Shorter Carbon Chain Length Research Articles

Chlorinated paraffins (CPs) in vegetable oils from the Dutch market and the effects of the refining process on their levels

Chlorinated paraffins (CPs) are of growing public health concern because of their ubiquitous presence in food samples. To get more insight into levels of CPs in vegetable oils from the Dutch market and human exposure via these oils, two series of samples were analysed in this study for the presence of CPs by UHPLC coupled with Q-Exactive Orbitrap mass spectrometry: 1) 39 vegetable oils from local supermarkets; 2) 13 paired crude and refined vegetable oils obtained from a contract refining company. Short chain CPs (SCCPs) and medium chain CPs (MCCPs) were detected in vegetable oils from supermarkets with an overall range from <LOQ to 78 ng/g lipid weight (lw) and <LOQ to 391 ng/g lw, respectively. The tridecane and tetradecane groups dominated in SCCPs and MCCPs, respectively. As regards to paired crude and refined oils from a refining company, a marked decrease in concentrations of both SCCPs and MCCPs were detected by the refining process (average reduction: 82% and 69% for SCCPs and MCCPs, respectively). Based on the data obtained, it can be concluded that CPs with a relatively short carbon chain length and low chlorination degree are more likely to be removed in the refining process. The estimated margins of exposure (MoEs) due to oil consumption alone were all higher than 1000, indicating no health concern from CPs for the Dutch population.

Effects of starch–fatty acid complexes with different fatty acid chain lengths and degrees of saturation on the rheological and 3D printing properties of corn starch

The effect of corn starch-fatty (CS-FA) complexes from varying carbon chain length and degree of unsaturation on the rheological and 3D printing properties of corn CS–FA complex gels. The CS-FA complexes with longer carbon chain lengths and lower saturation enhanced the ability of gels to bind water, promoting the formation of intermolecular hydrogen bonds. The CS-FA complexes inhibit retrogradation and increase the amount of bound water, thereby reducing the structural integrity and transforming the original skeleton structure into a flake-like structure. These changes in gel structure led to lower flow stress and storage modulus for CS-FA gels containing FAs with shorter carbon chain lengths and lower saturation, resulting in reduced “extrusion swelling” of the material and facilitating its extrusion. The decreased “extrusion swelling” of gel improved print line width and printing performance. The CS-FA complex gel-printed product with a 12-carbon chain FA has the greatest printing accuracy, thanks to its moderate G', flow stress, and viscosity. This study provides important information for the CS-FA complexes for the preparation of starch-based 3D printing materials.

Study on the Solubility of Industrial Lignin in Choline Chloride-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs) have emerged as a promising class of solvents for lignin dissolution, which could significantly expand the application potential of lignin. In this study, over forty ChCl-based DESs of three major types were synthesized and subjected to investigate the solubilisation of two industrial lignins in DES. The results showed that higher HBD content, shorter carbon chain length in the HBD, and fewer functional groups favored lignin solubilization. DESs containing carboxyl groups were found to be more favorable for breaking β-O-4 bonds and solubilizing lignin. Additionally, high temperature and appropriate water content were observed to promote lignin solubilization. The pretreatment of poplar and maize straw with ChC/FA(1:3), ChC/LA(1:3), ChC/Gly(1:3), ChC/EG(1:3), ChC/Urea(1:3), and ChC/TEOA(1:3) showed good solubilization of lignin, with ChCl/FA(1:3) being particularly effective in solubilizing poplar lignin and maize straw lignin, achieving lignin solubilization of 82% and 57%, respectively. Overall, these findings suggest that DESs have great potential as solvents for lignin dissolution.

