Prevalence and antimicrobial resistance of Salmonella isolated from an integrated broiler chicken supply chain in Qingdao,China

The present study analyzed the prevalence and antimicrobial resistance of Salmonella along an integrated broiler chicken supply chain. A total of 172 Salmonella isolates were recovered from 1148 samples collected from four sample sources (breeder farms, broiler farms, abattoir, and retail markets), representing nine production stages. These Salmonella isolates were examined for antimicrobial susceptibility to 12 different antimicrobial agents using a disk diffusion assay. Among them, 168 were identified as six different serotypes of Salmonella enterica. The predominant serotype was S. Enteritidis (n = 116), followed by S. Infantis (n = 18), S. Gueuletapee (n = 16), S. Derby (n = 12), S. Meleagridis (n = 4), and S. London (n = 2). The remaining four isolates were serogroup-untypeable. A majority of the 172 isolates (96.51%) was resistant to one or more antibiotics and 61.05% of the Salmonella isolates showed a multidrug resistance phenotype. Statistical analysis indicated the one risk product stage for Salmonella contamination occurred in the sample source at the abattoir, specifically the stage of Carcasses after chilling. The majority of S. Enteritidis isolates shared the same pulsed-field gel electrophoresis (PFGE) cluster, suggesting that the S. Enteritidis strain might spread along the broiler chicken supply chain. The prevalence and antimicrobial resistance of Salmonella in different production stages suggest the importance of controlling Salmonella in the broiler chicken supply chain for public health, underlying the need for improved measures of reducing carcass contamination in abattoirs and the appropriate use of antimicrobials in broiler flocks.     

A structural modeling on food safety knowledge,attitude, and behaviour among Bum Bum Island community of Semporna,Sabah

The objective of this study was to evaluate the relationship among food safety knowledge, attitude and behavior in Bum Bum Island community, Semporna, Sabah. Proportional stratified sampling method was used in this survey. A total of 250 respondents were selected randomly from ten villages in Bum Bum Island. Face-to-face interview was conducted to complete the questionnaire. In general, respondents exhibited average food safety knowledge level especially in their awareness of personal hygiene and kitchenware hygiene. Food safety attitude of the community was found strongly affected their food safety behavior in positive way, which was proven by the highest standard β among variables tested (β₁ = 0.885, p < 0.05). However, food safety knowledge was negatively affected the food safety behavior of the respondents (β₁ = −0.128, p < 0.05). Our result confirmed that Structural Equation Modeling (SEM) was successfully used to model the relationship among food safety knowledge, attitude and behavior.     

A survey on the occurrence of aflatoxin M1 in raw milk produced in Adana province of Turkey

During 2012, a total of 176 samples of raw milk obtained from dairy plants of Adana province of Turkey were analysed for the presence of aflatoxin M₁ (AFM₁). Aflatoxin M₁ analysis was carried out by centrifugation, liquid–liquid extraction, immunoaffinity column clean-up and high performance liquid chromatography with fluorescence detection (HPLC-FD). The limits of detection (LOD) and quantification (LOQ) of the analytical method were 0.021 μg kg⁻¹ and 0.025 μg kg⁻¹. Accuracy of the method obtained from bias ranged from 2.94 to 8.70. Aflatoxin M₁ was detected in 53 out of 176 samples analysed (30.1%). The ranges for positive samples were 0.042–0.552, 0.033–1.01, 0.047–0.150 and 0.025–0.102 μg kg⁻¹ in autumn, winter, spring and summer seasons, respectively. Thirty samples of raw milk (17%) were above the legal limits of Turkey and EU regulations.     

