Residual Surfactant Research Articles

Investigation of the detergency properties of mixtures of biocides and nonionic surfactants using a new simplified hard surface cleaning method

AbstractThe present study explores the cleaning efficacy of a set of nonionic surfactants (linear ethoxylated alcohol, secondary ethoxylated alcohols with 5, 7, and 9 ethoxy groups, glycoside surfactants, polyglycerol surfactants, and an ethoxylated sorbitan monolaurate) combined with cationic biocides—alkyl quaternary ammonium salts. A simple hard surface cleaning methodology was applied, which was shown to discriminate well between poor and good cleaning formulations. In addition to cleaning efficacy, surface aesthetics such as gloss and haze were evaluated together to assess surface streaking caused by a residual surfactant layer. The haziness determination turned out to be the key feature revealing the complex cleaning performance of multi‐component products.

Surfactant-Free Preparation of Conjugated Polymer Nanoparticles in Aqueous Dispersions Using Sulfate Functionalized Fluorene Monomers.

Conjugated polymer nanoparticles (CPNs) can be synthesized by a Suzuki-Miyaura cross-coupling miniemulsion polymerization to give stable dispersions with a high concentration of uniform nanoparticles. However, large amounts of added surfactants are required to stabilize the miniemulsion and prevent the aggregation of the nanoparticles. Removal of the excess surfactant is challenging, and residual surfactant in thin films deposited from these dispersions can reduce the performance of optoelectronic devices. We report a novel approach to prepare stable dispersions with no added surfactant using a fluorene monomer, 2,7-dibromo-9,9-bis(undecanesulfate)-9H-fluorene, with alkyl side chains terminated by negatively charged sulfate groups. This functionality mimics the structure of one of the most commonly used surfactants, sodium dodecyl sulfate (SDS). This charged monomer effectively stabilizes the miniemulsion through electrostatic repulsion without the use of any additional surfactant in molar ratios ranging from 2.0 to 20.0 mol % of total monomer content for the preparation of poly(9,9-dioctylfluorene) (PFO) and poly(9,9-dioctylfluorene-alt-bithiophene) (PF8T2). Incorporation of 5.0 mol % of the amphiphilic monomer gave stable dispersions with a surface potential below -40 mV and, and polymers with molar mass (Mn) above 10 kg mol-1. This method should be generally applicable to the preparation of dispersions of polyfluorenes for application in organic electronic and optoelectronic devices without the requirement for time-consuming processes to remove residual surfactant.

Impact of Surfactant to DNA Exchange on Carbon Nanotube Emission for Biosensing Applications

Synthesis methods of single walled carbon nanotubes (SWCNTs) result in mixtures of different chiralites. Chirality affects SWCNT diameter as well electronic and optical properties. For use in optical sensors, mono-chirality SWCNTs offer better signal compared to chirality mixtures. A common chirality separation method is aqueous two-phase extraction, where solutions of surfactants are used to partition SWCNTs based on chirality. The process results in a mono-chiral solution of SWCNTs wrapped in surfactant, however for sensing applications SWCNTs need to be exchanged from this surfactant wrapping to single stranded DNA wrapping. Concerns have been raised about residual surfactant remaining on the SWCNT surface after the exchange process and the effect this would have on the sensing capabilities of the SWCNT. To investigate this, we compared the emission spectra of covalently modified SWCNTs sonicated directly in DNA to that of SWCNTs exchanged from surfactant into DNA. We observed that emission from exchanged SWCNTs was red shifted compared to direct DNA sonicated SWCNTs, however exchanged SWCNTs had similar environmental responsivity to direct DNA sonicated SWCNTs.

Sustainable Utilization of Surfactant-Free Microemulsion Regulated by CO2 for Treating Oily Wastes: A Interpretation of the Response Mechanism.