Circulating Metabolomic and Lipidomic Signatures Identify a Type 2 Diabetes Risk Profile in Low-Birth-Weight Men with Non-Alcoholic Fatty Liver Disease

The extent to which increased liver fat content influences differences in circulating metabolites and/or lipids between low-birth-weight (LBW) individuals, at increased risk of type 2 diabetes (T2D), and normal-birth-weight (NBW) controls is unknown. The objective of the study was to perform untargeted serum metabolomics and lipidomics analyses in 26 healthy, non-obese early-middle-aged LBW men, including five men with screen-detected and previously unrecognized non-alcoholic fatty liver disease (NAFLD), compared with 22 age- and BMI-matched NBW men (controls). While four metabolites (out of 65) and fifteen lipids (out of 279) differentiated the 26 LBW men from the 22 NBW controls (p ≤ 0.05), subgroup analyses of the LBW men with and without NAFLD revealed more pronounced differences, with 11 metabolites and 56 lipids differentiating (p ≤ 0.05) the groups. The differences in the LBW men with NAFLD included increased levels of ornithine and tyrosine (PFDR ≤ 0.1), as well as of triglycerides and phosphatidylcholines with shorter carbon-chain lengths and fewer double bonds. Pathway and network analyses demonstrated downregulation of transfer RNA (tRNA) charging, altered urea cycling, insulin resistance, and an increased risk of T2D in the LBW men with NAFLD. Our findings highlight the importance of increased liver fat in the pathogenesis of T2D in LBW individuals.

Contamination of perfluorinated compounds (PFCs) in surface water and sediment collected from Nhue and Day rivers

Currently, there has been little data on contamination by perfluorinated compounds (PFCs) in the environment in developing countries such as Vietnam, especially for surface water systems flowing through densely populated urban areas and industrial zones. In this study, PFCs were analysed in 32 water samples and 14 sediment samples taken along Nhue and Day rivers, which flow through six high population density provinces in Northern Vietnam. PFCs were detected in 100% of water samples with an average total concentration of 7.85 ng/l (4.54-13.48 ng/l). In sediment, PFCs were found at low concentrations ranging from 0.06-2.60 ng/g d.w with a detection frequency of 40%). Perfluoro carboxylic acid with short carbon chain length (from C4 to C8) were dominant compounds observed in surface water while perfluoroalkyl sulfonates in sediment were found at low concentrations, approximately the threshold of quantitative limits.

Effects of Commercial No-Clean Flux on Reliability of Fine Pitch Flip-Chip Package With Solder Bumps and Copper Pillars

In this work, two commercial no clean fluxes, namely, extremely low residue no-clean flux (NCF) (NC-1) and ordinary NCF (NC-2), were used for the preparation of a fine pitch flip-chip package with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.6\,\times \,7.6$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Si die on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17\,\times \,17$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> organic substrate. One water-soluble (WS) flux was also used for comparison. Moisture sensitivity of the package was evaluated using JESD22-A113D (30 °C/60% relative humidity (RH), 192 h, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times $ </tex-math></inline-formula> reflow at 260 °C). Thermal cycling tests were performed following JESD22-A104D (−65 °C to 150 °C). The high-temperature storage life (HTSL) of the packages was investigated using JESD22-A103C (175 °C). Underfill delamination or voids in the package were investigated by confocal scanning acoustic microscopy (C-SAM). Failure characteristics of the packages were also studied using scanning electron microscopy (SEM). After moisture sensitivity level (MSL) test, vehicles prepared by NC-1 and NC-2 showed failure. SEM images revealed severe delamination between underfill and solder mask in the presence of amine/amide and carboxylic acid-based NCF residue. Solder bump crack were found at < 500 cycles for samples prepared with NC-1 which contains tertiary amine and long carbon chain (C8:C10:C12) carboxylic acid-based. However, failure occurred at < 1500 cycles for NC-2 containing secondary amide and shorter carbon chain length (C3) carboxylic acid. Samples prepared using WS did not show any failure for up to 2000 cycles. Thus, NCF-treated assemblies performed poorly in moisture sensitivity and temperature cycling tests.