Aflatoxins and ochratoxin A in dried eggplant and green bell pepper

In this study, 50 dried eggplant and 50 dried green bell pepper samples were analyzed in terms of their aflatoxin and ochratoxin A (OTA) content. Aflatoxins G₂, G₁, B₂, and B₁, and OTA contents were analyzed using high-performance liquid chromatography with a flame ionization detector (HPLC–FID). Total aflatoxin and, as well as aflatoxin G₂, G₁, B₂, and B₁ content in dried eggplant samples were ranged between 0.82 and 2.58, 0.10–0.23, 0.32–1.35, 0.12–0.67, and 0.17–0.71 μg kg⁻¹, respectively. Total aflatoxin and, as well as aflatoxin G₂, G₁, B₂ and B₁ content in dried green bell pepper samples were 0.81–2.42, 0.11–0.22, 0.32–1.38, 0.13–0.66, and 0.18–0.91 μg kg⁻¹, respectively. OTA content was varied from 8.88 to 21.35 μg kg⁻¹ in eggplant samples, and from 15.38 to 24.70 μg kg⁻¹ in dried green bell pepper samples. Of the dried eggplant samples and dried green bell pepper samples, 36% and 24% of them, respectively, had aflatoxin B₁ values which were below the minimum limit of detection (LOD) of 0.05 μg kg⁻¹. None of the analyzed samples exceeded the legal limit values of 10 μg kg⁻¹ for total aflatoxin content, and 5 μg kg⁻¹ for aflatoxin B₁ content. However, 80% of the dried eggplant samples and 100% of the dried green bell pepper samples exceeded the legal limit value for OTA content (15 μg kg⁻¹). According to the results, it was concluded that dried vegetables should be examined in terms of their aflatoxins. It is essential to analyze OTA content more thoroughly, as it has the potential to pose a risk for public health, as well as for the economy.     

Development of an aptasensor for the fast detection of Versicolorin A

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. The molds may contribute to pre-harvest aflatoxin contamination of susceptible crops. For the customer and food producer, a predictive model for aflatoxin detection is very desirable. Versicolorin A (VerA), which is the first precursor in the pathway of aflatoxin B₁ (AFB₁) biosynthesis, shares similar toxic group with the furofuran structure in aflatoxin B₁. VerA exhibits a much lower teratogenic toxicity than AFB₁ and may be used as a predictive indicator for aflatoxin B₁ contamination of storage crops. Therefore, the development of a fast detection method for VerA is important. One of the randomly computer-generated aptamers of VerA was confirmed by isothermal titration calorimetry with K_d = 9.26 × 10⁻⁶ mol l⁻¹. In addition, a simple and sensitive label-free aptasensor was developed for the electrochemical detection of VerA. According to the results from differential pulse voltammetry (DPV), a linear relationship existed between the log conc. of VerA (ranged from 0.01 to 100 ng ml⁻¹) and the current (△I_p) with a limit of detection (LOD) of 10 pg ml⁻¹. The resulting aptasensor exhibited good reproducibility for detecting VerA and stability after storage for 15 days at 4 °C with acceptable anti-interference against ZEN, OTA, DON, and FB₁. When used in corn samples, the recoveries of VerA were determined to be in the range of 81.3%–104.4 %. Although with some intercross, result suggests that the obtained aptamer for VerA is potentially used as a sorbent for the preparation of solid-phase-extraction procedure to clean up food samples in conjunction with high-performance liquid chromatography analysis.     

Natural mycotoxin contamination of maize (Zea mays L.) in the South region of Brazil

The natural co-occurrence of fungal metabolites in maize samples from the South region of Brazil was studied using an LC-MS/MS based multi-mycotoxin method. All maize samples (n = 148) were contaminated with fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂). Aflatoxin B₁ (AFB₁) and aflatoxin G₁ (AFG₁) were detected in 38 and 11 samples, respectively, while zearalenone (ZEN) and deoxynivalenol (DON), which were first regulated in 2014, were found in 110 and 71 samples, respectively. Apart from regulated mycotoxins, a broad range of non-regulated metabolites, from Aspergillus, Fusarium, Alternaria, Penicillium and other microbes, were also detected in maize sample. Fusarin C, a possible carcinogenic compound to humans, produced by Fusarium species and not addressed by Brazilian legislation, was detected in 54.2% of maize samples. All analysed maize samples were found to be contaminated by at least ten different metabolites, with the largest number of metabolites found in the same sample being 51.     

