Graphitized Carbon Black Research Articles

Mycoestrogen determination in cow milk: Magnetic solid-phase extraction followed by liquid chromatography and tandem mass spectrometry analysis.

Recently, magnetic solid-phase extraction has gained interest because it presents various operational advantages over classical solid-phase extraction. Furthermore, magnetic nanoparticles are easy to prepare, and various materials can be used in their synthesis. In the literature, there are only few studies on the determination of mycoestrogens in milk, although their carryover in milk has occurred. In this work, we wanted to develop the first (to the best of our knowledge) magnetic solid-phase extraction protocol for six mycoestrogens from milk, followed by liquid chromatography and tandem mass spectrometry analysis. Magnetic graphitized carbon black was chosen as the adsorbent, as this carbonaceous material, which is very different from the most diffuse graphene and carbon nanotubes, had already shown selectivity towards estrogenic compounds in milk. The graphitized carbon black was decorated with Fe3 O4 , which was confirmed by the characterization analyses. A milk deproteinization step was avoided, using only a suitable dilution in phosphate buffer as sample pretreatment. The overall process efficiency ranged between 52 and 102%, whereas the matrix effect considered as signal suppression was below 33% for all the analytes even at the lowest spiking level. The obtained method limits of quantification were below those of other published methods that employ classical solid-phase extraction protocols.

Enantiomeric determination and evaluation of the racemization process of atropine in Solanaceae seeds and contaminated samples by high performance liquid chromatography-tandem mass spectrometry

A new method has been developed for the enantioselective separation of (−) and (+) hyoscyamine in Solanaceaes seeds and contaminated buckwheat. Chromatographic separation was optimized, evaluating two chiral columns, Chirobiotic V and Chiralpal-AY3. Better resolution was obtained using a Chiralpak-AY3 column, utilizing as mobile phase ethanol (0.1% diethanolamine). An extraction procedure based on a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) was applied, using water and acetonitrile containing 1% of acetic acid, and a clean-up step utilizing primary secondary amine (PSA) and graphitized carbon black (GCB) as sorbents. The extract was diluted with ethanol (50/:50, v/v) prior to chromatographic analysis, and the separation was carried out avoiding the racemization during this stage. Enantiomerization process of atropine was studied in samples at different conditions such as temperature (30, 50 and 80°C) and pH (3, 5, 7 and 9), observing that racemization occurs at high pH (9) and temperature (80°C). Stramonium and Brugmansia seeds were analyzed and the concentration of (−)-hyoscyamine was 1500mg/kg and 320mg/kg respectively. Contaminated buckwheat was also determined and (−)-hyoscyamine was detected at 170μg/kg.

Determination of aniline and quinoline compounds in textiles

A simple method for simultaneous determination of twenty-one analytes, belonging to two classes of compounds, aromatic amines and quinolines, is presented. Several of the analytes considered in this study frequently occur in textiles goods on the open market and have been related to allergic contact dermatitis and/or are proven or suspected carcinogens. The method includes an efficient clean-up step using graphitized carbon black (GCB) that simplifies and improves the robustness of the subsequent GC–MS analysis. Briefly, after solvent extraction of the textile sample, the extract is passed through a GCB SPE cartridge that selectively retain dyes and other interfering compounds present in the matrix, producing a clean extract, suitable for GC–MS analysis, is obtained.The method was evaluated by spiking blank textiles with the selected analytes. Method quantification limits (MQL) ranged from 5 to 720ng/g depending on the analyte. The linear range of the calibration curves ranged over two order magnitude with coefficients of determination (R2) higher than 0.99. Recoveries ranged from 70 to 92% with RSDs 1.7–14%. The effectiveness of the method was tested on a variety of textile materials samples from different origin.In a pilot explorative survey, 2,6-dichloro-4-nitroaniline was detected in all the analysed clothing samples in concentrations ranging from 1.0 to 576μg/g. 2,4-dinitroaniline was detected in four of the seven samples with a highest concentration of 305μg/g. Quinoline was detected in all samples in concentrations ranging from 0.06 to 6.2μg/g.

