Samples Of Different Matrices Research Articles

In Situ Formed Organic Ion-Associate Liquid-Phase Microextraction without Centrifugation from Aqueous Solutions Using Thymol Blue and Estrogens

In this study, we present a method for ion-associated liquid phase (IALP) separation and concentration of analytes from an aqueous matrix into an IALP formed in situ by the charge neutralization reaction of organic cations and anions, without centrifugation. The effects of various factors on the extraction efficiency and other parameters are investigated, whereas no instrumental stirring, such as vortexing or ultrasonics, is required because the solvent (IALP) is formed in situ. The organic cation and anion used are ethylhexyloxypropylammonium and dodecyl sulfate, respectively. The developed in situ IALP microextraction method for phase separation without centrifugation is tested using the thymol blue dye and several endocrine disruptors. The tested endocrine disruptors (bisphenol A, 17β-estradiol, 17α-ethinylestradiol, and estrone) are analyzed via high-performance liquid chromatography/fluorescence detection, with respective detection limits of 0.02, 0.02, 0.02, and 0.4 μg L−1, and the corresponding enrichment factor ranging from 47 to 71. This IALP microextraction method can be used to separate and concentrate environmental water samples of different matrices. The employed IALP is fast and easy to use, enables an approximately 100-fold analyte concentration, and has a high affinity for estrogens, thus holding promise for the separation, concentration, and quantitation of diverse trace analytes.

Saline and hydrocarbon-bearing fluids detected in shallow aquifers of southern New Brunswick, Canada: Natural occurrence, or deep migration along faults and industrial wellbores?

Unconventional hydrocarbon production has sparked public concerns for several years, especially regarding potential potable groundwater contamination by hydrocarbons, brines, and various chemicals related to hydraulic fracturing operations. One possible contamination mechanism is upward migration of deep-seated contaminants over large vertical distances, through preferential pathways such as leaky well casings or permeable geological faults. In New Brunswick (Canada), thermogenic hydrocarbons and brackish water were previously reported in shallow water wells, some of them located close to unconventional gas wells or to major faults, but the exact origin of these fluids remained uncertain. The objective of this paper is to determine whether the presence of these fluids is the result of migration from the deep (>1 km) hydrocarbon bearing units (via natural or anthropogenic migration pathways), or whether they rather originate within the shallow aquifer (<100 m) or from intermediate zone. Tracking fluid origin was achieved by fingerprinting compositional and isotopic values of three indicators: 1) water isotopic signature (including tritium (3H), radiocarbon (14CDIC), δ18OH2O, δ2HH2O), 2) salinity (including Na, Ca, K, SO4, Cl, Br, 87Sr/86Sr), and 3) hydrocarbons (compositional data and δ13CCH4). These various analyses were conducted, when relevant, on samples of different matrices composing the hydrogeological system, namely shallow groundwater (12–90 m depth), shallow bedrock gas (8–131 m), and intermediate zone evaporitic rocks (173–332 m); they were compared with previously published values for deep basin brines and gases (1940–3168 m) from the hydrocarbon bearing Carboniferous Albert Formation. This unique suite of indicators, analytes and matrices allowed drawing the conclusion that thermogenic gas and high salinities present in the sampled wells were naturally occurring and originating from shallow and intermediate-zone bedrock units. Results obtained through this approach did not provide any evidence that hydrocarbon wells in this area have acted as preferential migration pathways for deep-seated fluids towards shallow aquifers.

Pesticides in soil, groundwater and food in Latin America as part of one health.