A reliable and sensitive time-resolved fluorescent immunochromatographic assay (TRFICA) for ochratoxin A in agro-products

Immunochromatographic assays (ICAs) are considered as a suitable diagnostic tool for the detection of mycotoxins. Mycotoxins and especially, ochratoxin A are analytes with more demanding sensitivity requirements. To enhance the sensitivity of current immunochromatographic assays for ochratoxin A (OTA), a novel sensitive ICA was developed in this study. In the assay, microspheres enclosing fluorescent europium (III) [Eu(III)] nanoparticles (EuNPs) were used as a label for OTA monoclonal antibody (OTA-mAb) conjugation. Accordingly, assay was called time-resolved fluorescent immunochromatographic assay (TRFICA). The test strip was composed of three parts: a sample pad, nitrocellulose membrane and an absorbent pad. As for detection, a proper concentration of conjugated microspheres was pipetted into the microtube and sample extract was added to it. Then the strip was inserted into the tube and the fluid flow along the strip. The TRFICA results were obtained in 8 min and read by a portable TRFICA strip reader. The established method allows quantitative determination of OTA with limit of detection as low as 1.0 μg kg⁻¹ in the samples. For validation, spiked samples including wheat, maize, soybean and rice were respectively assayed by TRFICA and a standard high performance liquid chromatography equipped with a fluorescence detector (HPLC-FLD), and good agreement of results was obtained between two methods.     

The effects of oxygenation aeration treatment on dissipation behaviors of tricaine mesylate in carp (Cyprinus carpio) muscle and water

Tricaine mesylate (MS-222) is one of the most used anesthetics in fish. It can be absorbed by the human body via food consumption, with related detriments to human health. In this study, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed for the determination of MS-222 in carp muscle and water samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). For cleanup procedure, multiplug filtration cleanup (m-PFC) method with n-Hexane delipidation was adopted. The extraction solvent, cleanup methods and sorbents were optimized. All method validation parameters were in the acceptable range. The dissipation behavior study was followed by the method development. Firstly, the anesthesia dose and time were optimized in application study. Secondly, carps were revived for different period of time with (experimental group) and without (control group) the oxygenation aeration treatment to compare the dissipation rate of MS-222. After being anesthetized for 6 h at 50 mg/L and 12 h of elimination, the concentrations of MS-222 in crap muscle and water of experimental group was lower than those of control group. After 36 h of elimination under oxygenation aeration, over 90% of MS-222 was dissipated in carp muscle. The results showed that the half-life of MS-222 in carp muscle was 6.2 h. The findings suggested that the commonly-used oxygenation aeration treatment in aquaculture production had potential effects in accelerating the dissipation of MS-222 in carp and water. In this study, three days of withdrawal period was recommended in carps after MS-222 administration under oxygenation aeration.     

Mycological quality and mycotoxin contamination of Sri Lankan peppers (Piper nigrum L.) and subsequent exposure assessment

The aim of the study was to characterize the toxigenic moulds and to screen different mycotoxins in peppers (Piper nigrum L.) of Sri Lankan origin. Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger and Penicillium spp. were found to be the most dominant fungi. Characterization of the moulds was carried out in A. flavus and parasiticus agar (AFPA) and malt extract agar (MEA) in 77 black pepper (BP) and 11 white pepper (WP) samples. In total, 73% of the BP and 64% of the WP samples were contaminated with A. flavus and/or A. parasiticus (AfAp). A BP sample with water activity (a_w) 0.70 recorded the highest count of AfAp (4.3*10⁴ CFU/g). Moreover, 75% of the BP samples exceeded the safe a_w limit (0.65) set by the European Spice Association (ESA). The frequency of occurrence of A. niger in BP was 62% with counts up to 1.3*10³ CFU/g. Penicillium spp. were found in 61% and 55% of the BP and WP samples, respectively. In BP 94% of the samples had a Penicillium contamination below 10³ CFU/g. Other Aspergillus spp, found in peppers included, Aspergillus terrus, Aspergillus tamarii, Aspergillus candidus, Aspergillus penicilloides, Aspergillus sydowii and Aspergillus fumigatus. Mould counts in BP (10²–10⁴ CFU/g) were significantly higher than that of WP (<10² CFU/g). Apart from the occurrence of “classical mycotoxins” of spices, aflatoxins (<LOQ-18 μg/kg) and ochratoxin A (<LOQ-79 μg/kg), other toxins including fumonisin B1 (<LOQ-135 μg/kg), sterigmatocystin (<LOQ-49 μg/kg) and citrinin (<LOQ-112 μg/kg) were detected in peppers. In total, 63% of the BP samples were contaminated with at least one mycotoxin. Mycotoxin contamination in WP was significantly less compared to BP. The exposure to aflatoxins and ochratoxin A by consuming pepper remains harmless considering the existing pepper dietary intake data of the Sri Lankan population.     