Effects of High Oxygen Permeability Ionomers on the Cathode Performance of Polymer Electrolyte Fuel Cells

For the large-scale commercialization of polymer electrolyte fuel cells (PEFCs), it is very important to reduce the amount of Pt by developing highly efficient cathode catalyst layers (CLs) due to the high cost and limited availability of Pt resources. In previous work, we demonstrated the importance of two factors for the design of high performance cathode CLs. The first is higher effective Pt surface area (S(e)Pt), which practically contributes to the oxygen reduction reaction (ORR) [1]; the n-Pt/AB250 catalyst, for which all of the Pt particles exist only on the AB250 exterior surface, is the most attractive in order to generate the large current densities required by actual fuel cell operation [2]. The second is the optimized distribution of ionomer on the surfaces both of Pt particles and carbon particles; short-side-chain (SSC) perfluorosulfonic acid ionomers with high ion-exchange capacity (IEC) showed better continuity and uniformity on the Pt and graphitized carbon black (GCB) particles than the conventional ionomer, which might have led to the improvement of both the mass transport and the proton-conducting network in CLs [3].In this study, we investigate the effects of high oxygen permeability ionomers on the cathode performance of PEFCs. The high oxygen permeability ionomers are expected to increase the flux of oxygen near the Pt surface of the three-phase boundary, in the case of extremely low Pt loadings [4]. The low Pt loading cathode CLs (ca. 0.05 ± 0.003 mg-Pt cm-2) were prepared from the AB250-supported Pt catalyst, with a higher effective Pt surface area (n-Pt/AB250: S(e)Pt = 107 m2 gPt -1, specific surface area of AB250: 219 m2 g-1, Denka Co., Ltd.) and ionomers developed by Asahi Glass Co., Ltd. (AGC); AGC PFSA (IEC = 1.13 meq g-1), AGC sample A (IEC = 1.17 meq g-1, O2 permeability 1.5 times higher than AGC PFSA) and AGC sample B (IEC = 1.50 meq g-1, O2 permeability 1.5 times higher than AGC PFSA). Figure 1 (a) shows the resistance-corrected (IR-free) polarization curves of the high oxygen permeability ionomers for the ORR at 80 oC fed with ambient pressure air humidified at 80% RH. The mass activity (MA) at 0.85 V and the mass power values, calculated from the maximum outputs of the IR-free polarization curves, are plotted as a function of RH in Figure 1 (b) and (c), respectively. The cathode cell performance was significantly increased by using the high oxygen permeability ionomers, i.e., AGC sample A and AGC sample B. However, the ionomers showed different performance behavior at low and high current densities. In the high potential regions (low current densities), in which there is a smaller effect of mass transport, the AGC sample B with the higher IEC of 1.50 exhibited higher cell performance than the other ionomers, as can be confirmed in the MA results in Figure 1 (b). In contrast, the AGC sample A with the lower IEC of 1.17 led to a significant improvement of the cathode performance in the high current density region, which led to the achievement of very high performance, greater than 22 W mgPt -1at 80-100% RH, as presented in the mass power results in Figure 1 (c). These results show that the improved oxygen permeability of the ionomers could result in highly efficient cathode CLs for PEFCs. Acknowledgment This work was supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cell” (SPer-FC) project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. The authors are grateful to Asahi Glass Co., LTD. for kindly providing the experimental ionomers. Also, the authors are grateful to Denka Co., Ltd. for kindly providing the experimental AB supports.

Influence of Graphite Powder and Carbon Black Weight Percentages on the Electrical Properties of Epoxy Composite Plates

There is a growing demand for polymeric composite materials, mainly, in industrial applications. For instance, bipolar plates for polymer electrolyte fuel cell in automobile applications. This kind of composite can replace with lower cost and greater efficiency metallic components. The basic requirement is that the composite must possess adequate electrical and mechanical properties for the particular application. The goal of the present paper is to analyze the effect of graphite powder and carbon Black weight percentages on the electrical properties of epoxy composite plates. Electrical conductivity tests were performed in different composites. This study shows that is possible to obtain a semiconductor behavior with both epoxy/graphite and epoxy/Carbon Black composites.

