Column Trapping Research Articles

Large volume headspace GC/MS analysis for the identification of volatile compounds relating to seafood decomposition.

Decomposition in seafood products in the United States is monitored by the Food and Drug Administration (FDA) laboratories using sensory testing, which requires highly trained analysts. A large‐volume headspace (LVHS) gas chromatography/mass spectrometry (GC/MS) method was developed to generate analytical results that can be directly compared to sensory evaluation. Headspace vapor was withdrawn from a 1‐L vial containing 50 g seafood sample using a large volume headspace autosampler. Various volatile compounds were collected simultaneously. Analytes were preconcentrated by a capillary column trapping system and then sent through a cryo‐focuser mounted onto the GC injector. A selected ion monitoring (SIM) MS acquisition method was used to selectively monitor 38 compounds of interest. Samples of red snapper, croaker, weakfish, mahi‐mahi, black tiger shrimp, yellowfin tuna, and sockeye salmon that have been assessed and scored by an FDA National Seafood Sensory Expert (NSSE) were used for method performance evaluation. Characteristic compounds potentially associated with seafood quality deterioration for each seafood species were identified by quantitative analysis using pooled matrix‐matched calibrations and two‐sample t‐test statistical analysis. Classification of fresh and decomposed samples was visualized on the analysis of variance (ANOVA)–principal component analysis (PCA) score plots. The results determined that the LVHS‐GC/MS technique appeared promising as a screening tool to identify compounds representative of sensory analysis.

A fast and simple method for determination of β-carotene in commercial fruit juice by cloud point extraction-cold column trapping combined with UV–Vis spectrophotometry

Cloud point extraction with cold column trapping (CPE-CCT) was used for the rapid preconcentration and UV–Vis spectroscopy of beta-carotene in fruit juice samples. A central composite design was employed to optimize parameters such as pH, incubation time, cloud point temperature and surfactant concentration. A detection limit of 0.01 mg/L of beta-carotene (3SB/m), a coefficient of determination of 0.998 and a linear range of 0.04–10 mg/L were obtained. The CPE-CCT method was confirmed in comparison with the corresponding direct HPLC standard method. A simple, portable and cost-effective device was also utilized. Owing to eliminating centrifugation, the conditions of CPE-CCT were more moderate and its sample handling easier compared to conventional CPE.

Determination of total cyanides and sulfides in wastewater using ion chromatography coupled with ultraviolet photo-dissociation/gas-membrane diffusion

An automated system for the determination of total cyanides and sulfides in wastewater has been developed using flow injection, ultraviolet (UV) photo-dissociation, gas-membrane diffusion, column trapping, ion chromatography separation and pulsed amperometric detection. When the sample was mixed with sulfuric acid and hypophosphorous acid medium containing the appropriate amount of sulfamic acid, ascorbic acid, EDTA and citric acid, metal-cyanide complexes such as Fe (CN)3-(6) can be photo-dissociated by 312 nm UV light, which results in hydrogen cyanide ( HCN) and similarly, sulfides release hydrogen sulfide (H2S). These products were diffused through a 0.45 µm hydrophobic porous polypropylene membrane and were then absorbed in the dilute NaOH solution, concentrated with a Metrosep A PCC 1 HC/4.0 column, separated on an IonPac AS7 column, and finally detected by the pulsed amperometric detector with Ag electrode. The total cyanides and sulfides were good linear in the range of 0.5-1,000 µg/L with correlation coefficients of 0.998 9 and 0.999 7 respectively. The recoveries were 93%-102% and the limits of detection were 0.5 µg/L for total cyanides and 1.0 µg/L for sulfides under the conditions of the sample volume of 100 µL and the signal to noise ratio of 5. The sample throughput of the system was six samples per hour. The results from this new method have been compared with the ones obtained with the standard method, which shows a good agreement.

Characterization of water bamboo husk biosorbents and their application in heavy metal ion trapping

The use of plant-based biosorbents for removing environmental pollutants from water is gaining widespread attention. In this paper, the 45–250μm biosorbents were prepared from the husks of water bamboo (Zizania caduciflora Turcz.), with a pore size distribution of 5.7–13.8nm and surface area of 1.87m2/g. These water bamboo husk particles contained OH and COOH groups and had a zero point of charge between pH2 and 3. An optimal negative charge on particle surface was achieved at pH5. Moreover, their cation exchange capacity was about 1.3meq/g. When trapping metal ions at pH5, the prepared biosorbents exhibited strong affinity to Cu2+, Cr3+, Pb2+, and Fe3+. Adsorption isotherms and breakthrough studies were generated for Fe3+ (stronger affinity) and Ni2+ (weaker affinity), and the interpretation of results indicated that the water bamboo husk particles are well suited to trap these ions at low concentrations. Also, column trapping of metal ions (breakthrough volume: 75 bed volume for Ni2+ and 90 bed volume for Fe3+) proved much more efficient than static adsorption.

