Graphitized Carbon Black Research Articles

Determination of thirteen acidic phytohormones and their analogues in tea (Camellia sinensis) leaves using ultra high performance liquid chromatography tandem mass spectrometry

Trace plant hormones play an important role in tea growth, development and quick response to biotic and abiotic stresses. However, lack of a sensitive method limits the research on plant hormone regulation for tea quality and yields. Herein, a highly sensitive method was developed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for profiling and quantification of 13 acidic phytohormones and their analogues, including auxins, abscisic acid and gibberellins in fresh tea leaves. After optimizing the different C18 columns and mobile phase systematically, an Agilent Eclipse Plus C18 column combined with the mobile phase A (acetonitrile) and B (water) was employed. Target acidic phytohormones were extracted using acidified methanol, and tea matrices were cleaned up by dispersive solid phase adsorbents of polyvinylpolypyrrolidone (PVPP) and graphitized carbon black (GCB) followed by polymer-based mixed-mode cation-exchange solid phase extraction. The method showed good linearity for all 13 analytes with regression coefficients (R2) > 0.998. Satisfactory recoveries of 12 analytes spiked with three levels ranged from 71.8% to 109.9%, while intra-day and inter-day precisions were below 20%. Limits of detection (LODs) and limits of quantitation (LODs) for 12 acidic phytohormones were 0.1–4.2 μg kg−1 and 0.3–13.9 μg kg−1, respectively. Finally, this method was firstly employed to analyze 13 analytes in fresh tea leaves (with the treatment of dormancy, light qualities, exogenous hormones and infestation of pests), highlighting its sufficient capability for rapid analysis of multiclass phytohormones in agriculture field.

Analysis of pesticides in cherimoya and gulupa minor tropical fruits using AOAC 2007.1 and ammonium formate QuEChERS versions: A comparative study

In this work, 48 representative pesticides of different chemical families were analysed in cherimoya (Annona cherimola) and gulupa (Passiflora pinnatistipula), two minor tropical fruits cultivated in Colombia. For this purpose, a comparative study between the AOAC 2007.1 QuEChERS method and its modification replacing the acetic acid/acetate buffer by ammonium formate was developed. Besides, the addition of graphitized carbon black (GCB) was also studied during the dispersive solid-phase extraction clean up to eliminate pigments. Gas chromatography tandem mass spectrometry analysis was performed. Triphenyl phosphate as quality control of the injection and atrazine-d5 as surrogate internal standard were used. Among both methods, the ammonium formate version with GCB addition provided the cleanest extracts (lowest amounts of co-extractive material) as well as consistent recovery values in the 70–120% range with relative standard deviation values below 20% for a higher number of analytes (spiked levels of 10, 100, and 400 μg/kg). Matrix-matched calibration was carried out obtaining determination coefficients above 0.9901. Matrix effects were also studied, finding soft matrix effects for most pesticides in both matrices. The analysis of 10 samples of each type revealed the presence of propoxur in two gulupa samples and propyzamide in one cherimoya sample, but below the lowest calibration level of the method (set at 5 µg/kg).

Optimization and validation of a single method for the determination of pesticide residues in Peumus boldus Molina leaves using GC-MSD, GC-MS/MS and LC-MS/MS

The QuEChERS methods, CEN 15662 and AOAC 2007.01, and different clean-up variations were applied to the determination of pesticide residues in Peumus boldus Molina leaves, using LC and GC coupled to single and tandem mass spectrometry. Boldo belongs to the class of medicinal and aromatic plants. Because of its complex chemical composition including terpene peroxides, alkaloids and phenolic acids at concentrations typically 100-fold higher than that of a possible contaminant, it is a very challenging matrix for pesticide residue determination. Thin layer chromatography was used to evaluate the efficacy of removal of matrix co-extractives using different clean-up sorbents, including neutral alumina, graphitized carbon black (GCB), octadecyl reverse phase silica gel (RP-C18) and pH modification in the extraction and clean-up steps. The most promising method was a combination of GCB, RP-C18 and primary-secondary amine (PSA) within the QuEChERS template. The final optimized method was validated according to the SANTE guidelines using LC–MS/MS and GC–MS/MS. The method scope includes 84 representative pesticide residues with recoveries ranging from 70 to 119% and within laboratory relative standard deviations below 15%. The method was initially validated for 25 representative pesticides using GC-MSD, making it applicable in those laboratories equipped only with a single mass detector. It is important to emphasize that the method complies with the requirements of international pharmacopoeias and food regulatory agencies, since herbal teas are found in both categories, as herbal remedies and foods.