Utilizing a novel sorbent in the solid phase extraction for simultaneous determination of 15 pesticide residues in green tea by GC/MS.

Pesticide residues exceeding standard in green tea is a widespread problem of the world's attention, containing organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), and pyrethroids. In this research, three dimensionally honeycomb Mg-Al layered double oxide (TDH-Mg-Al-LDO) combined with graphitized carbon black (GCB), packed as a column, was used as a novel solid phase extraction sorbent, applying in simultaneous determination of 15 pesticide residues in green tea coupled with GC-MS. Compared with different type of SPE column, it showed that TDH-Mg-Al-LDO exhibited great advantages in the extraction of 15 pesticide residues from green tea, which was seldom reported before. Different experiment conditions, such as combination order of Mg-Al-LDO and GCB, dosage of sorbents, type and volume of eluting solvent were thoroughly studied and optimized. The limits of detection (LODs) of 15 pesticides ranged from 0.9 to 24.2ng/g and the limits of quantifications (LOQs) were ranging from 3.0 to 80.0ng/g. The recoveries using this method at three spiked concentration levels (10, 100 and 500ng/g for Fenthion, P,P'-DDE, O,P'-DDT, P,P'-DDD and Bifenthrin, 100, 500 and 2000ng/g for the others) range from 71.1 to 119.0%. The relative standard deviation (RSD) was from 0.1 to 7.6% in all case. The result indicated that the proposed analytical method had been successfully applied for the simultaneous determination of 15 pesticide residues in commercial green tea.

Development, optimization and validation of QuEChERS based liquid chromatography tandem mass spectrometry method for determination of multimycotoxin in vegetable oil

In recent years, vegetable oils have been reported to be contaminated by mycotoxins. A new method was developed, optimized and validated for the simultaneous determination of aflatoxins (AFs), ochratoxin A (OTA), deoxynivalenol (DON) and zearalenone (ZEA) in vegetable oil by a modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) technique. A quick procedure of mycotoxins extraction and clean-up was achieved in two steps. Firstly, target analytes were extracted into the optimized solvent acetonitrile and followed by dispersive solid phase extraction (d-SPE) sorbent clean up with the optimized sorbents to remove the co-extracts. Three types of d-SPE sorbents; C18; Primary Secondary Amine (PSA); Graphitized Carbon Black (GCB) and four combination ratios of two selected d-SPE sorbent were evaluated to achieve an optimum and acceptable result. The maximum co-extracts were removed when C18 and GCB were used at ratio 3:1 with MgSO4 anhydrous followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The validation study showed all analytes could be detected between 0.01 and 650.17 ng g−1 concentration ranges with correlation coefficient >0.98. The limit of quantitation ranges from 0.04 to 2000 ng g−1. The recoveries were in a range of 87.9–106.6%. The repeatability and reproducibility of the analysis were between the ranges of 0.5–1.3, within the acceptable level for precision. Significant matrix effect was compensated using the matrix matched calibration curves. The method was successfully applied to 25 vegetable oil samples including corn oil, palm oil and sunflower oil. ZEA, AFG2, AFG1 and AFB1 were among the detected analytes.

Multiresidue analysis of endocrine-disrupting compounds and perfluorinated sulfates and carboxylic acids in sediments by ultra-high-performance liquid chromatography–tandem mass spectrometry

