Proficiency testing programmes as a tool in food quality assurance: Overview of Italian experiences

Proficiency testing involves the performance of test procedures on routine samples by a number of laboratories. Interlaboratory proficiency testings provide multiple benefits to participants since they play a key-role in the total quality control of laboratory activities. They serve as a means of self-improving, as a mechanism of continuing education and as a source of information for accreditation agencies. This review highlights basic principles, benefits, criteria and capabilities of a proficiency testing programme for food analysis laboratories as well as their role in the implementation of rapidly developing food control legislation.     

Mass spectrometric identification of a candidate biomarker peptide from the in vitro interaction of epichlorohydrin with red blood cells

The reaction products of epichlorohydrin with human alpha- and beta- globins, obtained through in vitro incubation of these compounds and red blood cells, were determined by using reversed-phase high-performance liquid chromatography (RP-HPLC), electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization tandem mass spectrometry. The alpha-globin was much more reactive than the beta-globin. At low incubation ratios, approximating the order of magnitude of epichlorohydrin concentration as found in workplaces, the only modified peptide still detectable was the 62-90 belonging to the alpha-chain and carrying an incremental mass of 92 u on either His72 or His89. Given that the two peptides co-eluted in a single chromatographic peak during RP-HPLC separation, they could be chosen as suitable biomarkers for quantification in the setting up of a new methodology for the biological monitoring of persons occupationally exposed, replacing currently known procedures.     

Mono- and diiodocyclophosphamide as possible internal standards for cyclophosphamide quantification: characterization by ion trap multi-stage mass spectrometry and effects of iodine-chlorine substitution on the fragmentation pattern

Hospital personnel involved in antineoplastic drug preparation and administration to patients are exposed to large amounts of these drugs. Labour legislation indicates the necessity of planning monitoring strategies aimed at prevention and/or reduction of drug exposure. Monitoring strategies consist of quantitative determinations of indicators, present in environmental and biological matrices. Among the antineoplastic drugs widely used, cyclophosphamide (CP) has been identified as a suitable indicator of potential exposure to mixtures of antineoplastic drugs. Many literature methods for quantitative analysis of CP involve either liquid (LC) or gas chromatography (GC) with mass spectrometry (MS), both of which require use of a suitable internal standard. The present work focuses on the synthesis of mono- and diiodocyclophosphamide (CPI and CPI(2)) to be used as internal standard. These compounds were analyzed by GC/EI-MS/MS and LC/ESI-MS(n) using ion trap mass spectrometry. The product ion mass spectra are interpreted in terms of proposed structures of fragment ions. Iodine-chlorine substitution resulted in a weakening of the carbon-halogen bond with a noteworthy influence on the ion fragmentation processes. The proposed suitability of CPI and CPI(2) as internal standards was based on similarities to CP as regards ionization and fragmentation processes. The results obtained suggest that CPI could be used as internal standard for CP quantification by LC/ESI-MS/MS, and CPI(2) for GC/EI-MS/MS analyses.     

Approximate Entropy of Brain Network in the Study of Hemispheric Differences

Human brain, a dynamic complex system, can be studied with different approaches, including linear and nonlinear ones. One of the nonlinear approaches widely used in electroencephalographic (EEG) analyses is the entropy, the measurement of disorder in a system. The present study investigates brain networks applying approximate entropy (ApEn) measure for assessing the hemispheric EEG differences; reproducibility and stability of ApEn data across separate recording sessions were evaluated. Twenty healthy adult volunteers were submitted to eyes-closed resting EEG recordings, for 80 recordings. Significant differences in the occipital region, with higher values of entropy in the left hemisphere than in the right one, show that the hemispheres become active with different intensities according to the performed function. Besides, the present methodology proved to be reproducible and stable, when carried out on relatively brief EEG epochs but also at a 1-week distance in a group of 36 subjects. Nonlinear approaches represent an interesting probe to study the dynamics of brain networks. ApEn technique might provide more insight into the pathophysiological processes underlying age-related brain disconnection as well as for monitoring the impact of pharmacological and rehabilitation treatments.     