Pulsed Electric Field Extraction of α and β-Acids From Pellets of Humulus lupulus (Hop).

This paper investigates the process of extracting hop pellets (hops) utilizing the pulsed electric field (PEF) technique and the contrasting effects of the technique between two distinct hop varieties (one bitter and one aromatic). The effect of PEF on the extraction was evaluated by measuring the concentration of α-acids and β-acids (humulones and lupulones). Regarding the aromatic character, the hop’s volatile caryophyllene, humulene and β-myrcene were analyzed both with and without employing the PEF treatment. In order to analyze the acids and the volatile fraction, the analytical method of UV–vis spectrophotometry was applied followed by gas chromatography coupled with mass spectrometry. For the second technique, the extracts were previously purified through a Graphitized Carbon Black syringe for Solid Phase Extraction. The results revealed that PEF had a positive impact on the alpha acids of bitter hops by increasing the extraction rate of these acids by 20%, while the volatiles demonstrated an increase of 5.6 and 7.4% for humulene and caryophyllene, respectively. Concerning the aromatic variety of hops, the PEF treatment appeared to have no noteworthy effects.

Comparative study of different sorbents for clean-up for pyrethroid analysis in cocoa powder by GC-ECD: A preliminary study

Three types of solvents and 13 combinations of sorbents were tested to extract pyrethroids (lambda-cyhalothrin, permethrin, cypermethrin, fenvalerate, and deltamethrin) from cocoa powder and to remove interferences during clean-up step before being quantified by gas chromatography coupled with electron capture detector (GC-ECD). The result was analysed based on recovery study by spiking the cocoa powder with known amount of targeted pyrethroids. Acetonitrile, methanol, and n-hexane were compared as the solvents and the result showed that acetonitrile is relatively better in extracting pyrethroids. Moreover, 13 treatments, singly or combination of primary secondary amine (PSA), graphitized carbon black (GCB), C18, and florosil, were tested for clean-up step. The clean-up study shows that only combination of PSA and GCB; combination of C18 and Florisil; and combination of GCB and florisil comply the recovery guideline suggested by AOAC and EU, thus are suggested for clean-up for pyrethroid analysis in cocoa powder.

Sorbent-incorporated dipstick for direct assaying of proteases.

Efficient removal of interferents from complex matrices would significantly improve the performance of state of the art dipstick assays. Herein, we evaluate a graphitized carbon black (GCB)-incorporated dipstick, a configuration that has not been explored before, for reliable and facile on-site analysis of complex matrices. Carrot juice, a highly pigmented sample matrix, is chosen for evaluating the retention of interferents within the sorbent-incorporated cleanup pad on the dipstick. A peptide with a specific cleavage site for botulinum neurotoxin A light chain (BoNT/A LC), a model protease for validation of the proposed dipstick assay, is incubated with the test samples containing BoNT/A LC. Subsequently, the BoNT/A LC digested substrate and sample matrix flow vertically through the GCB-deposited cleanup pad within which the matrix interferents are captured, while the substrate, with a minimum of interferents, continues to flow toward a conjugation pad for labelling with Europium particles. Finally, the cleaved and uncleaved substrates flow toward a detection zone, where they bind to the test line producing a pinkish band which is not visible in the absence of GCB incorporation. The dipstick assay yields a LOD of 0.1nM (5ng/mL) of BoNT/A LC in carrot juice, within 20min. The reported approach enables detection of proteases in a wide range of matrices upon incorporation of appropriate sorbents, ultimately aiming to exclude tedious laboratory-based sample pre-treatment protocols. Thus, merging extraction, cleanup, and pre-concentration steps with a sensitive optical detection approach is an attractive strategy for on-site assaying in complex matrices. Graphical abstract.