Surfactant-free microemulsions (SFMEs) have been explored extensively to avoid the residual surfactant problem caused by traditional surfactant microemulsions. Many researchers focused on the SFMEs with tertiary amine, which exhibited the typical CO2 response behavior. In this study, the phase diagram of the SFMEs consisting of tripropylamine (TPA), ethanol, and water was readily prepared via the measurements of electrical conductivity. The CO2 response behavior of SFME was confirmed by determination of conductivity and measurement of the average diameter of SFME, which was mainly dependent on the protonation of TPA induced by the additional CO2. The transition of protonated TPA to a more hydrophilic nature from lipophilicity to hydrophilicity should be responsible for the variation of SFME average diameter. In addition, the SFMEs exhibited remarkable solubilizing capacity of crude oil, and three types of SFMEs achieved more than 80% oil removal rate in the washing process of oil sands. It was noted that both oil-in-water and bicontinuous SFMEs could be circularly utilized at least three times with a relatively high oil removal rate (%). Our work provided the insight perspective on the mechanism of SFMEs with a CO2 response behavior.

Characterization of Nanoprecipitated PET Nanoplastics by 1H NMR and Impact of Residual Ionic Surfactant on Viability of Human Primary Mononuclear Cells and Hemolysis of Erythrocytes.

Manufactured nanoplastic particles (NPs) are indispensable for in vitro and in vivo testing and a health risk assessment of this emerging environmental contaminant is needed. The high surface area and inherent hydrophobicity of plastic materials makes the production of NPs devoid of any contaminants very challenging. In this study, we produced nanoprecipitated polyethylene terephthalate (PET) NPs (300 nm hydrodynamic diameter) with an overall yield of 0.76%. The presence of the ionic surfactant sodium dodecyl sulfate (SDS) was characterized by 1H NMR, where the relative ratio of NP/surfactant was monitored on the basis of the chemical shifts characteristic of PET and SDS. For a wide range of surfactant/NP ratios (17:100 to 1.2:100), the measured zeta potential changed from -42.10 to -34.93 mV, but with an NP concentration up to 100 μg/mL, no clear differences were observed in the cellular assays performed in protein-rich media on primary human cells. The remaining impurities contributed to the outcome of the biological assays applied in protein-free buffers, such as human red blood cell hemolysis. The presence of SDS increased the NP-induced hemolysis by 1.5% in protein-rich buffer and by 7.5% in protein-free buffer. As the size, shape, zeta potential, and contaminants of NPs may all be relevant parameters for the biological effects of NPs, the relative quantification of impurities exemplified in our work by the application of 1H NMR for PET NPs and the ionic surfactant SDS could be a valuable auxiliary method in the quality control of manufactured NPs.

Evidence of residual micellar structures in a lipid nanocapsule dispersion. A multi-technique approach

Nanoemulsions are metastable emulsions in the nanometric range which can be obtained using low-energy processes. A decade ago, it was demonstrated that a non-negligible amount of residual surfactant micelles may coexist with the oil nanodroplets in a model oil/surfactant system. Those micelles were called “wasted” micelles as they did not participate in the formation of the nanodroplets. Little attention has been focused on the potential presence or effect of such secondary structures in nanoemulsions used as drug delivery systems. Here, we present an extensive characterization of lipid nanocapsules, a nanoemulsion obtained from a medium-chain triglyceride mixed with a pegylated surfactant by a process comprising a temperature-dependent phase inversion followed by a cold-water quench. Lipid nanocapsules demonstrate a very good shelf stability. First, for clarity and academic purposes, we briefly present the pros and the cons of the various diffusion-based characterization techniques used i.e., multi-angle and single-angle dynamic light scattering, nanoparticle tracking analysis, fluorescence recovery after photobleaching, and diffusometry nuclear magnetic resonance. Then, combining all these techniques, we show that up to 40 wt% of the surfactant is not involved in the lipid nanocapsule construction but forms residual micellar structures. Those micelles also contain a small quantity of medium-chain triglyceride (2 wt% of the initial amount) and encapsulate around 40 wt% of a fluorescent dye originally dispersed in the oily phase.