Catalytic co-pyrolysis of oil sludge and biomass over ZSM-5 for production of aromatic platform chemicals

Hazardous oil sludge (OS) poses a great challenge to the environment, whereas conventional treatment methods (i.e., incineration or pyrolysis-incineration) are relatively less value-added and will bring about air pollution problems. To realize the high-value utilization of OS, catalytic co-pyrolysis with waste biomass to produce platform chemicals was studied using TG-FTIR and Py (pyrolyzer)-GC/MS methods. Results showed that for the non-catalytic co-pyrolysis of RH (rice husk) and OS, the main synergy on weight loss was the greatly lowered initial pyrolysis temperature of RH (for ∼55 °C) at the lower temperatures and the reduced weight loss ratio of OS (∼10–18 wt%) within the higher temperature range. ZSM-5 catalyst promoted the degradation of OS and RH mixtures at < 150 °C, yet showed minor effects on their weight loss at higher temperatures. The oxygenated and aliphatic compounds from non-catalytic co-pyrolysis were efficiently converted, resulting in an increased relative yield of aromatics to the highest of 46% and an elevated selectivity to BTX (as high as 60%). Despite the relatively short carbon chain length of OS components, ZSM-5 was proved effective to activate the OS pyrolysis products, thus enhancing the further aromatization reactions with biomass pyrolysis intermediates. This study provides a novel method for value-added co-utilization of hazardous OS waste and abundant biomass waste, and thus is beneficial to producing renewable chemicals while reducing the environment pollutant.

Hexafluoropropylene oxide dimer acid (GenX) exposure induces apoptosis in HepG2 cells

Hexafluoropropylene oxide dimer acid, also known as GenX, is a poly- and perfluoroalkyl substance (PFAS). PFASs are nonvolatile synthetic substances that can be readily disseminated into the environment during processing and use, making them easy to implement in the soil, drinking water, and air. Compared to other PFASs, GenX has a comparatively short carbon chain length and is expected to have a lower tendency to accumulate in humans; therefore, GenX has recently been used as a substitute to other PFASs. However, the mechanisms underlying GenX action and intoxication in humans remains unclear. In this study, the apoptotic capacity of GenX in human liver cells was investigated. When representative human-derived liver cells (HepG2 cells) were treated with GenX for 12 h, cell viability was reduced, and apoptosis was greatly increased. In addition, GenX increased the generation of intracellular reactive oxygen species (ROS), indicating the induction of oxidative stress in a dose-dependent manner. GenX treatment increased the expression of major apoptosis-related genes relative to the untreated control group. This research indicates that GenX causes apoptosis through ROS mediation in HepG2 cells, which may expand our knowledge of the molecular and toxicological mechanisms of GenX.

Hexafluoropropylene Oxide Dimer Acid (GenX) Exposure Induces Apoptosis in HepG2 Cells

Hexafluoropropylene oxide dimer acid (HFPO-DA), also known as a GenX, is one type of Poly- and perfluoroalkyl substances (PFASs). PFASs are nonvolatile synthetic substances that could be readily disembogued into the environment during processing and use, making them easy to implement into the soil, drinking water, and the air. Unlike other PFASs, GenX has a comparatively short carbon chain length and has recently been used as a new substitute due to its lower tendency for accumulation in humans. However, the mechanisms and human intoxication, especially as a result of GenX, remain unknown. In this research, GenX apoptotic capacity in human liver cells was investigated. When representative human-derived liver cells, HepG2 cells, were treated to GenX for 12 h, cell viability was reduced, and apoptosis was greatly increased. In addition, GenX increased the generation of intracellular reactive oxidative species (ROS), indicating oxidative stress in a dose-dependent manner. GenX treatment increased major apoptosis-related genes relative to the untreated control group. This research indicates that GenX causes apoptosis through ROS mediation in HepG2 cells and may expand our knowledge of GenX's molecular and toxicological mechanisms.