Mixed adsorption of hexadecylpyridinium bromide and Triton X surfactants at graphitized carbon black

Adsorption of cationic 1-hexadecylpyridinium bromide (HDPB) and non-ionic p-(1,1,3,3-tetramethylbutyl)-phenoxypolyoxyethylene glycols surfactants of the Triton X series (Triton X-45, Triton X-100 and Triton X-305) from their single and mixed aqueous solutions at thermally graphitized carbon black (CB) was studied. It was shown that the adsorption of the non-ionic surfactant from its individual solution decreased when a number of ethylene oxide units in the surfactant molecule increased. Addition of the non-ionic surfactants increased the amount of HDPB adsorbed from HDPB/Triton X mixtures. At low solution concentrations it was found that in HDPB/Triton X mixtures, the experimental values of total surfactants adsorption are higher than the adsorption values calculated for the ideal surfactant mixtures. The composition of the mixed HDPB/Triton X adsorption layer and the parameters of the intermolecular interaction (?s), between the components in this layer, were calculated using the Rubingh-Rosen approach. It was shown that ?s parameters have negative values, which indicate notable interactions between Triton X molecules and HDPB ions in the mixed adsorption layer. It was found that the composition of the mixed adsorption layer at CB surface is notably different from the surfactants composition in the bulk solution. The mixed HDPB/Triton X adsorption layer is enriched with Triton X surfactant and the mole fraction of Triton X increases with decreasing of ethoxylation degree of its molecules.

Accurate, sensitive and rapid determination of perchlorate in tea by hydrophilic interaction chromatography-tandem mass spectrometry.

Perchlorate is an environmental contaminant interrupting thyroid hormone production, and perchlorate in tea has raised wide concern recently. In this study, an accurate method was developed for the determination of perchlorate in tea using hydrophilic interaction chromatography-tandem mass spectrometry and a simplified QuEChERS procedure. The method utilized a zwitterion HILIC column for separation, and the optimal gradient eluents consisted of acetonitrile and aqueous solution with 0.1% formic acid and 20 mmol L-1 ammonium formate. Calibration curves were fitted by the quadratic model with 1/x weight instead of the linear model. As perchlorate was only partially extractable when using acetonitrile or methanol as the extraction solvent, acetonitrile/water (1 : 1, v/v) was chosen to extract perchlorate from tea samples. Graphitized carbon black was used as the dispersive solid phase extraction sorbent to clean up tea extracts. The method exhibited satisfactory accuracy with recoveries of 81.4-100.9% and relative standard deviations of 1.3-14.5% for green and black teas. The limit of quantitation was 0.005 mg kg-1, while the limits of detection were 0.0011 mg kg-1 for green tea and 0.0013 mg kg-1 for black tea, indicating an excellent sensitivity of this method. A 100% positive rate of perchlorate was found in 100 real tea samples, and the concentrations ranged from 0.0030 mg kg-1 to 0.78 mg kg-1. This accurate, sensitive and rapid method would be suitable for monitoring, risk assessment and source identification of perchlorate in tea.

Conifers as environmental biomonitors: A multi-residue method for the concomitant quantification of pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls by LC-MS/MS and GC–MS/MS

The conifer is a natural vascular land plant composed of very particular leaves called needles that are able to accumulate, throughout years, a wide range of non-volatile, semi-volatile and volatile compounds of different structure and polarity such as pesticides and persistent organic pollutants. However, the extraction of these compounds from such matrix remains mainly uncommitted. In this paper, a QuEChERS based extraction procedure was developed for the concomitant extraction and analysis of 134 pesticides, 22 polychlorinated biphenyls and 16 polycyclic aromatic hydrocarbons residues from conifer needles. The method included a liquid-liquid extraction using acetonitrile (ACN) followed by a clean-up step using, Primary Secondary Amine (PSA), graphitized carbon black (GCB) and C18 particles, in the presence of salts. The obtained extracts were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for their contamination by non-volatile pesticides. However, volatile pesticides, polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons were subjected to a concentration step using solid-phase microextraction (SPME) prior to their analysis by gas chromatography coupled to tandem mass spectrometry (GC–MS/MS). The method was developed and validated, and the obtained results revealed a recovery rate ranged between 60% and 121% for all the targeted compounds. In addition, the method showed high sensitivity and precision with detection and quantification limits less than 20 ng g−1 for most target compounds and low RSD for both inter and intra-day analysis. Once developed the method was applied on conifer samples collected from 15 different sites in northern Lebanon. The analysis of the collected samples showed a persistence of the different assessed pollutants depending of the characteristics of each site.