A multiresidue analytical method for the determination of 11 perfluorinated compounds and 22 endocrine-disrupting compounds (ECDs) including 13 natural and synthetic estrogens (free and conjugated forms), 2 alkylphenols, 1 plasticiser, 2 UV-filters, 1 antimicrobial, and 2 organophosphorus compounds in sediments has been developed. Ultrasound-assisted extraction followed by solid phase extraction (SPE) with graphitized carbon black (GCB) cartridge as clean-up step were used. The extraction process yield was optimized in terms of solvent composition. Then, a 32 experimental design was used to optimize solvent volume and sonication time by response surface methodology, which simplifies the optimization procedure. The final extract was analyzed by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. The optimized sample preparation method is simple and robust, and allows recovery of ECDs belonging to different classes in a complex matrix such as sediment. The use of GCB for SPE allowed to obtain with a single clean-up procedure excellent recoveries ranging between 75 and 110% (relative standard deviation <16%). The developed methodology has been successfully applied to the analysis of ECDs in sediments from different rivers and lakes of the Lazio Region (Italy). These analyses have shown the ubiquitous presence of chloro-substituted organophosphorus flame retardants and bisphenol A, while other analyzed compounds were occasionally found at concentration between the limit of detection and quantification.

Pesticide Residue Rapid Extraction from Ginseng Tea Using a Modified Luke Method for GC–MS

A modified Luke rapid detection method followed by gas chromatography–mass spectrometry (GC–MS) has been developed for the simultaneous determination of 42 pesticides in ginseng tea. This method uses acetone and n-hexane solution to extract and partition pesticides. Ginseng tea samples were mixed with acetone, water and n-hexane solution, and then partitioned by vortex. After the partition, the top layer (n-hexane) was transferred into a centrifuge tube containing primary secondary amine (PSA), graphitized carbon black (GCB) and C18 for purification. And then the centrifuge supernatant was injected into GC–MS. The Luke method was applied in ginseng tea sample detection, and we confirmed that this method can easily extract various types of pesticides from ginseng tea samples. The rates of recovery for pesticides studied were satisfactory, ranging from 65.5 to 109.0 % with a relative standard deviation (RSD) of less than 12 %. The limits of quantification (LOQs) ranged between 0.5 and 11.5 μg·kg−1. The modified Luke method is quick and easy.

Morphology and performance of styrene butadiene rubber filled with modified graphite nanoplatelet and carbon black

In our work, effects of 2-mercapto-1-methylimidazole modified graphite nanoplatelet (MMI–GN) and carbon black (CB) on static and dynamic mechanical properties of styrene butadiene rubber (SBR) composites were studied. MMI–GN is synthesized by ball-mill process, and the result reveals that π–π interactions existed between MMI and GN. The results demonstrate that the static and dynamic mechanical performances of SBR/CB/MMI–GN composites are significantly improved over these of SBR/CB and SBR/CB/GN composites. Compared with SBR/CB, the tensile strength, tear strength, and modulus at 300% elongation of SBR/CB/MMI–GN–3 are greatly improved by 45%, 27%, and 4%, respectively. And the rolling resistance of SBR/CB/MMI–GN–3 is reduced by 3.7% with remaining almost unchanged in the wet grip property. The superiority of MMI–GN in the enhancement for the overall performance of SBR/CB composites is attributed to the well dispersion of GN throughout the SBR matrix and the enhanced interfacial interactions between GN and the SBR matrix. This work might expedite synthesis of the graphite-based materials for enhancing rubber composites, and enlarge the potential applications of modified graphite to fabricate the high-performance rubber composites. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of Pt Loading and Cell Potential on the HF Ohmic Resistance of an Nb-Doped SnO2-Supported Pt Cathode for PEFCs

We measured highly accurate ohmic resistances of single cells at high frequency (HF) using Pt/Nb-SnO2 cathodes under several different conditions, including various cathode potentials and various atmospheres, in order to study the relationships between the ohmic resistances of single cells and the electrical conductivity of the Pt/Nb-SnO2 catalyst for polymer electrolyte fuel cells (PEFCs). The ohmic resistance of a cell using Pt/Nb-SnO2 increased with increasing cathode potential, in the range of typical cathode operation (0.4 V to 1.0 V vs. the reversible hydrogen electrode). The increase of Pt loading on the Nb-SnO2 support from 9 wt% to 17 wt% was effective in decreasing the ohmic resistance and in improving the cell performance. We propose that Pt oxidation might impede the effect of shrinking the depletion layer of the Nb-SnO2 surface. The addition of graphitized carbon black (GCB) to the Pt/Nb-SnO2 cathode was able to improve the cell performance by constructing both electronic pathways and gas diffusion pathways in the catalyst layer, under low and high current density operation, respectively. The performance of the Pt/Nb-SnO2 + GCB cathode was superior to that of the Pt/GCB cathode due to these effects.

