Dual-column Liquid Chromatography Research Articles

High-Throughput Proteomics Enabled by a Fully Automated Dual-Trap and Dual-Column LC-MS.

This Technical Note describes a dual-column liquid chromatography system coupled to mass spectrometry (LC-MS) for high-throughput bottom-up proteomic analysis. This system made full use of two 2-position 10-port valves and a binary pump with an integrated loading pump of a commercial LC instrument to provide successive operation of two parallel subsystems. Each subsystem consisted of a set of trap columns and an analytical column. A T-junction union was used to split the mobile phase from the loading pump into two parts. This allowed one set of columns to be washed and equilibrated, followed by the injection of the next sample, while the previous sample was eluting and being analyzed on the other set of columns, thereby greatly increasing the analysis throughput. This approach showed high reproducibility for the analysis of HeLa tryptic digests with average relative standard deviation (RSD) values of 1.75%, 6.90%, and 5.19% for the identification number of proteins, peptides, and peptide-spectrum matches (PSMs), respectively, across 10 consecutive runs. The capacity for peptide and protein identification, as well as proteome depth, of the dual-column LC system was comparable to a conventional single-column system. Due to its simple equipment requirements and set up process, this method should be highly accessible for other laboratories.

Characterizing substrate utilization during the fasted state using plasma high-resolution metabolomics

ObjectivesHigh-resolution metabolomics enables global assessment of metabolites and molecular pathways underlying physiologic processes, including substrate utilization during the fasted state. The clinical index for substrate utilization, respiratory exchange ratio (RER), is measured via indirect calorimetry. The aim of this pilot study was to use metabolomics to identify metabolic pathways and plasma metabolites associated with substrate utilization in healthy, fasted adults. MethodsThis cross-sectional study included 33 adults (mean age 27.7 ± 4.9 y, mean body mass index 24.8 ± 4 kg/m2). Participants underwent indirect calorimetry to determine resting RER after an overnight fast. Untargeted metabolomics was performed on fasted plasma samples using dual-column liquid chromatography and ultra-high-resolution mass spectrometry. Linear regression and pathway enrichment analyses identified pathways and metabolites associated with substrate utilization measured with indirect calorimetry. ResultsRER was significantly associated with 1389 metabolites enriched within 13 metabolic pathways (P < 0.05). Lipid-related findings included general pathways, such as fatty acid activation, and specific pathways, such as C21-steroid hormone biosynthesis and metabolism, butyrate metabolism, and carnitine shuttle. Amino acid pathways included those central to metabolism, such as glucogenic amino acids, and pathways needed to maintain reduction-oxidation reactions, such as methionine and cysteine metabolism. Galactose and pyrimidine metabolism were also associated with RER (all P < 0.05). ConclusionsThe fasting plasma metabolome reflects the diverse macronutrient pathways involved in carbohydrate, amino acid, and lipid metabolism during the fasted state in healthy adults. Future studies should consider the utility of metabolomics to profile individual nutrient requirements and compare findings reported here to clinical populations.

The impact of occupational exposure to dioxins and dioxin-like compounds on the blood metabolome