We here report of a conference about "Pesticides in Soil, Groundwater and Food in Latin America as part of One Health" that took place at the "IV Seminario Internacional de Sanidad Agropecuaria (SISA)" in Varadero, Cuba, 8-12 May 2023. Researchers of Latin America (Argentina, Brazil, Chile, Costa Rica, Colombia, Cuba, Mexico) and Switzerland (workshop initiator) held presentations about occurrence and effects of pesticides on the environment, human health, the replacement of highly hazardous pesticides (HHP) by agroecological alternatives and the agri-food value chain. In a subsequent round table discussion, the presenters identified deficits, needs, interests and opportunities. According to them, the lack of awareness of pesticide use affects the health and safety of workers applying the chemicals. Despite Latin America representing the main agricultural area in the world with a very intense pesticide use, monitoring data of pesticides in soil, surface and groundwaters, food, as well as in humans are missing. Risks of pesticides to humans should be assessed so that authorities can withdraw or limit within "short time" the access to corresponding formulations on the market. Also, communication is not state of the art and should be improved as, e.g. the teaching of workers and farmers, how to correctly use and apply pesticides or the briefing of decision makers. Pollinators suffer from multiple stressors not the least due to pesticides, and alternatives are badly needed. On the technical side, the different analytical methods to determine residues of active ingredients and transformation products in matrices of concern should be harmonized among laboratories.Seven future actions and goals were identified to overcome the above deficits. Next steps after the publishing of this conference report are to harmonize and complete the information status of the presenters by exchanging the results/data already present. Therefore, a platform of interaction to address issues described above and to enhance collaboration shall be created. Samples of different matrices shall be exchanged to harmonize the chemical analysis and establish interlaboratory comparisons. Such activities might be facilitated by joining international associations or organizations, where researchers can offer their expertise, or by forming a new pesticide network for Central and South America that could present tailored projects to national and international organizations and funding agencies.

A novel strategy to avoid sensitivity loss in pooled testing for SARS-CoV-2 surveillance: validation using nasopharyngeal swab and saliva samples.

At the peak of the COVID-19 pandemic, pooled surveillance strategies were employed to alleviate the overwhelming demand for clinical testing facilities. A major drawback of most pooled-testing methods is the dilution of positive samples, which leads to a loss of detection sensitivity and the potential for false negatives. We developed a novel pooling strategy that compensates for the initial dilution with an appropriate concentration during nucleic acid extraction and real-time PCR. We demonstrated the proof of principle using laboratory-created 10-sample pools with one positive and corresponding individual positive samples by spiking a known amount of heat-inactivated SARS-CoV-2 into viral transport medium (VTM) or pooled negative saliva. No Ct difference was observed between a 10-sample pool with one positive vs. the corresponding individually analyzed positive sample by this method, suggesting that there is no detectable loss of sensitivity. We further validated this approach by using nasopharyngeal swab (NPS) specimens and showed that there is no loss of sensitivity. Serial dilutions of the virus were spiked into VTM and pooled with negative saliva in simulated 10-sample pools containing one positive to determine the LOD and process efficiency of this pooling methodology. The LOD of this approach was 10 copies/PCR, and the process efficiencies are ~95%-103% for N1 and ~87%-98% for N2 with samples in different matrices and with two different master mixes tested. Relative to TaqPath 1-step master mix, the TaqMan Fast Virus 1-Step master mix showed better sensitivity for the N2 assay, while the N1 assay showed no Ct difference. Our pooled testing strategy can facilitate large-scale, cost-effective SARS-CoV-2 surveillance screening and maintain the same level of sensitivity when analyzed individually or in a pool. This approach is highly relevant for public health surveillance efforts aimed at mitigating SARS-CoV-2 spread.

Selective and efficient solid phase extraction of cadmium (II) in sub-trace limits based on alizarin red-S cross-linked-2-mercapto-N-(3-(triethoxysilyl) propyl) acetamide bi-functionalized graphene oxide nanocomposite from different environmental water samples

A novel bi-functionalized nanocomposite based on graphene oxide-alizarin red-S cross-linked-2-mercapto-N-(3-(triethoxysilyl) propyl) acetamide (ARS-MTPS@GO) was developed for the sequestration of cadmium Cd(II) ions from water. The nanocomposite fabrication was characterized through different physicochemical techniques (FTIR, XRD, SEM, TEM, Raman, and TGA). In addition to its hydrophilicity, high surface area, and ability to interact with the functionalized moieties, the ARS-MTPS@GO nanocomposite has improved Cd(II) adsorption. An optimization study was carried out on various analytical parameters that affect cadmium extraction, including the pH, contact time, and nanocomposite mass dosage. The maximum sorption capacity and percentage removal efficiency of Cd(II) ions reached 222.7 mg g−1 and 99.4 ± 3.7%, respectively, at pH = 6 within 30 minutes and the pseudo-second-order kinetic model best fits the sorption rate. Validation of the proposed method was evaluated for nine replicate measurements for recovery of Cd(II), showed favorable analysis precision, and the estimated detection limit was 0.18 ± 0.02 ng mL−1. Additionally, the reusability and stability of the nanocomposite and the effects of interfering cations and anions were investigated. Finally, the developed method was successfully applied for the selective extraction of Cd(II) from environmental water samples of different matrices, and the Cd(II) recoveries were 96.2–99.2%±2.3%. This study’s findings prove the potential applicability of the novel nanocomposite for removing cadmium ions from different environmental waters.