Compensation of matrix effects in seed matrices followed by gas chromatography-tandem mass spectrometry analysis of pesticide residues

Despite analytical advances, matrix effects (MEs) in pesticide residue analysis by gas chromatography – tandem mass spectrometry continue to be a challenge, especially in difficult samples such as seeds. In this study, the influence of different clean-up sorbents (chitin, chitosan, Z-Sep+, EMR-Lipid) and different mixtures of primary secondary amine (PSA), C18, graphitized carbon black (GCB) and MgSO4 were investigated in terms of MEs and recoveries in four types of seeds: cress, fennel, flax, and hemp. Additionally, different volumes of water (5, 7.5 and 10 mL) were investigated for QuEChERS extraction. Under the selected conditions: the largest volume of water (10 mL) and PSA/C18/GCB/MgSO4 (50/150/50/50 mg, respectively) as clean-up sorbent yielded acceptable recoveries of 70–120% for most of the pesticides (211–225 out of 248 compounds) and the lowest MEs were between −20%>MEs>20% (27–50 compounds). The final method was validated for 248 pesticides with LOQs equal to 0.005 mg kg−1. Additionally, matrix-matched calibration was used as a practical method to compensate for MEs. Among the 21 pesticides found in 12 of the samples, chlorpyrifos (0.008–1.1 mg kg−1), tebuconazole (0.071–0.96 mg kg−1), and trifloxystrobin (0.007–0.15 mg kg−1) were most commonly determined.

Modified QuEChERS method for phenolic compounds determination in mustard greens (Brassica juncea) using UHPLC-MS/MS

A modified QuEChERS method (Quick, Easy, Cheap, Effective, Rugged, and Safe) for the determination of fifteen phenolic compounds in mustard greens (Brassica juncea) using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis was developed. The QuEChERS partitioning step and dispersive solid phase extraction (d-SPE) clean-up sorbents were investigated, aimed at phenolic compound extraction and pigment removal, respectively. QuEChERS acetate version combined with 25 mg of diatomaceous earth (DE) and 5.0 mg of graphitized carbon black (GCB) provided the best conditions for sample preparation of the target compounds. Under the optimized conditions, all phenolic compounds showed good linearity (r ≥ 0.99) over the concentration range of 0.1 to 8000 μg kg−1, and the quantification limits were in the range of 0.06–230 μg kg−1. The spectrophotometric analysis showed that the clean-up step promoted a significant removal of chlorophyll, which is the major pigment present in the sample. Furthermore, antioxidant activity analysis was also carried out after the clean-up step and, together with chromatographic data, showed that no significant retention of the phenolic compounds occurs in the clean-up step. Two mustard greens varieties – Southern Giant Curled (SGC) and Florida Broadleaf (FB) - were analyzed with the proposed method. Seven phenolic compounds (4-hydroxybenzoic, p-coumaric, ferulic and sinapic acids, naringenin, apigenin and kaempferol) were found in both varieties, the greatest abundance being for sinapic acid (1261.5 ± 23 μg kg−1 in SGC and 1235.5 ± 26 μg kg−1 in FB) and ferulic acid (2861 ± 24 μg kg−1 in SGC and 3204.5 ± 45 μg kg−1 in FB).

Phospholipidome of extra virgin olive oil: Development of a solid phase extraction protocol followed by liquid chromatography–high resolution mass spectrometry for its software-assisted identification

The determination of phospholipids in olive oil is challenging due to their low concentration. For this reason, a comparison of two solid phase extraction procedures, namely weak anionic exchange (WAX) and graphitized carbon black (GCB), is presented for the enrichment of phospholipids. Analyses were performed by liquid chromatography-high resolution mass spectrometry (LC-HRMS) and lipids were identified by Lipostar software. Compared to the WAX solid phase extraction, GCB demonstrated the best performance and provided 82 identified phospholipids vs only 32. The final method was validated for some representative phospholipids, showing good repeatability and recovery (63–101%). High sensitivity was reached, with detection limits in the range 9–36 ng g−1, never reported before for phospholipids in olive oil. A semi-quantitative analysis indicated phosphatidic acids and phosphatidylglycerols as the most abundant species, both in number and concentrations. The GCB-LC-HRMS-Lipostar platform can be successfully applied for a comprehensive polar lipidomic characterization of olive oils.