Analysis of the Effects of Surfactants on Extracellular Polymeric Substances

Reservoirs after chemical flooding usually have residual chemicals, which can affect the driving effect of subsequent microbial drives. Among them, the effect of surfactants on the metabolites of oil-recovering bacteria is the most obvious. Therefore, this paper investigates the influence mechanism of sodium dodecyl sulfate (SDS) on the nature and structure of Extracellular Polymeric Substances (EPS) produced by metabolism of Enterobacter cloacae, through a variety of characterization to analysis the components and structure of EPS under SDS stress. The results showed that Enterobacter cloacae was identified as a glycolipid-producing strain, the main components of EPS were polysaccharides and proteins. The polysaccharide composition (%: w/w) was glucosamine, 37.2; glucose, 31.5; rhamnose, 26.3; xylose, 1.7; and unidentified sugar, 3.3; and the main component of proteins was polyglutamic acid. EPS under the stress of SDS showed an increase in the content of functional groups such as -C=O and -COOH and an increase in the cellular particle size, and production of EPS increased by 10.69 × 103 mg/L when the SDS concentration was 2.5 × 102 mg/L; 3D-EEM results showed that the components of all three types of EPS The 3D-EEM results showed that all three types of EPS fractions contained tryptophan and protein-like substances, humic acid-like substances were only distributed in the solubilized extracellular polymers (SL-EPS), and aromatic proteins were only present in the loosely bound type (LB-EPS) and tightly bound type (TB-EPS). In addition, the peaks representing humic-like substances showed a blue shift, indicating that SDS had the greatest effect on SL-EPS. This study provides a guidance for refining the mechanism of strain EPS response to reservoir residual surfactant SDS, and provides a more comprehensive and in-depth understanding of surfactant-protein interactions.

Heat treated graphene thin films for reduced void content of interlaminar enhanced CF/PEEK composites

Graphene enhanced thermoplastic composites offer the possibility of conductive aerospace structures suitable for applications from electrostatic dissipation, to lightning strike protection and heat dissipation. Spray deposition of liquid phase exfoliated (LPE) aqueous graphene suspensions are highly scalable rapid manufacturing methods suitable to automated manufacturing processes. The effects of residual surfactant and water from LPE on thin films for interlaminar prepreg composite enhancement remain unknown. This work investigates the effect of heat treatment on graphene thin films spray deposited onto carbon fibre/polyether ether ketone (CF/PEEK) composites for reduced void content. Graphene thin films deposited onto CF/PEEK prepreg tapes had an RMS roughness of 1.99 μm and an average contact angle of 11°. After heat treatment the roughness increased to 2.52 μm with an average contact angle of 82°. The SEM images, contact angle, and surface roughness measurements correlated suggesting successful removal of excess surfactant and moisture with heat treatment. Raman spectroscopy was used to characterise the chemical quality of the consolidated graphene interlayer. Spectral data concluded the graphene was 3–4 layered with predominantly edge defects suggesting high quality graphene suitable for electrical enhancement. Conductive-AFM measurements observed an increase in conductive network density in the interlaminar region after the removal of surfactant from the thin film. Heat treatment of the Control sample successfully reduced void content from 4.2 vol% to 0.4 vol%, resulting in a 149% increase in compressive shear strength. Comparatively, heat treatment of graphene enhanced samples (~ 1 wt%) reduced void content from 5.1 vol% to 2.8 vol%. Although a 25% reduction in shear strength was measured, the improved electrical conductivity of the interlaminar region extends the potential applications of fibre reinforced thermoplastic composites. The heat treatment process proves effective in reducing surfactant and thus void content while improving electrical conductivity of the interlayer in a scalable manner. Further investigations into graphene loading effects on conductive enhancement, and void formation is needed.

Remediation of Surfactants Used by VUV/O3 Techniques: Degradation Efficiency, Pathway and Toxicological Analysis.

Surfactants are increasingly used in systems that come into contact with the human body, such as food, pharmaceuticals, cosmetics and personal hygiene products. Increasing attention is being devoted to the toxic effects of surfactants in various human contact formulations, as well as the removal of residual surfactants. In the presence of ozone (O3), anion surfactants-a characteristic micro-pollutant-such as sodium dodecylbenzene sulfonate (SDBS) in greywater, can be removed using radical advanced oxidation. Herein, we report a systematic study of the SDBS degradation effect of O3 activated by vacuum ultraviolet (VUV) irradiation and the influence of water composition on VUV/O3, and determined the contribution of radical species. We show a synergistic effect of VUV and O3, while VUV/O3 reached a higher mineralization (50.37%) than that of VUV (10.63%) and O3 (29.60%) alone. The main reactive radicals of VUV/O3 were HO•. VUV/O3 had an optimal pH of 9. The addition of SO42- had almost no effect on the degradation of SDBS by VUV/O3, Cl- and HCO3- slightly reduced the reaction rate, and NO3- had a significant inhibition on the degradation. In total, SDBS had three isomers, with which the three degradation pathways were very comparable. Compared with SDBS, the toxicity and harmfulness of the degradation by-products of the VUV/O3 process decreased. Additionally, VUV/O3 could degrade synthetic anion surfactants from laundry greywater effectively. Overall, the results show the potential of VUV/O3 in safeguarding humans from residual surfactant hazards.

