Baseline correction method for dynamic pressure gradient modulated comprehensive two-dimensional gas chromatography with flame ionization detection.

A baseline correction method is developed for comprehensive two-dimensional (2D) chromatography (GC × GC) with flame-ionization detection (FID) using dynamic pressure gradient modulation (DPGM). The DPGM-GC × GC-FID utilized porous layer open tubular (PLOT) columns in both dimensions to focus on light hydrocarbon separations. Since DPGM is nominally a stop-flow modulation technique, a rhythmic baseline disturbance is observed in the FID signal that cycles with the modulation period (PM). This baseline disturbance needs to be corrected to optimize trace analysis. The baseline correction method has three steps: collection of a background "blank" chromatogram and multiplying it by an optimized normalization factor, subtraction of the normalization-optimized background chromatogram from a sample chromatogram, and application of Savitzky-Golay smoothing. An alkane standard solution, containing pentane, hexane and heptane was used for method development, producing linear calibration curves (r2 > 0.991) over a broad concentration range (7.8 ppm - 4000 ppm). Further, the limit-of-detection (LOD) and limit-of-quantification (LOQ) were determined for pentane (LOD = 2.5 ppm, LOQ = 8.2 ppm), hexane (LOD = 0.9 ppm, LOQ = 3.0 ppm), and heptane (LOD = 1.9 ppm, LOQ = 6.4 ppm). A natural gas sample separation illustrated method applicability, whereby the DPGM produced a signal enhancement (SE) of 30 for isopentane, where SE is defined as the height of the tallest 2D peak in the modulated chromatogram for the analyte divided by the height of the unmodulated 1D peak. The 30-fold SE resulted in about a 10-fold improvement in the signal-to-noise ratio (S/N) for isopentane. Additional versatility of the baseline correction method for more complicated samples was demonstrated for an unleaded gasoline sample, which enabled the detection (and visual appearance) of trace components.

Molecular analysis of black coatings and anointing fluids from ancient Egyptian coffins, mummy cases, and funerary objects.

Black organic coatings and ritual deposits on ancient Egyptian coffins and cartonnage cases are important and understudied sources of evidence about the rituals of funerary practice. Sometimes, the coatings were applied extensively over the surface of the coffin, resembling paint; in other cases, they were poured over the mummy case or wrapped body, presumably as part of a funerary ritual. For this study, multiple samples of black coatings and ritual liquids were taken from 20 Egyptian funerary items dating to a specific time period (c. 943 to 716 BC). Multiple sampling from each object enabled several comparisons to be made: the variability of the black coating within one application, the variability between two applications on one object, and the variability from object to object. All samples were analyzed for lipids using gas chromatography-mass spectrometry (GC-MS), and 51 samples from across the 20 items were further analyzed for the presence of bitumen using solid phase separation followed by selected ion monitoring GC-MS. The majority of the black substances were found to comprise a complex mixture of organic materials, including bitumen from the Dead Sea, conifer resin, and Pistacia resin, providing evidence for a continuation in international trade between Egypt and the eastern Mediterranean after the Late Bronze Age. Both the coating and the anointing liquid are very similar to mummification balms, pointing to parallels with Egyptian embalming rituals and raising questions about the practical aspects of Egyptian funerary practice.

Large-scale screening of natural genetic resource in the hydrocarbon-producing microalga Botrycoccus braunii identified novel fast-growing strains.

Algal biofuel research aims to make a renewable, carbon-neutral biofuel by using oil-producing microalgae. The freshwater microalga Botryococcus braunii has received much attention due to its ability to accumulate large amounts of petroleum-like hydrocarbons but suffers from slow growth. We performed a large-scale screening of fast-growing strains with 180 strains isolated from 22 ponds located in a wide geographic range from the tropics to cool-temperate. A fast-growing strain, Showa, which recorded the highest productivities of algal hydrocarbons to date, was used as a benchmark. The initial screening was performed by monitoring optical densities in glass tubes and identified 9 wild strains with faster or equivalent growth rates to Showa. The biomass-based assessments showed that biomass and hydrocarbon productivities of these strains were 12-37% and 11-88% higher than that of Showa, respectively. One strain, OIT-678 established a new record of the fastest growth rate in the race B strains with a doubling time of 1.2 days. The OIT-678 had 36% higher biomass productivity, 34% higher hydrocarbon productivity, and 20% higher biomass density than Showa at the same cultivation conditions, suggesting the potential of the new strain to break the record for the highest productivities of hydrocarbons.