Trace determination of tetrahydrocannabinol (THC) in cosmetic products by stir bar sorptive dispersive microextraction followed by liquid chromatography-tandem mass spectrometry

An analytical method for the determination of tetrahydrocannabinol (THC) at trace level in cosmetics is presented. As psychoactive compound, the presence of THC in consumer products should be avoided. However, it might be unintentionally present in cannabidiol-rich or hemp-based products by contamination or isomerization of cannabidiol. Due to the low concentrations expected, a sensitive and selective method is necessary for the analytical control of these products. In this sense, the presented method is based on stir bar sorptive dispersive microextraction (SBSDME) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this work, a magnetic composite made of CoFe2O4 magnetic nanoparticles embedded in a commercial reverse-phase polymer (Strata™-X-RP) was employed as magnetic sorbent material taking advantage of its affinity to the target analyte. Under the optimized conditions, the method was validated and showed good analytical features in terms of linearity (at least up to 10 ng mL−1), limits of detection and quantification (2.2 and 7.2 ng g−1, respectively) and repeatability (RSD <10%). Moreover, relative recoveries between 99 and 109% were obtained, showing matrix effects were negligible using deuterated THC (THC-D3) as surrogate. This new approach was successfully applied to ten commercially-available cosmetic samples of different matrices, thus showing it is suitable for the analytical control of THC in cosmetic products. The proposed methodology overcomes some of the drawbacks of the previous works with the same purpose, such as the higher limits of detection, time-consuming procedures, and consumption of large volumes of organic solvents.

Non-Invasive Sampling in the Aspect of African Swine Fever Detection-A Risk to Accurate Diagnosis.

African swine fever remains one of the most economically important and dangerous diseases of the Suidae family. Until now, neither a safe vaccine nor a treatment against ASF has been available, which is why prevention of the disease involves biosecurity measures and early recognition based on accurate diagnosis. Nowadays, different strategies for ASF detection are discussed to reduce both animal suffering and the costs of ASF surveillance. This article aims to indicate the risk, with regard to non-invasive sampling, for the detection of ASFV. In this study, we analyzed data from three independent animal trials, in the framework of the detection of positive samples in different matrices (blood, sera, oral and rectal swabs) collected from nineteen domestic pigs infected with similar doses but under different scenarios, including different ASFV strains or routes of infection. Genetic material of ASFV was found in all matrices, but detection occurred earlier in the blood samples than in the oral and the rectal swabs. Furthermore, analyses revealed that at relevant sampling timepoints, PCR-positive blood samples were detected more frequently and reached higher percentages (up to 100% during fever) than oral and rectal swabs. Moreover, mean Ct values in blood samples collected from animals infected with virulent strains were significantly lower than in oral and rectal swabs, ensuring a higher probability of ASFV detection. High Ct values and occasional shedding in all tested matrices, in the cases of animals infected by an attenuated ASFV-strain, showed that blood sampling may be necessary to confirm the presence of anti-ASFV antibodies in sera. This study showed that during veterinary surveillance, blood sampling (for both PCR and serological analyses) is essential for the accurate diagnosis of ASF and provides the highest probability of detection of the disease.

Temperature regime and formation of carcinogenic heterocyclic aromatic amines

The effects of thermal treatment conditions on the 2-amino-1-methyl-6- phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) levels formed in pork samples of different matrices (pork steak vs. pork mince) were studied. Oven air temperature oscillations above the set-point temperature of 200 °C were produced using an on-off controller. Oscillations that reached 1.2 °C amplitude showed formation of one-fifth to one-tenth the PhIP levels in the pork steak and mince compared to the maximum air temperature oscillations that produced temperatures of up to 211.5 °C. The MeIQx levels in pork steaks were not significantly affected by the temperature oscillations, while they were doubled in pork mince. To reduce the levels of these heterocyclic aromatic amines, an oven with precise temperature control is significantly more important than other options during the cooking of pork.