Antioxidant activities of lipophilic (−)-epigallocatechin gallate derivatives in vitro and in lipid-based food systems

The low lipophilicity of (−)-epigallocatechin gallate (EGCG) significantly limits its applications in lipophilic systems. Herein, EGCG was acylated with vinyl esters of different carbon chain lengths under the action of the lipase Novozym 435. Five EGCG derivatives (C2-EGCG, C4-EGCG, C6-EGCG, C8-EGCG, and C12-EGCG) with different lipophilicities were obtained, and their antioxidant activities were evaluated. Due to the loss of the phenolic hydroxyl group of EGCG, the capacities of these derivatives to scavenge the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS+•), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•), and hydroxyl radical (•OH) were lower than those of EGCG. In a homogeneous oil system, the antioxidant capacities of the EGCG derivatives were higher than that of EGCG. Upon increasing the lipophilicities of the derivatives, the antioxidant activities initially increased and later decreased, thus demonstrating the “cut-off effect.” Among the various derivatives, C8-EGCG possessed the highest antioxidant activity. In the oil-in-water emulsions, optimum antioxidant activity was observed for short carbon chain length (C2-EGCG). This study therefore provides useful information regarding the design of EGCG applications in food lipid systems.

Reduction of Vegetable Oil‐Derived Fatty Acid Methyl Esters toward Fatty Alcohols without the Supply of Gaseous H2

AbstractAn alternative route to the conventional one for fatty alcohol synthesis was investigated. It was possible to synthesize lauryl alcohol from methyl laurate via reduction by transfer of hydrogen and hydride in liquid phase, in noncatalytic reactions and without the supply of H2 gaseous. Pure NaBH4 or alumina‐supported NaBH4 and methanol were used as co‐reactants and 100% fatty alcohol selectivities were achieved. The aim of supporting the metal hydride was to increase its stability and achieve the full recovery of the solid at the end of reaction. When alumina‐supported NaBH4 was used, a final fatty alcohol yield of 93% was achieved. The use of methanol and NaBH4 in amounts higher than stoichiometric is important to generate alkoxyborohydride anions which act as better reducing species than NaBH4. The reaction conditions effect was investigated and the role of short carbon chain alcohol structure was elucidated. The effect of fatty acid methyl ester structure was also studied. Fatty acid methyl esters with shorter carbon chain length and without unsaturation (methyl laurate, methyl myristate) were easily reduced using NaBH4/Al2O3 and methanol reaching high conversions and fatty alcohol selectivities. Unsaturated fatty acid methyl ester with longer carbon chain (methyl oleate) introduced steric hindrance which disfavoured interaction between ester and reducing solid surface and fatty acid methyl ester conversion was noticeably lower. A reaction mechanism based on alkoxyborohydride anions as the actual reducing species was proposed. This mechanism fully interprets results obtained during fatty acid methyl ester reduction using short carbon chain alcohols and metal hydride.

Photochemical transformation of perfluoroalkyl acid precursors in water using engineered nanomaterials

The production of perfluoroalkyl acids (PFAAs) has been phased out over recent decades; however, no significant decline in their environmental concentrations has been observed. This is partly due to the photochemical decomposition of PFAAs precursors (PrePFAAs) which remain in extensive use. The decomposition of PrePFAAs may be accelerated by the light-activated engineered nanomaterials (ENMs) in water. In light of this hypothesis, we investigated the photochemical transformation of three PrePFAAs, which are 8:2 fluorotelomer sulfonic acid (8:2 FTSA), 8:2 fluorotelomer alcohol (8:2 FTOH), and 2-(N-ethylperfluorooctane-1-sulfonamido ethyl] phosphate (SAmPAP), in the presence of six ENMs under simulated sunlight irradiation. The transformation rates of 8:2 FTSA and 8:2 FTOH were increased by 2–6 times when in the presence of six ENMs. However, most of ENMs appeared to inhibit the decomposition of SAmPAP. The transformation rates of PrePFAAs were found to depend on the yield of reactive oxygen species generated by ENMs, but the rates were also related to compound photo-stability, adsorption to surfaces, and photo-shielding effects. The PrePFAAs are transformed to perfluorooctanoic acid (PFOA) or/and perfluorooctane sulfonate (PFOS) with higher toxicity and longer half-life, PFOA or PFOS and a few PFAAs having shorter carbon chain lengths. Higher concentrations of the PFAAs photodegradation products were observed in the presence of most of the ENMs.