Utilization of rice husk silica as adsorbent for BTEX passive air sampler under high humidity condition.

Selective adsorbent of benzene, toluene, ethylbenzene, and xylenes (BTEX) was developed based on mesoporous silica materials, RH-MCM-41. It was synthesized from rice husk silica and modified by silane reagents. The silane reagents used in this study were trimethylchlorosilane (TMS), triisopropylchlorosilane (TIPS), and phenyldimethylchlorosilane (PDMS). Physiochemical properties of synthesized materials were characterized by small-angle X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), and surface area analysis. Materials packed in passive air sampler were tested for BTEX uptake capacity. The tests were carried out under an influence of relative humidity (25 to 99 %). Overall, RH-MCM-41 modified by TMS outperformed compared to those modified by other silane agents. The comparative BTEX adsorption on this material and commercial graphitized carbon black was reported.

Occurrence of pesticide residues in candies containing bee products

Pesticides can be found in bee products as they are usually employed to protect the beehive, but they can also reach the hive due to environmental contamination. These contaminants could be present in processed foods. One of the most common and consumed comfitures based in bee products are honey and propolis candies, for which no analytical method has yet been developed. This work presents the development of an ethyl acetate based extraction method followed by dispersive clean up using Primary and Secondary Amine (PSA) plus Graphitized Carbon Black (GCB) with Gas Chromatography coupled to Mass Spectrometry (GC–MS) determination for pesticide residue monitoring candies containing honey and propolis from the Mercosur region. Sixteen pesticides found in bee products as well as three pesticide metabolites of toxicological significance were evaluated including acaricides and insecticides (pyrethroids, organophosphates and some organochlorines). The method was validated, with a LOQ of 0.01 mg/kg for most analyzed pesticides, showing a recovery rate of 70–120% with <20% RSD. Real samples from the Mercosur countries were analyzed. Coumaphos and chlorpyrifos residues were detected in most of them. From these findings a preliminary toxicological evaluation of coumaphos via admissible daily intake (ADI) estimation was conducted.

QuEChERS-Based Methods for the Determination of Pesticide Residues in a Dill Using Gas Chromatography with Electron Capture and Nitrogen Phosphorus Detection

In this study, three QuEChERS-based methods of improving sample extract preparation through reduction of unwanted matrix background for pesticide residue analysis in dill (a chlorophyll-containing matrix) were developed and compared. These methods involved the use of (1) dispersive solid-phase extraction (dispersive-SPE), (2) dispersive-SPE combined with liquid–liquid extraction (LLE), and (3) only LLE. Samples were analyzed by gas chromatography with electron capture and nitrogen phosphorus detection (GC-ECD/NPD). The results indicated that cleanup with primary secondary amine (PSA) and graphitized carbon black (GCB) sorbents followed by final solvent exchange from acetonitrile to petroleum ether was the best alternative of the tested methods, resulting in the cleanest extracts. The matrix effect of dill on the most favorable method herein was not significant, and the calibration performed well, with R 2 ≥ 0.99. The overall recoveries at three spiking levels of 0.01, 0.1, and 1.0 mg kg−1 fell in the range between 73 and 110 % (95 % on average) with relative standard deviation (RSD) values equal to or lower than 12 % (5 % on average). Uncertainty for the studied pesticides ranged from 7 to 14 % (with the overall average uncertainty of 11 %). Analyses of real samples revealed the presence of pesticides unapproved for use on dill, as well as exceedances of the maximum residue levels (MRLs) for some pesticides. The samples with residue violation results were also confirmed by gas chromatography–tandem mass spectrometry (GC-MS/MS). The proposed method of sample preparation and chromatographic analysis is sufficient and can be applied with all certainty to determine pesticide residues in dill and other plants of high pigment content, i.e., chlorophyll.

