Zsolt Bodai

Analysis of Potential Migrants from Plastic Materials in Milk by Liquid Chromatography–Mass Spectrometry with Liquid–Liquid Extraction and Low-Temperature Purification

A simple and fast analytical method was developed for the determination of six UV stabilizers (Cyasorb UV-1164, Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 327, and Tinuvin 1577) and five antioxidants (Irgafos 168, Irganox 1010, Irganox 3114, Irganox 3790, and Irganox 565) in milk. For sample preparation liquid-liquid extraction with low-temperature purification combined with centrifugation was used to remove fats, proteins, and sugars. After the cleanup step, the sample was analyzed with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). External standard and matrix calibrations were tested. External calibration proved to be acceptable for Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 327, Irganox 3114, and Irganox 3790. The method was successfully validated with matrix calibration for all compounds. Method detection limits were between 0.25 and 10 μg/kg. Accuracies ranged from 93 to 109%, and intraday precisions were <13%.

Shotgun Lipidomic Profiling of the NCI60 Cell Line Panel Using Rapid Evaporative Ionization Mass Spectrometry.

Rapid evaporative ionization mass spectrometry (REIMS) was used for the rapid mass spectrometric profiling of cancer cell lines. Spectral reproducibility was assessed for three different cell lines, and the extent of interclass differences and intraclass variance was found to allow the identification of these cell lines based on the REIMS data. Subsequently, the NCI60 cell line panel was subjected to REIMS analysis, and the resulting data set was investigated for its distinction of individual cell lines and different tissue types of origin. Information content of REIMS spectral profiles of cell lines were found to be similar to those obtained from mammalian tissues although pronounced differences in relative lipid intensity were observed. Ultimately, REIMS was shown to detect changes in lipid content of cell lines due to mycoplasma infection. The data show that REIMS is an attractive means to study cell lines involving minimal sample preparation and analysis times in the range of seconds.

HPLC Determination of Capsaicinoids with Cross-Linked C18 Column and Buffer-Free Eluent

A simple and efficient high-performance liquid chromatographic method was developed and validated for the separation and determination of capsaicin and its major dihydro- and homoderivatives in spice paprika products in 20 min with fluorescent and 35 min with mass-spectrometric detection. The separation was performed on reversed-phase chromatographic adsorbent of cross-linked endcapping with eluent consisting of 1:1 acetonitrile-water or acetonitrile-0.1% formic acid under isocratic conditions. Excellent separation of all the major and minor capsaicinoids with resolution index between 1.08 and 7.34 was achieved. The detection and quantification limits of capsaicinoids in standard material solutions were between 2 and 10 ng/mL. The lowest detectable amount of capsaicin, with fluorescent detection, was found to be <1 µg/g non-pungent spice paprika powder. The naturally occurring capsaicinoids could be distinguished from the non-capsaicinoids compounds appeared on liquid chromatography-fluorescence profile of extract from drastically processed paprika by applying mass spectroscopic detection. Hungarian spice paprika were evaluated as mild to very hot (capsaicinoid content: 334-1,660 µg/g) and chili products as very or extremely hot products (1,543-2,818 µg/g).

Rapid Evaporative Ionisation Mass Spectrometry (REIMS) Provides Accurate Direct from Culture Species Identification within the Genus Candida.

Members of the genus Candida, such as C. albicans and C. parapsilosis, are important human pathogens. Other members of this genus, previously believed to carry minimal disease risk, are increasingly recognised as important human pathogens, particularly because of variations in susceptibilities to widely used anti-fungal agents. Thus, rapid and accurate identification of clinical Candida isolates is fundamental in ensuring timely and effective treatments are delivered. Rapid Evaporative Ionisation Mass Spectrometry (REIMS) has previously been shown to provide a high-throughput platform for the rapid and accurate identification of bacterial and fungal isolates. In comparison to commercially available matrix assisted laser desorption ionisation time of flight mass spectrometry (MALDI-ToF), REIMS based methods require no preparative steps nor time-consuming cell extractions. Here, we report on the ability of REIMS-based analysis to rapidly and accurately identify 153 clinical Candida isolates to species level. Both handheld bipolar REIMS and high-throughput REIMS platforms showed high levels of species classification accuracy, with 96% and 100% of isolates classified correctly to species level respectively. In addition, significantly different (FDR corrected P value < 0.05) lipids within the 600 to 1000 m/z mass range were identified, which could act as species-specific biomarkers in complex microbial communities.