BACKGROUND AND AIM: Dioxins and dioxin-like compounds are a group of recognized environmental pollutants associated with an increase in all cancer combined. Evidence for specific cancer sites is more limited to non-Hodgkin lymphoma, an immune-related cancer. Our aim is to broaden our mechanistic understanding of metabolome alterations associated with dioxins and dioxin-like compounds, and link these metabolic changes to immunological markers. METHODS: 139 workers from two chlorophenoxy herbicides factories, who had been exposed to dioxins and dioxin-like compounds more than 30 years before blood collection were included. Blood levels of 21 dioxins, dioxin-like furans and biphenyls were determined, and historical 2,3,7,8-tetrachlorodibenzo-p-dioxin levels were estimated using a one-compartment first order kinetic model. Plasma metabolites were measured using dual column liquid chromatography with high-resolution mass spectrometry. A metabolome-wide association study (MWAS), based on linear regression and 20% false discovery rate, was used to evaluate the relationship between metabolic features and exposures. Enrichment of biological pathways was investigated using Mummichog. Differential network analysis was applied to link changed metabolic features to immunological markers. RESULTS:MWAS identified 1157 metabolic features associated with at least one dioxin species, with the majority associated with dioxin-like furans and biphenyls. Metabolic pathway enrichment identified 15 pathways associated with exposure, including pathways of de novo fatty acid biosynthesis, fatty acid activation, omega-3 fatty acid metabolism, fatty acids metabolism and linoleate metabolism, some of which have been previously observed in animal models and human studies exposed to dioxin-like compounds. Other lipid species, including glycerophospholipid, glycosphingolipid, leukotriene, androgen and estrogen were also identified. Besides inflammation mediators (arachidonic acid, prostaglandin, leukotriene), immunological markers were related to fatty acids and cell membrane lipids, which also participate in immune regulation and signaling. CONCLUSIONS:Our results emphasize the metabolome-regulated potency of dioxin-like compounds, mainly on disruption of lipid metabolism especially fatty acids, and provide further plausibility for immunotoxicity mechanism in human. KEYWORDS: dioxin-like compounds, untargeted metabolomics, immunotoxicity, metabolic pathway enrichment

Metabolomic Profiling Demonstrates Postprandial Changes in Saturated Fatty Acids and Glycerophospholipids Are Associated With Fasting Inflammation

ObjectivesMetabolic flexibility is the responsiveness to heterogeneous physiologic conditions, such as food ingestion. A key unresolved question is how inflammation affects metabolic flexibility. Our study objective was to compare metabolic flexibility, specifically the metabolomic response to a standardized meal, by fasting inflammation status, among Guatemalan adults. MethodsParticipants (n = 302, median age 44 years, 43.7% men) received a standardized, mixed-macronutrient liquid meal. Plasma samples (fasting, 2 hr post-meal) were assayed by dual column liquid chromatography (reverse phase [C18] and hydrophilic interaction liquid chromatography [HILIC]) with ultra-high resolution mass spectrometry, and for concentrations of 6 inflammation biomarkers (hsCRP, leptin, resistin, IL-10, adiponectin, TNFsR). We summed the 6 fasting inflammation biomarker Z-scores, after reverse-coding of anti-inflammation biomarkers. For feature selection, we identified features with peak areas differing between fasting and post-meal (FDR-adjusted q < 0.05) and compared median log2 postprandial/fasting peak area ratios by inflammation indicators. Results1,397 C18 and 967 HILIC features had significant log2 postprandial/fasting peak area ratios (q < 0.05). These log2 feature peak area ratios clustered differentially between people in the lowest tertile vs higher 2 tertiles of the inflammation index. The inflammation index was directly associated with log2 ratios of arachidic acid, and inversely associated with log2 ratios of caproic acid and lysophosphatidic acid, adjusting for age and sex (all P < 0.05). The log2 ratio of arachidic acid was negatively correlated with resistin, IL-10, adiponectin, and TNFsR concentrations (all P < 0.05). The log2 ratio of caproic acid was positively correlated with adiponectin and IL-10 concentrations, and negatively correlated with hsCRP concentration (all P < 0.05). The log2 ratio of lysophosphatidic acid was positively correlated with IL-10 and adiponectin, and log2 ratio of phosphatidylinositol was positively correlated with hsCRP (all P < 0.05). ConclusionsOur findings showed that postprandial responses of saturated fatty acids and glycerophospholipids were associated with fasting inflammation. Funding SourcesNational Institutes of Health (HD075784, HL007745).

Metabolomic Associations with Serum Bone Turnover Markers.

