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1.
The present research is based on the use of a recently developed comprehensive two‐dimensional gas chromatography thermal modulator, which is defined as solid‐state modulator. The transfer device was installed on top of a single gas chromatography oven, while benchtop low‐resolution time‐of‐flight mass spectrometry was used to monitor the compounds exiting the second analytical column. The solid‐state modulator was first described by Luong et al. in 2016, and it is a moving modulator that does not require heating and cooling gases to generate comprehensive two‐dimensional gas chromatography data. The accumulation and remobilization steps occur on a trapping capillary, this being subjected to thermoelectric cooling and micathermic heating. In this study, the effects of the gas linear velocity on the modulation performance were evaluated by using two different uncoated trapping capillaries, viz., 0.8 m × 0.25 mm id and 0.8 m × 0.20 mm id. Solid‐state modulator applications were carried out on a standard solution containing n‐alkanes (C9, C10, C12), and on a sample of diesel fuel. The results indicated that the type of trapping capillary and gas velocity have a profound effect on modulation efficiency.  相似文献   

2.
In this work a fast gas chromatography set‐up with on‐column injection was optimized and evaluated with a model mixture of C8–C28 n‐alkanes. Usual injection volumes when using narrow‐bore (e. g., 0.1 mm i.d.) analytical columns are ca. 0.1 μL. The presented configuration allows introduction of 10–30‐fold larger sample volumes without any distortion of peak shapes. In the set‐up a normal‐bore retention gap (1 m×0.32 mm i. d.) was coupled to a narrow‐bore (4.8 m×0.1 mm i. d.×0.4 μm film thickness) analytical column using a low dead volume column connector. The effects of the experimental conditions such as inlet pressure, sample volume, initial injection temperature, and oven temperature on a peak focusing are discussed. H‐u curves for helium and hydrogen are used to compare their suitability for high speed gas chromatography and to show the dependence of separation efficiency on the carrier gas velocity at high inlet pressures. In the fast gas chromatography system a baseline separation of C10–C28 n‐alkanes was achieved in less than 3 minutes.  相似文献   

3.
In this study, an improved online comprehensive two‐dimensional liquid chromatography platform coupled to tandem mass spectrometry was developed for the analysis of complex polyphenolic samples. A narrowbore hydrophilic interaction chromatography column (150 × 2.0 mm, 3.0 μm, cross‐linked diol) was employed in the first dimension, while a reversed‐phase column based on monodisperse sub‐2 μm fully porous particles (50 × 3.0 mm, 1.9 μm d.p.) with high surface area (410 m2/g) was employed in the second dimension. The combination of a trapping column modulation interface with the high retentive fully porous monodisperse reversed‐phase column in the second dimension resulted in higher peak capacity values (1146 versus 867), increased sensitivity, sharper and more symmetrical peaks in comparison with a conventional loop‐based method, with the same analysis time (70 min). The system was challenged against a complex polyphenolic extract of a typical Italian apple cultivar, enabling the simultaneous separation of multiple polyphenolic classes, including oligomeric procyanidins, up to degree of polymerization of 10. Hyphenation with an ion trap time‐of‐flight mass spectrometer led to the tentative identification of 121 analytes, showing how this platform could be a powerful analytical tool for the accurate profiling of complex polyphenolic samples.  相似文献   

4.
In the last decade, core–shell particles have gained more and more attention in fast liquid chromatography separations due to their comparable performance with fully porous sub‐2 μm particles and their significantly lower back pressure. Core–shell particles are made of a solid core surrounded by a shell of classic fully porous material. To embrace the developed core–shell column market and use these columns in pharmaceutical analytical applications, 17 core–shell C18 columns purchased from various vendors with various dimensions (50 mm × 2.1 mm to 100 mm × 3 mm) and particle sizes (1.6–2.7 μm) were characterized using Tanaka test protocols. Furthermore, four selected active pharmaceutical ingredients were chosen as test probes to investigate the batch to batch reproducibility for core–shell columns of particle size 2.6–2.7 μm, with dimension of 100 × 3 mm and columns of particle size 1.6 μm, with dimension 100 × 2.1 mm under isocratic elution. Columns of particle size 2.6–2.7 μm were also tested under gradient elution conditions. To confirm the claimed comparable efficiency of 2.6 μm core–shell particles as sub‐2 μm fully porous particles, column performances of the selected core–shell columns were compared with BEH C18, 1.7 μm, a fully porous column material as well.  相似文献   