Analysis of alkylphenols and bisphenols in soils using liquid chromatography-tandem mass spectrometry

ABSTRACT Methods useful for the extraction of alkylphenols from soil samples were assessed. A comparison is made of the four extraction techniques that are most commonly used to extract phenolic compounds from soil, such as bisphenol A, bisphenol F and alkylphenols (4-t-OP, iso-NP, 4-OP and 4-n-NP). Soxhlet extraction, ultrasonic-assisted extraction (USE), accelerated solvent extraction (ASE) and the so-called Quick, Easy, Cheap, Effective, Rugged and Safe extraction (QuEChERS) were included. Modifications of the QuEChERS technique such as original, citrate and acetate were investigated. The effects of basic purification sorbents used for QuEChERS extracts such as a primary and secondary amine (PSA), C18 endcapped sorbents and graphitised carbon black (GCB) were tested. A derivatisation step prior to the final analyses by liquid chromatography coupled to a triple quadrupole analyser operating in tandem mass spectrometry (LC–MS/MS) was performed by using dansyl chloride (DNSC). The best extraction of the monitored compounds from spiked soil was obtained using QuEChERS extraction. Recoveries of phenolic compounds using the QuEChERS technique were in the range from 67% to 114%. The lowest extraction recoveries (16–73%) were obtained using ultrasonic extraction. The QuEChERS method was successfully applied for the analysis of alkylphenols in soil samples. Instrumental limits of quantification and limits of detection ranged from 0.08 to 0.83 pg per injection and 0.02 to 0.25 pg per injection, respectively.

Electrocatalysts Supported on Nanocrystalline SnO2 for Polymer Electrolyte Fuel Cells

Introduction Since conventional PEFC electrocatalysts have a difficulty in durability against start-stop and load potential cycling, development of high-performance and high-durability cells for next-generation fuel cell vehicles is desired. SnO2 is known to be stable at a high potential under the PEFC cathode conditions, so that SnO2 is considered as an alternative support material for PEFC cathodes [1-4]. Here in this study, electrocatalysts are prepared using highly graphitized carbon black (GCB), which is a carbon material with an increased degree of graphitization, acting as a conductive framework in the electrocatalyst layers. Nanocrystalline SnO2 particles of several nm in diameter were deposited on the GCB. The use of nanocrystalline SnO2 enables to shorten the electron pathway between the catalyst and the GCB-based conductive framework, down to a few nm. Platinum catalysts were then deposited on SnO2 nanoparticles. The ultimate objective of this study is to develop high-performance cells with high durability by optimizing preparation conditions for nanostructuring. Drying procedure is mainly examined in this study. Experimental Nanocrystalline SnO2 was deposited on GCB (GCD200, Cabot) via the evaporation-to-dryness and the freeze drying. Pt deposition on SnO2 was made using platinum acetylacetonate in order to prepare Pt/SnO2/GCB electrocatalysts. Nanostructure of the electrocatalysts obtained was observed by field-emission scanning electron microscopy (FE-SEM) and scanning transmission electron microscopy (STEM). Thermogravimetry (TG) measurement was applied to quantify SnO2 loading. ICP analysis was made to quantify Pt loading. Average crystallite size of SnO2 and Pt in Pt/SnO2/GCB was measured by XRD. Electrochemical characterization of these electrocatalysts was carried out by half-cell measurements. Electrochemical surface area (ECSA) was measured by cyclic voltammetry (CV), and oxygen reduction reaction (ORR) activity was derived from kinetically controlled current density (ik ) after the rotating disk electrode (RDE) measurements. Results and discussion Figures 1 and 2 show FESEM images of Pt/SnO2/GCB prepared by using the evaporation-to-dryness and the freeze drying, respectively. Figure 1 reveals aggregation of platinum particles, and inhomogeneous distribution was confirmed for platinum particles. On the other hand, as shown in Fig. 2, the platinum particles were homogeneously supported in higher dispersion. The catalytic activity of these electrocatalysts was evaluated by the half-cell measurements. Pt/SnO2/GCB prepared by the evaporation-to-dryness process exhibited ECSA of 68.4 m2g-1, and mass activity of 82.9 Ag-1 at 0.9 VRHE. The electrocatalyst prepared by the freeze drying process exhibited larger ECSA of 80.8 m2g-1, and higher mass activity of 152.5 Ag-1 at 0.9 VRHE. From the results of microstructural observation and the half-cell measurements, the freeze drying process, which enables uniform dispersion of oxide nanoparticles, is suitable for the preparation of the nanocrystalline oxide support, leading to higher electrochemical properties. Acknowledgment Financial support by the Center-of-Innovation program, JST Japan, is gratefully acknowledged.