Re-Analysis of Abdominal Gland Volatilome Secretions of the African Weaver Ant, Oecophylla longinoda (Hymenoptera: Formicidae).

The African weaver ant, Oecophylla longinoda, is used as a biological control agent for the management of pests. The ant has several exocrine glands in the abdomen, including Dufour's, poison, rectal, and sternal glands, which are associated with pheromone secretions for intra-specific communication. Previous studies have analyzed the gland secretions of Dufour's and poison glands. The chemistry of the rectal and sternal glands is unknown. We re-analyzed the secretions from Dufour's and poison glands plus the rectal and sternal glands to compare their chemistries and identify additional components. We used the solid-phase microextraction (SPME) technique to collect gland headspace volatiles and solvent extraction for the secretions. Coupled gas chromatography-mass spectrometry (GC-MS) analysis detected a total of 78 components, of which 62 were being reported for the first time. These additional components included 32 hydrocarbons, 12 carboxylic acids, 5 aldehydes, 3 alcohols, 2 ketones, 4 terpenes, 3 sterols, and 1 benzenoid. The chemistry of Dufour's and poison glands showed a strong overlap and was distinct from that of the rectal and sternal glands. The different gland mixtures may contribute to the different physiological and behavioral functions in this ant species.

Treatment of wastewater containing oil and grease by biological method- a review.

One of the complex environmental problems that triggers at present is oily wastewater contamination arising out of the activities related to engineering vehicular (automobile) workshop or garage, kitchens in houses and restaurants, gas stations, metal finishing house, petrochemical industry, edible oil production unit etc. Oily wastewater discharge is a major issue of environmental pollution in the present decade as some of its constituents are hazardous in nature. Hence, appropriate treatment technology for oily wastewater needs to be addressed. Biological treatment (BT) technique would be the best option in this regard, because it has multiple advantages over various other techniques as available today. BT degrades effectively the harmful constituents of oily wastewater into innocuous products that are environment friendly and it is considered to be the economical method. The resulting effluent of pretreatment followed by biological treatment of oily wastewater can be reused after conforming discharge limits. Again, numerous research works in these days have optimized the function and result of existing laboratory and pilot scale treatment technologies. This review paper describes a comprehensive understanding of the origin and characteristics, existing techniques in laboratory and pilot scale, screening of different methods, justification for advocating biological methods for treatment of oily wastewater.

Total-transfer comprehensive three-dimensional gas chromatography with time-of-flight mass spectrometry.

Although comprehensive two-dimensional (2D) gas chromatography (GC × GC) is a powerful technique for complex samples, component overlap remains likely. An intriguing route to address this challenge is to utilize the additional peak capacity and chemical selectivity provided by comprehensive three-dimensional (3D) gas chromatography (GC3), especially with time-of-flight mass spectrometry detection (GC3-TOFMS). However, the GC3-TOFMS instrumentation reported to date has employed one or both modulators with a duty cycle < 100%, making the potential gain in detection sensitivity over GC × GC modest, or perhaps even worse. Herein, we describe instrumentation for GC3-TOFMS in which both modulators provide total-transfer (100% duty cycle). Specifically, the instrument is based on the facile modification of a commercial thermally modulated comprehensive GC × GC-TOFMS platform for modulation from the 1D column to the 2D column, with recently described dynamic pressure gradient modulation (DPGM) as the second modulator from the 2D column to the 3D column, which is a total-transfer flow modulation technique. Area measurements of 1D peaks are compared to the sum of 3D peak areas to validate the assumption that total-transfer from 1D to 3D is accomplished. Additionally, peak heights were amplified by as high as a factor of 177 (x̅ = 130, s = 47) via comparison of 1D peak heights to the maximum 3D peak heights. Column selection is explored, with emphasis on the resulting peak width-at-base on each dimension and usage of 3D space as evaluation metrics. Using a nonpolar × polar × ionic liquid column combination, an effective peak capacity which considers modulation-induced broadening as high as 32,300 for select analytes was achieved (x̅ = 19,900, s = 10,700). The analytical benefits of employing three selective phases, mass spectrometry detection, and total-transfer modulation are explored with separations of a metabolomics-type sample, i.e., derivatized porcine serum, and a jet fuel spiked with various sulfur-containing compounds.