5.
The use of larger volume injection with on‐column injection and fast GC commercial instrumentation was evaluated with the model mixture of n‐alkanes of a broad range of volatility (C10–C28). The presented configuration allows introduction of 40–80‐fold larger sample volumes without any distortion of peak shapes compared to “usual” fast GC set‐ups using narrow‐bore columns. A normal‐bore retention gap (1–5 m×0.32 mm ID) was coupled to a narrow‐bore (5 m×0.1 mm ID×0.4 μm film thickness) analytical column using a standard press‐fit connector. The connection was tight and reliable, and hence suitable for hydrogen as carrier gas. The effect of pre‐column and analytical column connector, injection volume, pre‐column length, column inlet pressure, and analyte volatility on peak shape, peak broadening, and focusing are discussed. The precision of chromatographic data measurements and peak capacity under optimised temperature programmed conditions for fast separations with large volume injection were found to be very good. The presented fast GC set‐up with on‐column injection extends the applicability of the technique to trace analysis.  相似文献   

6.
Ground porous silica monolith particles with an average particle size of 2.34 μm and large pores (363 Å) exhibiting excellent chromatographic performance have been synthesized on a relatively large scale by a sophisticated sol–gel procedure. The particle size distribution was rather broad, and the d(0.1)/d(0.9) ratio was 0.14. The resultant silica monolith particles were chemically modified with chlorodimethyloctadecylsilane and end‐capped with a mixture of hexamethyldisilazane and chlorotrimethylsilane. Very good separation efficiency (185 000/m) and chromatographic resolution were achieved when the C18‐bound phase was evaluated for a test mixture of five benzene derivatives after packing in a stainless‐steel column (1.0 mm × 150 mm). The optimized elution conditions were found to be 70:30 v/v acetonitrile/water with 0.1% trifluoroacetic acid at a flow rate of 25 μL/min. The column was also evaluated for fast analysis at a flow rate of 100 μL/min, and all the five analytes were eluted within 3.5 min with reasonable efficiency (ca. 60 000/m) and resolution. The strategy of using particles with reduced particle size and large pores (363 Å) combined with C18 modification in addition to partial‐monolithic architecture has resulted in a useful stationary phase (C18‐bound silica monolith particles) of low production cost showing excellent chromatographic performance.  相似文献   

7.
Offline multidimensional supercritical fluid chromatography combined with reversed‐phase liquid chromatography was employed for the carotenoid and chlorophyll characterization in different sweet bell peppers (Capsicum annuum L.) for the first time. The first dimension consisted of an Acquity HSS C18 SB (100 × 3 mm id, 1.8 μm particles) column operated with a supercritical mobile phase in an ultra‐performance convergence chromatography system, whereas the second dimension was performed in reversed‐phase mode with a C30 (250 × 4.6 mm id, 3.0 μm particles) stationary phase combined with photodiode array and mass spectrometry detection. This approach allowed the determination of 115 different compounds belonging to chlorophylls, free xanthophylls, free carotenes, xanthophyll monoesters, and xanthophyll diesters, and proved to be a significant improvement in the pigments determination compared to the conventional one‐dimensional liquid chromatography approach so far applied to the carotenoid analysis in the studied species. Moreover, the present study also aimed to investigate and to compare the carotenoid stability and composition in overripe yellow and red bell peppers collected directly from the plant, thus also evaluating whether biochemical changes are linked to carotenoid degradation in the nonclimacteric investigated fruits, for the first time.  相似文献   