Compositional analysis and structural characterization of raffinose family oligosaccharides from Eupatorium

Raffinose family oligosaccharides (RFOs) are commonly applied as functional food ingredients. RFOs mixture derived from Eupatorium were analyzed by hydrophilic interaction liquid chromatography-evaporative light scattering detector (HILIC-ELSD) method with a Click Xion column, and then separated by graphitized carbon black (GCB) chromatography. RFOs with a specific degree of polymerization (DP) from 3 to 6 were obtained. The specific ions from glycosidic bond cleavage and cross-ring cleavage of RFOs were produced in Electrospray-collision-induced dissociation-mass spectroscopy/mass spectroscopy (ESI-CID-MS/MS), which are in accordance with the linkage of (1→6) between galactans. The anomeric configuration and glycosidic linkage of RFOs were confirmed to be [α-Gal-(1→6)]n-α-Glc-(1→2)- β-Fru (n = 1–4) by 2D-NMR. In this study, we developed a HILIC-ELSD method for the compositional analysis of RFOs and obtained RFOs with a specific DP and high purity, and their structures were completely elucidated. Our work provides a basis for further research on the structure–activity relationship of RFOs.

Graphitized Carbon Black Enrichment and UHPLC-MS/MS Allow to Meet the Challenge of Small Chain Peptidomics in Urine.

Short peptide sequences represent emerging analytes in a variety of fields, including biomarker discovery, but also a well-known analytical challenge in complex matrices, due to the low abundance, extensive suppression during MS analysis, and lack of workflows, as they cannot be identified by ordinary peptidomics strategies and coverage is extremely limited by metabolomics as well. In this context, in this work, a solid phase extraction method was developed for the cleanup and enrichment of dipeptides, tripeptides, and tetrapeptides in urine using graphitized carbon black Carbograph 4 as the sorbent. The method was first developed on analytical standards spiked in urine, with recoveries in the range of 60-100%. Then the method was applied to urine samples from healthy volunteers. The enriched urine samples were analyzed by ultrahigh performance liquid chromatography (UHPLC) using an orthogonal strategy in which both a reversed phase (RP) C18 column and a zwitterionic hydrophilic interaction liquid chromatography (HILIC) column were used, for better coverage of peptide polarity and improved detection of peptides. High-resolution mass spectra were acquired in data-dependent mode using a suspect screening strategy with inclusion list; peptides were identified by a semiautomated workflow for feature extraction, candidate mass filtering, and MS/MS spectra comparison with in silico mass spectra. The complementarity of the orthogonal separation strategy was confirmed by peptide identification, resulting in 101 peptides identified from the RP runs and 111 peptides from the HILIC runs, with 60 common identifications. The method is applicable to both hydrophobic and hydrophilic peptides. Peptides were stable over 2 h after collection and protease inhibitors were not necessary, as no formation of artifacts was observed.

ANALYSIS OF INTERMOLECULAR INTERACTIONS IN MIXED ADSORPTION LAYERS OF SURFACTANTS

The adsorption of the surfactants mixtures of different chemical nature such as Triton X-100 and sodium hexadecyl sulfate at the surface of graphitized carbon black was studied. Using the model of phase separation (the Rubi–Rosen approach), the composition of the mixed adsorption layers and parameters of interaction between the surfactant molecules in the adsorption layers were calculated. It was found that mixed adsorption layers are enriched with molecules of the non-ionic surfactant Triton X-100.
 The purpose of the work was to study the adsorption of binary mixtures of surfactants of various chemical nature on the surface of non-porous hydrophobic carbon sorbent at different SAS ratio in mixtures.
 The results of calculations show that the composition of the adsorption layer on the surface of the GC is significantly different from the ratio of surfactants in the solution. The value of the parameter χ indicates that the mixed adsorption layer on the surface of the GC is enriched with non-ionic surfactant molecules, even with a small its content in the solution (αTХ-100 = 0,2). With an increase in the ТХ-100 molar fraction in the binary solution from 0,2 to 0,8 its share in the adsorption layer increases in approximately 1.5 times. Negative values of the interaction parameters βs indicate excessive attraction of the molecules and ions of the mixture components in the mixed adsorption layers. An increase in the absolute value of the parameter βs with an increase in αTХ-100 in the solution characterizes the enhancement of the interactions between the components in the adsorption layer.
 Thus, in the course of experiments carried out for mixed systems of SHDS-ТХ-100, the existence of a synergistic effect in relation to an increase in the adsorption of surfactants on the GC surface was established. It is found that mixed adsorption layers are enriched with molecules of the non-ionic surface active substance of the triton X-100.