Determination of Total Hydrocarbons in Contaminated Soil with "Thin Layer Sorptive Extraction Coupled with Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy".

Soil analysis using infrared spectroscopy has been proposed as an alternative to conventional soil analysis to detect soil contamination. This study therefore aims to develop an innovative, in situ, rapid, precise, and inexpensive method that is easy to implement in order to assess soil contamination with hydrocarbons. This work describes the development and validation of a new extraction method by thin-layer sorptive extraction and attenuated total reflectance-Fourier transform infrared spectroscopy (TLSE-ATR-FTIR). First, this method allows the preconcentration of thermodesorbed pollutants on a polymer thin film and then, their quantification by ATR-FTIR using a standard addition method. A five factor fractional factorial design was used to identify the most significant factors impacting the analysis. These factors include soil texture, total organic carbon (TOC), humidity, and concentrations of contaminants. The results showed that TOC, nature (clay, sandy, and loamy) of the soil, and the concentration of pollutants can affect the infrared absorbance. The analytical method has been validated by verifying the different performance criteria such as linearity, accuracy, precision, and quantitation limit. The comparison of the results obtained by TLSE-ATR-FTIR to the results of conventional analyses carried out by accredited laboratories confirms that the use of the proposed method can become an effective alternative to the current methods for the determination of the total hydrocarbons in soils.

Determination of biodiesel and used cooking oil in automotive diesel/green diesel fuels through high-performance liquid chromatography.

This study reports a simple and convenient analytical method for the simultaneous determination of biodiesel and vegetable oils or used cooking oils in petrodiesel and green diesel (hydrotreated vegetable oils or paraffinic diesel). The approach is based on normal-phase high-performance liquid chromatography with refractive index detection. It employed silica stationary phase, n-hexane mobile phase with isopropanol modifier to achieve optimum separation between hydrocarbons (petrodiesel or green diesel), fatty acid methyl esters (biodiesel) and triglycerides (vegetable oils and used cooking oil). In addition to determining vegetable oils or used cooking oils as adulterants in diesel, this method is also proposed as a better alternative to the standard method ASTM D7371, which is currently recommended for determining fatty acid methyl esters in petrodiesel. The method development involved screening of various stationary and mobile phases, with and without modifiers, to achieve acceptable chromatographic resolutions between analytes. Under the optimized method conditions, silica column, and n-hexane containing 0.6% isopropanol as the mobile phase provided the best results. The real-world scenario was simulated for the method validation carried out by fortifying Jatropha seed oil, soybean oil, and used cooking oil in the biodiesel blended petrodiesel and green diesel. Measurement of all analytes was accompanied by high precision, low limit of detection/quantification and linear response range of 0.05 to 50% for biodiesel, and 0.05 to 30% for vegetable oils. The proposed method is simple, fast (runtime 7 min), and does not require sample pre-treatment and backflushing.

Computational Modeling of Environmental Co-exposure on Oil-Derived Hydrocarbon Overload by Using Substrate-Specific Transport Protein (TodX) with Graphene Nanostructures.

BACKGROUND: Bioremediation is a biotechnology field that uses living organisms to remove contaminants from soil and water; therefore, they could be used to treat oil spills from the environment. METHODS: Herein, we present a new mechanistic approach combining Molecular Docking Simulation and Density Functional Theory to modeling the bioremediation-based nanointeractions of a heterogeneous mixture of oil-derived hydrocarbons by using pristine and oxidized graphene nanostructures and the substrate-specific transport protein (TodX) from Pseudomonas putida. RESULTS: The theoretical evidences pointing that the binding interactions are mainly based on noncovalent bonds characteristic of physical adsorption mechanism mimicking the "Trojan-horse effect". CONCLUSION: These results open new horizons to improve bioremediation strategies in over-saturation conditions against oil-spills and expanding the use of nanotechnologies in the context of environmental modeling health and safety.