8.
Three mixed‐mode high‐performance liquid chromatography columns packed with superficially porous carbon/nanodiamond/amine‐polymer particles were used to separate mixtures of cannabinoids. Columns evaluated included: (i) reversed phase (C18), weak anion exchange, 4.6 × 33 mm, 3.6 μm, and 4.6 × 100 mm, 3.6 μm, (ii) reversed phase, strong anion exchange (quaternary amine), 4.6×33 mm, 3.6 μm, and (iii) hydrophilic interaction liquid chromatography, 4.6 × 150 mm, 3.6 μm. Different selectivities were achieved under various mobile phase and stationary phase conditions. Efficiencies and peak capacities were as high as 54 000 N/m and 56, respectively. The reversed phase mixed‐mode column (C18) retained tetrahydrocannabinolic acid strongly under acidic conditions and weakly under basic conditions. Tetrahydrocannabinolic acid was retained strongly on the reversed phase, strong anion exchange mixed‐mode column under basic polar organic mobile phase conditions. The hydrophilic interaction liquid chromatography column retained polar cannabinoids better than the (more) neutral ones under basic conditions. A longer reversed phase (C18) mixed‐mode column (4.6 × 100 mm) showed better resolution for analytes (and a contaminant) than a shorter column. Fast separations were achieved in less than 5 min and sometimes 2 min. A real world sample (bubble hash extract) was also analyzed by gradient elution.  相似文献   

9.
A novel, simple, and reliable method based on high‐performance liquid chromatography coupled with fluorescence detection has been developed for the determination of nosiheptide in feed. The feed samples were extracted with acetonitrile 0.1% formic acid aqueous solution and then purified via a dispersive solid‐phase extraction procedure using silica gel powder as the sorbent. Using a mixture of acetonitrile and 5 mM ammonium acetate solution (containing 0.1% formic acid) as the mobile phase, good separation and peak shape were obtained for nosiheptide on a Poroshell C8 column (250 × 4.6 mm id, 4 μm) via the isocratic elution program. The resulting calibration curve shows high levels of linearity (r> 0.999) for nosiheptide concentrations of 50–1000 μg/L. At three spiked levels, i.e., 0.500, 2.50 and 5.00 mg/kg, the intra‐ and interday recoveries of nosiheptide in five types of feed ranged from 78.5–96.8 and 84.9–94.2%, respectively. The intra‐ and interday relative standard deviations were less than 10.8%. The limits of quantification for nosiheptide in complete feed and premixes were measured as 50 and 100 μg/kg, respectively. Compared with other common adsorbents, silica gel presents stronger recovery and purification results for feed samples during the dispersive solid‐phase extraction process.  相似文献   

10.
The composition of polycyclic aromatic hydrocarbons in crude oil is usually too complex to use standard capillary gas chromatography to separate all of the components. In this study, a multidimensional gas chromatography–mass spectrometry (GC-MS) technique was used to analyze polycyclic aromatic hydrocarbon fractions of crude oil collected from the Dongying oil field in the Bohai Sea. A DB-17MS column (30?m?×?0.25?mm?×?0.25?µm) was used as a prefractionating column and only selected heart-cuts were transferred to the second chromatographic dimension (HP-5MS, 15?m?×?0.25?mm?×?0.25?µm) by a pressure-adjusted continual flow-type switching device for quantification of the polycyclic aromatic hydrocarbons. The chromatographic elements and parameters, such as detector selection and column combinations, were optimized. Naphthalene, phenanthrene, fluorene, dibenzothiophene, chrysene, and their C1–C4 alkyl homologs were identified. The profile of the polycyclic aromatic hydrocarbons obtained using the multidimensional GC-MS method was compared with the results obtained by traditional one-dimensional GC-MS.  相似文献   

