Internal Diameter Column Research Articles

Recent advances in micro-scale and nano-scale high-performance liquid-phase chromatography for proteome research

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS-MS) is regarded as one of the most powerful techniques for separation and identification of proteins. Recently, much effort has been made to improve the separation capacity, detection sensitivity, and analysis throughput of micro- and nano-HPLC, by increasing column length, reducing column internal diameter, and using integrated techniques. Development of HPLC columns has also been rapid, as a result of the use of submicrometer packing materials and monolithic columns. All these innovations result in clearly improved performance of micro- and nano-HPLC for proteome research.

Destabilisation of homogeneous bubbly flow in an annular gap bubble column

AbstractExperimental results are presented to show that there are very significant differences in the mean gas void fractions measured in an open tube and a annular gap bubble column, when operated at the same gas superficial velocity, using a porous sparger. Measurements were carried out in a vertical 0.102 m internal diameter column, with a range of concentric inner tubes to form an annular gap, giving diameter ratios from 0.25 to 0.69; gas superficial velocities in the range 0.014–0.200 m/s were investigated. The mean gas void fraction decreases with increasing ratio of the inner to outer diameter of the annular gap column and the transition to heterogeneous flow occurs at lower gas superficial velocities and lower void fractions. Two reasons are proposed and validated by experimental investigations: (1) the presence of the inner tube causes large bubbles to form near the sparger, which destabilise the homogeneous bubbly flow and reduce the mean void fraction; this was confirmed by deliberately injecting large bubbles into a homogeneous dispersion of smaller bubbles, and (2) the shape of the void fraction profiles changes with gap geometry and this affects the distribution parameter in the drift‐flux model. Both of these effects serve to reduce the mean gas void fraction in an annular gap bubble column compared to an open tube at the same gas superficial velocity.

Evaluation of 1.0 mm i.d. column performances on ultra high pressure liquid chromatography instrumentation

The present study focuses on the evaluation of 1.0 mm i.d. (internal diameter) columns on a commercial Ultra-High Pressure system. These systems have been developed specifically to operate columns with small volumes, typically 2.1 mm i.d., by reducing extra-column volume dispersion. The use of columns with smaller i.d. results in a reduced solvent consumption and required sample volume. The evaluation of the columns was carried out with samples containing neutral and pharmaceutical compounds. In isocratic mode, the extra-column volume produced additional band broadening leading to poor performances compared to equivalent 2.1 mm i.d. columns. By increasing the length of the column, the influence of the extra-column bandspreading could be reduced and 75,000 plates were obtained when four columns were coupled. In gradient mode, the effect of the extra-column contribution on efficiency was limited and about 80% of the performance of the 2.1 mm i.d. columns was obtained. Optimum conditions in gradient mode were further investigated by changing flow rate, gradient time and column length. A different approach of the calculation of peak capacity was also considered for the comparison of the influence of these different parameters.

Large‐scale isolation and purification of C‐phycocyanin from the cyanobacteria Anabaena marina using expanded bed adsorption chromatography

AbstractBACKGROUND: Phycobiliproteins are water soluble proteins useful as fluorescent markers of cells and macromolecules, and as natural colorants, and are anticarcinogenic. Although phycobiliproteins have many applications, their use is limited by the high cost of the purified macromolecules, mainly related with the cost of extraction and purification. In this study a fast and scalable method for preparative extraction and purification of C‐phycocyanin (C‐PC) from Anabaena marina is developed.RESULTS: The method developed consists in the extraction of phycobiliproteins using repeated single contact strategy, separation being performed by expanded bed adsorption (EBA) chromatography using Streamline‐DEAE. Optimal conditions for EBA were obtained at small scale, using a 15 mm internal diameter column, these being a sample load of 0.9 mg C‐PC mL−1 adsorbent, an expanded bed volume twice the settled bed volume and a sample viscosity of 1.109 mP. The process was then scaled up 36 times, the success of the scale‐up process being verified. Finally, to obtain pure C‐PC conventional ion‐exchange chromatography was utilized.CONCLUSION: Small diameter columns was shown to be useful to simulate the behavior of larger diameter columns for use in scaled up systems. Expanded bed adsorption was demonstrated to be a scalable technology allowing large quantities of C‐PC to be obtained, maintaining high protein recovery while reducing both processing cost and time. The proposed methodology allows recovery of more than 62% of the C‐PC contained in the biomass in the form of pure C‐PC concentrates. Copyright © 2010 Society of Chemical Industry