Mild mixed-solvent extraction for determination of total mineral oil hydrocarbon contaminants in milk powder products.

A mild mixed-solvent of n-hexane/isopropanol is proposed for extracting total mineral oil hydrocarbons (MOH) from commercial milk powder products. Unlike acid-hydrolysis, the mixed-solvent extraction was performed at ambient temperature and the low-boiling-point hydrocarbons were retained to the greatest extent. After extraction, total MOH was determined by on-line liquid chromatography-gas chromatography with a flame ionization detector (LC-GC-FID). The validation of the proposed extraction method revealed a recovery efficacy of 83.0-107.5% and a limit of quantification of 0.5 mg/kg. Then, the total MOH in ten commercial milk powders was determined and mineral oil saturated hydrocarbons (MOSH)/polyolefin oligomeric saturated hydrocarbons (POSH) were found to be within the range of 0.61-5.46 mg/kg. The comparison of the total and surface MOSH/POSH indicated that a major part of the contamination was derived from sources before packaging. The present study provides a robust method for the extraction and determination of total MOH in milk powders.

Chemical Components and Antibacterial Activity of the Essential Oil of Six Pyrrosia Species.

The present study was aimed at analyzing the chemical components of the essential oil from six Pyrrosia species by GC/MS and evaluating their in vitro antibacterial activities. Seventy volatile compounds were identified in the essential oil of six Pyrrosia samples. The identified volatile components were divided into following nine categories: aldehydes, terpenoids, fatty acids, ketones, furans, hydrocarbons, alcohols, esters, and phenols. The major components of the essential oil were 2,4-pentadienal, phytol and nonanal. The antimicrobial assays showed that the essential oils from Pyrrosia samples exhibited a broad-spectrum antimicrobial activity. However, P. lingua had the highest antibacterial activity against Staphylococcus aureus (ATCC 25923) with a minimum inhibitory concentration (MIC) of 2.5 µL/mL. This article is the first report of the chemical components and antimicrobial activity of the essential oil from six Pyrrosia species, which will lay the foundation for developing medicinal resources from Pyrrosia fronds.

Factors affecting pluronic-coated iron oxide nanoparticle binding to petroleum hydrocarbon-impacted sediments.

Effective targeted delivery of nanoparticle agents may enhance the remediation of soils and site characterization efforts. Nanoparticles coated with Pluronic, an amphiphilic block co-polymer, demonstrated targeted binding behaviour toward light non-aqueous phase liquids such as heavy crude oil. Various factors including coating concentration, oil concentration, oil type, temperature, and pH were assessed to determine their effect on nanoparticle binding to heavy crude oil-impacted sandy aquifer material. Nanoparticle binding was increased by decreasing the coating concentration, increasing oil concentration, using heavier oil types, and increasing temperature, while pH over the range of 5-9 was found to have no effect. Nanoparticle transport and binding in columns packed with clean and oily porous media demonstrated the ability for efficient nanoparticle targeted binding. For the conditions explored, the attachment rate coefficient in columns packed with clean sand was 2.10 ± 0.66 × 10-4 s-1; however, for columns packed with oil-impacted sand a minimum attachment rate coefficient of 8.86 ± 0.43 × 10-4 s-1 was estimated. The higher attachment rate for the oil-impacted sand system indicates that nanoparticles may preferentially accumulate to oil-impacted zones present at heterogeneous impacted sites. Simulations were used to demonstrate this hypothesis using the set of parameters generated in this effort. This work contributes to our understanding of the application conditions that are required for efficient targeted binding of nanoparticles to crude-oil impacted porous media.

Production and Application of Biosurfactant Produced by Bacillus Licheniformis Ali5 in Enhanced Oil Recovery and Motor Oil Removal from Contaminated Sand.