Accumulation and effects of perfluoroalkyl substances in three hydroponically grown Salix L. species.

The potential of young rooted cuttings of three Salix L. species plants to accumulate a mixture of eleven perfluoroalkyl substances (PFASs), in particular, perfluoroalkyl acids (PFAAs), from the nutrient solution and their effects on plant growth and photosynthesis were assessed in an 8-day experiment. The growth rate of the willow plants exposed to the PFAA mixture was not much affected except for S. triandra. Regarding photosynthesis, the gas exchange parameters were affected more than those related to chlorophyll fluorescence, with significant increase of the net CO2 assimilation rate and parameters related to stomatal conductance. A decreasing trend in the PFAA concentration in leaves with increasing carbon chain length was observed, whereas long-chain PFAAs showed higher concentrations in roots. Accordingly, the foliage to root concentration factor highlighted that PFAAs with shorter carbon chain length (C≤7) translocated and accumulated relatively more in leaves compared to roots. Removal efficiency of individual PFAAs for leaves and roots were comparatively higher with S. eleagnos and S. purpurea than S. triandra, with mean removal values at the whole plant level ranging around 10% of the amount initially spiked, suggesting their potential for phytoremediation of PFASs.

Fate of 6:2 fluorotelomer sulfonic acid in pumpkin (Cucurbita maxima L.) based on hydroponic culture: Uptake, translocation and biotransformation

6:2 fluorotelomer sulfonic acid (6:2 FTSA) is currently used as an alternative to perfluorooctanesulfonate (PFOS) and is widely detected in the environment. The uptake, translocation and biotransformation of 6:2 FTSA in pumpkin (Cucurbita maxima L.) were investigated by hydroponic exposure for the first time. The root concentration factor (RCF) of 6:2 FTSA was 2.6–24.2 times as high as those of perfluoroalkyl acids (PFAAs) of the same or much shorter carbon chain length, demonstrating much higher bioaccumulative ability of 6:2 FTSA in pumpkin roots. The translocation capability of 6:2 FTSA from root to shoot depended on its hydrophobicity. Six terminal perfluorocarboxylic acid (PFCA) metabolites, including perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA), perfluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA) were found in pumpkin roots and shoots. PFHpA was the primary metabolite in roots, while PFBA was the major product in shoots. 1-aminobenzotriazole (ABT), a cytochromes P450 (CYPs) suicide inhibitor, could decrease the concentrations of PFCA products with dose-dependent relationships in pumpkin tissues, implying the role of CYP enzymes involved in plant biotransformation of 6:2 FTSA. This study indicated that the application of 6:2 FTSA can lead to the occurrence of PFCAs (C2–C7) in plants.

Exposure of Juncus effusus to seven perfluoroalkyl acids: Uptake, accumulation and phytotoxicity

The extensive use of poly- and perfluoroalkyl substances (PFAS) has led to perfluoroalkyl acids (PFAAs) contamination in various environmental matrices. To remove PFAAs from contaminated water, this study investigated plant uptake of PFAAs by a native wetland plant species in the US, Juncus effusus. The results showed that J. effusus translocated selected PFAAs, including perfluoropentanoic acid (PFPA), perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). During the 21-day experimental period, the uptake of PFAAs increased with increasing PFAAs exposure concentration and time. PFOS was largely accumulated in the roots with limited upward translocation. PFAAs with shorter carbon chain length were taken up by J. effusus roots and tended to accumulate in plant shoots. The highest removal efficiency (11.4%) of spiked PFAAs by J. effusus was achieved when it was exposed to PFAAs at around 4.6 mg/L for 21 days. The exposure to PFAAs stimulated the antioxidative defense system in J. effusus shoots but inhibited the superoxide dismutase (SOD) and catalase (CAT) activities and damaged the antioxidative defense system in J. effusus roots. These results warrant further studies to evaluate J. effusus's long-term performance in a PFAAs contaminated environment.