11.
A simple method for the determination of betaine, l ‐carnitine, and choline in human urine was developed based on column‐switching ion chromatography coupled with nonsuppressed conductivity detection by using a self‐packed column. A pretreatment column (50 mm × 4.6 mm, id) packed with poly(glycidyl methacrylate‐divinylbenzene) microspheres was used for the extraction and cleanup of analytes. Chromatographic separation was achieved within 10 min on a cationic exchange column (150 mm × 4.6 mm, id) using maleic anhydride modified poly(glycidyl methacrylate‐divinylbenzene) as the particles for packing. The detection was performed by ion chromatography with nonsuppressed conductivity detection. Parameters including column‐switching time, eluent type, flow rates of eluent, and interfering effects were optimized. Linearity (r 2 ≥ 0.99) was obtained for the concentration range of 0.50–100, 0.75–100, and 0.25–100 μg/mL for betaine, l ‐carnitine, and choline, respectively. Detection limits were 0.12, 0.20, and 0.05 μg/mL for betaine, l ‐carnitine, and choline, respectively. The intra‐ and interday accuracy and precision for all quality controls were within ±10.11%. Satisfactory recovery was observed between 92.5 and 105.0%. The validated method was successfully applied for the determination of betaine, l ‐carnitine, and choline in urine samples from healthy people.  相似文献   

12.
The overall kinetic performance of three production columns (2.1 mm × 100 mm format) packed with 1.6 μm superficially porous CORTECS‐C18+ particles was assessed on a low‐dispersive I‐class ACQUITY instrument. The values of their minimum intrinsic reduced plate heights (hmin = 1.42, 1.57, and 1.75) were measured at room temperature (295 K) for a small molecule (naphthalene) with an acetonitrile/water eluent mixture (75:25, v/v). These narrow‐bore columns provide an average intrinsic efficiency of 395 000 plates per meter. The gradient separation of 14 small molecules shows that these columns have a peak capacity about 25% larger than similar ones packed with fully porous BEH‐C18 particles (1.7 μm) or shorter (50 mm) columns packed with smaller core–shell particles (1.3 μm) operated under very high pressure (>1000 bar) for steep gradient elution (analysis time 80 s). In contrast, because their permeabilities are lower than those of columns packed with larger core–shell particles, their peak capacities are 25% smaller than those of narrow‐bore columns packed with standard 2.7 μm core–shell particles.  相似文献   

13.
A new straightforward method based on cloud‐point extraction has been developed, optimized, and validated for the determination of doxepin in human plasma by high‐performance liquid chromatography separation and UV detection. The nonionic surfactant Triton X‐114 was chosen as the extraction solvent. Chromatography separation was performed on a μBondapakR C18 column (4.6 mm id × 300 mm, 3 μm particle size), which was used for isocratic elution at a detection wavelength of 289 nm. Under the optimum conditions, the linear range of doxepin in human plasma was 0.1–0.9 μg/mL. Also, the detection limit, preconcentration factor, and enrichment factor were 0.08 μg/mL, 50, and 49.0, respectively.  相似文献   

14.
A fast, green, sensitive, and accurate analytical method using high‐performance liquid chromatography couple with fluorescence detection was established and validated for the simultaneous determination of amlodipine besylate and celecoxib in their recently approved fixed‐dose combination tablets (1:20). Separation of the two drugs was achieved on C18 reversed‐phase column (Thermo ODS Hypersil, 4.6 × 250 mm, particle size 5 µm) using acetonitrile:potassium phosphate buffer (50 mM; pH 5.5, 60:40 v/v) as a mobile phase at 40°C, which eluted at a rate of 1 mL/min. Detection was carried out with excitation and emission wavelengths of 360 and 446 nm for amlodipine and 265 and 359 nm for celecoxib, respectively. The method was linear over a concentration range of 0.05‐2 and 0.05‐10 µg/mL and limit of detection reached to 0.017 and 0.0167 µg/mL for amlodipine and celecoxib, respectively. The developed method was successfully applied to assess the cited drugs in their newly FDA approved fixed‐dose combination tablet dosage form. Furthermore, the method was found to be sensitive and eco‐friendly green alternative to the reported methods as it was evaluated according to the green analytical procedure index tool guidelines and analytical Eco‐Scale.  相似文献   