Visualising Co nanoparticle aggregation and encapsulation in Co/TiO2 catalysts and its mitigation through surfactant residues

Due to the reducible nature of TiO2, the encapsulation of cobalt nanoparticles (CoNPs) by reduced TiO2-x is often reported to decrease their catalytic performance in reactions such as Fisher-Tropsch synthesis (FTS). Here, we show using HAADF-STEM imaging and electron energy loss spectroscopy (EELS) that a residual C12E4 surfactant used to prepare the CoNPs, remains on the surface of a TiO2 rutile support, preventing the formation of Ti3+/Ti2+ oxides and therefore TiO2-x migration. Furthermore, the presence of these surfactant residues prevents the coalescence and aggregation of CoNPs during catalyst preparation, maintaining the dispersion of CoNPs. As such, using C12E4 in the preparation of Co/TiO2 can be considered beneficial for producing a catalyst with a greater number of active Co species.

Influence of surfactant on glass transition temperature of poly(lactic-co-glycolic acid) nanoparticles.

Poly(D,L-lactic-co-glycolic acid) (PLGA) is one of the most commonly used drug carriers in nanomedicines because of its biodegradability, biocompatibility and low toxicity. However, the physico-chemical characterization and study of drug release are often lacking the investigation of the glass transition temperature (Tg), which is an excellent indicator of drug release behavior. In addition, the residual surfactant used during the synthesis of nanoparticles will change the glass transition temperature. We thus prepared PLGA nanoparticles with polymeric (poly(vinyl alcohol) (PVA)) and ionic (didodecyldimethylammonium bromide (DMAB)) surfactant to investigate their influence on the glass transition temperature. Determination of Tg in dry and wet conditions were carried out. The use of concentrated surfactant during synthesis resulted in a larger amount of residual surfactant in the resulting particles. Increasing residual PVA content resulted in an increase in particle Tg for all but the most concentrated PVA concentrations, while increasing residual DMAB content resulted in no significant change in particle Tg. With the presence of residual surfactant, the Tg of particle and bulk samples measured in wet conditions is much lower than that in dry conditions, except for bulk PLGA containing the ionic surfactant, which may be related to the plasticizing effect of the DMAB molecules. Notably, the Tg of both particles in wet conditions is approaching physiological temperatures where subtle changes in Tg could have dramatic effects on drug release properties. In conclusion, the selection of surfactant and the remaining amount of surfactant are crucial parameters to utilize in designing the physico-chemical properties of PLGA particles.

Correlating the drying kinetics and dried morphologies of aqueous colloidal gold droplets of different particle concentrations

The evaporation of a gold nanorod (Au-NR) dispersion droplet, containing residual surfactant, on a hydrophilic silicon substrate results in a coffee stain with different microstructures. The distinct regions in the coffee stain, formed during different stages of droplet drying, are presumably correlated with the dynamics of the evaporating droplet. We drop-cast 2 μL CTAB capped Au-NR dispersion droplets on a hydrophilic substrate, and study their evaporation kinetics, and dried patterns using optical, electron, and atomic force microscopy. We report that droplet retraction, pinning, and quick evaporation during the initial, intermediate, and final phases of droplet drying are clearly correlated with the different coffee stain aggregation regions for a range of Au-NR concentrations. The receding velocity of the evaporating gold colloidal droplet decreases with increasing Au-NR concentration, resulting in random to cluster-like aggregations of Au-NRs outside the coffee stain. Droplet depinning is followed by a concentration-dependent droplet pinning process which results in the formation of a coffee stain edge comprising distinct domains that consist of smectic phase-like structures of Au-NRs. The duration of droplet pinning, the widths and heights of the outer coffee stain edge increase with increasing gold nanorod concentration and are consistent with theoretical predictions. Finally, the rapid evaporation of the droplet leads to the formation of non-uniform depletion region and inner coffee stain regions. Our study demonstrates that the solute deposition pattern can be tailored by controlling the evaporating droplet kinetics. The unique assemblies of Au-NRs in the coffee stain edge are potentially excellent candidates for the development of plasmonic sensors for the selective detection of trace amounts of molecules, while the large clusters of end-to-end aligned Au-NRs outside the stain could be used for the fluorescence enhancement of low quantum yield molecules.