Bone is a dynamic tissue that is in a constant state of remodeling. Bone turnover markers (BTMs), procollagen type I N-terminal propeptide (P1NP) and C-terminal telopeptides of type I collagen (CTX), provide sensitive measures of bone formation and resorption, respectively. This study used ultra-high-resolution metabolomics (HRM) to determine plasma metabolic pathways and targeted metabolites related to the markers of bone resorption and formation in adults. This cross-sectional clinical study included 34 adults (19 females, mean 27.8 years), without reported illnesses, recruited from a US metropolitan area. Serum BTM levels were quantified by an ELISA. Plasma HRM utilized dual-column liquid chromatography and mass spectrometry to identify metabolites and metabolic pathways associated with BTMs. Metabolites significantly associated with P1NP (p < 0.05) were significantly enriched in pathways linked to the TCA cycle, pyruvate metabolism, and metabolism of B vitamins important for energy production (e.g., niacin, thiamin). Other nutrition-related metabolic pathways associated with P1NP were amino acid (proline, arginine, glutamate) and vitamin C metabolism, which are important for collagen formation. Metabolites associated with CTX levels (p < 0.05) were enriched within lipid and fatty acid beta-oxidation metabolic pathways, as well as fat-soluble micronutrient pathways including, vitamin D metabolism, vitamin E metabolism, and bile acid biosynthesis. P1NP and CTX were significantly related to microbiome-related metabolites (p < 0.05). Macronutrient-related pathways including lipid, carbohydrate, and amino acid metabolism, as well as several gut microbiome-derived metabolites were significantly related to BTMs. Future research should compare metabolism BTMs relationships reported here to aging and clinical populations to inform targeted therapeutic interventions.

Metabolomic Profiling After a Meal Shows Greater Changes and Lower Metabolic Flexibility in Cardiometabolic Diseases.

ContextMetabolic flexibility is the physiologic acclimatization to differing energy availability and requirement states. Effectively maintaining metabolic flexibility remains challenging, particularly since metabolic dysregulations in meal consumption during cardiometabolic disease (CMD) pathophysiology are incompletely understood. ObjectiveWe compared metabolic flexibility following consumption of a standardized meal challenge among adults with or without CMDs. Design, Setting, and ParticipantsStudy participants (n = 349; age 37-54 years, 55% female) received a standardized meal challenge (520 kcal, 67.4 g carbohydrates, 24.3 g fat, 8.0 g protein; 259 mL). Blood samples were collected at baseline and 2 hours postchallenge. Plasma samples were assayed by high-resolution, nontargeted metabolomics with dual-column liquid chromatography and ultrahigh-resolution mass spectrometry. Metabolome-wide associations between features and meal challenge timepoint were assessed in multivariable linear regression models. ResultsSixty-five percent of participants had ≥1 of 4 CMDs: 33% were obese, 6% had diabetes, 39% had hypertension, and 50% had metabolic syndrome. Log2-normalized ratios of feature peak areas (postprandial:fasting) clustered separately among participants with versus without any CMDs. Among participants with CMDs, the meal challenge altered 1756 feature peak areas (1063 reversed-phase [C18], 693 hydrophilic interaction liquid chromatography [HILIC]; all q < 0.05). In individuals without CMDs, the meal challenge changed 1383 feature peak areas (875 C18; 508 HILIC; all q < 0.05). There were 108 features (60 C18; 48 HILIC) that differed by the meal challenge and CMD status, including dipeptides, carnitines, glycerophospholipids, and a bile acid metabolite (all P < 0.05). ConclusionsAmong adults with CMDs, more metabolomic features differed after a meal challenge, which reflected lower metabolic flexibility relative to individuals without CMDs.

Novel Metabolic Pathways Associated with Serum Bone Turnover Markers in Healthy Young Adults