Identification and engineering of the key residues at the crevice-like binding site of lipases responsible for activity and substrate specificity.

Rational engineering of the crevice-like binding site of lipases for improvement of lipases' catalytic properties. The residues located at the crevice-like binding site of four representative lipases including Thermomyces lanuginosus lipases (TLL and Lip), Rhizopus oryzae lipase (ROL), and Rhizomucor miehei lipase (RML) were identified through structural analysis. The residues at the bottom of the crevice-like binding site recognizing the substrates with short/medium carbon chain length and those located at the right-hand wall of the surface crevice region affecting the product release were changed by site-directed mutagenesis. The corresponding double mutants exhibited ~ 5 to 14-fold higher activity towards p-nitrophenyl esters than their wild types, and their substrate preference shifted to acyl moiety with shorter carbon chain length. In addition, the mutations led to an increase of B-factor, resulting in decrease of their optimum temperature by 10-20°C. The key residues located at the crevice-like binding site play important roles in determining lipase activity, substrate preference and optimum temperature, which offers a useful new paradigm for facilitating rational design of lipases.

Effects of carbon chain length of imidazolium-based ionic liquid in the interactions between heavy crude oil and sand particles for enhanced oil recovery

Increasing demand and dwindling supply of crude oil have spurred efforts towards enhancing heavy oil recovery. Recently, applications of ionic liquids (ILs) for heavy oil recovery and catalytic upgrading have been intensively studied due to their novelty as green surfactants. This paper presents the effects of different carbon chain lengths (n = 0, 2, 4, 6, 8, 10, 12) and concentrations from 1000 to 8000 ppm of imidazolium-based ILs on the oil-sand detachment efficiency at room temperature. Overall, the longest carbon chain length (n = 12), 1-dodecyl-3-methylimidazolium chloride ([DODmim][Cl]), showed highest oil-sand detachment efficiency of approximately 80% at 4000 ppm and beyond, indicating that a CMC point has been achieved. In contrary, the IL without carbon chain length (n = 0), 1-methylimidazolium chloride ([Mmim][Cl]), showed lowest oil-sand separation of a mere 5.7% at all concentrations. Interfacial tension (IFT) and zeta potential measurements further verified the above oil-sand detachment efficiencies, whereby the high oil-sand detachment efficiencies correlated to low IFT of approximately 9.78 mN/m for [DODmim][Cl] at 8000 ppm and high net zeta potential measurements of positively charged oil and sand particles. It is interesting to note that while the zeta potential measurements were all positive for oil particles in IL, the zeta potential measurements of sand particles in IL turned to negative for low concentrations of [Omim][Cl] and shorter carbon chain lengths (n ≤ 6), thus resulting in a mild attraction between the oil and sand particles. Further analysis using the Derjaguin-Landau, Verwey Overbeek (DLVO) theory which showed the inter-particle forces further validated the former oil-sand detachment efficiencies whereby repulsive forces between oil and sand particles occurred only for longer carbon chain lengths of [DODmim][Cl] and [Dmim][Cl].

Nonionic surfactants and their effects on asymmetric reduction of 2-octanone with Saccharomyces cerevisiae

In an aqueous buffer system, serious reverse and side reactions were found in the asymmetric reduction of 2-octanone with Saccharomyces cerevisiae. However, some nonionic surfactants added to the aqueous buffer system improved the bioreduction process by decreasing the reverse and side reaction rates in addition to effectively increasing the average positive reaction rate. Further, a shorter carbon chain length of hydrophilic or hydrophobic moieties in surfactants resulted in a higher yield of (S)-2-octanol. The alkylphenol ethoxylate surfactants had a less influence than polyoxyethylenesorbitan trialiphatic surfactants on the product e.e. It suggested that the product e.e. resulting from the change of carbon chain length of the hydrophobic moieties varied markedly compared with the change of carbon chain length of the hydrophilic moiety. Emulsifier OP-10 and Tween 20 markedly enhanced the yield and product e.e. at the concentration of 0.4 mmol L−1 with a yield of 73.3 and 93.2%, and the product e.e. of 99.2 and 99.3%, respectively, at the reaction time of 96 h.

