Discrimination of plastic waste pyrolysis oil feedstocks using supercritical fluid chromatography

Advanced chemical recycling techniques provide new avenues for handling and recycling mixed plastic waste; pyrolysis is a prominent approach involving heating plastic waste in an oxygen-free environment to create pyrolysis oils. Pyrolysis oils must be thoroughly characterized before being refined into fuels and chemical feedstocks. Here, a method based on supercritical fluid chromatography with ultraviolet detection was developed to analyze plastic waste pyrolysis oils. Multiple stationary phases were examined, and 2-ethyl pyridine was chosen as the best stationary phase for resolving pyrolysis oil components. Different standards and different plastic waste pyrolysis oils were compared across the different stationary phases. Up to three columns were serially coupled to increase efficiency and column capacity. It was found that a general method using ethanol as a modifier and two 2-ethyl pyridine columns could effectively resolve plastic waste pyrolysis oils. The potential for differentiating polyethylene and polypropylene feedstocks was demonstrated using principal component analysis.

Investigation of operational fundamentals for vacuum-assisted headspace high-capacity solid-phase microextraction and gas chromatographic analysis of semivolatile compounds from a model solid sample

Vacuum-assisted headspace solid-phase microextraction (Vac-HS-SPME) is a technique used to enhance SPME sampling of semi-volatile organic compounds. Here, it was combined with a high-capacity SPME Arrow, which features a larger volume of extraction phase and a more rugged configuration than traditional extraction fibers. An in-depth assessment of the critical parameters was conducted to achieve optimal extraction of representative compounds from a model solid sample matrix (Ottawa sand). Operational fundamentals investigated included the types of seals needed to create a leak-free environment under vacuum conditions; the magnitude of the vacuum applied and time needed to activate the Vac kinetics; order of sample vial preparation methods (VPMs); and other standard variables associated with extract analysis by gas chromatography-mass spectrometry. When exploring the limits of sample VPMs, results indicated an ideal workflow requires the solid sample to be spiked before sealing the vial, allow the sample to rest overnight, then apply vacuum at a pressure of -677 mbar (out of -789 mbar maximum possible vacuum with pump and compressor used), exerted on the vial for 90 s. This work provides the necessary workflow for the optimization of Vac-HS-SPME sampling of analytes from solid matrices.

Determination of psilocybin and psilocin content in multiple Psilocybe cubensis mushroom strains using liquid chromatography - tandem mass spectrometry

A method for clinical potency determination of psilocybin and psilocin in hallucinogenic mushroom species Psilocybe cubensis was developed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Five strains of dried, intact mushrooms were obtained and analyzed: Blue Meanie, Creeper, B-Plus, Texas Yellow, and Thai Cubensis. An extraction protocol was developed; this included an evaluation of sample milling technique, extraction solvents, and recovery/stability. Reversed phase chromatography on fused-core particle phases was developed for the determination of the two analytes using internal standard calibration with deuterated isotopologues of each analyte. The separation takes less than 5 min. Matrix effects were investigated by comparing signal response of calibration samples in neat solution and several mushroom matrices; no significant matrix effects were observed. The limit of detection for psilocybin was 1.5 ng/mL (1.5 pg on-column; 300 ng/g mushroom) and for psilocin was 0.15 ng/mL (0.15 pg on-column; 30 ng/g mushroom) using a Shimadzu LCMS-8050 triple quadrupole mass spectrometer. Assessment of the accuracy and precision of the method indicated percent error and RSD were <6 % at all concentration levels. Three whole, intact mushrooms from each strain were analyzed individually to obtain average content differences both between strains and between mushrooms of the same strain. From most to least potent, the study found that the average total psilocybin and psilocin concentrations for the Creeper, Blue Meanie, B+, Texas Yellow, and Thai Cubensis strains were 1.36, 1.221, 1.134, 1.103, and 0.879 % (w/w), respectively. A subset of these mushrooms was also tested in a separate non-affiliated laboratory, and the results were comparable between the two laboratories. Results from the secondary laboratory showed improved precision when multiple mushrooms were homogenized together, prior to extraction.

Thermodynamic characterization of interactions between environmental contaminants and room temperature ionic liquids using static headspace gas chromatography with vacuum ultraviolet detection

Understanding the thermodynamic interactions between an analyte and the sample phase is of paramount importance when choosing a co-solvent in headspace analysis. A sample phase - gas phase equilibrium partition coefficient (Kp) is used fundamentally to describe the distribution of the analyte between the two phases. Kp determinations by headspace gas chromatography (HS-GC) were acquired by two methods: vapor phase calibration (VPC) and phase ratio variation (PRV). Here, we demonstrated a pressurized - loop headspace system in conjunction with gas chromatography vacuum ultraviolet detection (HS-GC-VUV) to directly calculate the concentration of analytes in the gas phase from room temperature ionic liquids (RTILs) sample phases, using pseudo-absolute quantification (PAQ). PAQ, an attribute of VUV detection, allowed for quick determination of Kp and other thermodynamic properties, such as enthalpy (ΔH) and entropy (ΔS) of the system through the use of van't Hoff plots in the temperature range of 70-110 °C. The Kp determinations by PAQ were comparable to those obtained using the VPC method with percent difference ranging from ≤ 1-33%. Kp determinations were made for analytes (cyclohexane, benzene, octane, toluene, chlorobenzene, ethylbenzene, m-,p-, and o-xylene) at the varying temperatures (70-110 °C) using different RTILs (1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ESO₄]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and tris(2-hydroxyethyl)methylammonium methylsulfate ([MTEOA][MeOSO₃])) and (1-ethyl-3-methylimidazolium bis(trisfluoromethanesulfonyl)imide ([EMIM] [NTF₂])). The results from the van't Hoff analysis revealed that [EMIM] cation-based RTILs exhibit strong solute-solvent interactions with analytes that have π- electrons.