The present study describes the production of biosurfactant from isolate B. licheniformis Ali5. Seven different, previously-reported minimal media were screened for biosurfactant production, and two selected media were further optimized for carbon source. Further, various fermentation conditions such as (pH 2-12, temperature 20-50 °C, agitation speed 100-300 rpm, NaCl (0-30 g·L-1) were investigated. The partially purified biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and found a lipopeptide mixture, similar to lichenysin-A. Biosurfactant reduced surface tension from 72.0 to 26.21 ± 0.3 and interfacial tension by 0.26 ± 0.1 mN.m-1 respectively, biosurfactant yield under optimized conditions was 1 g·L-1, with critical micelle concentration (CMC) of 21 mg·L-1 with high emulsification activity of (E24) 66.4 ± 1.4% against crude oil. Biosurfactant was found to be stable over extreme conditions. It also altered the wettability of hydrophobic surface by changing the contact angle from 49.76° to 16.97°. Biosurfactant efficiently removed (70-79%) motor oil from sand, with an efficiency of more than 2 fold as compared without biosurfactant (36-38%). It gave 32% additional oil recovery over residual oil saturation upon application to a sand-packed column. These results are indicative of potential application of biosurfactant in wettability alteration and ex-situ microbial enhanced oil recovery.

Recent Advances in Graphene Oxide Membranes for Gas Separation Applications.

Graphene oxide (GO) can dramatically enhance the gas separation performance of membrane technologies beyond the limits of conventional membrane materials in terms of both permeability and selectivity. Graphene oxide membranes can allow extremely high fluxes because of their ultimate thinness and unique layered structure. In addition, their high selectivity is due to the molecular sieving or diffusion effect resulting from their narrow pore size distribution or their unique surface chemistry. In the first part of this review, we briefly discuss different mechanisms of gas transport through membranes, with an emphasis on the proposed mechanisms for gas separation by GO membranes. In the second part, we review the methods for GO membrane preparation and characterization. In the third part, we provide a critical review of the literature on the application of different types of GO membranes for CO2, H2, and hydrocarbon separation. Finally, we provide recommendations for the development of high-performance GO membranes for gas separation applications.

Current Status of Microporous Metal-Organic Frameworks for Hydrocarbon Separations.

Separation of hydrocarbon mixtures into single components is a very important industrial process because all represent very important energy resources/raw chemicals in the petrochemical industry. The well-established industrial separation technology highly relies on the energy-intensive cryogenic distillation processes. The discovery of new materials capable of separating hydrocarbon mixtures by adsorbent-based separation technologies has the potential to provide more energy-efficient industrial processes with remarkable energy savings. Porous metal-organic frameworks (MOFs), also known as porous coordination polymers, represent a new class of porous materials that offer tremendous promise for hydrocarbon separations because of their easy tunability, designability, and functionality. A number of MOFs have been designed and synthesized to show excellent separation performance on various hydrocarbon separations. Here, we summarize and highlight some recent significant advances in the development of microporous MOFs for hydrocarbon separation applications.

Remediation of oil-based drill cuttings using low-temperature thermal desorption: Performance and kinetics modeling.

A bench-scale apparatus was used for the low-temperature thermal desorption (LTTD) treatment of oil-based drill cuttings (OBDCs). The effects of treatment temperature, treatment duration, sand/OBDCs mixing ratio, and initial oil content on the LTTD treatment performance were investigated. It was found that the petroleum hydrocarbons (PHCs) were barely left in the high-oil-content drill cuttings after LTTD (at 300 °C for 20 min), and thus the overall soil health was improved. The desorption kinetics models of PHCs under various conditions were established, and it was found that the LTTD of OBDCs followed nonlinear least-squares exponential kinetics (adjusted R2 > 0.9). The energy consumption models of LTTD treatment under different temperatures were also developed. The modeling results are of practical guiding significance and useful for designing effective LTTD treatment systems of OBDCs.

Simulating a Spill of Diluted Bitumen: Environmental Weathering and Submergence in a Model Freshwater System.