15.
Most of the anti‐breast cancer drugs are often limited owing to drug resistance and serious adverse reactions. Therefore, development of more targeted and low toxic drugs from traditional Chinese medicines for breast cancer are needed. At the same time, establishment of fast and effective drug screening methods are urgently required. We describe here a 2D LC method of MDA‐MB‐231 cell membrane chromatography combined with HPLC/MS for recognition, separation, and identification of target components from traditional Chinese medicine Cortex Magnolia officinalis. The MDA‐MB‐231 cells membrane was used to prepare the chromatographic stationary phase in the first dimension. The active compounds had a retention characteristic on the cell membrane chromatography model (10 × 2.0 mm, 5 μm). The retention fractions were enriched using an online C18 column (10 × 1.0 mm, 5 μm) and were analyzed by the second dimension RP chromatography. Finally, the activity of the retention fractions was tested through in vitro experiments. Results showed that the retention fractions were honokiol and magnolol and the inhibition rate on MDA‐MB‐231 cell growth were 23 and 64 μM, respectively. These results support the conclusion that this coupled analytical technique could be an efficient method in drug discovery.  相似文献   

16.
In this work, the chromatographic performance of superficially porous particles (Halo core–shell C18 column, 50 mm × 2.1 mm, 2.7 μm) was compared with that of sub‐2 μm fully porous particles (Acquity BEH C18, 50 mm × 2.1 mm, 1.7 μm). Four parabens, methylparaben, ethylparaben, propylparaben, and butylparaben, were used as representative compounds for calculating the plate heights in a wide flow rate range and analyzed on the basis of the Van Deemter and Knox equations. Theoretical Poppe plots were constructed for each column to compare their kinetic performance. Both phases gave similar minimum plate heights when using nonreduced coordinates. Meanwhile, the flat C‐term of the core–shell column provided the possibilities for applying high flow rates without significant loss in efficiency. The low backpressure of core–shell particles allowed this kind of column, especially compatible with conventional high‐performance liquid chromatography systems. Based on these factors, a simple high‐performance liquid chromatography method was established and validated for the determination of parabens in various seafood sauces using the Halo core–shell C18 column for separation.  相似文献   

17.
6‐(4‐Aminophenyl)‐5‐methyl‐4,5‐dihydro‐3(2H)‐pyridazinone is a key synthetic intermediate for cardiotonic agent levosimendan. Very few studies address the use of chiral stationary phases in chromatography for the enantioseparation of this intermediate. This study presents two efficient preparative methods for the isolation of (R)(?)‐6‐(4‐aminophenyl)‐5‐methyl‐4,5‐dihydro‐3(2H)‐pyridazinone in polar organic solvent chromatography and supercritical fluid chromatography using polysaccharide‐based chiral stationary phases and volatile organic mobile phases without additives in isocratic mode. Under optimum conditions, Chiralcel OJ column showed the best performance (α = 1.71, Rs = 5.47) in polar organic solvent chromatography, while Chiralpak AS column exhibited remarkable separations (α = 1.81 and Rs = 6.51) in supercritical fluid chromatography with an opposite enantiomer elution order. Considering the sample solubility, runtime and solvent cost, the preparations were carried out on Chiralcel OJ column and Chiralpak AS column (250 × 20 mm i.d.; 10 µm) in polar organic mode and supercritical fluid chromatography mode with methanol and CO2/methanol as mobile phases, respectively. By utilizing the advantages of chromatographic techniques and polysaccharide‐based chiral stationary phases, this work provides two methods for the fast and economic preparation of (R)(?)‐6‐(4‐aminophenyl)‐5‐methyl‐4,5‐dihydro‐3(2H)‐pyridazinone, which are suitable for the pharmaceutical industry.  相似文献   