Method validation for the determination of fraction of modern (F14C) in wood samples using conventional method

Abstract The radiocarbon laboratory at the Lebanese Atomic Energy Commission is undertaking environmental studies, in order to determine the anthropogenic impact of technologies on the ecosystem through the determination of radiocarbon content in tree leaves and plants. Thus, it was important to validate the method used to demonstrate that the applied procedure gives reliable results. Method validation is universally applied in analytical laboratories as an essential part of quality assurance system and as a basic technical requirement of the ISO 17025 standard. The conventional method used for determination of Fraction Modern (F14C) is a standard method issued by the American Society for Testing and Materials in 2011 with a code ASTM-D 6866-11 Method C. According to Eurachem guide, internal validation was expressed in terms of accuracy that was evaluated by trueness and precision. Trueness was expressed in terms of relative bias, while for precision ten consecutive replicates were carried out to under repeatability conditions and five duplicates were analyzed under reproducibility conditions. The limit of detection and the minimum detectable activity (MDA) were calculated. Uncertainty sources were defined and their relative standard uncertainties were calculated in order to determine the combined standard uncertainty. Five reference samples of different matrices were analyzed; calculated z score values were acceptable as being between –2 and +2. The calculation and results are presented in this work.

Optimized microscale detection of amino acid decarboxylase for rapid screening of Salmonella in the selective enrichment step

To develop a high-throughput spectrophotometric screen for Salmonella contamination, modified amino acid decarboxylase broths with pH indicators supplemented with selective agents were studied in microwell plates. The goal was to develop a rapid, reliable, and efficient procedure for resource-poor settings or food industry with large sample numbers. Detection depends on the broth changing from neutral to acidic pH due to sugar fermentation reflecting cell growth and then to basic due to decarboxylase generating amines, indicating presence of decarboxylase-positive bacteria. The visible absorption spectra of three pH indicators that change color at neutral pH were compared from pH 4.5 to 9. In the modified decarboxylase broth, phenol red showed the largest 550 nm absorbance changes when the pH was shifted from neutral to acidic and basic compared to bromocresol purple and bromothymol blue. Most of tested Salmonella serovars rapidly and specifically metabolized ornithine and lysine and showed positive decarboxylase activity (red broth turning pink) within 6–8 h. All Salmonella serovars possessed arginine decarboxylase, but arginine metabolism took at least 24 h to attain pink broth. Salmonella Typhi and Salmonella Paratyphi A are void of ornithine and lysine decarboxylases, respectively. Therefore, both ornithine and lysine were used as decarboxylase substrates in the selective enrichment media formulated to detect all Salmonella serovars. Three selective inhibitors: magnesium chloride, novobiocin, and magnesium chloride with malachite green (from Rappaport-Vasilliadis soy broth) were chosen to be included in seven new amino acid decarboxylase broths. They were tested for their ability to screen for Salmonella contamination in the selective enrichment step. Collectively, the broth formulations with different amino acid substrates and selective inhibitors not only identified decarboxylase-positive bacteria, but further distinguished between decarboxylase-positive salmonellae and non-salmonellae. The developed screening method was tested on some naturally- and artificially-contaminated food samples of different matrices; homogeneous liquid (pasteurized milk), solid (cooked chicken), and complex food matrix (ready-to-eat food). With proper sample pre-enrichment, this procedure with its seven newly developed broths could reliably and rapidly identify food samples with Salmonella contamination without risking false negative results.