Semi-automated cloud point extraction with cold column trapping of surfactant-rich phase for phenazopyridine determination in human serum

A semi-automated cold column trapping-cloud point extraction (CCT-CPE) method was developed and applied to the determination of phenazopyridine in human serum. In the proposed technique, a mixture of sample (pH 8) and Triton X-100 (0.4 % v/v) was incubated at 90 °C for 5 min in a heating sample cell. The developed turbid solution was then flowed through a CCT preconcentration column packed with C18 sorbent using a peristaltic pump. A pair of thermal electric cooler (TEC) plates was used for cooling the column. The surfactant-rich phase was retained on the CCT at 0 °C and desorbed, subsequently, in an elevated temperature by ethanol. The analytical parameters such as pH, surfactant concentration, temperature and incubation time were optimized by a central composite design (response surface) method. Six replicated analyses at the optimized conditions resulted in a recovery of 99.7 % and a relative standard deviation of 2.45 for phenazopyridine. The detection limit of the method (3σ) was 0.50 mg L−1 for the analyte. Compared to conventional CPE, the proposed CCT-CPE method required less sample handling, eliminated the centrifugation step and was substantially faster. The method was successfully applied to the determination of phenazopyridine in some human serum and tablet samples.

Identification of Niemann-Pick C1 disease biomarkers through sphingolipid profiling

Niemann-Pick type C (NPC)1 is a rare neurodegenerative disease for which treatment options are limited. A major barrier to development of effective treatments has been the lack of validated biomarkers to monitor disease progression or serve as outcome measures in clinical trials. Using targeted metabolomics to exploit the complex lipid storage phenotype that is the hallmark of NPC1 disease, we broadly surveyed Npc1(-/-) mouse tissues and identified elevated species across multiple sphingolipid classes that increased with disease progression. There was a striking accumulation of sphingoid bases, monohexosylceramides (MCs), and GM2 gangliosides in liver, and sphingoid bases and GM2 and GM3 gangliosides in brain. These lipids were modestly decreased following miglustat treatment, but markedly decreased in response to treatment with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), two drugs that have shown efficacy in NPC1 animal models. Extending these studies to human subjects led to identification of sphingolipid classes that were significantly altered in the plasma of NPC1 patients. Plasma MCs and ceramides were elevated, whereas sphingoid bases were reduced in NPC1 subjects. Intervention with miglustat in NPC1 patients was accompanied by striking alterations in plasma (reductions in GM1 and GM3 gangliosides) and cerebrospinal fluid (CSF) (increased MCs) sphingolipids. Similar alterations were observed in the CSF from the NPC1 feline model following HP-β-CD treatment. Our findings suggest that these lipid biomarkers may prove useful as outcome measures for monitoring efficacy of therapy in clinical trials.

In-line cold column trapping of organic phase in dispersive liquid–liquid microextraction: Enrichment and determination of curcumin in human serum

A new temperature controlled cold column trapping (CCT) system was developed for in-line sequestration of organic phase in dispersive liquid–liquid microextraction (DLLME) method. In the developed CCT–DLLME method, the dispersed organic extraction phase is solidified and trapped in the CCT, packed with glass particles. Subsequently, the sequestered phase is washed out in an elevated temperature by using an appropriate solvent. The column temperature is controlled by a pair of thermal electric cooler (TEC) plates. The new device is simple and portable and can eliminate the need for centrifugation in the DLLME method for solvents with an appropriate melting point. Some important parameters such as types of extraction and disperser solvents and their volumes, minimum and maximum column temperatures and extraction time were optimized for the extraction of curcumin, as a model compound. Using 1-dodecanol as the organic solvent and acetone as the disperser, recoveries exceeding 90% and a relative standard deviation of 2.87% were obtained for 5 replicated analyses of curcumin by an HPLC method. The detection limit of curcumin (3σ) extracted by the CCT–DLLME system was 28μgL−1. The method was successfully applied to the determination of curcumin in some human serum samples.

RECENT ADVANCEMENTS IN HPLC-NMR AND APPLICATIONS FOR NATURAL PRODUCT PROFILING AND IDENTIFICATION

This review provides a summary of the recent advances in high pressure liquid chromatography (HPLC) coupled to nuclear magnetic resonance (NMR) spectroscopy. Significant improvements have included the miniaturization of NMR components as well as the use of cryogenically cooled probes. Further hyphenated applications such as HPLC-SPE-NMR, column trapping and HPLC-NMR-MS are also discussed. Finally, an overview of the application of these methodologies to the profiling and dereplication of natural products is provided.