18.
Two‐dimensional liquid chromatography largely increases the number of separated compounds in a single run, theoretically up to the product of the peaks separated in each dimension on the columns with different selectivities. On‐line coupling of a reversed‐phase column with an aqueous normal‐phase (hydrophilic interaction liquid chromatography) column yields orthogonal systems with high peak capacities. Fast on‐line two‐dimensional liquid chromatography needs a capillary or micro‐bore column providing low‐volume effluent fractions transferred to a short efficient second‐dimension column for separation at a high mobile phase flow rate. We prepared polymethacrylate zwitterionic monolithic micro‐columns in fused silica capillaries with structurally different dimethacrylate cross‐linkers. The columns provide dual retention mechanism (hydrophilic interaction and reversed‐phase). Setting the mobile phase composition allows adjusting the separation selectivity for various polar substance classes. Coupling on‐line an organic polymer monolithic capillary column in the first dimension with a short silica‐based monolithic column in the second dimension provides two‐dimensional liquid chromatography systems with high peak capacities. The silica monolithic C18 columns provide higher separation efficiency than the particle‐packed columns at the flow rates as high as 5 mL/min used in the second dimension. Decreasing the diameter of the silica monolithic columns allows using a higher flow rate at the maximum operation pressure and lower fraction volumes transferred from the first, hydrophilic interaction dimension, into the second, reversed‐phase mode, avoiding the mobile phase compatibility issues, improving the resolution, increasing the peak capacity, and the peak production rate.  相似文献   

19.
For the enantioselective and simultaneous analysis of lactate and 3‐hydroxybutyrate, a validated online two‐dimensional high‐performance liquid chromatography system using 4‐nitro‐7‐piperazino‐2,1,3‐benzoxadiazole as a fluorescent derivatization reagent has been developed. For the reversed‐phase separation in the first dimension, a Capcell Pak C18 ACR column (1.5 × 250 mm, particle size 3 μm) was used, and the target fractions were isolated by their hydrophobicity. In the second dimension, a polysaccharide‐coated enantioselective column, Chiralpak AD‐H (2.0 × 250 mm, 5 μm), was used. The system was validated by the calibration curve, intraday precision, interday precision, and accuracy using standards and real human samples, and satisfactory results were obtained. The present method was applied to human plasma and urine, and in the plasma, trace amounts of d‐ lactate (8.4 μM) and l‐ 3‐hydroxybutyrate (1.0 μM), besides high levels of l‐ lactate (860.9 μM) and d‐ 3‐hydroxybutyrate (59.4 μM), were successfully determined. In urine, trace levels of d‐ lactate (3.7 μM), d‐ 3‐hydroxybutyrate (2.3 μM), and l‐ 3‐hydroxybutyrate (3.3 μM) in addition to a relatively large amount of l‐ lactate (15.4 μM) were observed. The present online two‐dimensional high‐performance liquid chromatography system is useful for the simultaneous determination of all the lactate and 3‐hydroxybutyrate enantiomers in human physiological fluids, and further clinical applications are ongoing.  相似文献   

20.
Tianshu Capsule, consisting of Ligusticum chuanxiong Hort and Gastrodia elata Blume, is a widely used Traditional Chinese Medicine preparation for the treatment of migraine. Ferulic acid and gastrodin are main active constituents in Ligusticum chuanxiong Hort and Gastrodia elata Blume, and have been used as marker components for quality control of Tianshu Capsule. In this study, a selective, sensitive, and reliable ultra‐fast liquid chromatography with tandem mass spectrometry method was developed for simultaneous determination of ferulic acid and gastrodin in rat plasma using geniposide as internal standard. The plasma samples were extracted by protein precipitation with methanol after acidification and separated on a Shim‐Pack XR‐ODS C18 column (75 × 3.0 mm, 2.2 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.6 mL/min. Detection was performed on 3200 QTRAP mass spectrometry equipped with turbo ion spray source in negative ionization mode. Validation parameters were within acceptable ranges. The validated method was applied to compare the pharmacokinetic profiles of ferulic acid and gastrodin in normal and migraine rats. Our results showed that there were remarkable differences in the pharmacokinetic properties of the analytes between the normal and migraine groups.  相似文献   

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