Dissolved Ammonia Adsorption in Water Using Over Burnt Brick

Problem statement: The groundwater of Kathmandu Valley contained very high concentration of ammonia nitrogen which was in excess of WHO guideline value for drinking water. Approach: This study mainly focused on the removal of ammonia nitrogen in water by adsorption in locally available over burnt brick. The study was carried out in a 4.2 cm internal diameter column of 120 cm length packed with over burnt brick in up flow mode. Results: The study showed that the ammonia nitrogen removal rate increased with increase in contact time which decreased with time until steady state condition is attained. The contact time varied from 4-9.5 h for different particle sizes. Conclusion: The optimal value of adsorption rate constant was found as 0.1097 for particle size of 0.850-0.600 mm at corresponding contact time of 7 h. The adsorption data appears to fit the Freundlich's isotherm. The fixed bed adsorption operation indicated that the ammonia nitrogen removal is the function of service time, bed depth and flow. Linear regression model showing correlation of these parameters has been developed.

Bed depth service time model for the biosorption of reactive red dye using the Portunus sanguinolentus shell

AbstractBiosorption is an efficient and regenerative technique that often uses low‐cost adsorbent materials, particularly for the treatment of wastewaters containing dyes and heavy metals. This study investigates the ability of crab shell (Portunus sanguinolentus) to remove reactive red dye in a packed bed up‐flow column (internal diameter 2 cm; height 35 cm). Crab shell has high surface area (after proper size reduction) and high regenerative capacity. The experiments were performed with different bed heights (20 and 30 cm) and using different flow rates (12 and 17 ml/min) in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. The column regeneration studies were carried out for five different sorption–desorption cycles. The elutant used for the regeneration of the sorbent was 0.01 M EDTA (disodium) solution at pH 9.8 adjusted using NH4OH. This solution was found to have the best bed regeneration capacity and could be reused for several sorption–desorption cycles. The elution efficiency was greater than 99.1% in all seven cycles. Continuous use of the crab shell leads to a decrease in the adsorptive performance, as observed by the breakthrough curves becoming flatter and also because of a broader mass transfer zone. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

Enhanced resolution comprehensive two-dimensional gas chromatography applied to the analysis of roasted coffee volatiles

The present research is based on the full exploitation of the separation power of a 0.05 mm internal diameter (ID) capillary, as a comprehensive two-dimensional (2D) GC (GC × GC) secondary column, with the objective of attaining very high-resolution second dimension separations. The aim was achieved by using a split-flow system developed in previous research [P.Q. Tranchida, A. Casilli, P. Dugo, G. Dugo, L. Mondello, Anal. Chem. 79 (2007) 2266], and a dual-oven GC × GC instrument. The column combination employed consisted of a polar 30 m × 0.25 mm ID column connected, by means of a T union, to a detector-linked high-resolution 1.1 m × 0.05 mm ID apolar analytical column and to a 0.33 m × 0.05 mm ID retention gap; the latter was connected to a manually operated split valve. As previously demonstrated, the use of a split valve enables the regulation of gas flows through both analytical columns, generating the most appropriate gas linear velocities. Comprehensive 2D GC experiments were carried out on Arabica roasted coffee volatiles (previously extracted by means of solid-phase microextraction) with the split-valve closed (equal to what can be defined as conventional GC × GC) and with the split-valve opened at various degrees. The reasons why it is absolutely not effective to use a 0.05 mm ID column as second dimension in a conventional GC × GC instrument will be discussed and demonstrated. On the contrary, the use of a 0.05 mm ID column as second dimension, under ideal conditions in a split-flow, twin-oven system, will also be illustrated and discussed.

FAST ANALYSIS OF PAH BY GC AND GC/MS USING ISOMER SPECIFIC GC CAPILLARY COLUMNS

The required separation of polycyclic aromatic hydrocarbons (PAH) by GC, to meet regulatory requirements, depends largely on column selectivity. Liquid crystal (LC) capillary columns are highly selective for PAH separation. In the current investigation analysis and separation of PAH on columns coated with only the LC stationary phase, the combination of LC and non-polar stationary phase and only non-polar stationary phase, have been studied. The complete separation of isomeric PAH in the mixture of 16 priority PAH is achieved on the LC column. The inherent advantage of higher efficiency for microbore columns compared to conventional 0.25 mm internal diameter (ID) columns of the same length, in combination with the selectivity of the LC stationary phase, resulted in the fast analysis of 16 PAH on the columns with the combination of LC and non-polar stationary phases. Using this column, designated as the ICB-PAH column, separation of the USEPA 16 priority PAH in addition to other isomeric PAH (except benzo[j]fluoranthene) is achieved. Complete separation of 16 priority PAH was achieved in less than 5 minutes on a 6 m × 0.10 mm ID column, and in less than 7 minutes on a 15 m × 0.25 mm ID column. Separations of 16 priority PAH plus five additional isomeric PAH on LC, non-polar, and a combination of LC and non-polar stationary phase columns are discussed.