Simultaneous determination of aflatoxins and ochratoxin A in baby foods and paprika by HPLC with fluorescence detection: a single-laboratory validation study

Mycotoxins are toxic secondary metabolites of fungal origin, the major mycotoxins of food concern are aflatoxins and ochratoxin A. Due to the wide range of matrices susceptible to mycotoxin contamination, the possible co-occurrence, and the very wide range of concentration, validated versatile multi-mycotoxin and multi-matrix methods are strongly requested. A reversed phase HPLC method for the simultaneous determination of aflatoxins and ochratoxin A in baby foods and paprika was set up. Three bulk samples were prepared according to commercial availability, one for paprika and for baby foods, two different bulks were set, a corn based and a multi-cereal based baby food. A single-laboratory validation was performed, for each investigated level ten analyses were performed, relative standard deviations of repeatability (RSD_r) and recovery factors were calculated; RSD_r values ranged from 2% to 10% for AFB₁ and from 3% to 10% for OTA, while the recovery factors ranged from 86% to 96% for AFB₁ and from 77% to 96% for OTA. The checked compliance of the RSD_r and recovery with the values reported in the current EU Regulations confirmed the fitting for purpose of the method. Limit of detection and LoQ values of the method were respectively 0.002 and 0.020 μg/kg for AFB₁ and 0.012 and 0.080 μg/kg for OTA in baby foods; and 0.002 and 0.200 μg/kg for AFB₁ and 0.012 and 0.660 μg/kg for OTA in paprika. The current method represents a good example of the possibility of a multi-mycotoxin and/or a multi-matrix analysis depending on the laboratory research or official control purposes.     

Surface growth mechanisms and structural faulting in the growth of large single and spherulitic titanosilicate ETS-4 crystals

Morphological, surface and crystallographic analyses of titanosilicate ETS-4 products, with diverse habits ranging from spherulitic particles composed of submicron crystallites to large single crystals, are presented. Pole figures revealed that crystal surfaces with a-, b- and c- axes corresponded to 110, 010 and 001 directions, respectively. Thus, technologically important 8-membered ring pores and titania chains in ETS-4 run along the b-axis of single crystals and terminate at the smallest crystal face. Height of the spiral growth steps observed on 1 0 0 and 0 0 1 surfaces corresponded to the interplanar spacings associated with their crystallographic orientation, and is equivalent to the thickness of building units that form the ETS-4 framework. Data suggest that the more viscous synthesis mixtures, with a large driving force for growth, increased the two- and three-dimensional nucleation, while limiting the transport of nutrients to the growth surface. These conditions increase the tendency for stacking fault formation on 1 0 0 surfaces and small angle branching, which eventually results in spherulitic growth. The growth of high quality ETS-4 single crystals (from less viscous synthesis mixtures) occurred at lower surface nucleation rates. Data suggest that these high quality, large crystals grew due to one-dimensional nucleation at spiral hillocks, and indicate that under these conditions un-faulted growth is preferred.     

Immunoaffinity column cleanup with liquid chromatography for determination of aflatoxin B1 in corn samples: interlaboratory study

An interlaboratory study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for the determination of aflatoxin B1 levels in corn samples, enforced by European Union legislation. A test portion was extracted with methanol-water (80 + 20); the extract was filtered, diluted with phosphate-buffered saline solution, filtered on a microfiber glass filter, and applied to an immunoaffinity column. The column was washed with deionized water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. Aflatoxin B1 was separated and determined by reversed-phase LC with fluorescence detection after either pre- or postcolumn derivatization. Precolumn derivatization was achieved by generating the trifluoroacetic acid derivative, used by 8 laboratories. The postcolumn derivatization was achieved either with pyridinium hydrobromide perbromide, used by 16 laboratories, or with an electrochemical cell by the addition of bromide to the mobile phase, used by 5 laboratories. The derivatization techniques used were not significantly different when compared by the Student's t-test; the method was statistically evaluated for all the laboratories. Five corn sample materials, both spiked and naturally contaminated, were sent to 29 laboratories (22 Italian and 7 European). Test portions were spiked with aflatoxin B1 at levels of 2.00 and 5.00 ng/g. The mean values for recovery were 82% for the low level and 84% for the high contamination level. Based on results for spiked samples (blind pairs at 2 levels) as well as naturally contaminated samples (blind pairs at 3 levels), the values for relative standard deviation for repeatability (RSDr) ranged from 9.9 to 28.7%. The values for relative standard deviation for reproducibility (RSDR) ranged from 18.6 to 36.8%. The method demonstrated acceptable within- and between-laboratory precision for this matrix, as evidenced by the HorRat values.     

Relationship between the crystal structure and the reentrant superconducting properties of (Sn1-xErx)Er4Rh6Sn18

Single crystals of (Sn_1-xEr_x)Er₄Rh₆Sn₁₈ are superconducting (T_c = 1.3K) for x 0, are reetrant superconducting (T_c = 1.24K and T_M = 0.34K) for x ～.30 and undergo a singel magnetic transition (T_M=0.68K) for x～.75. Since the occupancy of the [Sn(1)_1-xEr(1)_x]Er(2)₄ sublattice is responsible for the variation of the low-temperature properties, one can make predictions as to new reentrant superconductors in the MRh_xSn_y series (M=RE). This appears to be the first system of reentrant superconductors where stoichiometry within a sublattice controls both magnetic ordering and superconductivity.