Quantitation of small molecules from liquid chromatography-mass spectrometric accurate mass datasets using CycloBranch

Gaussian and exponentially modified Gaussian functions were incorporated into integrating algorithms used by an open-source, cross-platform tool called CycloBranch. The quantitation is demonstrated on bacterial pyoverdines separated by fine isotope features. Using our algorithm, we can separate the m/z values 694.25802 and 694.26731 (a 0.009 Da difference), where the former belongs to the most intense peak of pyoverdine D (PvdD), and the latter to the second most intense peak of pyoverdine E (PvdE) in the respective isotopic clusters of [M + Fe-H]²⁺ ions. The areas under chromatographic curves of standards were analyzed for the limit of detection (LOD), limit of quantitation (LOQ), and regression coefficient calculations. The quantitative module returned a LOD and LOQ of 1.4 and 4.3 ng/mL, respectively, for both PvdD and PvdE in human urine. If present and detected in mass spectra, the intensities of user-defined [M + H]⁺, [M + Na]⁺, [M + K]⁺, [M + Fe-H]²⁺, or other ion types, can be accumulated and used for quantitation. The quantitation result is returned by CycloBranch in seconds or minutes, contrary to an hours-long manual approach, prone to user-born errors originating from necessary copying among various software environments. Native Bruker, Waters, Thermo, txt, mgf, mzML, and mzXML data formats are supported in CycloBranch, which is freely available at https://ms.biomed.cas.cz/cyclobranch.

Solid phase extraction as sample pretreatment method for top-down quantitative analysis of low molecular weight proteins from biological samples using liquid chromatography - triple quadrupole mass spectrometry

Targeting and quantifying intact proteins from biological samples is still a very challenging research area. Several crucial steps exist in the analytical workflow, including development of a reliable sample preparation method. Here, we developed and applied for the first time a non-immunoaffinity sample preparation method based on a generally widely available micro-elution solid phase extraction (μSPE) strategy for the extraction of multiple lower molecular weight intact proteins (<30 kDa) from various biological matrices. Omission of a time-consuming drying and reconstitution step after extraction resulted in a more simple and rapid sample preparation procedure. A model set of eleven intact proteins (molecular weights: 5.5-29 kDa; isoelectric points: 4.5-11.3) were analyzed in multiple biological fluids using reversed-phase liquid chromatography with a triple quadrupole mass spectrometer operated in multiple reaction monitoring mode. Various sample pre-treatment reagents, sorbent types, and washing and elution solvents were experimentally tested and optimized to obtain the μSPE clean-up condition for a broad mixture of intact proteins having variable physicochemical properties. 1% trifluoroacetic acid and 0.2% Triton 100-X were selected as suitable sample pre-treatment reagents for releasing protein-protein interactions in human serum/plasma and human urine, respectively. Hydrophilic lipophilic balanced μSPE sorbent was selected as a high performing stationary phase. Addition of 1% trifluoroacetic acid to all washing and elution solutions showed the most beneficial effect for the extraction recovery of the proteins. Under the optimized conditions, reproducible extraction recoveries >65% for all targeted proteins (up to 30 kDa) in human urine and >50% for most of the proteins in serum/plasma were achieved. The selected conditions were applied also for the analysis of clinical serum and urine samples to demonstrate the feasibility of the developed method to target intact proteins directly by more affordable μSPE sample preparation and triple quadrupole mass spectrometry, which could be beneficial in many application fields.

Accredited Forensics Laboratories Are Not Properly Validating and Controlling Their Blood Alcohol Determination Methods

The lack of proper method validation has important implications in blood alcohol concentration (BAC) determinations. We examine this issue, addressing the importance of gas chromatography (GC) for BAC determination, why certain validation procedures are important, and why accreditation bodies need to step up their game.

Laboratory Accreditation Is Not a Cloak of Infallibility

Those working in a technical field are always trying to innovate and increase operational efficiency to produce the most value out of any given project. This requires making data-driven decisions to identify patterns and to forecast the potential implications of specific strategic moves. As with anything, these decisions are only as good as the information that they are predicated upon, and the data are only as good as the people and processes that generate them.

Unraveling the Complex Composition of Produced Water by Specialized Extraction Methodologies

Produced water (PW), a waste byproduct of oil and gas extraction, is a complex mixture containing numerous organic solubles and elemental species; these constituents range from polycyclic aromatic hydrocarbons to naturally occurring radioactive materials. Identification of these compounds is critical in developing reuse and disposal protocols to minimize environmental contamination and health risks. In this study, versatile extraction methodologies were investigated for the untargeted analysis of PW. Thin-film solid-phase microextraction with hydrophilic-lipophilic balance particles was utilized for the extraction of organic solubles from eight PW samples from the Permian Basin and Eagle Ford formation in Texas. Gas chromatography-mass spectrometry analysis found a total of 266 different organic constituents including 1,4-dioxane, atrazine, pyridine, and PAHs. The elemental composition of PW was evaluated using dispersive solid-phase extraction followed by inductively coupled plasma-mass spectrometry, utilizing a new coordinating sorbent, poly(pyrrole-1-carboxylic acid). This confirmed the presence of 29 elements including rare earth elements, as well as hazardous metals such as Cr, Cd, Pb, and U. Utilizing chemometric analysis, both approaches facilitated the discrimination of each PW sample based on their geochemical origin with a prediction accuracy above 90% using partial least-squares-discriminant analysis, paving the way for PW origin tracing in the environment.