Abstract Objectives Optimal bone health is maintained through a remodeling cycle consisting of resorption followed by formation. Procollagen type I N-terminal propeptide (P1NP) and C-terminal telopeptides of type I collagen (CTX) are biomarkers of bone metabolism that capture changes in bone formation and bone resorption, respectively. This study aimed to identify unique metabolic pathways related to bone turnover markers (BTMs) in healthy young adults. Methods This cross-sectional study included 34 healthy, young adults (19 females, average age 27.8 years). Bone mineral density (BMD) was assessed by dual-energy x-ray absorptiometry. Fasting plasma was analyzed using dual column liquid chromatography and ultra-high-resolution mass spectrometry for metabolomics. Serum levels of P1NP and CTX were measured with ELISA. Linear regression and pathway enrichment analyses were used to identify metabolic pathways related to the BTMs. Results All participants had a normal whole-body BMD T-score. Metabolites significantly associated with P1NP (at P &amp;lt; 0.05) were significantly enriched in pathways linked to the TCA cycle, pyruvate metabolism, and metabolism of B-vitamins important for energy production (e.g., niacin, thiamin). Other nutrition-related metabolic pathways associated with P1NP were amino acid (proline, arginine, glutamate) and vitamin C metabolism, which are important for collagen formation. Metabolites were associated with CTX levels (at P &amp;lt; 0.05), which were enriched within lipid and fatty acid beta-oxidation metabolic pathways, as well as fat soluble micronutrients pathways including, vitamin D metabolism, vitamin E metabolism, and bile acid biosynthesis. Conclusions High-resolution metabolomics identified several distinct plasma metabolic pathways, including energy-yielding metabolic pathways and pathways related to fatty acid, amino acid, and micronutrient metabolism that were associated with markers of bone formation and bone resorption. Characterizing these metabolism-related pathways associated with BTMs in healthy adults is an important step towards understanding the metabolic perturbations that lead to low bone mass in older and clinical populations. Funding Sources National Institutes of Health and Emory University.

Metabolomic Profile Responses to a Standardized Meal Challenge Differ by Cardiometabolic Disease Status

Abstract Objectives Metabolic flexibility is the physiologic adaptation to differing energy availability and requirement states, such as during meal consumption. Metabolic inflexibility is definitional of some cardiometabolic diseases (CMDs), however the metabolomic profile response (metabolomic flexibility) after meal consumption, relative to a fasting state, in CMDs remains unclear. We compared metabolomic flexibility following consumption of a standardized meal challenge among adults with or without CMDs. Methods Study participants (n = 349; 37–54 years, 55% female) received a standardized meal challenge (520 kcal, 67.4 g carbohydrates, 24.3 g fat, 8.0 g protein; 259 mL). Blood samples were collected at baseline and two hours post-challenge. Plasma samples were assayed by high-resolution metabolomic profiling with dual column liquid chromatography (carbon 18 (C18], negative electrospray ionization; hydrophilic interaction liquid chromatography [HILIC], positive electrospray ionization) coupled to ultra-high-resolution mass spectrometry. Participants were categorized by obesity, hypertension, diabetes and metabolic syndrome. Metabolome-wide associations between features and meal challenge timepoint were assessed in feature-by-feature multivariate generalized linear regression models, including disease profile, age, and sex. Results Two hundred and twenty-six participants (65%) had at least one of the four CMDs: 33% were considered obese, 6% had diabetes, 39% had hypertension, and 50% had metabolic syndrome. Log2-normalized ratios of feature peak areas (post-prandial: fasting) clustered separately among participants with versus without any CMDs. Among participants with CMDs, the meal challenge altered &amp;gt;1700 feature peak areas (all q &amp;lt; 0.05). In individuals without CMDs, the meal challenge changed &amp;gt;1100 feature peak areas (all q &amp;lt; 0.05). The response to the meal challenge of &amp;gt; 100 feature peak areas (C18, HILIC) differed by CMD status (all P &amp;lt; 0.05). These features included dipeptides, lipids (carnitines, glycerophospholipids), and a bile acid metabolite (all P &amp;lt; 0.05). Conclusions Compared to individuals without CMDs, macronutrient metabolism following a standardized meal challenge differed among those with CMDs, reflecting altered metabolic flexibility. Funding Sources National Institutes of Health.

