Alltech集束毛细管柱和常规毛细管柱的比较

对集束毛细管气相色谱柱的色谱性能,如流速对柱效的影响、柱温对柱效的影响、柱容量等进行了考察,并将其对典型火炸药成分ＤＮＴ,ＴＮＴ的分离与常规毛细管气相色谱柱进行了比较。结果表明,集束毛细管气相色谱柱综合了填充柱与石英毛细管气相色谱柱之优点,弥补了二者的不足,是一种柱容量较大且分离效能好、可以在高载气流速下操作的新型气相色谱柱。     

Spiral multicapillary columns

It was shown in a theoretical study and confirmed by experiment that a spiral multicapillary column had maximum efficiency if the bunch of capillaries was additionally coiled around its longitudinal axis to produce an integral number of coils. This technique made it possible to manufacture gas-chromatographic columns with performance as high as 12 to 16 thousand theoretical plates. These columns can find various applications, especially if quick separation is required.     

The use of a moving wire detector system for the study of liquid chromatographic columns

A detector system for liquid columns which employs a moving wire system and a gas-liquid chromatographic detector, is described. The performance of silicic acid columns was studied by investigating the effect of particle size, sample size and flow rate of the mobile phase on the HETP of squalane for coiled and straight columns. The effect of sample size on the resolution of methyl oleate and olive oil on coiled and straight columns was also studied.     

Multicapillary Chromatographic Columns

The possibilities for multicapillary tubes with channels 3–10 μm in diameter and a total number of channels of about 2 × 10⁵−10⁶ to be used as chromatographic columns are studied. It is shown that substances with a sufficiently high boiling point can be separated at temperatures of 20–30°C in 2–3 min with an efficiency of about 1500 theoretical plates per meter (300 theoretical plates for a 20-cm column). __________ Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 10, 2005, pp. 1075–1079. Original Russian Text Copyright ? 2005 by Rudenko, Shoromov, Kumakhov, Naida.     

The Effect of Column Diameter on HPLC Separations Using Constant Length Columns

Abstract

The effect of column dimensions on resolution, sample capacity, mobile-phase use and efficiency using both constant flow-rate and constant linear velocity was studied. The four columns selected have the same length (238 mm), but different diameters (column A: 4.6 mm; column B: 4.0 mm; column C: 3.2 mm and column D: 2.1 mm). It was observed that at constant floworate the reduced plate height was the lowest for columns B and C, higher for column A and highest for column D. On the other hand increasing the injected quantity while keeping injected volume constant revealed columns B and C to have a better efficiency only at the low concentrations. Column A with the largest diameter was superior at high concentrations and thus offers the best loadability. Column D offered, as expected, poor loadability. Examination of the columns at the same calculated linear velocity, showed no appreciable changes in efficiency for the four columns. Preferable detection limits and big solvent savings were obtained when small column diameters were used.     

Potentiality of optical diffraction grating technology in the fabrication of miniaturized multicapillary chromatographic and electrophoresis columns.

A possible way of fabricating miniaturized multicapillary columns for gas and liquid chromatographs or electrophoresis devices containing many thousands of identical channels with a width (or depth) of approximately 1-30 microm by means of industrial technology for the production of optical plane reflecting diffraction gratings is proposed.     

Sol-gel multicapillary columns for gas-solid chromatography

In this work, we report the method for the preparation of multicapillary columns (MCCs) for gas-solid chromatography. The porous layer adsorbent is formed on capillary walls by the hydrolysis of aluminum alkoxide in the presence of polypropylene glycol (PPG) and HCl. Porosity and selectivity of the adsorbent depend on reaction conditions and the concentration of PPG. Sol-gel MCCs are well suited for high-speed chromatographic analysis of light hydrocarbons by gas-solid chromatography. Nine-component mixtures of C1-C4 hydrocarbons are separated within 8-12 s. The efficiency of 25-30 cm long alumina sol-gel MCCs consisting of approximately 1400 capillaries of 40 microm diameter is up to 2500-3000 theoretical plates.     

Multicapillary columns with a porous layer based on the divinylbenzene copolymer

A method for preparing a multicapillary column with a porous layer based on the styrene-divinylbenzene copolymer has been developed. The column makes it possible to quickly separate C₁–C₄ hydrocarbons and oxygen-containing compounds. The main chromatographic properties of the columns were studied.     

A multicapillary gas chromatographic column with a Sol-Gel sorbent based on aluminum oxide

A multicapillary gas chromatographic column with an adsorption layer based on alumina was prepared. The column allowed the high-speed separation of C₁-C₄ light hydrocarbons to be performed in 8–12 s. The possibility of creating columns with various selectivities was demonstrated.     

Simultaneous three-dimensional gas-liquid chromatography on wall-coated glass-capillary columns

Summary A new system for multiple simultaneous gas-liquid chromatographic analysis is described. A commercially available gas chromatograph was modified to accommodate three wall-coated glass-capillary columns. A novel design of both the injection port and sample splitter allows the admission of equal portions of the sample into each of the three columns from a single injection. This provides the analyst either with data for the sample in question on three different liquid phases, or with a single result in triplicate if the same liquid phase is used on all columns. This presentation briefly describes the geometry of the inlet system; details will be published shortly. The performance of this system is illustrated with a simple example. In an artificial mixture, the quantitative GLC-data of 6 compounds obtained on three different columns were unequivocally correlated. A correlation number (CN) is derived which gives the maximum possible number of compounds that can be theoretically correlated in a mixture by the system described.     