Evaluation of Dispersive Solid-Phase Extraction (d-SPE) as a Clean-up Step for Phenolic Compound Determination of Myrciaria cauliflora Peel

In this study, dispersive solid-phase extraction (d-SPE) was evaluated as a clean-up step for the determination of phenolic compounds in Myrciaria cauliflora peel using an ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method. For the d-SPE clean-up step, the sorbents, diatomaceous earth (DE), chitosan (CT), and graphitized carbon black (GCB), were evaluated in different proportions. The d-SPE clean-up step efficiency was evaluated through total anthocyanin content (ACC) and spectrophotometric scanning of the extracts. The use of DE with GCB in a ratio of 100:10 (m/m) was the best clean-up step condition. The ACC showed an 83% reduction of the amount of anthocyanins, and the scanning spectra confirmed that all extracts submitted to the clean-up step presented pigment reduction. A total of eight compounds were found in M. cauliflora peel, with the highest abundance of ellagic acid (1643 ± 353 mg kg−1), gallic acid (252 ± 10 mg kg−1), and 4-hydroxybenzoic acid (154 ± 133 mg kg−1), indicating the antioxidant potential of the peel, which is frequently considered a by-product of Myrciaria cauliflora fruits.

Application of high-surface-area graphitized carbon black with primary secondary amine as an alternative quick, easy, cheap, effective, rugged, and safe cleanup material for pesticide multi-residue analysis in spinach.

A multi-residue method has been developed and validated to determine 46 pesticides in spinach using liquid chromatography tandem mass spectrometry. The method is based on modified quick, easy, cheap, effective, rugged, and safe sample preparation, where high-surface-area graphitized carbon black was used first as sorbent material in the dispersive solid-phase extraction. The method was compared with the quick, easy, cheap, effective, rugged, and safe method. The morphology, surface area, pore size, and pore volume of the sorbent was determined. The results obtained show that the sorbent consists of high surface area (233m2 /g) and large pore volume (1.5cm3 /g). The calibration curve correlation coefficient (R2 ) of the method was at least 0.99. The average recoveries ranged from 74 to 116%, and limits of detection and quantification from 0.0001 to 0.002mg/kg and from 0.0002 to 0.005mg/kg, respectively. Using the method, the pesticides exhibited low matrix effect (<20%), except for nicosulfuron (29.86%), methomyl (26.77%), and flufenoxuron (24.65%). The method showed better potential to remove pigments than the quick, easy, cheap, effective, rugged, and safe method. It is demonstrated that the proposed method could be useful alternative for sample preparation of spinach and other matrices in future.

Development and Validation of a Multiresidue Method for Fluazifop‐p–butyl and Its Two Major Relevant Metabolites in Panax ginseng Using a Modified QuEChERS Method and HPLC‐ESI‐MS/MS

AbstractFluazifop‐p‐butyl (FPB) is used to control the gramineous weeds in Panax ginseng field, which has the risk of exceeding the maximum residue limit of FPB in Panax ginseng. A modified QuEChERS sample preparation method was developed for the simultaneous determination of FPB and its two major relevant metabolites, fluazifop‐p‐acid (FP) and 2‐hydroxy‐5‐ trifluoromethylpyridin (TFMP) in Panax ginseng by using Carboxylated multi‐walled carbon nanotubes (MWCNTs‐COOH) mixed with ostade‐cylsilane (C18), primary secondary amine (PSA), and graphitized carbon black (GCB) as purification materials. Furthermore, the HPLC‐MS/MS parameters were optimized. The method was further validated by determining the linearity (R2&gt;0.999), fortified recovery (77.6‐97.8%), relative standard deviation (&lt;13.6%) and sensitivity (LOQ, 2.0‐ 8.6 μg kg‐1 for FPB, 3.9‐5.8 μg kg−1 for FP and 3.5‐9.0 μg kg−1 for TFMP in Panax ginseng root, leaf, and seed samples, respectively). The main advantages of the method are high recovery, high sample throughput, facile sample preparation, a smaller volume of organic solvents and low cost per sample. The entire method can withstand practice testing expected to be used for the screening of FPB residue in Panax ginseng samples.