Assessment of exposure to pesticides: residues in 24 h duplicate diets versus their metabolites in 24 h urine using suspect screening and target analysis.

Human biomonitoring can add value to chemical risk assessment by reducing the assumptions regarding consumption rates, residue occurrence, and processing effects and by integrating exposures from different sources (diet, household use, environmental). However, the relationship between exposure and concentration in human matrices is unknown for most pesticides. Therefore, we conducted a pilot study to gain more insight into the qualitative and quantitative relationship between dietary intake of pesticides (external exposure) and urinary excretion (reflecting internal exposure). In this cross-sectional observational study, 35 healthy consumers aged 18-65 years from the region of Wageningen, Netherlands, collected an exact duplicate portion of their diets during 24 h. On the same day, they also collected all their urine. The duplicate diets were analyzed using target screening by GC- and LC-HRMS; each duplicate diet contained at least five, up to 21, pesticide residues. The 24 h urine samples were analyzed using LC-HRMS in a suspect screening workflow. Metabolites were tentatively detected in all 24 h urine samples, ranging from six metabolites corresponding to four pesticides up to 40 metabolites originating from 16 pesticides in a single urine sample. In total, 65 metabolites originating from 28 pesticides were tentatively detected. After prioritization and additional confirmation experiments, 28 metabolites originating from 10 pesticides were identified with confidence level 1 or 2b. Next, quantitative analysis was performed for a selection of pesticides in duplicate diets and their metabolites in 24 h urine to assess quantitative relationships. In the quantitative comparisons between duplicate diet and 24 h urine, it was found that some metabolites were already present in the duplicate diet, which may give an overestimation of exposure to the parent pesticide based on measurement of the metabolites in urine. Additionally, the quantitative comparisons suggest a background exposure through other exposure routes. We conclude that suspect screening of 24 h urine samples can disclose exposure to mixtures of pesticide on the same day in the general population. However, more research is needed to obtain quantitative relationships between dietary intake and exposure.

Septic shock due to Clostridium botulinum: a case report.

BACKGROUND: Clostridium botulinum is an anaerobic, Gram-positive, rod-shaped bacterium that forms spores and the neurotoxin botulinum. It is best known for its toxin-induced flaccid paralytic disease, which is deadly without correct treatment. In this report, we show a completely different clinical course with fatal outcome. CASE PRESENTATION: A 37-year-old African man born in Sierra Leone was admitted. After admission, his condition rapidly worsened due to severe septic shock and progressive multiorgan failure. No neurological signs were seen. Despite treatment with antibiotics, fluid resuscitation, and norepinephrine, the multiorgan failure deteriorated further and he died as a result. Blood and synovial fluid cultures showed Clostridium botulinum. No botulinum toxins were found. CONCLUSION: This is a rare case of fatal septic shock due to Clostridium botulinum-induced septic arthritis without any sign of the classic clinical syndrome of botulism.

Controlling spin relaxation in hexagonal BN-encapsulated graphene with a transverse electric field.

We experimentally study the electronic spin transport in hexagonal BN encapsulated single layer graphene nonlocal spin valves. The use of top and bottom gates allows us to control the carrier density and the electric field independently. The spin relaxation times in our devices range up to 2 ns with spin relaxation lengths exceeding 12 µm even at room temperature. We obtain that the ratio of the spin relaxation time for spins pointing out-of-plane to spins in-plane is τ(⊥)/τ(||) ≈ 0.75 for zero applied perpendicular electric field. By tuning the electric field, this anisotropy changes to ≈ 0.65 at 0.7 V/nm, in agreement with an electric field tunable in-plane Rashba spin-orbit coupling.

Spin-dependent quantum interference in nonlocal graphene spin valves.

Up to date, all spin transport experiments on graphene were done in a semiclassical regime, disregarding quantum transport properties such as phase coherence and interference. Here we show that in a quantum coherent graphene nanostructure the nonlocal voltage is strongly modulated. Using nonlocal measurements, we separate the signal in spin-dependent and spin-independent contributions. We show that the spin-dependent contribution is about 2 orders of magnitude larger than the spin-independent one, when corrected for the finite polarization of the electrodes. The nonlocal spin signal is not only strongly modulated but also changes polarity as a function of the applied gate voltage. By locally tuning the carrier density in the constriction via a side gate electrode we show that the constriction plays a major role in this effect. Our results show the potential of quantum coherent graphene nanostructures for the use in future spintronic devices.

Spin transport in high-quality suspended graphene devices.

We measure spin transport in high mobility suspended graphene (µ ≈ 10(5)cm(2)/(V s)), obtaining a (spin) diffusion coefficient of 0.1 m(2)/s and giving a lower bound on the spin relaxation time (τ(s) ≈ 150 ps) and spin relaxation length (λ(s) = 4.7 µm) for intrinsic graphene. We develop a theoretical model considering the different graphene regions of our devices that explains our experimental data.

Screening of plant toxins in food, feed and botanicals using full-scan high-resolution (Orbitrap) mass spectrometry.

A generic method based on LC with full-scan high-resolution (Orbitrap) mass spectrometry (MS) was systematically investigated for the simultaneous detection of a wide range of plant toxins in a variety of food and feed matrices. For a selection of 150 substances, representing various chemical classes, the limit of detection was established using fixed LC-MS conditions. Ion suppression effects and selectivity were evaluated using generic extracts from representative and relevant matrices (food supplement, honey, silage, compound feed). The majority of the substances could be measured as positive ions after electrospray ionisation (ESI(+)). Using a mass resolving power of 100,000 a reliable high mass accuracy was obtained despite the high abundance of co-extractants in the sample extracts. This enabled the use of ±5 ppm mass extraction windows, which in turn resulted in a high degree of selectivity. On the other hand, except for honey, strong ion suppression effects were frequently observed which adversely affected the detection limits. Nevertheless, for the majority of the substances the detection limits were in the range 0.01-0.05 mg kg(-1). Since non-selective sample preparation and non-targeted data acquisition were performed, the presence of plant toxins initially not targeted for during data review can be subsequently investigated, which is a very useful option because for many known toxins no analytical reference standards are yet available. The applicability of the method was demonstrated by analysis of a variety of real-life samples purchased on the market or from cases of intoxication. These included honey, herbal tea, food supplements, poppy seeds, traditional Chinese medicines, compound feed, silage and herb-based feed additives. Plant toxins that were detected included various pyrrolizidine alkaloids, grayanotoxins, opium alkaloids, strychnine, ricinine (a marker for ricin), aconitine, aristolochic acid and cardiac glycosides (e.g. digitoxin, digoxin).