Profiling of contemporary beer styles using liquid chromatography quadrupole time-of-flight mass spectrometry, multivariate analysis, and machine learning techniques

Although all beer is brewed using the same four classes of ingredients, contemporary beer styles show wide variation in flavor and color, suggesting differences in their chemical profiles. A selection of 32 beers covering five styles (India pale ale, blonde, stout, wheat, and sour) were investigated to determine chemical features, which discriminate between popular beer styles. The beers were analyzed in an untargeted fashion using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). The separation and detection method were tuned to include compounds from important beer components, namely iso-α-acids and phenolic compounds. Due to the sheer number of unknown compounds in beer, multivariate analysis and machine learning techniques were used to pinpoint some of the compounds most influential in distinguishing beer styles. It was determined that while many phenols and iso-α-acids were present in the beers, they were not the compounds most responsible for the variations between styles. However, it was possible to discriminate each beer style using multivariate analysis. Principal component analysis (PCA) was able to separate and cluster the individual beer samples by style. A combination of statistical tools were used to predict formulas for some of the most influential metabolites from each style. Machine learning models accurately classified patterns in the five beer styles, indicating that they can be precisely distinguished by their nonvolatile chemical profile.

Exploiting targeted and untargeted approaches for the analysis of bacterial metabolites under altered growth conditions

In the host, pathogenic microorganisms have developed stress responses to cope with constantly changing environments. Stress responses are directly related to changes in several metabolomic pathways, which could hamper microorganisms' unequivocal identification. We evaluated the effect of various in vitro stress conditions (acidic, basic, oxidative, ethanolic, and saline conditions) on the metabolism of Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa, which are common lung pathogens. The metabolite profiles of the bacteria were analyzed using liquid chromatography coupled to triple quadrupole and quadrupole time-of-flight mass spectrometry. The advantages of targeted and untargeted analysis combined with univariate and multivariate statistical analysis (principal component analysis, hierarchical cluster analysis, partial least square discriminant analysis, random forest) were combined to unequivocally identify bacterial species. In normal in vitro conditions, the targeted methodology, based on the analysis of primary metabolites, enabled the rapid and efficient discrimination of the three bacteria. In changing in vitro conditions and specifically in presence of the various stressors, the untargeted methodology proved to be more valuable for the global and accurate differentiation of the three bacteria, also considering the type of stress environment within each species. In addition, species-specific metabolites (i.e., fatty acids, polysaccharides, peptides, and nucleotide bases derivatives) were putatively identified. Good intra-day repeatability and inter-day repeatability (< 10% RSD and < 15% RSD, respectively) were obtained for the targeted and the untargeted methods. This untargeted approach highlights its importance in unusual (and less known) bacterial growth environments, being a powerful tool for infectious disease diagnosis, where the accurate classification of microorganisms is sought.

Interlaboratory study of a supercritical fluid chromatography method for the determination of pharmaceutical impurities: Evaluation of multi-systems reproducibility

Modern supercritical fluid chromatography (SFC) is now a well-established technique, especially in the field of pharmaceutical analysis. We recently demonstrated the transferability and the reproducibility of a SFC-UV method for pharmaceutical impurities by means of an inter-laboratory study. However, as this study involved only one brand of SFC instrumentation (Waters®), the present study extends the purpose to multi-instrumentation evaluation. Specifically, three instrument types, namely Agilent®, Shimadzu®, and Waters®, were included through 21 laboratories (n = 7 for each instrument). First, method transfer was performed to assess the separation quality and to set up the specific instrument parameters of Agilent® and Shimadzu® instruments. Second, the inter-laboratory study was performed following a protocol defined by the sending lab. Analytical results were examined regarding consistencies within- and between-laboratories criteria. Afterwards, the method reproducibility was estimated taking into account variances in replicates, between-days and between-laboratories. Reproducibility variance was larger than that observed during the first study involving only one single type of instrumentation. Indeed, we clearly observed an 'instrument type' effect. Moreover, the reproducibility variance was larger when considering all instruments than each type separately which can be attributed to the variability induced by the instrument configuration. Nevertheless, repeatability and reproducibility variances were found to be similar than those described for LC methods; i.e. reproducibility as %RSD was around 15 %. These results highlighted the robustness and the power of modern analytical SFC technologies to deliver accurate results for pharmaceutical quality control analysis.

Target profiling of beer styles by their iso-α-acid and phenolic content using liquid chromatography-quadrupole time-of-flight-mass spectrometry

Beer styles show wide variation in color, flavor, and clarity, due to differences in their chemical content. Some of the major flavor compounds in beer are isomerized alpha acids and phenolic compounds. These were investigated as potentially discerning features between beer styles. A selection of 32 American beers covering five styles was analyzed using liquid chromatography quadrupole time-of-flight mass spectrometry, which resulted in high mass accuracy chromatograms of the studied analytes. Distinctions between the presence or relative concentrations of certain compounds were observed and related back to brewing ingredients and procedures. For example, vanillin was only observed in stout beers due to the use of roasted barley malts for brewing, while chlorogenic acid isomers were found in two sours at relatively high concentrations (189 and 34 mg/L) because of the fruits used to flavor the beers. Distinctions were further confirmed using multivariate analysis techniques, which separated three of the five beer styles (India pale ales, stouts, and sours).