Pesticide determination in rose concrete and rose absolute using dispersive‐solid phase extraction followed by gas chromatography‐tandem mass spectrometry

AbstractThe rose species Rosa damascena and Rosa centifolia are cultivated for their use as perfume raw materials. The solvent extract of rose petals provides the concrete that is further transformed into the absolute. Both, concrete and absolute contain a variety of organic molecules. As a result of the lack of an adequate analytical procedure and the complexity of the matrices, the accurate quantification of pesticides in concrete and absolute remains challenging. Here we describe the first analytical method to quantify 57 pesticide residues in rose concrete and 56 pesticide residues in rose absolute. The method uses a multistep dispersive‐solid phase extraction (d‐SPE) cleanup followed by injection in a gas chromatography‐tandem mass spectrometer. Sample preparation includes the extraction of analytes from the matrix using acetonitrile and a mixture of salts and a double clean‐up step using sorbents in the form of primary and secondary amines (PSA), magnesium sulphate, C18 and graphitized carbon black (GCB). Two fortification levels, 0.025 to 0.15 and 0.5 mg/kg, were assessed. For 56 pesticides, the obtained recoveries were within the range of 70% to 120 % with a relative standard deviation (RSD) lower than 20% at each spiked level. The validation parameters proved that the developed method can be used for the quantification of 57 pesticide residues in rose concrete and 56 pesticide residues in rose absolute with a limit of quantification (LOQ) ranging from 0.025 to 0.1 mg/kg in concrete and from 0.05 to 0.15 mg/kg in absolute, depending on the active substance. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Application of the QuEChERS procedure and LC–MS/MS for the assessment of neonicotinoid insecticide residues in cocoa beans and shells

The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure was applied and validated for the analysis of neonicotinoid insecticide residues in cocoa bean matrix with high fat and high pigments. Samples employed in the study were fermented and dried beans obtained from major cocoa producing regions in Ghana where neonicotinoids are extensively used. Shells covering the beans were removed and analyzed separately to examine insecticide distribution. Analytes in both matrices were extracted in acetonitrile with sodium acetate and magnesium sulfate salts, cleaned up using a sorbent mixture of primary secondary amine (PSA), C18 and graphitized carbon black (GCB), and quantified using liquid chromatography tandem mass spectrometry (LC–MS/MS). Average recoveries at four levels of fortification ranged from 92 to 111% with relative standard deviation of ≤16% for all analytes. Limits of quantification ranged from 3 to 10μg/kg for all neonicotinoids. Imidacloprid was the most frequently encountered neonicotinoid and was quantified in more than 10% of deshelled bean and 30% of cocoa shell samples, with concentrations ranging from 11.5 to 35.6μg/kg and 11.8 to 214μg/kg in cocoa beans and shells, respectively. The findings from this study suggest a need for greater efficiency in neonicotinoid application, to avoid the build-up of these insecticides to unsafe levels in cocoa beans.

Removal of acidic interferences in multi-pesticides residue analysis of fruits using modified magnetic nanoparticles prior to determination via ultra-HPLC-MS/MS