Metabolome Wide Association Study and the Exposome: Linking Exposure to Internal Dose, Biological Response and Disease

The metabolic phenotype provides a central measure linking exposure to internal dose, biological response and disease. Use in molecular and environmental epidemiology studies demonstrate application of metabolomic techniques for new insight into how environment contributes to disease; however, key data analyses issues include the need to protect against false discovery, the use of unidentified measures in analysis and strategies to link multiple significant features into common conceptual models for interpretation. In this presentation, we will demonstrate how biological network inference can be applied through a metabolome-wide association framework to delineate exposure biological response in complex organisms and human populations. Applications will include a multi-platform, mass spectrometry-based approach providing in-depth coverage of the exposome and metabolome to characterize a C. elegans exposome model, a critically-ill population and patients with primary sclerosing cholangitis. Results from these studies show gas-chromatography with ultra-high resolution mass spectrometry (UHRMS) makes possible detection &amp;gt;75,000 molecular features in plasma, which includes &amp;gt;250 confirmed environmental pollutants. HRM by dual column liquid chromatography with UHRMS detects over 25,000 chemical signals that arise from core nutrient metabolism, lipids, the microbiome, diet-derived chemicals, pharmaceuticals and environmental contaminants, providing measures of biological response, metabolic health and toxicodynamics. Integration of these two platforms and identifying how network topology is associated with metabolic pathway enrichment allows identified and unidentified metabolic signals to be linked to underlying exposure and disease pathobiology. Combined with complementary OMIC measures, such as gene expression, epigenetic and proteomic changes, now makes possible a systems-biology understanding of chemical toxicology and environmental health in humans.

Development of simultaneous targeted metabolite quantification and untargeted metabolomics strategy using dual-column liquid chromatography coupled with tandem mass spectrometry

Targeted quantification and untargeted global profiling are the two mainstream approaches, a merging of which could provide enhanced analytical potential in metabolomics research. Here, a simultaneous targeted quantification and untargeted metabolomics (STQUM) strategy was developed for more efficient, accurate and comprehensive metabolomics research by using ultra-high-performance liquid chromatography coupled with high-resolution tandem mass spectrometry (UPLC-HRMS/MS). First, we selected 110 cancer-related metabolites as targets and established a dual LC sequential separation method for simultaneous analysis of strong and weak polar metabolites. In order to achieve efficient acquisition for synchronous qualitative and quantitative analysis, high-resolution, data-dependent parallel reaction monitoring (PRM) method and data-independent all ion fragmentation (AIF) method were established. Their performance in targeted confirmation and quantification, and untargeted analysis were systematically investigated and assessed. In total, 78 metabolites were confidently confirmed in positive ion mode in both PRM and AIF assays, in which 73 metabolites can be accurately quantified. In addition, simultaneously untargeted profiling of 4651 features of high reliability and validity were achieved. Both AIF and PRM methods revealed high confidence, sensitivity and accuracy. In the STQUM approach, another 15 metabolites could be accurately quantified in negative ion mode. The method offers a new perspective for merging the hypothesis-based targeted quantitative validation and untargeted biomarkers discovery in one run for improved analysis efficiency and integrity.

Lewisite Metabolites in Urine by Solid Phase Extraction-Dual Column Reversed-Phase Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry.

Lewisite (2-chlorovinyldichloroarsine) is a chemical warfare agent developed during World War I. A quantitative method using solid phase extraction (SPE) followed by dual column liquid chromatography (LC)-isotope dilution tandem mass spectrometry(MS-MS) was developed for the determination of (2-chlorovinyl)arsonic acid (CVAOA), a metabolite of Lewisite, in human urine. The sample was treated with hydrogen peroxide to oxidize any (2-chlorovinyl)arsonous acid (CVAA) that remained in the trivalent arsenic oxidation state. There was 1.19% (arsenic purity) of bis-(2-chlorovinyl)arsinic acid (BCVAOA), a minor Lewisite metabolite, in the stock CVAA material. The high-throughput method qualitatively assessed BCVAOA simultaneously utilizing normal-phase silica SPE followed by reversed-phase C18 LC for an orthogonal separation. The chromatographic method results in a5.8-min cycle time with adequate retention (k'=2.4) of CVAOA. The mass spectrometer was operated in positive electrospray ionization mode with quantitativem/z 186.9→61.0 and confirmation 186.9→91.0 mass transitions. This selective method demonstrated linearity, accuracy and reproducibility for the clinically relevant calibration range (25-3,200 µg/L as CVAA). The method detection limit was 3.3 µg/L as CVAA from a 10µL injection. This LC-MS-MS emergency response method has a throughput of >240 samples(2.5 extracted 96-well plates) per day.