Oil removal from solid surface by using surfactant-free microemulsion regulated by CO2: A sustainable approach for treating oily waste

Facing the issues of residual surfactant by using surfactant-based microemulsion, the surfactant-free microemulsion (SFME) are chosen as the alternate for extraction process. Especially, the sustainable separation for oil by using SFME has been not completed. Herein, the CO2-responsive SFME were formed and perform excellent behavior on oil removal and separation, providing the sustainable approach for oil removal. Here, this SFME were simply formed with hydrophobic tertiary amine as oil phase, ethanol as “amphisolvent” and water. This SFME exhibit reversible transformation of microstructure controlled by CO2, and also perform thermal-stable microstructure. Moreover, the SFME have good oil solubilization behavior that can be improved by the oil phase content (N,N-Dimethylbenzylamine) of SFME and the reduced interfacial tension between SFME and oil. After introducing CO2, the oil solubilized by SFME is separated. Furthermore, due to the reduced free energy for oil detachment by using this SFME, the coated oil was removed from solid surface. Finally, the application for washing oil sands was completed, where above 90% oil was removed. Moreover, the oil is separated upon CO2 and the SFME was reused after treating N2 at 55 °C, implying the sustainable process for oil removal from oily waste.

One‐step synthesis of polymer dispersions with large narrow‐size‐distribution particles via heterophase polymerization in the presence of surface‐active water‐insoluble organosilicon macromers

AbstractPolymerizable water‐insoluble surface‐active macromers (SAMs), namely α,ω‐divinylpolydimethylsiloxane (DVPDMS), α,ω‐dipropylmethacrylatepolydimethylsiloxane (DPMPDMS) and α,ω‐pair(vinylbenzyl)polydimethylsiloxane (PVBPDMS), were synthesized and characterized using NMR. The colloidal‐chemical properties of the synthesized compounds were studied in comparison with non‐polymerizable polydimethylsiloxane. Using DVPDMS, DPMPDMS and PVBPDMS as copolymerizable emulsifiers, polystyrene and poly(methyl methacrylate) suspensions with large particles, narrow particle size distribution and with the absence of the residual surfactant in the waste water were obtained. It is shown that in the presence of DPMPDMS it is possible to obtain polymer suspensions with an average particle diameter of 1.6 μm. The proposed mechanism of the effects of the SAMs on the polymerization is based on the copolymerization with the main monomers in the monomer–polymer particle interphases which results in stabilization of the particle protective layers from early stages of the reaction. © 2021 Society of Chemical Industry

Adsorption of Saponin Natural Surfactant on Carbonate Rock and Comparison to Synthetic Surfactants: An Enhanced Oil Recovery Prospective

Surfactant flooding is one technique of chemical enhanced oil recovery (EOR) aimed at improving the microscopic displacement efficiency of trapped residual oil via reducing the oil–water interfacial tension and wettability alteration. Success of surfactant flooding strongly relies on surfactant loss through its adsorption onto reservoir minerals to ensure maximum transfer to target reservoir. The current study examines the adsorption behavior of saponin natural surfactant onto carbonate rock outcrops. As an environmentally friendly extract from plants, saponins have shown the potential to increase oil recovery, although saponin loss or adsorption on surfaces is yet to be studied. Common synthetic surfactants of various types (i.e., cationic and anionic) and different molecular structures (other nonionic surfactants) have also been studied to provide comparisons to saponin. The surfactant adsorption onto carbonate samples was studied by batch adsorption experiments, with the residual surfactant concentration determined by the surface tension technique. It was found that saponin, a natural nonionic surfactant, adsorbed less than the ionic surfactants, since saponin adsorption is not governed by electrostatic interactions but weaker hydrogen bonding. Such data concludes that saponins are likely to yield less retention than the ionic surfactants, but compared to other nonionic surfactants its retention is greater. This is likely attributed to differing surfactant molecular structures. Due to its branch-like structure with more terminal functional groups, saponin adsorbs more on the rock surface compared to other long-chain nonionic surfactants. The findings of the current study provide a useful guide in surfactant selection for EOR and highlight a potential of natural and environmentally friendly surfactants.