The authors describe magnetite (Fe3O4) nanoparticles modified with 3-(N,N-diethylamino) propyltrimethoxysilane (Fe3O4-PSA NPs) for use as a sorbent for dispersive solid phase extraction of pesticide residues. The Fe3O4-PSA NPs were prepared by silanizing Fe3O4 NPs and modifying them with 3-(N,N-diethylamino) propyltrimethoxysilane. Field-emission scanning electron microscopy, FTIR and zeta potential measurements were employed to characterize the modified NPs. They were then used as an adsorbent to remove acidic interferences (such as malic acid and succinic acid), which are major interferences in LC-MS/MS analysis in causing ion suppression in the MS spectra of pesticides. In addition, graphitized carbon black (GCB) was used as an adsorbent to eliminate interferences by pigments. The use of Fe3O4-PSA NPs can replace time-consuming centrifugation as used in the so-called QuEChERS (quick, easy, cheap, effective, rugged and safe) method. This improvement is particularly significant in high-throughput analysis. Following the optimization of the quantities of Fe3O4-PSA NPs and GCB, the method was applied to the determination of 56 pesticides in (spiked) fruits (apple, kiwi, orange and pear) by ultra-HPLC-MS/MS. The analytical ranges typically extend from 1 to 200 ng∙mL−1, and recoveries range from 60.2 to 130 % at different concentrations of all four kinds of fruits. The LOQs for the pesticides are 10 ng∙kg−1, which makes the method a viable tool for pesticide monitoring in fruits.

Two-step dispersive-solid phase extraction strategy for pesticide multiresidue analysis in a chlorophyll-containing matrix by gas chromatography–tandem mass spectrometry

Two-step dispersive-solid phase extraction strategy for the cleanup of QuEChERS extracts in multiresidue analysis of current-use pesticides in a chlorophyll-containing matrix was evaluated and is reported for the first time. The proposed approach combines two sequential steps of dispersive-solid phase extraction (d-SPE) to reduce matrix co-extractives. In the first step, primary secondary amine (PSA) together with a new type of sorbent, known as ChloroFiltr, was employed. This was followed by a second step of d-SPE using octadecyl (C18) and graphitized carbon black (GCB). Also, new zirconium dioxide-based sorbents (Z-Sep+ and Z-Sep/C18) were evaluated but the use of GCB/C18 provided the highest pesticide coverage with recoveries in the range of 70–120% from spiked green soybean samples. The final extracts were analyzed by gas chromatography coupled to tandem mass spectrometry (GC–MS/MS). The overall recoveries at three spiking levels of 0.01, 0.05 and 0.2mgkg−1 were 96±15%, 93±13% and 92±13% with relative standard deviations of 10±7%, 9±5%, and 11±5%, respectively. The proposed method provided matrix effect <20% for 77% of the target compounds, which may be considered as negligible because such variability is closed to the accepted repeatability. For the rest of 8 and 15% of the compounds, the matrix effect was 20–30% and >30%, respectively. The developed method was successfully applied to study dissipation patterns of pesticides applied to soybean in experimental plot trials, thus contributing to establish safe and proper use of pesticides by extension of authorization on minor crops in Poland.

Effect of Added Graphitized Carbon Black on Both Performance and Durability of Pt/Nb-SnO2 Cathodes for PEFCs