A review of ASTM D7979 for the analysis of per- and polyfluorinated alkyl substances in non-potable water by co-solvation with methanol and using liquid chromatography-tandem mass spectrometry

Per- and polyfluorinated alkyl substances are large class of man-made compounds known in the media as "forever chemicals". In 2015, ASTM International published ASTM D7979, for the analysis of per- and polyfluorinated alkyl substances in non-potable water samples. This method extracts the substances by co-solvation with methanol and measures targeted compounds using liquid chromatography-tandem mass spectrometry. ASTM D7979 is a performance-based method that analyzes 31 compounds plus 14 isotopically labeled surrogates. The minimum reporting limit is approximately 10 ng/L with an analytical range of 10-200 ng/L for most compounds. Expected recovery of surrogates and spiked matrices is 70-130%. Samples containing high suspended solids can be analyzed with minimal interferences and potential loss of analyte. The method is consistent with ASTM and EPA's sustainable development goals by using reduced volumes of sample, solvent, and minimizing hazardous solvents and sample preparation materials while maintaining data quality and detection limits that are suitable for the intended use. This paper covers the rationale, outlines some of the challenges associated with analysis of per- and polyfluorinated alkyl substances, and describes the steps taken by the ASTM Committee D19 task group to develop, optimize, and validate this method.

Reservoir optimized plunger lift technology reduces hydrocarbon emissions from aging gas wells

Gas well liquification is a problematic process whereby liquids collect in the wellbore and near wellbore reservoir resulting in production impedance in aging gas wells. Removal of these liquids is traditionally performed through human operated blowdown events; however, this practice results in the release of hydrocarbon emissions into the atmosphere. The removal process, called 'deliquification', can also be accomplished through the utilization of various plunger lift technologies. These allow the extraction of retained fluids from the wellbore and near-wellbore reservoir; however, these technologies vary greatly with respect to automation, intelligence, and efficacy. Here we examined the rates of production loss and the frequency of emission events in mature natural gas wells equipped with various automated plunger lift technologies. Overall, 'intelligent' plunger lift systems that base their optimization on reservoir and wellbore conditions, as opposed to standardized or scheduled operations, performed the best exhibiting a 0.13% loss of production gas to atmospheric emissions compared to a 1.37% loss of production observed from wells without a plunger lift system. Additionally, wells equipped with a next generation reservoir optimized plunger lift demonstrated a reduced rate of production decline compared to those wells without a plunger lift technology (-0.066%/day and -0.242%/day, respectively). These data have widespread implications for the operational and environmental management of a consistently increasing count of aging natural gas production wells.

Gas chromatography-vacuum ultraviolet spectroscopic analysis of organosilanes

Organosilanes are used in a broad range of industrial, cosmetic, and personal care products. They serve as bridges between inorganic or organic substrates and organic/polymeric matrices. They are also versatile intermediates and can be used for a variety of synthetic applications. They do not exist naturally and have to be synthesized. Evaluation of intermediates and products resulting from the synthesis processes of organosilanes can be challenging. In this study, gas chromatography with vacuum ultraviolet spectroscopic detection (VUV) was used to analyze Si-containing compounds that are commercially available or were synthetically prepared. VUV measures full scan absorption in the range of 120-240 nm, a region that provides unique absorption signatures for chemical compounds. VUV absorption spectra of organosilanes showed rich and featured characteristics in this wavelength range. Theoretical computations of VUV absorption spectra based on time-dependent density functional theory were also explored as a complementary tool for identification. In addition, the synthesis process of isomeric benzodioxasiline compounds (ortho-, meta-, and para-) was monitored by GC-VUV. It was demonstrated that GC-VUV can be used for easy and rapid differentiation of organosilanes, including structural isomers.

Characterizing anecdotal claims of groundwater contamination in shale energy basins

The increased societal monitoring of unconventional oil and gas development (UD) has brought forth tremendous scrutiny over the environmental stewardship and subsequent public health impacts of surface and sub-surface activities. Concerns over groundwater quality in shale energy basins have prompted concerned citizens into monitoring UD activities for a series of qualitative parameters, and even coordinating sampling efforts for chemical analysis. Here we present a list of analytical parameters, hierarchically structured to guide concerned citizens through an efficient and cost-effective monitoring program. Utilizing this multi-step testing regime, we assessed groundwater quality from 36 private water wells involved in 19 anecdotal claims of alleged UD-related contamination across the Barnett, Eagle Ford, Haynesville, and Marcellus Shale formations in the United States. Our analytical findings aligned with the landowners' accounts of their situation in only 5 of the 36 collected samples, with several cases revealing environmental abnormalities that were unbeknownst to the landowners but likely unrelated to UD activities. These data are some of the first to assess the relationship between landowner perception and analytical determination in a cohort of highly variable anecdotal cases of alleged groundwater contamination, revealing a notable disconnect that is likely attributable to a myriad of societal and environmental factors. The analytical modalities presented here also serve as a step-wise method in a weight of evidence approach to assess the presence or absence of anthropogenic contamination under the most variable hydrogeological conditions.