Real-time pixel based early apple bruise detection using short wave infrared hyperspectral imaging in combination with calibration and glare correction techniques

High speed data processing for online food quality inspection using hyperspectral imaging (HSI) is challenging as over hundred spectral images have to be analyzed simultaneously. In this study, a real-time pixel based early apple bruise detection system based on HSI in the shortwave infrared (SWIR) range has been developed. This systems consists of a novel, homogeneous SWIR illumination unit and a line scan camera. The system performance was tested on Jonagold apples bruised less than two hours before scanning. Partial least squares-discriminant analysis was used to discriminate bruised pixel spectra from sound pixel spectra. As the glossiness of many fruit and vegetables limits the accuracy in the detection of defects, several reflectance calibrations and pre-processing techniques were compared for glare correction and maximizing the signal to noise ratio. With the best combination of first derivative and mean centering, followed by image post-processing, this system was able to detect fresh bruises in thirty apples with 98% accuracy at the pixel level with a processing time per apple below 200 ms.     

Moiety and linker site heterologies for highly sensitive immunoanalysis of cyprodinil in fermented alcoholic drinks

Cyprodinil is a new-generation anilinopyrimidine fungicide widely used in crop protection and frequently found in fruits. In this study, novel derivatives of cyprodinil with linker site heterologies were synthesized and employed in order to produce antibodies with enhanced affinity. Moreover, moiety-heterologous haptens were designed and prepared for assay sensitivity improvement. Two competitive enzyme-linked immunosorbent assays for the analysis of this active substance were developed using direct and indirect formats, achieving IC₅₀ values around 0.15 μg/L. Analytical figures of merit and usability of the optimized assays were evaluated with wine and cider as model food processed matrices. The obtained recoveries were from 90% to 120%, and the limit of quantification was in the 1–5 μg/L range. Finally, a monitoring study (n = 150) was performed to estimate the occurrence and the concentration of cyprodinil in commercial wine and cider products from different origins. We found that 28% of the analysed wine samples contained cyprodinil residues at levels higher than 5 μg/L.     

Development and validation of an LC–MS/MS/MS method for the quantification of fluoroquinolones in several matrices from treated turkeys

The study presents a sensitive and reliable confirmatory method for the extraction, identification, quantification of five fluoroquinolones (FQ) namely enrofloxacin, ciprofloxacin, difloxacin, sarafloxacin and flumequine, in plasma, liver, kidney, muscle, skin + fat, lung and intestinal content from turkeys.For the extraction and matrix clean-up of FQ residues from all biological matrices, the Quick Easy Cheap Effective Rugged Safe (QuEChERS) methodology was adopted; only for plasma samples acetonitrile was used.The analyses were performed by liquid chromatography with mass spectrometry detection (LC–MS). LC separation was performed on a C18 Kinetex column (100 × 2.1 mm, 2.6 μm, Phenomenex, CA, USA) with gradient elution using ammonium acetate solution (10 mM, pH 2.5) and methanol containing 0.1% formic acid. Mass spectrometric identification was done using an LTQ XL ion trap (Thermo Fisher Scientific, CA, USA), with a heated electrospray ionization probe, in positive ion mode.The method was validated according to the European Legislation (decision 2002/657/EC) and EMA guideline (EMA/CVMP/VICH/463202/2009); selectivity, linearity response, trueness (in terms of recovery), precision (within-day repeatability and within-laboratory reproducibility), limit of detection, limit of quantification, decision limits, detection capability, absolute recovery and robustness were evaluated using turkey blank matrices. All data were within the required limits established for confirmatory methods except for flumequine which presented a recovery value slightly higher than 110% in muscle and intestinal content. For all FQs, all the extraction rates were greater than 70% and limits of quantification ranged from 1.2 μg kg⁻¹ to 118.8 μg kg⁻¹.This fast and robust method was suitable for the identification and quantification of FQ residues in tissues, plasma and intestinal content as confirmed by data obtained from incurred samples of turkeys treated at farm for therapeutic purposes.     