Liquid distribution and liquid hold-up in modern high capacity packings

In order to model and optimise industrial gas/liquid contactors such as those used for distillation or for post-combustion capture of CO 2, liquid hold-up and liquid distribution have been measured for two modern high capacity packings, a structured packing and a random packing. A gamma-ray tomographic system has been used to obtain liquid flow maps over a cross section of a 400 mm internal diameter column from which liquid hold-up values can be deduced. It is observed that the liquid flow is homogeneously distributed for both packings, the structured packing giving better results. Correlations are proposed to estimate the liquid hold-up, the effect of the liquid flowrate and the liquid viscosity being taken into account. A non-negligible static liquid hold-up is considered for the structured packing, which can be explained by the texture on the packing walls. As long as there is a little effect of the counter current gas, then below the loading point, results can be extrapolated to larger columns.

Hydrodynamics of gas–liquid slug flow along vertical pipes in turbulent regime–An experimental study

An experimental study on free-bubbling gas–liquid (air–water) vertical slug flow was developed using a non-intrusive image analysis technique. The flow pattern in the near-wake of the bubbles and in the main liquid between bubbles was turbulent. A single correlation for the bubble-to-bubble interaction is proposed, relating the trailing bubble velocity to the length of the liquid slug ahead of the bubble. The proposed correlation is shown to be independent of column diameter, column vertical coordinate, superficial liquid and gas velocities and the velocity and length of the leading bubble. Frequency distribution curves, averages, modes and standard deviations are reported, for distributions of bubble velocity, bubble length and liquid slug length, for each experimental condition studied. Good agreement was found between theoretical predictions and experimental results regarding the upward velocity of undisturbed bubbles, in a 0.032 m internal diameter column. A considerable discrepancy was found, though, for a 0.052 m internal diameter column. The acquired experimental data are crucial for the development and validation of a robust slug flow simulator.

Chromium Speciation in Water by Sorption on Calcite and Determination by Electrothermal Atomic Absorption Spectrometry

A rapid, sensitive, and accurate method for the separation and speciative determination of chromium (Cr)(VI) and Cr(III) in water samples has been developed using sorption as the separation technique in conjunction with final determination by electrothermal atomic absorption spectroscopy (ETAAS). The present method, where granular calcite is used as selective sorbent, separates Cr(III) with retention values up to 99%, resulting in high accuracy determination of Cr(VI). Total Cr was likewise determined by ETAAS after an efficient reduction of Cr(VI) to Cr(III) using ascorbic acid as reducing agent, deriving Cr(III) concentration from the difference between total Cr and Cr(VI). The parameters of the separation technique, solution pH (4.5–5.5), solution flow rate through the calcite column (0.14–0.42 mL min−1), and calcite column internal diameter (1.5–3.0 cm), were evaluated. Best results were achieved with pH of 5.5, flow rate of 0.42 mL min−1, and column internal diameter of 1.5 cm. Optimum determination conditions were found using magnesium nitrate [Mg(NO3)2] as chemical modifier, pyrolysis, and atomization temperatures of 1400 and 2200°C, respectively. In such conditions, the detection limits (n=10) were 1.5 and 0.8 µg L−1 for Cr(III) and Cr(VI), respectively.

Multi-residue method for the determination of basic/neutral pharmaceuticals and illicit drugs in surface water by solid-phase extraction and ultra performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry

The paper presents the development and validation of a new multi-residue method for the determination of 28 basic/neutral pharmaceuticals (antiepileptics, antibacterial drugs, β-blockers, analgesics, lipid-regulating agents, bronchodilators, histamine-2-blockers, anti-inflammatory agents, calcium channel blockers, angiotensin-II antagonists and antidepressants) and illicit drugs in surface water with the usage of a new technique: ultra performance liquid chromatography–positive electrospray tandem mass spectrometry (UPLC–MS/MS). The usage of the novel UPLC system with 1.7 μm particle size and 1 mm internal diameter column allowed for low mobile phase flow rates (0.07 mL min −1) and short retention times (from 1.3 to 15.5 min) for all compounds analysed. As a result, a fast and cost-effective method was developed. SPE with the usage of Oasis MCX strong cation-exchange mixed-mode polymeric sorbent was chosen for pharmaceuticals extraction from environmental samples. The influence of matrix-assisted ion suppression and low SPE recovery on the sensitivity of the method was studied. The instrumental limits of quantification varied from 0.2 to 10 μg L −1. The method limits of quantification were at low nanogram per litre levels and ranged from 0.3 to 50 ng L −1. The instrumental and method intra- and inter-day repeatabilities were on average less than 10%. The method was applied for the determination of pharmaceuticals in Rivers Taff (UK) and Warta (Poland). Fifteen compounds were determined in river water at levels ranging from single nanograms to single micrograms per litre.