The development of cathode catalysts that have both high activity for the oxygen reduction reaction (ORR) and high durability is an important subject for the application of PEFCs in fuel cell vehicles. At present, Pt nanoparticle catalysts supported on carbon black (Pt/CB) are typically being used in PEFC cathodes. While CB supports are essential for the high performance of PEFCs because of their large surface area, high electrical conductivity and well-developed pore structure, they corrode seriously during startup and shutdown of the fuel cell. Graphitized carbon black (GCB), which has a high degree of graphitization, has been used to mitigate such corrosion. According to our previous studies, the high stability of a Pt catalyst supported on GCB (Pt/GCB) was confirmed by use of simulated startup/shutdown evaluation.1 Electrochemical catalysts for PEFCs are required to have both electrically conductive paths and gas diffusion paths in order to form effective catalyst layers (CL). Therefore well-developed pore structures are needed in addition to high conductivity. We have developed Pt catalysts supported on doped SnO2 (Pt/Sb-SnO2, Nb-SnO2, and Ta-SnO2) with fused aggregate structures, which are similar to that of CB, constructed by the fusion of nearest-neighbor particles to form a branched structure.2,3 The Pt/doped SnO2 catalyst provides high electronic conductivity due to the low grain boundary resistance and also has a large micropore volume. Due to the effect of the doped SnO2 with fused aggregate structure, the high performance of these cathodes, which was superior to that of Pt/CB, was confirmed by use of single cell measurements.4,5 In this research,6 we report a detailed investigation of a single cell using Pt/Nb-SnO2 with the fused aggregate structure under actual operating conditions. For instance, we confirmed that the steady-state current-potential (I–E) curves of membrane-electrode assemblies (MEAs) were strongly dependent on the humidity condition of the supplied gases. We also investigated the effects of the addition of GCB into the Pt/Nb-SnO2cathode for the improvement of the cell performance. In Fig.1, the single cell performances using Pt/Nb-SnO2 with/without GCB as function of relative humidity were compared with that of a cell using Pt/GCB at 80◦C and hydrogen/air under 1 atm. The Pt-mass specific power of the Pt/Nb-SnO2 cathode under low humidity conditions was superior to that of the Pt/GCB cathode, because the hydrophilic SnO2 support helped to increase the proton conductivity of the ionomer, which led to high Pt effectiveness. The addition of GCB to the Pt/Nb-SnO2 cathode improved the cell performance under high humidity, and the Pt-mass specific power value reached more than 10 kW gPt −1. The improved performance was attributed to the formation of gas diffusion paths due to the addition of hydrophobic GCB. Fig. 2 shows that the Pt/Nb-SnO2 cathodes, with/without GCB, had greater durability than that of the Pt/GCB cathode after 60,000 cycles of potential sweep cycle evaluation (1.0-1.5 V, 0.5 V s-1). Fig. 3 shows transmission electron microscopic (TEM) images of the Pt/Nb-SnO2 CL and Pt/GCB CL both before and after durability evaluation. The Pt nanoparticle size on the Pt/Nb-SnO2 surface increased to 4.9 ± 0.8 nm (after 60000 cycles) from 3.0 ± 0.6 nm (initial state) in diameter during durability evaluation, becoming spherical in shape (Fig. 3(a) and 3(b)). In contrast, it can be observed that the Pt particles on GCB formed elongated clusters, most likely due to the aggregation of spheres, after 60000 cycles in Fig. 3(d). Moreover, we confirmed that the Pt (111) lattice planes were parallel to those of SnO2 (110), and that the Pt nanoparticles were well oriented on the Nb-SnO2 surface in the initial state, as shown in Fig. 4. We consider that such interaction between the Pt nanoparticles and the Nb-SnO2 support could also have suppressed the migration of the Pt nanoparticles during the durability evaluation. We conclude that the Pt/Nb-SnO2 cathodes, both with and without GCB, exhibited outstanding durability during the startup / shutdown potential sweep evaluation in PEFCs.6 Acknowledgement This research was supported by funds for the “Research on Nanotechnology for High Performance Fuel Cells” (HiPer-FC) project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and the JSPS KAKENHI grant Number B24350093. References M. Uchida et al., Physical Chemistry Chemical Physics, 15, 11236 (2012). K. Kakinuma et al., Electrochimica Acta, 56, 2881 (2011). Y. Senoo et al., RSC Advances, 4, 32180 (2014). K. Kakinuma et al., Electrochimica Acta, 110, 316 (2013). Y. Senoo et al., Electrochemistry Communications, 51, 37 (2015). Y. Chino et al., Journal of the Electrochemical Society, 162, F736 (2015). Figure 1

Modulation of the Reactivity of a WO3/Al Energetic Material with Graphitized Carbon Black as Additive

Although pyrotechnic performance is fundamental, the strong mechanical and electrostatic intrinsic sensitivities of nanothermite energetic composites represent an obstacle to their development. The addition of a ternary component to the classical binary energetic composite appears to be a promising idea to overcome the problem. A carbon black additive (V3G) was used on a WO3/Al nanothermite. The effect of the pristine and modified carbon particles on the mechanical and electrical sensitivities of the composites was measured together with the pyrotechnic properties. The results show a complete desensitization to friction with a ball-milled carbon when the combustion velocity is slightly reduced.