Solubility determination as an alternative to migration measurements

ABSTRACT Solubility values for six UV stabilisers (Cyasorb UV-1164, Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 327 and Tinuvin 1577) and five antioxidants (Irgafos 168, Irganox 1010, Irganox 3114, Irganox 3790 and Irganox 565) were determined in all the liquid food simulants (3% (m/V) acetic acid–water mixture, 10% (V/V), 20% (V/V), 50% (V/V) ethanol–water mixture and vegetable oil) proposed in European Union Regulation No. 10/2011/EC, as well as in fruit juice and cola drink. The applied method was obtained by modification of the method for the determination of water solubility as described in OECD guideline Test No. 105. By using ultrasonication and shorter equilibration time, the time demand of the solubility determinations were decreased notably. Solubility values proved to be lower than the specific migration limits (as specified in 10/2011/EC) at 25°C for almost all target compounds in food simulants A, B, C and D1 as well as in fruit juice and cola drink. The exceptions were Tinuvin P and Irganox 3790 in simulant D1. The solubility in food simulant D2 was higher than 1000 µg ml–1 for all target compounds. These results show that the solubility of some additives in food simulants can be so low that it makes migration studies for certain additive–food simulant pairs dispensable.

Optimisation of solid-state urea clathrate formation as a chemical separation method coupled to compound-specific stable carbon isotope analysis

ABSTRACT Solid-state urea clathrate formation (SSUCF) as a chemical separation method prior to stable carbon isotope fingerprinting of diesel fuel contaminations was studied. The stable carbon isotope ratios (δ13C) of n-alkanes in diesel fuel can be used to trace the origin of a contamination. The accurate measurement of the stable isotopic composition of individual compounds requires baseline separation from any other co-eluting compounds. For this purpose silica gel column chromatography (SGCC) and SSUCF were applied. Detailed optimisation of SSUCF was performed: different activators, clathrate formation temperatures, activator volumes, clathrate formation times and sample capacity were investigated. The main benefits of the developed method are reduced clathrate formation time and increased recoveries for lower molecular weight n-alkanes. The recoveries of the developed SSUCF method ranged between 63 and 100% for C10–C24 n-alkanes with relative standard deviation no more than 7%. The precision of the gas chromatography-isotope ratio mass spectrometry measurement was acceptable with a standard deviation of the δ13C values ranging between 0.08 and 0.15‰. The absence of isotopic fractionation was also investigated. The robustness of the method was tested within a model experiment. Nine different water samples including distilled water, tap water, river water, industrial wastewaters and groundwater samples were spiked with the same diesel fuel. The water samples were extracted with n-hexane and after purification with both SGCC and SSUCF n-alkanes were measured. The δ13C values of n-alkanes were found to be similar for all samples. The importance of sample purification prior to compound-specific isotope analysis (CSIA) was also demonstrated within this model experiment by analysing samples from different stages of the sample preparation. Our results show that the proposed method can remarkably improve the precision of compound-specific stable carbon isotope analysis of n-alkanes originating from diesel contamination of the aquatic environment.

Comparison of directly compressed vitamin B12 tablets prepared from micronized rotary-spun microfibers and cast films

Abstract Fiber-based dosage forms are potential alternatives of conventional dosage forms from the point of the improved extent and rate of drug dissolution. Rotary-spun polymer fibers and cast films were prepared and micronized in order to direct compress after homogenization with tabletting excipients. Particle size distribution of powder mixtures of micronized fibers and films homogenized with tabletting excipients were determined by laser scattering particle size distribution analyzer. Powder rheological behavior of the mixtures containing micronized fibers and cast films was also compared. Positron annihilation lifetime spectroscopy was applied for the microstructural characterization of micronized fibers and films. The water-soluble vitamin B12 release from the compressed tablets was determined. It was confirmed that the rotary spinning method resulted in homogeneous supramolecularly ordered powder mixture, which was successfully compressed after homogenization with conventional tabletting excipients. The obtained directly compressed tablets showed uniform drug release of low variations. The results highlight the novel application of micronized rotary-spun fibers as intermediate for further processing reserving the original favorable powder characteristics of fibrous systems.

