 °C and 8.5, respectively. It could catalyze the selective hydrolysis of the (S)-enantiomer of racemic naproxen methyl ester, giving optically pure (S)-naproxen with 98% enantiomeric excess. A mechanic-grinding approach to substrate dispersion was also reported, which was considered to be an alternative to take the place of deleterious surfactants such as Tween-80, with improved performance of the hydrolysis reaction. Batch production of (S)-naproxen was repeatedly carried out in a solid-water biphasic system at 2-L scale, achieving an average total yield of about 85% after ten runs with complete recycling of (R)-substrate.

The Effective Temperature of Ions Stored in a Linear Quadrupole Ion Trap Mass Spectrometer

The extent of internal energy deposition into ions upon storage, radial ejection, and detection using a linear quadrupole ion trap mass spectrometer is investigated as a function of ion size (m/z 59 to 810) using seven ion-molecule thermometer reactions that have well characterized reaction entropies and enthalpies. The average effective temperatures of the reactants and products of the ion-molecule reactions, which were obtained from ion-molecule equilibrium measurements, range from 295 to 350 K and do not depend significantly on the number of trapped ions, m/z value, ion trap q _z value, reaction enthalpy/entropy, or the number of vibrational degrees of freedom for the seven reactions investigated. The average of the effective temperature values obtained for all seven thermometer reactions is 318?±?23 K, which indicates that linear quadrupole ion trap mass spectrometers can be used to study the structure(s) and reactivity of ions at near ambient temperature.