Determination of aflatoxins in walnut sujuk and Turkish delight by HPLC-FLD method

This study aims to assess the risk of aflatoxins (AFs) in traditional confectionery products (walnut sujuk and Turkish delight) of Turkey. A high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) method was used for the determination of AFs. Evaluation of the method showed good selectivity, linearity, recovery and precision. The limit of quantification (LOQ) ranged from 0.106 to 0.374 μg kg⁻¹. The expanded measurement uncertainty was less than 40% for all target analytes. The validated method was successfully applied to the determination of AFs in 112 traditional confectionery products containing nuts (hazelnuts and walnuts). AFs were detected in 43.8% of walnuts and 60.9% of hazelnuts used as ingredients in walnut sujuk and Turkish delight and at levels ranging from 0.58 to 15.2 μg kg⁻¹ and 0.43–63.4 μg kg⁻¹, respectively. This means that AFs levels in walnut sujuk and Turkish delight were up to levels of 6.1 and 9.5 μg kg⁻¹, respectively. Six walnut samples and twenty-one hazelnut samples were above the EU maximum limits (MLs) of 2 and 5 μg kg⁻¹ for aflatoxin B₁ (AFB₁), respectively.     

Aflatoxin B1 production by Aspergillus parasiticus and strains of Aspergillus section Nigri in currants of Greek origin

Aflatoxin B₁ (AFB₁) mostly produced by Aspergillus flavus and Aspergillus parasiticus, is an extremely toxic and carcinogenic metabolite. Currants are used in the Mediterranean diet as a food with antioxidant properties. Four strains of Aspergillus section Nigri have been isolated from currants originated from Crete and Corinth. In this study AFB₁ production by A. parasiticus and the four strains of Aspergillus section Nigri in Cretan and Corinthian currants (Vitis vinifera L.) is investigated. AFB₁ determination was performed by HPLC–FID. Results revealed that the four strains Aspergillus section Nigri, as well as the aflatoxigenic strain A. parasiticus produced AFB₁ (0.0052–1.31 μg AFB₁ 15 g⁻¹, corresponding to 0.0003–0.087 μg AFB₁ g⁻¹) in both type of currants (Cretan and Corinthian) on the 12th day of observation. Moreover, AFB₁ production, by A. parasiticus in the synthetic Yeast Extract Sucrose (YES) medium was also studied. The ability of AFB₁ production has been affected by the special characteristics of each isolate and the currants substrate.     

Using phytosterol as a target compound to identify edible animal fats adulterated with cooked oil

Incidents of edible oil adulteration have increased all over the world, and improving analytical methods that are capable of identifying adulterated oils has become more important. In this study, we developed an analytical method that uses 4 target compounds belong to phytosterol family to identify lard that has been adulterated with cooked oils. For this, we used five kinds of animal fat, including lard, tallow, duck fat, goose fat, and chicken fat, to estimate the matrix effect, and lard samples were used to verify this analytical method. Specifically, samples inspected by sanitation authorities in a 2014 lard adulteration incident in Taiwan were saponified, and phytosterols were extracted and analyzed by a liquid chromatography-tandem mass spectrometer (LC/MS/MS) equipped with an atmospheric pressure chemical ionization (APCI) source. Parameters for sample extraction, including temperature, concentration of alkaline solution, and duration of saponification, were optimized. Our proposed method was then validated for linearity, matrix effect, precision, accuracy, limit of detection (LOD), and limit of quantitation (LOQ). After using our proposed method to analyze 28 lard samples, we determined that the phytosterol contents of inspected lard obtained from companies that had been found guilty in the 2014 lard adulteration incident were ranged from 19.5 to 205.3 μg/g in campesterol and 17.3–408.8 μg/g in β-sitosterol, and were at most 270-fold higher than that of homemade lard, commercial lard, and inspected lard (ranged from 4.5 to 29.6 μg/g in campesterol and 1.5–44.2 μg/g in β-sitosterol) obtained from companies that had not been found guilty in the 2014 adulteration incident. Therefore, our proposed method should be useful to discriminate between adulterated and unadulterated animal fats.     