Multiresidue trace analysis of pharmaceuticals, their human metabolites and transformation products by fully automated on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry

A novel, fully automated analytical methodology based on dual column liquid chromatography coupled to tandem mass spectrometry (LC-LC-MS2) has been developed and validated for the analysis of 12 pharmaceuticals and 20 metabolites and transformation products in different types of water (influent and effluent wastewaters and surface water). Two LC columns were used – one for pre-concentration of the sample and the second for separation and analysis – so that water samples were injected directly in the chromatographic system. Besides the many advantages of the methodology, such as minimization of the sample volume required and its manipulation, both compounds ionized in positive and negative mode could be analyzed simultaneously without compromising the sensitivity. A comparative study of different mobile phases, gradients and LC pre-concentration columns was carried out to obtain the best analytical performance. Limits of detection (MLODs) achieved were in the low ngL−1 range for all the compounds. The method was successfully applied to study the presence of the target analytes in different wastewater and surface water samples collected near the city of Girona (Catalonia, Spain). Data on the environmental presence and fate of pharmaceutical metabolites and TPs is still scarce, highlighting the relevance of the developed methodology.

Multi-residue analytical method for the determination of endocrine disruptors and related compounds in river and waste water using dual column liquid chromatography switching system coupled to mass spectrometry

The present study describes a novel, fully automated method, based on column switching using EQuan™ columns for an integrated sample preconcentration and liquid chromatography coupled to tandem mass spectrometry (LC–LC–MS/MS). The method allows the unequivocal identification and quantification of the most relevant environmental endocrine disruptors compounds (EDCs) and compounds suspected to be EDCs, such as natural and synthetic estrogens and their conjugates, antimicrobials, parabens, bisphenol A, alkylphenolic compounds, benzotriazoles, and organophosphorus flame retardants, in surface river water and wastewater samples.Applying this technique, water samples were directly injected into the chromatographic system and the target compounds were concentrated into the loading column. Thereafter, the analytes were transferred into the analytical column for subsequent detection by MS–MS (QqQ). A comparative study employing three types of columns, with different chemical modifications, was performed in order to determine the optimal column that allowed maximum retention and subsequent elution of the analytes. Using this new optimized methodology a fast and easy online methodology for the analysis of EDCs in surface river water and wastewater with low limits of quantification (LOQ) was obtained. LOQs ranged from 0.008 to 1.54ng/L for surface river water and from 0.178/0.364 to 12.5/25.0ng/L (except for alkylphenol monoethoxylates) for effluent/influent waste water. Moreover, employing approximately 1h, a complete analysis was performed which was significant improvement in comparison to other methods reported previously.This method was used to track the presence and fate of target compounds in the Ebro River which is the most important river in Spain whose intensive agricultural and industrial activities concentrate mainly close to the main cities in the basin, deteriorating soil and water quality.

Increasing sample throughput in pharmacological studies by using dual-column liquid chromatography with tandem mass spectrometry

A robust novel technology of parallel chromatography combined with tandem mass spectrometry was successfully applied to a biological matrix extract for analyte detection. The presented study shows how only by using an additional isocratic pump, a second column and a 10-port valve the throughput is twice of that of a conventional single column system with the same sensitivity. Analytes and matrix were separated and eluting peaks of the first column were detected while the second column was equilibrated. The system was tested and used for the determination of several drugs, metabolites and endogenous compounds (i.e., propiverine, talinolol, scopolamine and leukotrienes).