CFD Simulation of Gas–Liquid Performance in Two Direction Vapour Horn

The computational fluid dynamics (CFD) simulation package was used to investigate gas–liquid dynamic performance of two direction vapour horn, such as gas distribution, pressure drop and entrainment rate. The performance of two direction vapour horn in a laboratorial-scale column (1 m diameter) was simulated by CFD to confirm the validity of this method and provide the detailed hydraulics hardly found by experiment. Euler–Lagrangian multiphase model was chosen to capture the two-phase flow characteristics, and k– ∈ model and stochastic tracking (random walk) model were applied to simulate turbulence of gas flow and dispersion of liquid particles respectively. The empirical correlation for momentum interaction of two-phase flow was incorporated into the model to provide the closure relation, and the model was solved by FLUENT. The simulation results agreed well with the experimental data. To overcome amplification effect of experimental results to commercial design, the CFD model proposed was used to study the effect of some factors on performance of a commercial-scale two direction vapour horn in a 7.4 m internal diameter column, such as number and radial slope angles of flow vanes and spacing between inside vertical cylindrical wall and tower wall. Designer should find some valuable information in this paper when they design two direction vapour horn in large diameter column.

Adsorption of arsenic from aqueous solution on synthetic hydrous stannic oxide

The hydrated stannic oxide (HSO) was synthesized and arsenic adsorption behaviour is reported. HSO is found to be amorphous, and stable thermally up to 700 °C. The adsorption of As(III) is much higher than As(V) in the drinking water pH (6.5–8.5) range. The time required for reaching equilibrium is 4.0 and 3.0 h, respectively for As(III) and As(V). The adsorption kinetic data obtained at pH 7.0 (±0.1) and temperature 27(±1) °C follow the pseudo-second-order kinetic model best ( R 2 > 0.98). The analyzes of isotherm adsorption data by two parameter isotherm model equations show the order to obey: Langmuir > Freundlich > Temkin for As(III), and Langmuir > Temkin > Freundlich for As(V). The monolayer adsorption capacities (mg/g) obtained for As(III) and As(V) are 15.85 and 4.30, respectively. Excepting phosphate, other anions studied show no adverse effect on adsorption of As(III) onto HSO. A fixed bed HSO packed column (internal diameter 0.70 cm, bed height 3.7 cm and particle size 0.14–0.29 mm) generates 2400 and 450 BV of potable water (As < 0.01 mg/L), respectively, for As(III) and As(V) from arsenic spiked (1.0 mg/L) water samples at pH 7.0 (±0.1), which indicated that HSO can be used as an efficient scavenger for As(III) from the contaminated water.

Liquid chromatography determination of natural dyes in extracts from historical Scottish textiles excavated from peat bogs

Textiles excavated from Scottish sites belonging now to the collections of the National Museums of Scotland, including seventeenth century textiles from peat bogs in the Scottish Highlands and Islands, were selected for analysis by high performance liquid chromatography with photodiode array detection (PDA HPLC) to detect whether any dyes remained and, if so, to identify their biological sources. Dye components were identified in 36 of the 81 samples analysed. Although it was not possible to identify the exact sources of the dyestuffs because of the wide-spread occurrence of these natural dyes components, the study has shown that textiles previously not thought to have been coloured had detectable traces of dye. Before the historical textiles were analyzed, an improved extraction procedure that combined the routine acid hydrolysis method with one using dimethylformamide (DMF) was applied. The DMF method enabled increased recovery of major flavonoid and anthraquinoid compounds, and very high efficiency of recovery of indigotin even in textiles with no colour visible, thereby complementing the acid hydrolysis method already in use. Extracts from historical thread samples were analysed by PDA HPLC using a reversed-phase gradient system comprising of a C18 column (150 mm × 4.6 mm i.d., 25 ± 1 °C) with water, methanol and o-phosphoric acid at an eluent flow rate of 1.2 ml/min. A preliminary investigation to improve the detection limits further for a selection of natural dyes was made by comparing results from the 4.6 mm internal diameter (i.d.) column with a narrow bore C18 column (2.1 mm i.d.). An increase in the detector response was observed for narrow-bore column proving its possibility of enhancement of sensitivity.