473. Qualification of a p24 ELISA Assay for Quantitation of Total Lentiviral Vector Concentration

Lentiviral vectors (LVV) are efficient gene transfer vehicles used in a growing list of gene therapy applications that are currently being evaluated clinically. We are conducting clinical trials in subjects with β-thalassemia major, severe sickle cell disease, and childhood cerebral adrenoleukodystrophy, which employ autologous CD34+ cells transduced with LVV encoding a corrective transgene, βA-T87Q-Globin or ABCD1. Essential to LVV process development is the availability of reliable analytical tools to characterize the purified LVV product and in-process samples. Total lentiviral vector particle titers can be estimated by quantitation of HIV-1 p24 antigen concentration using commercial ELISA kits. In support of late-stage process characterization, it is essential to qualify the assay and demonstrate its suitability to test in-process samples in different matrices. Following ICH Q2 R1 guidelines, assay accuracy, repeatability, intermediate precision, quantitation limit, linearity, and linear range were evaluated. Additionally, qualification tests for specificity and dilutional linearity were performed on in-process samples and buffers to assess potential matrix interference. The results of these tests were used to define appropriate dilutions and acceptance criteria for p24 ELISA in-process samples. The assay has shown to be linear between 400 pg/mL and 25 pg/mL, while maintaining accuracy for p24 detection with the limit of quantitation being 25 pg/mL. To demonstrate assay repeatability, various concentrations within the linear range were tested resulting in coefficients of variation below 5%. The coefficient of variation across different days and different operators was below 8% for all concentrations tested, indicating consistent assay precision. Spike recovery studies have shown consistent recovery of spiked p24 antigen (73-126%), demonstrating assay specificity and lack of matrix interference in all in-process matrices tested while maintaining dilutional linearity. To conclude, the p24 ELISA assay used for LVV quantitation has shown precision, repeatability, specificity and accuracy, within an established linear quantitation range, adequate to support late-stage process characterization activities.

Removal of Cd(II) and Pb(II) from wastewater by using triethylenetetramine functionalized grafted cellulose acetate-manganese dioxide composite

In this manuscript, we have studied the removal of Cd(II) and Pb(II) ions from aqueous solution by using triethylenetetramine functionalized cellulose acetate grafted with the copolymer-manganese dioxide composite. The novel sorbent cellulose was extracted from the mangrove trees (Avicennia marina) and it was then acetylated and grafted with acrylamide. The sorbent composite was designed to interact simultaneously with higher metal loading by complexation-adsorption process.FT-IR, SEM, EDAX and TGA techniques were employed to characterize the cellulose modified composite. Sorption equilibria were established after 30min and their data were described by Langmuir and Freundlich models. The functionalized hybrid cellulose composite showed maximum adsorption capacity 82.06 and 196.84mgg−1 for Cd(II) and Pb(II), respectively. The studied metal ions were successfully recovered from real wastewater samples of different matrices.

Application of bifunctional Mangifera indica L.-loaded Saccharomyces cerevisiae as efficacious biosorbent for bivalent cobalt and nickel cations from different wastewaters: equilibrium and kinetic studies

Baker’s yeast (Saccharomyces cerevisiae) was immobilized on mango (Mangifera indica L.) leaves to prepare a novel, low cost, and eco-friendly biosorbent Mi-yeast. The fabricated biosorbent was characterized by FTIR and SEM and applied to remove Co(II) and Ni(II) ions from aqueous solutions via batch mode technique. The biosorption equilibria were established in 30 min and the experimental data were applied to Freundlich, Langmuir, and Dubinin–Radushkevich isotherm models. The maximum biosorption capacities were found to be 526 mg g−1 for Co(II) at pH 6 and 250 mg g−1 Ni(II) at pH 7. Among four kinetic models, the experimental data were best described by the second-order expression. Different foreign ions were found to have a negligible interfering effect on the biosorption capacities. Mi-yeast could be regenerated using 0.2M HCl during repeated biosorption–desorption cycles with 4–7% loss in metal efficiency after five cycles. The potential applications of Mi-yeast for selective removal of Co(II) and Ni(II) from different real wastewater samples of different matrices were also applied using a micro-column technique.

Pulsed microdischarge with inductively coupled plasma mass spectrometry for elemental analysis on solid metal samples.

Pulsed microdischarge employed as source for direct solid analysis was investigated in N2 environment at atmospheric pressure. Compared with direct current (DC) microdischarge, it exhibits advantages with respect to the ablation and emission of the sample. Comprehensive evidence, including voltage-current relationship, current density (j), and electron density (ne), suggests that pulsed microdischarge is in the arc regime while DC microdischarge belongs to glow. Capability in ablating metal samples demonstrates that pulsed microdischarge is a viable option for direct solid sampling because of the enhanced instantaneous energy. Using optical spectrometer, only common emission lines of N2 can be acquired in DC mode, whereas primary atomic and ionic lines of the sample are obtained in the case of pulsed mode. Calculations show a significant difference in N2 vibrational temperatures between DC and pulsed microdischarge. Combined with inductively coupled plasma mass spectrometry (ICPMS), pulsed microdischarge exhibits much better performances in calibration linearity and limits of detection (LOD) than those of DC discharge in direct analysis of samples of different matrices. To improve transmission efficiency, a mixture of Ar and N2 was employed as discharge gas as well as carrier gas in follow-up experiments, facilitating that LODs of most elements reached ng/g.

