Introduction to This Special Issue of Toxins: Application of Novel Methods for Mycotoxin Analysis

Crop contamination by mycotoxins is a global problem that poses significant economic burdens due to the food/feed losses that are caused by reduced production rates; the resulting adverse effects on human and animal health and productivity; and the trade losses associated with the costs incurred by inspection, sampling, and analysis before and after shipments [...

Introduction to This Special Issue of <i>Toxins</i>: Application of Novel Methods for Mycotoxin Analysis

Crop contamination by mycotoxins is a global problem that poses significant economic burdens due to the food/feed losses that are caused by reduced production rates; the resulting adverse effects on human and animal health and productivity; and the trade losses associated with the costs incurred by inspection, sampling, and analysis before and after shipments [...

Neosynthesis of Cardiolipin in Rhodobacter sphaeroides under Osmotic Stress

The phospholipid composition of Rhodobacter sphaeroides cells resuspended in various hypertonic solutions has been examined by thin-layer chromatography and ESI mass spectrometry. R. sphaeroides responds to hyperosmotic stress by increasing the amount of cardiolipin in the membranes; this phenomenon occurs in spheroplasts also. Cardiolipin increases quickly and continuously during the time when the cells are resuspended in hypertonic medium. The optimum of stimulation of the neosynthesis of cardiolipin during osmotic stress was found to be at external 1 osm. ESI-MS analyses allowed the identification of two different cardiolipins in R. sphaeroides: the tetravaccenylcardiolipin ([M - H]-, m/z 1456.9) and the trivaccenylmonopalmitoylcardiolipin ([M - H]-, m/z 1430.0)

A fast method for the chemical analysis of clays by total-reflection x-ray fluorescence spectroscopy (TXRF)

A new, fast and cheap method for the analysis of clays using total-reflection x-ray fluorescence spectroscopy (TXRF) has been developed following a full factorial experimental design to optimize the sample preparation conditions. The optimized method consists of the dispersion of 50 mg of clay into 2.5 ml of 1% Triton X-100 solution, the deposition of 5 μl of the suspension onto a siliconized quartz reflector and drying it at 50 °C on a heating plate. By using a commercial benchtop instrument, 15 major and trace elements were correctly quantified with 1000 s live time acquisitions. Thirty minutes were sufficient for both sample preparation and analysis. Validation experiments, performed using a certified reference material, showed recoveries in the range 80–120% for the main targeted elements, whereas the within laboratory reproducibility (RSDWLR) and the repeatability (RSDr) were lower than 20%, demonstrating the good precision and reliability of the method. Only in the case of Si, the RSDWLR and RSDr were higher than 20%, due to the variable contribution of the quartz reflector. Suitable LOD and LOQ values were estimated, varying from 0.1–0.4% for Al to 1–2 mg/kg for Sr, with higher sensitivity for elements with higher fluorescence energy (and high atomic number, Z). Finally, a good agreement was obtained between the results of the analysis of reference materials performed with the new TXRF method and a reference method, such as wavelength dispersive x-ray fluorescence spectroscopy (WDXRF). Based on the above performances, this method may represent a valuable and reliable alternative analytical tool when only small amounts of clay samples are available such as in the case of mineral synthesis, clays extraction from soils and sorption tests

Novel Sulfonolipid in the Extremely Halophilic Bacterium Salinibacter ruber

Salinibacter ruber is an extremely halophilic bacterium, phylogenetically affiliated with the Flavobacterium/Cytophaga branch of the domain Bacteria. Electrospray mass analyses (negative ion) of the total lipid extract of a pure culture of S. ruber shows a characteristic peak at m/z 660 as the most prominent peak in the high-mass range of the spectrum. A novel sulfonolipid, giving rise to the molecular ion [M-H](−) of m/z 660, has been identified. The sulfonolipid isolated and purified by thin-layer chromatography was shown by chemical degradation, mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance analysis to have the structure 2-carboxy-2-amino-3-O-(13′-methyltetradecanoyl)-4-hydroxy-18-methylnonadec-5-ene-1-sulfonic acid. This lipid represents about 10% of total cellular lipids, and it appears to be a structural variant of the sulfonolipids found as main components of the cell envelope of gliding bacteria of the genus Cytophaga and closely related genera (W. Godchaux and E. R. Leadbetter, J. Bacteriol. 153:1238-1246, 1983) and of diatoms (R. Anderson, M. Kates, and B. E. Volcani, Biochim. Biophys. Acta 528:89-106, 1978). Since this sulfonolipid has never been observed in any other extreme halophilic microorganism, we consider the peak at m/z 660 the lipid signature of Salinibacter. This study suggests that this novel sulfonolipid may be used as a chemotaxonomic marker for the detection of Salinibacter within the halophilic microbial community in saltern crystallizer ponds and other hypersaline environments

In-house validation and small-scale collaborative study to evaluate analytical performances of multimycotoxin screening methods based on liquid chromatography–high-resolution mass spectrometry: Case study on fusarium toxins in wheat

A strong trend toward using highly selective mass spectrometry technologies for screening of multiple mycotoxins has been observed in recent years. In the present study, the process of validation of a multimycotoxin screening method based on liquid chromatography–high-resolution mass spectrometry method is presented. The method was intended for the simultaneous screening of the major Fusarium toxins (deoxynivalenol, 3- and 15-acetyl deoxynivalenol, T-2 and HT-2 toxins, zearalenone, enniatins A, A1, B, and B1, and beauvericin) in wheat. The sample preparation protocol was based on a double extraction (methanol followed by acetonitrile/water mix-ture) and purification through solid-phase extraction C18 column. To provide insights for full exploitation of the potential of the double-stage high-resolution mass spectrometry detection, a full-scan acquisition event followed by a sequence of 5 fragmentation events (variable data-independent acquisition) was set for mycotoxin detection, the latter to be exploited for confirmatory purposes. Method analytical performances were evaluated through in-house validation and small-scale interlaboratory study, designed according to Commission Regulation 519/2014/EU, setting performance requirements for screening methods for mycotoxins. Screening target concentrations were close to European Union maximum permitted or indicative levels. The in-house validation provided the precision of the response under repeatability conditions and the intermediate precision (both resulting lower than 30%), the cutoff value, and the rate of false suspect results for negative (free of the mycotoxin of interest) samples, which resulted lower than 0.1% in all cases. The collaborative study provided reproducibility and laboratory independent cutoff values. Analysis of reference materials proved method trueness and suitability for screening of the major Fusarium mycotoxins in wheat. Finally, the applicability of the full-scan/variable data-independent acquisition detection approach was successfully tested on a set of naturally contaminated wheat samples, where 2 characteristic product ions could be detected for all identified mycotoxins even at levels in the low μg/kg range