Species determination of pine nuts in commercial samples causing pine nut syndrome

Consumption of pine nuts from the species of Pinus armandii has been reported to cause dysgeusia, commonly known as pine mouth, or pine nut syndrome (PNS). However, the number of reports on pine nut consumptions of the different species and PNS is limited. This leaves open the possibility that other pine species than P. armandii could be involved in PNS as well. This study investigated 18 samples involved in PNS and received at the Danish Veterinary and Food Administration in 2011 through 2012. Samples were subjected to gas chromatographic analysis of fatty acids. The content of 11 individual fatty acids was used together with the diagnostic index and the sum of Δ5-fatty acids as diagnostic parameters. Diagnostic parameters from samples were then compared to reference material and literature data to determine the species. In a limited number of samples, the diagnostic parameters matched neither our reference materials nor literature data. However, the morphology, the fatty acid analysis, and externally obtained DNA sequencing data suggest a P. armandii subspecies or a variety. With these possible P. armandii subspecies, P. armandii was identified in all analyzed samples. The application of principal component analysis (PCA) to the data set showed a satisfactory separation of the majority of the 13 pine species included in the study.     

The efficacy of disinfectant misting in the lairage of a pig abattoir to reduce Salmonella and Enterobacteriaceae on pigs prior to slaughter

Water misting/showers are used in abattoir lairages to improve meat quality, and to cool and calm pigs after transport and during hot weather. One novel approach, which has not been investigated to date, is to add a disinfectant to the misting water as a means of topically reducing Salmonella on pigs prior to slaughter, thereby potentially controlling this organism in the abattoir. The objective of this study was therefore to evaluate misting with water or with Virkon^® S (an approved disinfectant for use in the presence of animals), for their ability to topically reduce Salmonella on high seroprevalence pig herds before stunning and to reduce Enterobacteriaceae.Three experimental groups were investigated: control group (i.e., no misting); water group (misting with cold, 15–17 °C, water, herein referred to as water); and a disinfectant group (misting with 0.5% Virkon^® S). As pigs entered the abattoir, each animal was swabbed along its back before being allocated to its experimental group. Each group was randomly assigned to one of 3 lairage pens that were separated by non-trial pens. After 30 min of misting with water or disinfectant, pigs were moved to the stunning area, where each pig was again swabbed, as above. Swabs were analyzed for the presence of Salmonella and enumeration of Enterobacteriaceae.Before misting, Salmonella prevalence on the pigs was 79.0%, 72.1% and 83.6% for the control, water and disinfectant groups, respectively. After misting, Salmonella prevalence increased to 94.3% in the water group; whereas for the disinfectant group, the prevalence increased marginally to 85.9%. No change in Salmonella prevalence was detected for the control group. In line with the Salmonella results, no significant differences were observed in Enterobacteriaceae counts in the control group at either time point (4.37 and 5.01 log₁₀ CFU/cm², respectively) or in the disinfectant group before and after misting (4.02 and 4.26 log₁₀ CFU/cm², respectively). However, a 2.3 log₁₀ CFU/cm² increase in Enterobacteriaceae was recorded for the water group after misting as compared to before misting (p < 0.05).Since misting with water alone increased topical Salmonella contamination on pigs before slaughter, a risk assessment based on known Salmonella data, meat quality and welfare is recommended to determine whether its use is justifiable. On the other hand, the findings from this study suggest that misting with Virkon^® S at 0.5% could have a role in topical antisepsis of pigs contaminated with Salmonella prior to slaughter and as such this warrants further investigation.     