Effect of difluoroacetic acid and biological matrices on the development of a liquid chromatography-triple quadrupole mass spectrometry method for determination of intact growth factor proteins

In biological systems, variable protein expression is a crucial marker for numerous diseases, including cancer. The vast majority of liquid chromatography-triple quadrupole mass spectrometry-based quantitative protein assays use bottom-up methodologies, where proteins are subjected to proteolytic cleavage prior to analysis. Here, the effect of difluoroacetic acid and biological matrices on the developement of a multiple reaction monitoring based top-down reversed-phase liquid chromatography-triple quadrupole mass spectrometry method for analysis of cancer-related intact proteins was evaluated. Seven growth factors (5.5-26.5 kDa; isoelectric points: 4.6-9.9) were analyzed on a wide-pore C4 column. The optimized method was performed at 30°C, using a 0.2 mL/min flow rate, a 10 %B/min gradient slope, and 0.05% v/v difluoroacetic acid as a mobile phase modifier. The increase of mass spectrometry sensitivity due to the difluoroacetic acid (estimated limits of detection in biological matrices 1-500 ng/mL) significantly varied for proteins with lower and higher charge state distributions. Matrix effects, as well as the specificity of the method were assessed for variable biological samples and pretreatment methods. This work demonstrates method development to improve the ability to target intact proteins directly by more affordable triple quadrupole mass spectrometry instrumentation, which could be beneficial in many application fields.

Simulation of Vacuum Ultraviolet Absorption Spectra: Paraffin, Isoparaffin, Olefin, Naphthene, and Aromatic Hydrocarbon Class Compounds

The advent of a new vacuum ultraviolet (VUV) spectroscopic absorption detector for gas chromatography has enabled applications in many areas. Theoretical simulations of VUV spectra using computational chemistry can aid the new technique in situations where experimental spectra are unavailable. In this study, VUV spectral simulations of paraffin, isoparaffin, olefin, naphthene, and aromatic (PIONA) compounds using time-dependent density functional theory (TDDFT) methods were investigated. Important factors for the simulations, such as functionals/basis sets and formalism of oscillator strength calculations, were examined and parameters for future PIONA compound simulations were obtained by fitting computational results to experimental spectra. The simulations produced satisfactory correlations between experimental observations and theoretical calculations, and enabled potential analysis applications for complex higher distillate fuels, such as diesel fuel. Further improvement of the methods was proposed.

Characterization of ethoxylated alcohols in friction reducers using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

RATIONALE

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) provides detailed information for the analysis of ethoxylated alcohols and polymers. In this study, five friction reducers used in commercial hydraulic fracturing processes were analyzed in their as-received form to identify their ethoxylated alcohol content. The friction reducers were then subjected to lab-simulated downhole conditions. Characterization of friction reducers before and after being subjected to reactive conditions can provide fingerprints associated with produced oilfield waste for source apportionment and information on the stability of these key hydraulic fracturing additives.

METHODS

Five different industrially used friction reducers were analyzed for their ethoxylated alcohol content using MALDI-TOF-MS. Three different matrices were assessed for optimal response: α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid, and 2,5-dihydroxybenzoic acid with 2,2,2-trifluoroethanol (2,5-DHB + E). Reaction times, temperatures, and sample matrices (deionized water, produced water inorganic, produced water, and produced water + shale core) were varied to assess changes in molecular weight distribution and polydispersity of the ethoxylated alcohols relative to their as-received content.

RESULTS

A preference for the 2,5-DHB + E matrix was observed. The friction reducers were found to contain ethoxylated alcohols with carbon chain lengths of 12 and 14 with degrees of ethoxylation ranging from 6 to 18. Upon being subjected to 100°C for 24 hours, the ethoxylated alcohols tended to polymerize further, returning higher average molecular weights. Less polymerization was seen in more complex matrices, as supported by dispersity calculations.

CONCLUSIONS

Ethoxylated alcohol content was effectively determined in friction reducers using MALDI-TOF-MS. Although this is not a new technique to characterize ethoxylated alcohols, it has proven to be a quick and effective way to determine ethoxylated alcohol content in friction reducers in complex oilfield matrices. This technique can be used as a rapid and straightforward way to determine ethoxylated alcohol content in friction reducers and hydraulic fracturing wastewater for fingerprinting.

Online Comprehensive High pH Reversed Phase × Low pH Reversed Phase Approach for Two-Dimensional Separations of Intact Proteins in Top-Down Proteomics

A proof-of-concept study is presented on the use of comprehensive two-dimensional liquid chromatography mass spectrometry (LC × LC-MS) for the separation of intact protein mixtures using a different mobile phase pH in each dimension. This system utilizes mass spectrometry (MS) friendly pH modifiers for the online coupling of high pH reversed phase liquid chromatography (HPH-RPLC) in the first dimension (¹D) followed by low pH reversed phase liquid chromatography (LPH-RPLC) in the second dimension (²D). Owing to the ionic nature of proteins, the use of a different mobile phase pH was successful to provide altered selectivity between the two dimensions, even for closely related protein variants, such as bovine cytochrome c and equine cytochrome c, which differ by only three amino acids. Subminute gradient separation of proteins in the second dimension was successful to minimize analysis time, while maintaining high peak capacity. Unlike peptides, the elution order of studied proteins did not follow their isoelectric points, where acidic proteins would be expected to be more retained at low pH (and basic proteins at high pH). The steep elution isotherms (on-off retention mechanism) of proteins and the very steep gradients utilized in the second-dimension column succeeded in overcoming pH and organic solvent content mismatch. The utility of the system was demonstrated with a mixture of protein standards and an Escherichia coli protein mixture.