Potential of glucose measurement in soil and food sample using low molecular weight O-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride nanoparticle-glucose oxidase immobilised on a natural fibre membrane

Low, medium and high molecular weights O-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride nanoparticles (L-, M- and H-O-HTCC NP) have been synthesised and used to immobilise glucose oxidase on eggshell membranes for glucose biosensing. Among these O-HTCC NP-based biosensors, L-O-HTCC NP provides the highest sensitivity to glucose with a linear response of 0.012–0.60 mM and a detection limit of 12 μM (S/N = 3). The effect of L-O-HTCC NP and enzyme loading ratio, pH, temperature and phosphate buffer concentration on the sensitivity of the biosensor was studied in detail. The biosensor exhibits fast response time (40 s), good repeatability (3.0%, n = 10) and storage stability (95% of initial sensitivity after 1-year storage). Common interferents including acetic acid, DL-α-alanine, L-ascorbic acid, butyric acid, citric acid, DL-cysteine, ethanol, folic acid, glycine, lactic acid, lactose, propionic acid, sodium benzoate and sucrose do not cause significant interference on the L-O-HTCC NP biosensor. The recoveries 88.3%–102% and 102%–116% and relative standard deviations (RSDs) 3.90%–5.56% and 1.25%–3.00% are respectively, for the soil and food sample analyses. The proposed biosensor method has been applied to determine glucose in soil and food samples with good accuracy and recovery, inferring that it has potential for detection and quantification of diversified samples of different matrices. Finally, it has successfully monitored the changes of glucose contents in soil samples at various incubation times, demonstrating its potential use in environmental and geochemical analysis.

Enhanced lipid isomer separation in human plasma using reversed-phase UPLC with ion-mobility/high-resolution MS detection

An ultraperformance LC (UPLC) method for the separation of different lipid molecular species and lipid isomers using a stationary phase incorporating charged surface hybrid (CSH) technology is described. The resulting enhanced separation possibilities of the method are demonstrated using standards and human plasma extracts. Lipids were extracted from human plasma samples with the Bligh and Dyer method. Separation of lipids was achieved on a 100 × 2.1 mm inner diameter CSH C18 column using gradient elution with aqueous-acetonitrile-isopropanol mobile phases containing 10 mM ammonium formate/0.1% formic acid buffers at a flow rate of 0.4 ml/min. A UPLC run time of 20 min was routinely used, and a shorter method with a 10 min run time is also described. The method shows extremely stable retention times when human plasma extracts and a variety of biofluids or tissues are analyzed [intra-assay relative standard deviation (RSD) <0.385% and <0.451% for 20 and 10 min gradients, respectively (n = 5); interassay RSD <0.673% and <0.763% for 20 and 10 min gradients, respectively (n = 30)]. The UPLC system was coupled to a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer, equipped with a traveling wave ion-mobility cell. Besides demonstrating the separation for different lipids using the chromatographic method, we demonstrate the use of the ion-mobility MS platform for the structural elucidation of lipids. The method can now be used to elucidate structures of a wide variety of lipids in biological samples of different matrices.

Conductometric determination of ammonium by a multisyringe flow injection system applying gas diffusion

A multisyringe flow injection system (MSFIA) coupled to a gas-diffusion cell has been developed for the conductometric determination of ammonium in different water samples. Operation strategies, membrane, reagent concentrations, and flow rates have been studied to optimize the sensitivity of detection and to fit the required working range. The proposed MSFIA system has been compared with former FIA and SIA systems using gas diffusion. The system was applied to the determination of ammonium in water samples of different matrices in order to evaluate its performance. These samples were coastal waters, pond waters, and compost aqueous extracts. Good recoveries of 102 ± 13% were obtained and no significant differences with the reference methods were found. The system can be used for a wide concentration range of ammonia, from 0.075 to 360 mg L−1, without sample dilution and with a precision better than 2% of RSD. The throughput of the method was 32 injections per hour.