A mixed-mode chromatographic separation method for the analysis of dialkyl phosphates

While reversed-phase (RP) liquid chromatography can separate a wide range of analytes, for strongly acidic compounds such as environmentally relevant dialkyl phosphates (DAPs), this remains a challenge because they have low affinity for standard RP columns or they exhibit inferior peak shapes. Mixed-mode chromatographic (MMC) columns, which contain both RP and ion-exchange functionalities, can address these resolution problems. However, using current MMC separation approaches, analyte peaks are relatively broad as compared to conventional RP chromatography. Herein we present an enhanced MMC-based UHPLC/ESI-MS method for the analysis of DAPs. In contrast to commonly available MMC-based methods, we applied the MMC Luna® Omega PS C18 column that was conditioned by 0.1% formic acid and equilibrated with the initial mobile phase before sample injection. This conditioning step tremendously improved the retention and separation of the DAPs, especially for those with high water solubility and shorter carbon chain lengths. Using water/methanol (95 v/5 v) and ammonium acetate in methanol as the mobile phases, nine DAPs could be baseline resolved with very sharp peaks, including the shorter-chain dimethyl phosphate, diethyl phosphate and bis(2-chloroethyl) phosphate. Other columns were examined to facilitate method optimization, and to identify stationary phases with the ability to separate DAPs as well as to elucidate the retention and separation mechanisms. With this novel UHPLC and post-column dication ion-pairing ESI-MS/MS method, instrumental detection limits as low as 0.01 ng/mL level were achieved. Representing other strongly acidic analytes, the short-chain perfluoroalkyl acid, perfluorobutyl sulfonic acid could also be analyzed with this method.

Antennal olfactory responses of adult meadow spittlebug, Philaenus spumarius, to volatile organic compounds (VOCs).

The meadow spittlebug, Philaenus spumarius L. (Hemiptera, Aphrophoridae) is a commonly found vector of Xylella fastidiosa Wells et al. (1987) strain subspecies pauca associated with the “Olive Quick Decline Syndrome” in Italy. To contribute to the knowledge of the adult P. spumarius chemoreceptivity, electroantennographic (EAG) responses of both sexes to 50 volatile organic compounds (VOCs) including aliphatic aldehydes, alcohols, esters, and ketones, terpenoids, and aromatics were recorded. Measurable EAG responses were elicited by all compounds tested. In both sexes, octanal, 2-octanol, 2-decanone, (E)-2-hexenyl acetate, and vanillin elicited the strongest antennal amplitude within the chemical groups of aliphatic saturated aldehydes, aliphatic alcohols, aliphatic acetates and aromatics, respectively. Male and female EAG responses to sulcatol, (±)linalool, and sulcatone were higher than those to other terpenoinds. In both sexes, the weakest antennal stimulants were phenethyl alcohol and 2-pentanone. Sexual differences in the EAG amplitude were found only for four of test compounds suggesting a general similarity between males and females in antennal sensitivity. The olfactory system of both sexes proved to be sensitive to changes in stimulus concentration, carbon chain length, and compound structure. Compounds with short carbon chain length (C5—C6) elicited lower EAG amplitudes than compounds with higher carbon chain length (C9—C10) in all classes of aliphatic hydrocarbons with different functional groups. The elucidation of the sensitivity profile of P. spumarius to a variety of VOCs provides a basis for future identification of behaviorally-active compounds useful for developing semiochemical-based control strategies of this pest.