A review of the analytical methods used for beer ingredient and finished product analysis and quality control

Beer is an incredibly complex beverage containing more than 3000 different compounds, including carbohydrates, proteins, ions, microbes, organic acids, and polyphenols, among others. Beer becomes even more complex during storage, for over time it may undergo chemical changes that negatively affect the flavor, aroma, and appearance. Thus, it can be expected that maintaining the quality of beer throughout its lifetime is a difficult task. Since it is such a popular drink throughout the world, being familiar with proper analytical techniques for beer evaluation is useful for researchers and brewers. These techniques include, but are not limited to, gas chromatography, liquid chromatography, matrix assisted laser desorption/ionization, capillary electrophoresis, mass spectrometry, ultraviolet-visible spectroscopy, and flame ionization detection. This review aims to summarize the various ingredients and components of beer, discuss how they affect the finished product, and present some of the analytical methods used for quality control and understanding the formation of chemicals in beer during the brewing process.

Comparison of the degree of fouling at various flux rates and modes of operation using forward osmosis for remediation of produced water from unconventional oil and gas development

Driven by increased energy demands and technological advancements, the energy landscape of the United States has been changed by the expansion of unconventional oil and gas extraction. Unconventional development requires well stimulation, which uses millions of gallons of water per well and generates billions of gallons of wastewater annually. The waste matrix, referred to as produced water, has proven to be challenging to treat due to the complex physical, chemical, and biological composition, which can change over the lifetime of a production well. Here, forward osmosis was used as a remediation technique to extract fresh water from produced water procured from the Permian Basin region of west Texas. These data examine the durability of thin-film hollow-fiber membranes by determining how quickly the membranes irreversibly fouled at various flux rates during two modes of operation: a) active layer in contact with the draw solution (AL-DS); and b) active layer in contact with the feed solution (AL-FS). Membranes used in AL-DS mode fouled faster than their counterparts used in AL-FS mode. Additionally, membranes used with higher flux rates fouled more quickly than those used under low flux conditions. Ultimately, it was determined that produced water will require pretreatment prior to being concentrated using forward osmosis.

Supercharging and multiple reaction monitoring of high-molecular-weight intact proteins using triple quadrupole mass spectrometry

RATIONALE

Different supercharging agents were tested to study their effect on the intensity and charge state distributions of high-molecular-weight intact proteins. The goal of this work was to increase chargeability and ionization efficiency for proteins ranging from 66 to 150 kDa, to enable subsequent optimization of multiple reaction monitoring (MRM) mode transitions with a triple quadrupole mass spectrometer for potential top-down quantitative analysis.

METHODS

Supercharging agents, such as meta-nitrobenzyl alcohol (m-NBA), dimethylsulfoxide, trifluoroethanol (TFE), and sulfolane were tested in different concentrations in 50/50 acetonitrile/water with 0.5% formic acid to examine the electrospray ionization response for three model proteins: bovine serum albumin (66 kDa), holo-transferrin (78 kDa), and immunoglobulin G (150 kDa). The settings of ionization source temperature and mobile phase flow rate were also examined. MRM transitions were developed for a wide range of precursor ions for each protein, and limits of detection were determined for the proteins in the presence of favorable additive combinations.

RESULTS

For most of the proteins, m-NBA (1%) and TFE (5%) worked most effectively, both to shift the charge state and increase intensity. This is the first report of the use of TFE as an effective agent for both increasing protein chargeability and ionization response. TFE increased ionization efficiency between 3- and 14-fold for the model proteins studied. Increases in both source temperature and flow rate reduced the magnitude of the average charge state observed. The MRM transitions of six to eight different precursor ions of the proteins were optimized and limits of detection in the nanogram quantity on column were determined.

CONCLUSIONS

The feasibility for top-down quantitative analysis of high-molecular-weight proteins with a triple quadrupole mass spectrometer was demonstrated. Further, additives such as TFE can be highly beneficial for increased chargeability and response of the proteins.

Evaluation of Different Stationary Phases in the Separation of Inter-Cross-Linked Peptides

Chemical cross-linking coupled with mass spectrometry (MS) is becoming a routinely and widely used technique for depicting and constructing protein structures and protein interaction networks. One major challenge for cross-linking/MS is the determination of informative low-abundant inter-cross-linked products, generated within a sample of high complexity. A C18 stationary phase is the conventional means for reversed-phase (RP) separation of inter-cross-linked peptides. Various RP stationary phases, which provide different selectivities and retentions, have been developed as alternatives to C18 stationary phases. In this study, two phenyl-based columns, biphenyl and fluorophenyl, were investigated and compared with a C18 phase for separating BS³ (bis(sulfosuccinimidyl)suberate) cross-linked bovine serum albumin (BSA) and myoglobin by bottom-up proteomics. Fractions from the three columns were collected and analyzed in a linear ion trap (LIT) mass spectrometer for improving detection of low abundant inter-cross-linked peptides. Among these three columns, the fluorophenyl column provides additional ion-exchange interaction and exhibits unique retention in separating the cross-linked peptides. The fractioned data was analyzed in pLink, showing the fluorophenyl column consistently obtained more inter-cross-linked peptide identifications than both C18 and biphenyl columns. For the BSA cross-linked sample, the identified inter-cross-linked peptide numbers of the fluorophenyl to C18 column are 136 to 102 in "low confident" results and 11 to 6 in "high confident" results. The fluorophenyl column could potentially be a better alternative for targeting the low stoichiometric inter-cross-linked peptides.