Determination of particulate phase polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives using gas chromatography–mass spectrometry and liquid chromatography–tandem mass spectrometry

An analytical method has been developed for the quantitative determination of polycyclic aromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives (nitro- and oxy-PAHs respectively) in particulate matter (PM) samples. The sample preparation procedure included only a simple and quick sonication-assisted extraction step, clean-up based on addition of water and centrifugation as well as pre-concentration under N2 stream. The determination of 16 PAHs and 4 oxy-PAHs was carried out by gas chromatography-mass spectrometry, while liquid chromatography-tandem mass spectrometry was used in the case of the 11 investigated nitro-PAHs. The optimized method was fully evaluated in terms of trueness, precision (repeatability), limit of detection (LOD), limit of quantification (LOQ), sensitivity and linearity. The LOQ values ranged at pgm-3 level for the investigated PAHs (42pgm-3), oxy-PAHs (either 42 or 83pgm-3) and nitro-PAHs (either 83 or 167pgm-3) as well. The developed method was applied for the quantitative determination of PAHs, nitro- and oxy-PAHs in urban PM2.5 (particles with aerodynamic diameter smaller than 2.5μm) samples (n=36) collected in Budapest, Hungary. Almost 100% of the PM2.5 samples contained the investigated PAHs and oxy-PAHs in detectable and quantifiable amounts; however, the concentration of the nitro-PAHs was generally lower than the corresponding LOD/LOQ values. According to our results, during the 3-year long sampling campaign the concentration of benzo(a)pyrene never exceeded the limit value (1ngm-3) set by the European Commission.

Migration of Tinuvin P and Irganox 3114 into milk and the corresponding authorised food simulant

Migration of Tinuvin P (UV stabiliser) and Irganox 3114 (antioxidant) from high-density polyethylene (HDPE) was studied. HDPE pieces were soaked in either milk (1.5% or 3.5% fat content) or 50% (v/v) ethanol–water mixture – the food simulant for milk as specified in Regulation No. 10/2011/EC. The obtained extracts were analysed by LC-MS/MS. For statistical assessment variography was used. It proved to be a useful tool for making a distinction between the early migration range and the equilibrium, despite the variance of the data. Regulation No. 10/2011/EC specifies 10 days of contact time for milk at 5°C. Our experiments with the food simulant with 24 dm2 kg−1 surface/mass ratio showed that both Tinuvin P and Irganox 3114 need less than 1 h to reach equilibrium. Furthermore, 10-day experiments with daily sampling showed that these additives are stable in milk, as well as in the food simulant. The effect of the concentration of the additives in HDPE was studied in the 0.01–5% (m/m) range. For both Tinuvin P and Irganox 3114 and all three extractants the migrated amount became independent of the concentration of the additive in the HDPE approximately at 1% (m/m). For Tinuvin P the food simulant gave a close estimate for the milk samples. However, using the food simulant for modelling the migration of Irganox 3114 into milk gave an overestimation with a factor of minimum 3.5. In the case of Tinuvin P special care must be taken, since the recommended amount in the HDPE can result in additive concentrations near or even over the specific migration limit (SML). However, Irganox 3114 cannot reach the SML either in milk or in the food simulant. Graphical Abstract

Effect of Electrode Geometry on the Classification Performance of Rapid Evaporative Ionization Mass Spectrometric (REIMS) Bacterial Identification

AbstractThe recently developed automated, high-throughput monopolar REIMS platform is suited for the identification of clinically important microorganisms. Although already comparable to the previously reported bipolar forceps method, optimization of the geometry of monopolar electrodes, at the heart of the system, holds the most scope for further improvements to be made. For this, sharp tip and round shaped electrodes were optimized to maximize species-level classification accuracy. Following optimization of the distance between the sample contact point and tube inlet with the sharp tip electrodes, the overall cross-validation accuracy improved from 77% to 93% in negative and from 33% to 63% in positive ion detection modes, compared with the original 4 mm distance electrode. As an alternative geometry, round tube shaped electrodes were developed. Geometry optimization of these included hole size, number, and position, which were also required to prevent plate pick-up due to vacuum formation. Additional features, namely a metal “X”-shaped insert and a pin in the middle were included to increase the contact surface with a microbial biomass to maximize aerosol production. Following optimization, cross-validation scores showed improvement in classification accuracy from 77% to 93% in negative and from 33% to 91% in positive ion detection modes. Supervised models were also built, and after the leave 20% out cross-validation, the overall classification accuracy was 98.5% in negative and 99% in positive ion detection modes. This suggests that the new generation of monopolar REIMS electrodes could provide substantially improved species level identification accuracies in both polarity detection modes. Graphical abstract