Affinity–reversed-phase liquid chromatography assay to quantitate recombinant antibodies and antibody fragments in fermentation broth

An automated dual-column liquid chromatography assay comprised of affinity and reversed-phase separations that quantifies the majority of antibody-related protein species found in crude cell extracts of recombinant origin is described. Although potentially applicable to any antibody preparation, we here use samples of anti-CD18 (Fab′2LZ) and a full-length antibody, anti-tissue factor (anti-TF), from various stages throughout a biopharmaceutical production process to describe the assay details. The targeted proteins were captured on an affinity column containing an anti-light-chain (κ) Fab antibody (AME5) immobilized on controlled pore glass. The affinity column was placed in-line with a reversed-phase column and the captured components were transferred by elution with dilute acid and subsequently resolved by eluting the reversed-phase column with a shallow acetonitrile gradient. Characterization of the resolved components showed that most antibody fragment preparations contained a light-chain fragment, free light chain, light-chain dimer and multiple forms of Fab′. Analysis of full-length antibody preparations also resolved these fragments as well as a completely assembled form. Co-eluting with the full-length antibody were high-molecular-mass variants that were missing one or both light chains. Resolved components were quantified by comparison with peak areas of similarly treated standards. By comparing the two-dimensional polyacrylamide gel electrophoresis patterns of an Escherichia coli blank run, a production run and the material affinity captured (AME5) from a production run, it was determined that the AME5 antibody captured isoforms of light chain, light chain covalently attached to heavy chain, and truncated light chain isoforms. These forms comprise the bulk of the soluble product-related fragments found in E. coli cell extracts of recombinantly produced antibody fragments.

Development of a method for the determination of phthalate esters in sewage sludge including chromatographic separation from polychlorinated biphenyls, pesticides and polyaromatic hydrocarbons

A method was developed that allows phthalate esters (PEs) to be determined in sewage sludge samples by use of gas chromatography (GC) with electron-capture detection. Discrimination of the PEs in the split injector of the GC system was detected and the resulting problems are discussed. The ultrasonic technique was optimised for extraction time and number of extractions and compared with the Soxhlet extraction technique. It was shown that extraction efficiency is slightly better with ultrasonication than using Soxhlet extraction. The Soxhlet extraction also yielded much higher blank levels. The extract clean-up was carried out by dual column liquid chromatography with neutral alumina and Florisil. In this way separation of polychlorinated biphenyls, pesticides and polyaromatic hydrocarbons from the PEs was attained. This procedure was used successfully to determine PEs in several sewage sludge samples.

Determination of dextromethorphan and its metabolites in plasma by dual column liquid chromatography and fluorimetric detection

Dextromethorphan and its metabolites were determined in plasma by a dual column liquid chromatographic switching system, after a prepurification on Sep-Pak C(18) cartridges. A polar precolumn (CN) and two hydrophobic analytical columns (C(18)) were used with mobile phases optimised regarding trace enrichment, selectivity and speed by the content of organic modifier. Dextromethorphan and its metabolites could be quantified at 5 ng ml(-1) with an intra-assay precision better than 6% (RSD).

Determination of atenolol in plasma by dual-column liquid chromatography and fluorimetric detection

A simple and rapid liquid chromatographic method for the determination of atenolol in plasma is described. Plasma proteins were precipitated with zinc sulphate and sodium hydroxide prior to injection onto a precolumn, which was connected to the analytical column by a switching valve. When atenolol was eluted onto the analytical column, the precolumn was cleaned by backflushing to eliminate strongly retained endogenous compounds. The atenolol fluorescence was measured after excitation at 197 nm. The limit of quantitation in plasma was 15 ng/ml. The within-day precision of atenolol was 1.6% at a level of 210 ng/ml, 5.0% at 25 ng/ml and the between-day precision was 3.3% at 50 ng/ml.