Use of a Continuous Stirred Tank Reactor for the Determination of Electrospray Response Factors and Its Application to Underivatized Sugars Under Various Solvent Parameters

The relationship between the electrospray ionization (ESI)-mass spectrometric (MS) response of an analyte and its concentration has been well studied for permanently charged and basic analytes in the positive ionization mode, but there has been a lack of research effort for other analytes, and for the negative ionization mode, in general. In this study, this relationship was investigated for various adducts and deprotonated species of glucose, sucrose, and raffinose using a continuous stirred tank reactor (CSTR) coupled with ESI-tandem MS to obtain a continuum of response factors across a wide concentration range in both the positive and negative ionization modes with a single injection under 18 different combinations of solvents and additives. Profiles of response factors vs. concentrations varied widely and were dependent upon the analyte and solvent parameters. The use of ammonium trifluoroacetate resulted in the highest response factors for methanol-based and acetonitrile-based solvents in the positive and negative ionization modes, respectively. Ammonium acetate, ammonium formate, and sodium chloride in 80:20 acetonitrile:water in the negative ionization mode resulted in good linearities, useful for quantitative analysis. In the positive ionization mode, response factors tended to increase with an increase in the molecular weight of the analyte, and acetonitrile was generally found to decrease response factors. We have also demonstrated the ability of CSTR-ESI-MS to visualize ionization suppression in the presence of co-analytes. These data should be useful for liquid chromatography-ESI-MS method development for sugar analysis, to help guide the choice of mobile phase that will result in high sensitivity and linearity. Graphical Abstract.

Forward osmosis remediation of high salinity Permian Basin produced water from unconventional oil and gas development

Unconventional oil and gas operations are on the rise, and they are an integral component to meeting the nation's energy needs. Produced water is the primary by-product of oil and gas operations, and it has proven challenging to treat to date. The aim of this study was to evaluate the feasibility of using forward osmosis with thin-film composite hollow fiber membranes as a remediation option for produced water with high total dissolved solids levels from the Permian Basin. Trials consisted of a series of 5 experiments in order to evaluate the performance of the membrane. Three PW samples, each from different locations, were used to conduct the series of experiments and compare the performance of the membranes on samples with TDS levels ranging from 16,000 to 210,000 mg/L. It was concluded that forward osmosis can be used to extract water from high salinity oil field brines and PW. Flux decreased over the course of the trials due to a combination of membrane fouling, concentration polarization, and temperature fluctuations. The flux of the PW was similar to the flux measured for the PW mimic with small difference due to the influence of activity on the osmotic pressure. The flux was also influenced by temperature and the linear velocity of the feed solution and draw solution.

Lab-simulated downhole leaching of formaldehyde from proppants by high performance liquid chromatography (HPLC), headspace gas chromatography-vacuum ultraviolet (HS-GC-VUV) spectroscopy, and headspace gas chromatography-mass spectrometry (HS-GC-MS)

The ability of different methods to analyze formaldehyde and other leachates from proppants was investigated under lab-simulated downhole conditions. These methods include high performance liquid chromatography (HPLC), headspace gas chromatography-vacuum ultraviolet spectroscopy (HS-GC-VUV), and headspace gas chromatography-mass spectrometry (HS-GC-MS). Two different types of resin-coated proppants, phenol-formaldehyde- and polyurethane-based, were examined. Each proppant was tested at different time intervals (1, 4, 15, 20, or 25 hours) to determine the timeframe for chemical dissolution. Analyses were performed at room temperature and heated (93 °C) to examine how temperature affected the concentration of leachates. Multiple matrices were examined to mimic conditions in subsurface environment including deionized water, a solution surrogate to mimic the ionic concentration of produced water, and recovered produced water. The complexity of these samples was further enhanced to simulate downhole conditions by the addition of shale core. The influence of matrix components on the analysis of formaldehyde was greatly correlated to the quantity of formaldehyde measured. Of the three techniques surveyed, HS-GC-MS was found to be better suited for the analysis of formaldehyde leachates in complex samples. It was found that phenol-formaldehyde resin coated proppants leached higher concentrations of formaldehyde than the polyurethane resin coated proppants.

Analysis of bacteria stress responses to contaminants derived from shale energy extraction

In order to survive environmental changes, bacteria have stress responses, which protect them from adverse and variable conditions. Contamination can be a source of stress and bacterial responses can serve as an indicator of environmental abnormality. In this work, the biochemical effects of toxic compounds that stem from hydraulic fracturing were measured on the whole cell-derived fatty acid and protein compositions of Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas stutzeri, Aeromonas hydrophila, Bacillus cereus, and Bacillus subtilis. These microorganisms were exposed to elevated levels of benzene, ethanol, propanol, toluene, and salt. These were chosen to represent significant subsurface contamination or a surface spill. The fatty acid and protein profiles for the bacteria were analyzed using gas chromatography - vacuum ultraviolet spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry, respectively. Overall, different fatty acid and protein profiles were observed when the microorganisms were grown in the presence of the toxic compounds. The cells exhibited an increase in the saturated/unsaturated ratio and displayed the presence of branched and cyclopropane fatty acids when in the presence of common fracture fluid constituents to decrease membrane permeability which was confirmed by the analysis of produced water. This approach provides a potentially useful tool for environmental diagnosis, since proteins and fatty acids can act as a harbinger of ecological health.