High-performance liquid chromatography of seized drugs at elevated pressure with 1.7 μm hybrid C18 stationary phase columns

High-performance liquid chromatography (HPLC) separation of drugs at elevated pressure with 1.7 μm hybrid C18 stationary phase columns was investigated. This technique, which uses instrumentation engineered to handle the narrow peaks and high back pressures generated by 1.7 μm particle columns, provided significantly better resolution and/or faster analysis than conventional HPLC and capillary electrophoresis (CE). The use of 2 mm internal diameter (i.d.) columns of 3–10 cm length has been evaluated for the separation of basic and neutral drugs, drug profiling, and general screening (including acidic drugs). For these applications, compared to conventional HPLC and CE, it provided up to 12× and 3× faster analyses, respectively. Precision was excellent for both isocratic and gradient analyses. For retention time and peak area, RSDs of ≤0.1% were obtainable. Fifteen anabolic steroids and esters were well separated in a 2.5 min gradient. For drug profiling, compared to HPLC and CE, approximately twice as many peaks were resolved. HPLC at elevated pressure is also well suited as a general screening technique. Twenty-four solutes of varying drug classes including narcotic analgesics, stimulants, depressants, hallucinogens, and anabolic steroids were fully separated in a 13.5 min gradient.

Influence of the viscosity on the liquid hold-up in trickle-bed reactors with structured packings

The influence of liquid viscosity on liquid hold-up in structured packings under co-current gas–liquid downward flow operation has been investigated for liquid viscosity from 1 to 20 cP. The liquid hold-up has been determined on a 400 mm internal diameter column by gamma tomographic cross-sectional measurements. An important influence of the viscosity on the liquid hold-up is observed. It is shown that, the widely used model supported by Bravo et al. [J.L. Bravo, J.A. Rocha, J.R. Fair, Hydrocarbon Process. January (1985) 91] assuming 1D fully established vertical liquid film flow does not agree with the experimental data. From experiments, the different assumptions used in the 1D model are discussed. On the basis of these results, a new correlation is proposed, which enables to calculate the hold-up from the viscosity, the liquid flow rate and the geometry of the packing. A comparison with data of literature is done.

Optimization of the coupling of high-temperature liquid chromatography and flame ionization detection: Application to the separations of alcohols

The feasibility of coupling high-temperature liquid chromatography (HTLC) to flame ionization detection (FID) has been studied. FID parameter values (hydrogen flow-rate, air flow-rate and FID temperature), typically set in gas chromatography are rarely suitable for liquid chromatography. Best values depend obviously on the water flow rate which is defined depending on both column temperature and column internal diameter. The FID parameters were optimized according to the water flow-rate by means of an experimental design. The potential of the method is shown with some alcohol separations and the value of increasing column temperature while reducing the column diameter is highlighted.

Fast GC analysis of major volatile compounds in distilled alcoholic beverages: Optimisation of injection and chromatographic conditions

The principal secondary flavour compounds in distilled spirits can be successfully quantified by split injection to a 0.15 mm internal diameter (I.D.) capillary column. Initial conditions for split ratio, gas velocity, initial oven temperature and oven ramp rate are given by method translation from a similar method on a standard 0.25 mm internal diameter column with the same phase. These parameters were then investigated in an experimental design comprising a series of experiments in which the responses were the resolution of two critical peak pairs, the analysis time and the limit of quantification (LOQ) of the eight major compounds. The LOQ is the concentration corresponding to a signal 10 times greater than the noise. The experiments were replicated at two different concentration levels, which encompassed the natural levels of the compounds of interest found in distilled spirits. From the chemometric evaluation of these data, a validated model was constructed, which allowed the prediction of conditions for optimum chromatographic analysis. Three additional concentration levels were then added to the model to establish linearity, repeatability and sensitivity. Modern gas chromatographic hardware allows the use of these narrow-bore capillary columns for routine use without operational difficulties. Major advantages are a substantial decrease in analysis time allowing high throughput processing of samples.

Hydrodynamics in two-phase flow within porous media

Ultra-fast magnetic resonance imaging techniques are used to image liquid distribution in two and three dimensions during air-water co-current down flow through a fixed bed of cylindrical porous pellets of length and diameter 3 mm, packed within a 43 mm internal diameter column in both the trickle- and pulsing-flow regimes. The data acquisition times used were 20 and 280 ms, giving 2-D and 3-D spatial resolutions of 1.4 mm x 2.8 mm and 3.75 mm x 3.75 mm x 1.87 mm, respectively. This work reports images of local pulsing events within the bed occurring during the trickle-to-pulse flow transition. The evolution of the local instabilities is studied as a function of increasing liquid velocity at constant gas velocity.