(Invited) Critical Effect of Particle Size in Ru-Catalyzed Electrosynthesis of Ammonia

Electrochemical reduction of N2 to NH3 has recently received considerable attention, because it may enable sustainable, distributed production of NH3 when powered by solar- or wind-generated electricity. However, typical catalysts show a low activity and selectivity for N2 reduction reaction (NRR) due to the barrier for N2 activation and the competing hydrogen evolution reaction (HER). A rational design of NRR catalysts relies on our understandings of structure-activity relationships and active sites for the NRR, and such study requires model catalysts with well-defined structures. Here we present a study of size-dependent activity for the NRR on Ru nanoparticle catalysts. We first tried colloidal synthesis method with polyvinylpyrrolidine (PVP) as a surfactant to control the size of Ru nanoparticles, while the derived Ru catalysts showed negligible activity for NRR, which was attributed to residual surfactant molecules that blocked catalyst surfaces. Therefore, we used atomic layer deposition (ALD) method to prepare Ru nanoparticles with controlled sizes and clean surfaces. We also quantified the electrochemical active surface areas of Ru samples and measured surface-area-normalized activity for the NRR. Consequently, the effect of Ru nanoparticle size on the NRR activity and Faradaic efficiency was revealed, which can provide insights into the active sites for the NRR and guidance on the design of NRR catalysts via surface site engineering.

Role of surfactants in cleaning of PVDF ultrafiltration membranes fouled by emulsified cutting oil

Chemical cleaning with anionic, cationic and non-ionic surfactants was studied for polyvinylidene (PVDF) hollow fiber ultrafiltration (UF) membranes irreversibly fouled by cutting fluid with anionic emulsifiers. The membrane cleaning efficiency of the surfactants was determined by pure water permeability and the results are in agreement with morphological observations of the membrane surfaces and molecular vibrational analyses. The anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulphonate (SDBS), showed better cleaning through the combined effect of electrostatic repulsion with emulsified oil particles and re-emulsification of the oil layer. Inclusion of the phenyl group in the dodecyl sulfate anion had a significant role in cleaning. Molecular vibrational analyses indicated a higher presence of residual surfactant on the membranes after cleaning with cationic (cetyltrimethylammonium bromide (CTAB)) and non-ionic (Tween 85 (T-85)) surfactants, which also resulted in higher apparent hydrophilicity of the membrane surface. Alkalizing the anionic surfactant solution improved cleaning efficiency, but had no significant effect for cationic and non-ionic surfactants. The effect of surfactant concentration and ionic strength on cleaning efficacy was analyzed for SDBS. As mass transport increased, higher cleaning efficacy was observed at higher SDBS concentration. The cleaning efficacy of SDBS was also influenced to varying degrees by solution pH and ionic strength.

Reduced cytotoxicity of CTAB-templated silica layer on gold nanorod using fluorescence dyes and its application in cancer theranostics

Cytotoxicity of cetyltrimethylammonium bromide (CTAB)-templated silica-coated gold nanorod (CGNR@SiO2) was confirmed to be severe even after the washing process because of the residual CTAB surfactant. Calcination to eliminate the CTAB template induced dissolution of the gold nanorod (GNR) core and caused a blue-shift in the longitudinal surface plasmon resonance (LSPR) mode of the GNR from the near-infrared to visible wavelength. In contrast, the CTAB template was effectively removed from CGNR@SiO2 without interference of the plasmonic property of the core GNR by amine-functionalized fluorescence dyes such as methylene blue (MB) and rhodamine B (RB). The RB was more efficient in substituting the residual CTAB through electrostatic interactions than the MB. Moreover, the resulting products exhibited excellent surface-enhanced Raman scattering performance to detect a few cancer cells. The MB and RB molecules as visible light photosensitizer (PS) were activated by near-infrared (NIR) excitation light through transfer of the NIR-driven plasmonic hot electrons from the core GNR to the PS molecules. It is noteworthy that the RB-loaded CGNR@SiO2 exhibited excellent cancer cell killing efficiency via generation of abundant reactive oxygen species (ROS) under NIR laser irradiation, although the concentration of the intracellular GNR was too low to induce the photothermal effect.