Treatment modalities for the reuse of produced waste from oil and gas development

Unconventional oil and gas development is achieved through a series of sub-processes, which utilize large amounts of water, proppant, and chemical additives to retrieve sequestered hydrocarbons from low permeability petroliferous strata. As a result, a large amount of wastewater is produced, which is traditionally disposed of via subsurface injection into non-productive stratum throughout the country. However, this method of waste management has been linked to the induction of seismic events in a number of regions across North America, calling into question the environmental stewardship and sustainability of subsurface waste disposal. Advancements in water treatment technologies have improved the efficacy and financial viability of produced water recycling for beneficial reuse in the oil and gas sector. This review will cover the various treatment options that are currently being utilized in shale energy basins to remove organic, inorganic, and biological constituents, as well as some emerging technologies that are designed to remove pertinent contaminants that would otherwise preclude the reuse of produced water for production well stimulation.

Characterizing variable biogeochemical changes during the treatment of produced oilfield waste

At the forefront of the discussions about climate change and energy independence has been the process of hydraulic fracturing, which utilizes large amounts of water, proppants, and chemical additives to stimulate sequestered hydrocarbons from impermeable subsurface strata. This process also produces large amounts of heterogeneous flowback and formation waters, the subsurface disposal of which has most recently been linked to the induction of anthropogenic earthquakes. As such, the management of these waste streams has provided a newfound impetus to explore recycling alternatives to reduce the reliance on subsurface disposal and fresh water resources. However, the biogeochemical characteristics of produced oilfield waste render its recycling and reutilization for production well stimulation a substantial challenge. Here we present a comprehensive analysis of produced waste from the Eagle Ford shale region before, during, and after treatment through adjustable separation, flocculation, and disinfection technologies. The collection of bulk measurements revealed significant reductions in suspended and dissolved constituents that could otherwise preclude untreated produced water from being utilized for production well stimulation. Additionally, a significant step-wise reduction in pertinent scaling and well-fouling elements was observed, in conjunction with notable fluctuations in the microbiomes of highly variable produced waters. Collectively, these data provide insight into the efficacies of available water treatment modalities within the shale energy sector, which is currently challenged with improving the environmental stewardship of produced water management.

Effects of solvent parameters on the electrospray ionization tandem mass spectrometry response of glucose

RATIONALE

The importance of saccharides, the most abundant biomolecules on Earth, extends beyond their biological roles and to consumer products and industrial processes. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) is an attractive tool for the analysis of underivatized saccharides (US), but they tend to have relatively low sensitivities due to their low surface activities and lack of easily protonable or deprotonable chemical groups. An understanding of the influences that solvent parameters have on their signal intensities would enhance the usefulness of ESI-MS/MS for their analysis.

METHODS

Solutions of glucose, a model analyte for US, in various combinations of solvent, additive, additive concentration, and pH were analyzed by flow injection analysis ESI-MS/MS in both the positive and negative ionization mode. The blank-corrected signal intensities of the solvent parameter combinations were then compared.

RESULTS

The addition of acetonitrile led to severe ionization suppression in the positive ionization mode through its competition with glucose for cation adduction. High signal intensity was achieved under wide pH and concentration ranges for methanol: water solutions containing ammonium trifluoroacetate in the positive ionization mode. The highest signal intensities for acetonitrile: water solutions were those containing ammonium formate or lithium fluoride in the negative ionization mode.

CONCLUSIONS

An understanding of the influence of solvent parameters on the signal intensity of a given analyte is useful for guiding the selection process of mobile phases/flow solvents that lead to low limits of detection or the minimization of matrix effects by allowing its detection at high dilution factors.

An integrated multipath liquid chromatography-mass spectrometry system for the simultaneous preparation, separation, and detection of proteins and small molecules

A multipath liquid chromatography with mass spectrometry instrument was constructed with the help of restricted access media to online segregate small and large molecules. This liquid chromatography system was custom built with five pumps and three two-position six-port valves to control the flow in a multipath system for the simultaneous analysis of small molecules and proteins. On separate chromatographic channels, small molecules trapped and proteins excluded from the online restricted access media were analyzed downstream using high-efficiency columns and a triple quadrupole mass spectrometer. A model sample, which included five proteins and 22 small molecules with different physicochemical properties, was used to evaluate the system. Following injection, the complete multipath separation and detection was performed in 22 min. Protein exclusion by the restricted access media was not quantitative. Four commercial trap columns were evaluated for their exclusion efficiency toward the proteins. Exclusion efficiency varied from <50% to only a maximum of 75% exclusion across the trap columns tested. An attempt was made to optimize the exclusion efficiency using different flow rates, flow rate gradients, and different additives both in the sample and the mobile phases. Protein exclusion was still erratic and generally nonquantitative.

Characterization of bacterial diversity in contaminated groundwater using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Groundwater is a major source for drinking water in the United States, and therefore, its quality and quantity is of extreme importance. One major concern that has emerged is the possible contamination of groundwater due to the unconventional oil and gas extraction activities. As such, the impacts of exogenous contaminants on microbial ecology is an area to be explored to understand what are the chemical and physical conditions that allow the proliferation of pathogenic bacteria and to find alternatives for water treatment by identifying organic-degrading bacteria. In this work, we assess the interplay between groundwater quality and the microbiome in contaminated groundwaters rich in hydrocarbon gases, volatile organic and inorganic compounds, and various metals. Opportunistic pathogenic bacteria, such as Aeromonas hydrophila, Bacillus cereus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia, were identified, increasing the risk for consumption of and exposure to these contaminated groundwaters. Additionally, antimicrobial tests revealed that many of the identified bacteria were resistant to different antibiotics. The MALDI-TOF MS results were successfully confirmed with 16S rRNA gene sequencing, proving the accuracy of this high-throughput method. Collectively, these data provide a seminal understanding of the microbial populations in contaminated groundwater overlying anthropogenic activities like unconventional oil and gas development.