The main petroleum product transported through pipelines in Canada is diluted bitumen (dilbit), a semiliquid form of heavy crude oil mixed with natural gas condensates to facilitate transport. The weathering, fate, behavior, and environmental effects of dilbit are crucial to consider when responding to a spill; however, few environmental studies on dilbit have been completed. We report on 11-d-long experimental spills of dilbit (Cold Lake Winter Blend) in outdoor microcosms meant to simulate a low-energy aquatic system containing natural lake water and sediments treated with low (1:8000 oil:water) and high (1:800 oil:water) volumes of dilbit. In the first 24 h of the experiment, volatile hydrocarbons quickly evaporated from the dilbit, resulting in increased dilbit density and viscosity. These changes in dilbit's physical and chemical properties ultimately led to its submergence after 8 d. We also detected rapid accumulation of polycyclic aromatic compounds in the water column of the treated microcosms following the spills. The present study provides new information on the environmental fate and behavior of dilbit in a freshwater environment that will be critical to environmental risk assessments of proposed pipeline projects. In particular, the study demonstrates the propensity for dilbit to sink under ambient environmental conditions in freshwaters typical of many boreal lakes. Environ Toxicol Chem 2019;38:2621-2628. © 2019 SETAC.

Parametric optimization of domestic wastewater treatment in an activated sludge sequencing batch reactor using response surface methodology.

In this work, the parametric optimization of real domestic wastewater treated in an activated sludge sequencing batch reactor (SBR) was performed by means of the response surface methodology (RSM). The influences of influent organic matter concentration as chemical oxygen demand (CODinf), biomass concentration (Xs) and aeration time (t) on the COD, organic matter removal efficiency as COD (η) and sludge volume index (SVI) were determined to evaluate the performance of activated sludge SBR. The results showed that organic matter efficiency and maximum SVI were obtained at a t of 12 h, 300 mg L-1 of CODinf and 2000 mg L-1 of Xs. The SBR-activated sludge exhibited a η of 73% and an SVI of 119 mL g-1. Both values indicated a very good performance. Furthermore, the COD of the effluent under these conditions complied with Mexican regulations for wastewater discharged into water bodies.

VOC Profiles of Saliva in Assessment of Halitosis and Submandibular Abscesses Using HS-SPME-GC/MS Technique.

Halitosis and submandibular abscesses are examples of mouth-related diseases with the possible bacterial origin. Salivary volatile organic compounds (VOCs) are potential biomarkers of them, once they can be addressed as metabolites of bacterial activity. Healthy patients (n = 15), subjects with submandibular abscesses located in fascial deep space (n = 10), and subjects with halitosis (n = 5) were enrolled in the study. Saliva samples were subjected to headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC/MS) analysis. A total number of 164 VOCs was detected by the developed methodology, 23 specific for halitosis and 41 for abscess. Halitosis' profiles were characterized by a larger number of sulfur compounds, while for abscess they had a higher variety of alcohols, aldehydes, and hydrocarbons-biomarkers of inflammatory processes. Principal components analysis allowed visualization of clusters formed according to the evaluated conditions. Kruskal-Wallis test indicated that 39 VOCs presented differentiated responses between the studied groups, with statistical relevance (p < 0.05). Random forest was applied, and a prediction model based on eight VOCs (2-butanone, methyl thioacetate, 2-methylbutanoic acid, S-methyl pentanethioate, dimethyl tetrasulfide, indolizine, pentadecane, and octadecanal) provided 100% of sensitivity, 82% of specificity, and 91% of balanced accuracy, indicating the specific presence of submandibular abscess.

Addition Polyalkylnorbornenes: A Promising New Class of Si-Free Membrane Materials for Hydrocarbons Separation.

Nanoporous glassy polymers are perspective materials for the fabrication of gas separation membranes, especially for the application of gaseous hydrocarbon separation. However, the drawback of such materials is the pronounced physical aging resulting in the dramatic drop of gas transport properties due to relaxation of high-free-volume fraction in time. Herein, a novel and readily available group of such glassy polymers is reported based on 5-alkylnorbornenes. These polymers are easily synthesized from dicyclopentadiene and α-olefins by Diels-Alder reaction and vinyl (addition) polymerization of the formed cycloadducts in the presence of ([(η3 -C3 H5 )PdCl]2 /PCy3 /Na+ [B(3,5-(CF3 )2 C6 H3 )4 ]- catalyst. The obtained polymers display low-fraction free volume, stable gas permeability over time, and possess a unique feature for the glassy polymers-solubility controlled permeation of hydrocarbons and enhanced C4 H10 /CH4 selectivity.