Analysis for Phthalate Esters in Environmental Samples: Separation from PCB's and Pesticides Using Dual Column Liquid Chromatography

Abstract A method was developed which allows phthalate esters (PE's) to be determined in environmental samples along with PCBs and several organochlorine pesticides, using a single sample extract. The extract is fractionated by dual column liquid chromatography (LC) into four fractions prior to analysis by GC/ECD. This new LC fractionation scheme for PE's involves (a) elution from an alumina column with benzene (separation from PCBs and pesticides which are eluted with hexane) followed by (b) elution from silica gel by an acetone/benzene mixture (separation from interfering moderately polar organics). Selected GC conditions enable nine different PE's to be resolved sufficiently for quantitation. The observation that PE's exhibit a decrease in ECD response as the detector temperature increases was investigated, and an optimum temperature was selected. Analysis of soil, sediment, and landfill leachate samples using the new methods gave PE results comparable to other results on environmental samples.

Additives in Plastics

Research ArticleOpen AccessAdditives in plastics. R D Deanin R D Deanin Search for more papers by this author Published:1 June 1975https://doi.org/10.1289/ehp.751135Cited by:11AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products.FiguresReferencesRelatedDetailsCited By Loizidou X, Loizides M and Orthodoxou D (2018) Persistent marine litter: small plastics and cigarette butts remain on beaches after organized beach cleanups, Environmental Monitoring and Assessment, 10.1007/s10661-018-6798-9, 190:7, Online publication date: 1-Jul-2018. Tato T, Salgueiro-González N, León V, González S and Beiras R (2018) Ecotoxicological evaluation of the risk posed by bisphenol A, triclosan, and 4-nonylphenol in coastal waters using early life stages of marine organisms ( Isochrysis galbana, Mytilus galloprovincialis, Paracentrotus lividus, and Acartia clausi ), Environmental Pollution, 10.1016/j.envpol.2017.09.031, 232, (173-182), Online publication date: 1-Jan-2018. Lambert S and Wagner M (2017) Environmental performance of bio-based and biodegradable plastics: the road ahead, Chemical Society Reviews, 10.1039/C7CS00149E, 46:22, (6855-6871) Worm B, Lotze H, Jubinville I, Wilcox C and Jambeck J (2017) Plastic as a Persistent Marine Pollutant, Annual Review of Environment and Resources, 10.1146/annurev-environ-102016-060700, 42:1, (1-26), Online publication date: 17-Oct-2017. Yu J, Sun L, Ma C, Qiao Y and Yao H (2016) Thermal degradation of PVC: A review, Waste Management, 10.1016/j.wasman.2015.11.041, 48, (300-314), Online publication date: 1-Feb-2016. Gewert B, Plassmann M and MacLeod M (2015) Pathways for degradation of plastic polymers floating in the marine environment, Environmental Science: Processes & Impacts, 10.1039/C5EM00207A, 17:9, (1513-1521) Seltenrich N (2015) New Link in the Food Chain? Marine Plastic Pollution and Seafood Safety, Environmental Health Perspectives, 123:2, (A34-A41), Online publication date: 1-Feb-2015. Waheed S, Rahman S, Husnain S and Siddique N (2011) Hazardous and other element characterization of new and used domestic plastic food containers using INAA and AAS, Journal of Radioanalytical and Nuclear Chemistry, 10.1007/s10967-011-1036-8, 292:3, (937-945), Online publication date: 1-Jun-2012. Russell D and McDuffie B (1986) Chemodynamic properties of phthalate esters: Partitioning and soil migration, Chemosphere, 10.1016/0045-6535(86)90553-9, 15:8, (1003-1021), Online publication date: 1-Jan-1986. Russell D and McDuffie B (2006) Analysis for Phthalate Esters in Environmental Samples: Separation from PCB's and Pesticides Using Dual Column Liquid Chromatography, International Journal of Environmental Analytical Chemistry, 10.1080/03067318308071916, 15:3, (165-183), Online publication date: 1-Jul-1983. Aronson C, Serlick E and Preti G (1978) Effects of di-2-ethylhexyl phthalate on the isolated perfused rat heart, Toxicology and Applied Pharmacology, 10.1016/0041-008X(78)90295-8, 44:1, (155-169), Online publication date: 1-Apr-1978. Vol. 11June 1975Metrics Downloaded 191 times About Article Metrics Publication History Originally published1 June 1975Published in print1 June 1975 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.