Sensitive determination of a pharmaceutical compound and its metabolites in human plasma by ultra-high performance liquid chromatography–tandem mass spectrometry with on-line solid-phase extraction

This paper describes the determination of a drug candidate and two metabolites in human plasma by column-switching LC–MS/MS after protein precipitation. Starting from a standard method with a quantitation limit of 0.5ng/mL, a highly sensitive assay was developed, employing UHPLC separation and detection on an API 5000 mass spectrometer. The injected plasma equivalent was increased from 6 to 20μL; conventional column trapping for compound enrichment and removal of matrix constituents was combined with high-pressure analytical separation using small particle columns to improve resolution and signal-to-noise ratio. Quantitation limits were thus lowered to between 5 and 20pg/mL, offering the possibility to provide bioanalytical support for microdosing studies in humans. Excellent assay quality and robustness were achieved by both methods.

Application of liquid chromatography-two-dimensional nuclear magnetic resonance spectroscopy using pre-concentration column trapping and liquid chromatography–mass spectrometry for the identification of degradation products in stressed commercial amlodipine maleate tablets

Application of the HPLC hyphenated techniques of LC-two-dimensional (2D) NMR using pre-concentration column trapping and LC–MS was demonstrated by the identification of two major degradation products, DP-1 and DP-2, in stressed commercial tablets of amlodipine maleate. The molecular formulas were estimated by LC–MS. Sample pre-concentration by column trapping was conducted to obtain adequate 2D-NMR signals by reducing the peak widths of the degradation products and making sure that the maximum amount of each component was inside the flow cell for NMR detection. Double-quantum filtered correlation spectroscopy (DQF-COSY) was applied to identify DP-1 as β- N-lactosylamlodipine by suppressing the residual water signal without affecting the sample signal and by measuring the coupling constant of the lactose anomeric proton. Heteronuclear multiple bond coherence spectroscopy (HMBC) was applied to characterize DP-2 as an aspartic acid derivative of amlodipine by detecting long-range CH correlations. The chemical structures of the degradation products could be successfully elucidated unambiguously without an isolation process.

Signal enhancement in HPLC/microcoil NMR using automated column trapping.

A new HPLC NMR system is described that performs analytical separation, preconcentration, and NMR spectroscopy in rapid succession. The central component of our method is the online preconcentration sequence that improves the match between postcolumn analyte peak volume and microcoil NMR detection volume. Separated samples are collected on to a C18 guard column with a mobile phase composed of 90% D2O/10% acetonitrile-D3 and back-flushed to the NMR microcoil probe with 90% acetonitrile-D3/10% D2O. To assess the performance of our unit, we separated a standard mixture of 1 mM ibuprofen, naproxen, and phenylbutazone using a commercially available C18 analytical column. The S/N measurements from the NMR acquisitions indicated that we achieved signal enhancement factors up to 10.4 (+/-1.2)-fold. Furthermore, we observed that preconcentration factors increased as the injected amount of analyte decreased. The highest concentration enrichment of 14.7 (+/-2.2)-fold was attained injecting 100 microL of solution of 0.2 mM (approximately 4 microg) ibuprofen.

Narrow-bore sample trapping and chromatography combined with quadrupole/time-of-flight mass spectrometry for ultra-sensitive identification of in vivo and in vitro metabolites

The identification of in vitro and in vivo metabolites is vital to the discovery and development of new pharmaceutical therapies. Analytical strategies to identify metabolites at different stages of this process vary, but all involve the use of liquid chromatography separations combined with detection via mass spectrometry (HPLC/MS). Reported here is the use of narrow-bore column (0.5-1.0 mm i.d.) trapping of metabolites, followed by back-flushing onto a matching analytical column. Separated metabolites were then identified using quadrupole time-of-flight mass spectrometry (MS) and tandem MS. Metabolites in human plasma and from low-level in vitro incubations, that were not identified using standard HPLC/MS approaches, were characterized using the instrumental configuration described here.

Developments in Hyphenated Spectroscopic Methods in Natural Product Profiling

Overviews of the principal techniques that have found application in the profiling of natural products are given, including advances in capillary and column trapping LC-NMR-MS. Single hyphenated spectroscopic techniques, like LC-NMR and LC-MS, currently offer robust and efficient approaches for the rapid dereplication of natural product extracts. Multiple hyphenation techniques, such as (HP)LC-UV-NMR-MS-FTIR, now give an effective and comprehensive method for the deconvolution of complex mixtures. Ongoing improvements include miniaturization and cryogenic NMR probes and the hyphenation to capillary scale LC separations to analyse smaller quantities of samples. Extensions in hyphenation techniques required for natural product and other drug discovery programs include the need for LC-13C NMR and the combination of bioassays with already well-established hyphenated separationspectroscopic techniques, coupled with automated database searching capabilities (data libraries for LC, UV, NMR, MS and other search criteria).