Automated regenerable microarray-based immunoassay for rapid parallel quantification of mycotoxins in cereals

An automated flow-through multi-mycotoxin immunoassay using the stand-alone Munich Chip Reader 3 platform and reusable biochips was developed and evaluated. This technology combines a unique microarray, prepared by covalent immobilization of target analytes or derivatives on diamino-poly(ethylene glycol) functionalized glass slides, with a dedicated chemiluminescence readout by a CCD camera. In a first stage, we aimed for the parallel detection of aflatoxins, ochratoxin A, deoxynivalenol, and fumonisins in cereal samples in a competitive indirect immunoassay format. The method combines sample extraction with methanol/water (80:20, v/v), extract filtration and dilution, and immunodetection using horseradish peroxidase-labeled anti-mouse IgG antibodies. The total analysis time, including extraction, extract dilution, measurement, and surface regeneration, was 19 min. The prepared microarray chip was reusable for at least 50 times. Oat extract revealed itself as a representative sample matrix for preparation of mycotoxin standards and determination of different types of cereals such as oat, wheat, rye, and maize polenta at relevant concentrations according to the European Commission regulation. The recovery rates of fortified samples in different matrices, with 55-80 and 58-79%, were lower for the better water-soluble fumonisin B1 and deoxynivalenol and with 127-132 and 82-120% higher for the more unpolar aflatoxins and ochratoxin A, respectively. Finally, the results of wheat samples which were naturally contaminated with deoxynivalenol were critically compared in an interlaboratory comparison with data obtained from microtiter plate ELISA, aokinmycontrol® method, and liquid chromatography-mass spectrometry and found to be in good agreement.

Determination of three endocrine disrupting chemicals, triclosan, 4-n-nonylphenol, and di-n-butyl phthalate using stir bar sorptive extraction in samples of different matrices

Three endocrine disrupting chemicals (EDCs), triclosan (TCS), 4-n-nonylphenol (4-n-NP), and di-n-butyl phthalate (DBP) were determined using stir bar sorptive extraction (SBSE) along with high-performance liquid chromatography/photodiode array detection (HPLC/DAD). Benzyl butyl phthalate was used as an internal standard. The targeted analytes could be rapidly determined with limits of quantification (LOQ) ranging from 4.1 (DBP), 10 (TCS), to 34 (4-n-NP) µg L−1 in real samples such as bottled waters, personal care products, soaps, lotions, and urine. The results show that the developed analytical scheme is solvent-saving, efficient, and capable of fast screening samples for these common EDCs.

Multiple headspace solid-phase microextraction after matrix modification for avoiding matrix effect in the determination of ethyl carbamate in bread

This study presents the potential of multiple headspace solid-phase microextraction (multiple HS-SPME) for the quantification of analytes in solid samples. Multiple HS-SPME shares the same advantages as SPME. It also enables a complete recovery of the target compound and therefore the matrix effect, which commonly appears in SPME-based analysis, is avoided. A method based on multiple HS-SPME for the determination of the toxic contaminant ethyl carbamate (EC) in bread samples has been developed and validated, using gas chromatography with flame ionization detector. A novel polyethylene glycol/hydroxy-terminated silicone oil fiber was prepared for the first time and subsequently used instead of commercial ones because of its high extraction ability and good operational stability. An important problem still remained in multiple HS-SPME of EC in fresh bread samples. The adsorption of EC by water in the samples caused low transport of analyte to the headspace, which made multiple HS-SPME invalidated. Mixing with anhydrous sodium sulphate, the sensitivity of the method was improved and the problem was solved. The proposed method showed satisfactory linearity (0.15–1500 μg g −1), precision (1.6%, n = 5) and limit of detection (0.041 μg g −1). Good recoveries, from 92.5 to 103.4%, were observed at three spiking levels. The method was applied to 14 bread samples. The multiple HS-SPME technique offers several advantages including reducing the manipulation time and cost, and avoiding analyte losses, especially in the analysis of a large number of samples in different matrices.