Top-Down Proteomics of Endogenous Membrane Proteins Enabled by Cloud Point Enrichment and Multidimensional Liquid Chromatography-Mass Spectrometry.

Although top-down proteomics has emerged as a powerful strategy to characterize proteins in biological systems, the analysis of endogenous membrane proteins remains challenging due to their low solubility, low abundance, and the complexity of the membrane subproteome. Here, we report a simple but effective enrichment and separation strategy for top-down proteomics of endogenous membrane proteins enabled by cloud point extraction and multidimensional liquid chromatography coupled to high-resolution mass spectrometry (MS). The cloud point extraction efficiently enriched membrane proteins using a single extraction, eliminating the need for time-consuming ultracentrifugation steps. Subsequently, size-exclusion chromatography (SEC) with an MS-compatible mobile phase (59% water, 40% isopropanol, 1% formic acid) was used to remove the residual surfactant and fractionate intact proteins (6-115 kDa). The fractions were separated further by reversed-phase liquid chromatography (RPLC) coupled with MS for protein characterization. This method was applied to human embryonic kidney cells and cardiac tissue lysates to enable the identification of 188 and 124 endogenous integral membrane proteins, respectively, some with as many as 19 transmembrane domains.

Surfactant-Based Treatment Fluids Mitigate Fracture Hits in Parent Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 197097, “Fracture-Hit Mitigation Through Surfactant-Based Treatment Fluids in Parent Wells,” by Liang Xu, James Ogle, and Todd Collier, SPE, Halliburton, prepared for the 2019 SPE Liquids-Rich Basins Conference - North America, Odessa, Texas, 11-12 September. The paper has not been peer reviewed. Preloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied extensively in liquids-rich shale plays. However, why specific chemical packages help improve parent-well production remains unclear. The complete paper presents a strategy for selecting a surfactant/solvent package for parent wells. Oil recovery and associated water saturation in the microfluidic-based device, with or without surfactant, are quantified and reveal that the oil recovery is enhanced with surfactant. Water saturation in the parent well could be reduced, thereby mitigating water blocks from primary fracturing-fluid invasion from child wells. Introduction During child-well completions in development of liquids-rich shale plays, fracturing fluids and proppants are likely to infiltrate the parent-well fracture net-work and wellbore through hydraulically connected flow paths. Parent wells, after producing for a period, serve as a pressure sink that attracts new fracture propagation and extension initiated from a child-well fracture. As a result, parent wells could lose production because of a potentially plugged fracture network filled with new sand from child wells. The production of child wells also could suffer because of unwanted fracture extension and loss of reservoir pressure. The technique of reloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied recently in environments where intense infill drilling and tighter well spacings are prerequisites for improved production and economic return. Preloads can provide a significant temporary increase in fracture network pressure if performed properly and are most effective with a surfactant and solvent package. However, why specific chemical packages help improve the parent-well production remains unclear, although the notion of capillary force resistance reduction for further treatment-fluid leakoff into fractures and rock- wettability alteration by surfactant has been proposed in the literature. Recent residual surfactant analysis in produced water from both parent and child wells indicates that hydraulic communication exists after fracture hits; additionally, field trials in the Wolfcamp suggest that the same surfactant package in primary fracture fluids in child wells can migrate gradually to parent wells, potentially activating various secondary oil-recovery mechanisms. This study provides an evidence-based strategy for selecting a surfactant solvent package by a commercial microfluidic device (MD) and spontaneous imbibition (SpI), thus eliminating unnecessary testing that does not involve formation rocks. Surfactant optimization permits further leakoff into secondary fractures, potentially increasing fracture network pressure. Surfactant migration from child wells presents a unique enhanced-oil-recovery mechanism for parent wells. Field trials in different liquids-rich shale plays, including the Wolfcamp, appear to support this finding.