Determination of tacrine metabolites in microsomal incubate by high performance liquid chromatography–nuclear magnetic resonance/mass spectrometry with a column trapping system

A column trapping system has been incorporated into high performance liquid chromatography–nuclear magnetic resonance–mass spectrometry (HPLC–NMR–MS) to reduce data acquisition time of NMR experiments. The system uses a trapping column to capture analytes after the HPLC column and back flush trapped analyte to the flow cell of the NMR probe for detection. A dilution solvent is mixed with eluent from HPLC column to reduce the influence of the organic content in the mobile phase before column trapping. The trapping column is also coupled with a mass spectrometer (MS) to get complementary MS data on the same peak. Studies on 1-hydroxylated 9-amino-1,2,3,4-tetrahydro-acridine (1-OH tacrine), indomethacin and testosterone with the column trapping system showed good recovery of analytes and over 3-fold mean increase in UV–VIS signal intensity. The time saving on NMR experiments with the column trapping system was demonstrated by the analysis of dog microsomal incubate with tacrine.

Optimization of LC–NMR. III—Increased signal‐to‐noise ratio through column trapping

Significant gains in LC–NMR signal-to-noise ratio are obtained by selective concentration of chromatographic peaks on a chromatographic column using D2O to fix the sample on the solid phase. A deuterated organic solvent is used to remove the sample from the column and into the NMR flow cell, which removes the need for presaturation of solvent resonances. Deuterated solvents unrelated to the original eluent are used in order to minimize spectral overlap between solvent and solute. © 1998 John Wiley & Sons, Ltd.

Optimization of LC-NMR. III—Increased signal-to-noise ratio through column trapping

Significant gains in LC–NMR signal-to-noise ratio are obtained by selective concentration of chromatographic peaks on a chromatographic column using D2O to fix the sample on the solid phase. A deuterated organic solvent is used to remove the sample from the column and into the NMR flow cell, which removes the need for presaturation of solvent resonances. Deuterated solvents unrelated to the original eluent are used in order to minimize spectral overlap between solvent and solute. © 1998 John Wiley & Sons, Ltd.

Gaschromatographische Kopfraum-Analyse der erhitzten Chardonnay- und Semillon-Weine

Volatile compounds of Chardonnay and Semillon wines were analysed using a dynamic headspace method based on selective capillary column trapping and gas chromatography with another column. The effect of thermal treatment on the volatile composition of the wines was studied. Some grape derived norisoprenoid compounds, important to the aroma of aged wine, were formed at 45°C by hydrolysis from the glycosidic precursors. The heat treatment increased the proportion of 1,1,6-Trimethy1-1,2-dihydronaphthalene (TDN) and vitispirane in Chardonnay and Semillon wines. Headspace volatiles of model wines, to which the glycosidic fraction of Chardonnay and Semillon juices was added, were also analysed.

Volatile compounds of blackcurrant juice and wine

Volatile compounds of blackcurrant juice, concentrate and wine were analysed by applying a dynamic headspace gaschromatographic method based on selective capillary column trapping. A significant sensorial difference between the wine made from blackcurrant juice and that from concentrate was found by duo-trio assessment for aroma, while only a slight difference was observed in the volatile composition of the wines. Blackcurrant wines contained only a few terpene compounds, whereas numerous terpenes were identified from the juice. Differences between the blackcurrant juice and concentrate were found, with some terpene compounds appearing in higher amounts in the former.

Method of Sensitive Analysis of Wine Headspace Volatiles Based on Selective Capillary Column Trapping

Method of Sensitive Analysis of Wine Headspace Volatiles Based on Selective Capillary Column Trapping

Methods for Examination of Flavonoids in Fruits: Application to Flavonol Glycosides and Aglycones of Apples, Pears, and Strawberries

Abstract Extraction and isolation methods developed for flavonoids in fruits and fruit products include a choice of column trapping or solvent extraction, plus a method of isolating flavonoid compounds for GLC by selective lead precipitation, based upon control of pH. The methods were applied to apples, pears, and strawberries. Two-dimensional TLC on cellulose was used to compare flavonol glycoside patterns. GLC identification was based upon the identities and relative amounts of the flavonol aglycones, chromatographed as the trimethylsilyl derivatives. Free flavonol aglycones are shown to occur in damaged and/or decomposed fruit.