Determination of melamine in infant formulas by fluorescence quenching based on the functionalized Au nanoclusters

An environmentally benign and cost-effective assay was developed for the fast determination of melamine (MA) with tiopronin-stabilized gold nanoclusters (TPN-AuNCs) as a fluorophore. The TPN-protected gold nanoclusters which exhibit strong fluorescence emission were prepared by a simple one-vessel procedure. Upon addition of melamine to TPN-AuNCs, a dramatic decrease in their fluorescence intensity was observed, attributing to the electrostatic attraction between the MA and the surface of the TPN-AuNCs which induces the aggregation of TPN-AuNCs. Parameters affecting the detection of MA were investigated including pH, amount of TPN-AuNCs, temperature as well as reaction time. Under the optimized experimental conditions, trace amounts of MA could be analyzed based on the reduction in the fluorescence intensity of TPN-AuNCs. A linear relationship was established at concentrations ranging from 0.09 μM to 100 μM. The detection limit at 32 nM was achieved for this method. The developed method has been successfully applied to the determination of MA in several spiked infant formulas samples purchased from a local supermarket. Excellent recoveries at 92.0–102.2% and precision (RSD: 1.14–2.80%) were attained, respectively, which confirmed the great potential of tiopronin-stabilized gold nanoclusters toward practical measurement of melamine in infant formulas of samples.     

Multi-walled carbon nanotubes-based magnetic solid-phase extraction for the determination of zearalenone and its derivatives in maize by ultra-high performance liquid chromatography-tandem mass spectrometry

A simple and rapid magnetic solid-phase extraction (M-SPE) procedure using multi-walled carbon nanotube-magnetic nanoparticles (MWCNT-MNPs) as sorbents was established for purification of zearalenone (ZEA), α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), zearalanone (ZAN), α-zearalanol (α-ZAL) and β-zearalanol (β-ZAL) in maize. The main parameters affecting the clean-up efficiency were thoroughly investigated, and high purification efficiencies for all analytes were obtained. The resulting MWCNT-MNP-ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was validated for maize samples. The matrix effects were greatly minimized using the M-SPE approach, with signal suppression/enhancement values decreased from 69.9–127.6% to 92.1–103.8%. Consequently, complex matrix-matched calibration curves were not necessary and the calibrations constructed in acetonitrile could be applied for accurate quantification of the targeted mycotoxins in real samples. The average recoveries ranged from 75.8 to 104.1% and the inter- and intra-day precision values expressed as RSDs, were all lower than 14%. Limits of detection and quantification were in the range of 0.03–0.04 and 0.07–0.10 μg/kg, respectively. The analytical performance of the developed method was also successfully evaluated with maize samples, and this method was proved to be a powerful tool for monitoring ZEA and its derivatives in maize.     

A fast and simple LC-ESI-MS/MS method for detecting pyrrolizidine alkaloids in honey with full validation and measurement uncertainty

A fast and simple method was developed to determine pyrrolizidine alkaloids (PAs) in honey using liquid chromatography tandem mass spectrometry (LC- MS/MS) with electrospray ionization (ESI). An efficient extraction procedure was carried out by simply diluting with water, without the need of any additional clean-up steps. A full validation of the method was performed according to Commission Decision 2002/657/EC. The method was linear in the 050 μg kg⁻¹ range and presented satisfactory intra-day and inter-day precision with relative standard deviations of 1.45–10.2% and 1.60–1–0.2%, respectively. The measurement uncertainty, limit of detection (LOD) (0.1–1.0 μg kg⁻¹) and limit of quantification (LOQ) (0.2–1.5 μg kg⁻¹) were also calculated. The proposed method was applied to analyse eight PAs, namely, senecionine, senecionine-N-oxide, echimidine, intermedine, lycopsamine, retrorsine, monocrotaline and retrorsine-N-oxide, in 92 commercial honey samples from Brazil. At least three PAs were detected in 99.1% of the samples. PAs were not detectable (<LOD) in only one sample. Because PAs are natural toxins biosynthesized by plants, the importance of monitoring their concentration in honey is evident. For this purpose, a simple, low-cost extraction procedure was performed, and a high-throughput method was developed.