Cycling gradient capillary electrophoresis: a low-cost tool for high-throughput analysis of genetic variations

In the present work, we introduce a new type of DNA variation detection. This method represents a transfer of melting gel technique onto multicapillary electrophoresis DNA sequencing instrument with further improvements to achieve maximum sample throughput while maintaining a high performance. The main improvement comes from application of cycling (revolving) temporal temperature gradient in place of a single-sweep gradient, commonly used in similar gel-based techniques. This improvement enables utilization of multiple-injection technique, in which multiple samples are injected into the same capillary (or sets of capillaries) separated by predefined time intervals of partial electrophoresis. The periodic oscillation of the temperature results in identical separation conditions of all samples injected in such series. Using this novel approach, we demonstrate a dramatic increase in separation throughput by turning a standard commercial 96-capillary array instrument into a semicontinuous flow mutation detection system capable to screen over 15 000 samples in 24 h of operation on a single 96-capillary commercial instrument. This represents a 10-fold increase in sample throughput over the current comparable technology.     

Packing capilllary electrochromatography columns using vacuum--a preliminary study

This paper introducesa novel method for packing Capillary Electrochromatography Columns (CEC). Using vacuum packing methodology, silica particles as small as 1 microm were successfully packed into the capillary columns with 75 microm inner diameter. The columns are verystable and show no noticeable loss in efficiency after 200 sample injections. The performance of these vacuum packed capillary columns was evaluated with a mixture of aromatic and non-aromatic compounds. A 24 cm long capillary column can produce peak efficiencies of around 45,000 plates for benzene.     

Etudes theoriques et pratiques sur la realisation et le fonctionnement de colonnes preparatives de diametre moyen. Modification de la structure interne de ces colonnes

The dependence of the efficiency and productivity of preparative-scale gas-chromatographic columns on various parameters is discussed. The minimum HETP is experimentally shown to increase almost proportionally to the column diameter in the range 1–5 cm. The HETP also increases with a power of the sample amount which depends on the quality of the column packing and can be as low as 1.2. High-diffusivity carrier gases (H₂ and He) arc shown to allow a three-fold increase of columns productivity.The productivity (amount of sample separated/unit time) increases with the column diameter. Given a fixed volume of stationary phase and a known mixture, the column diameter which will accept the largest sample can be calculated. The performance of a preparative unit is limited more by the loadability of columns than by loss of efficiency witli increasing diameters. The performances of preparative columns can be improved by putting rods parallel to the column axis regularly spaced in the packing. The column can be heated internally cither for programmed temperature separations or to allow thermal equilibrium to be reached rapidly.     

Rapid separation of elemental species by multicapillary GC

Multicapillary gas chromatography has been applied to the speciation of organomercury compounds. Basic investigation of the fundamental properties of multicapillary columns, to evaluate their potential and limitations as a rapid separation unit, are presented. For analysis of methylated and ethylated mercury compounds a complete separation can be performed within 45 s under isothermal conditions. The adaptation of the technique for use with a purge and trap system and with an element-selective plasma-emission detector results in a compact and effective system for mercury speciation. Results from analysis of certified reference materials were in good agreement with certified values within the significance levels.     

A comparative study of large volume injection techniques for microbore columns in HPLC

Summary This paper focuses attention on the potentially larger signal-to-noise ratios produced by microbore columns in comparison with conventional columns. The increased chromatographic signals by the application of microbore columns are due to the lower chromatographic dilution of elution profiles which are proportional to the square of the column inner radius. Generally less than 1μl sample should be injected into microbore systems to obtain the full benefit of the column performance. However, since more sample can be loaded on conventional columns compared to microbore columns the advantage of improved signal-to-noise ratio can only be realised in situations where very little sample is available. To inject more than 1μl sample, at the same time avoiding extra band-broadening effects, suitable injection techniques must be available. In this study three injection methods for microbore systems that meet this condition, are studied and compared.     

Fast liquid chromatography for the determination of drugs in plasma and combination with liquid-solid extraction in a fully automated system.

Fast liquid chromatography was applied to the assay of several drugs in plasma. Short columns, 3.3-4 cm long, packed with C18 material, 3 microns particle size, were used. The peaks were little subject to extra-column band-broadening because the investigated drugs were eluted with high capacity factors in order to obtain an adequate separation from plasma components. The main influences on efficiency were the response time of the detector and the solvent composition of the injected sample. Conventional apparatus was used. A fully automated analytical system combining liquid-solid extraction via disposable extraction columns and fast liquid chromatography on a small-dimensioned 3 microns particle size column is described for the assay of drugs in plasma. Automation was accomplished by using the Automatic Sample Preparation with Extraction Columns system.     

Ion-chromatographic determination of trace anions with direct sample injection

The influence of the sample volume on the ion-chromatographic determination of anions was examined using various separation columns. Unlike conventionally used columns, Akvilain Al columns exhibit higher capacity factors for weakly retained anions. Thus, increasing the injected sample volume does not result in the masking of peaks of weakly retained anions by the negative system peak. The determination of anions at a level of several Μg/L is possible over a wide pH range. A double-loop system was used to eliminate the effect of residual ions in water used for the preparation of calibration solutions.     

Some practical comparisons of the efficiency and overloading behaviour of sub-2 μm porous and sub-3 μm shell particles in reversed-phase liquid chromatography

At their optimum flow, sub-3 μm superficially porous or "shell" particles demonstrate similar efficiency to sub-2 μm totally porous particles. The performance of 0.21 cm i.d shell columns is however inferior to those of 0.46 cm i.d., presumably due to packing difficulties. At high flow, shell columns can give flatter Knox curves due to lower operating pressure (half or less of that of the totally porous particles) producing less frictional heating, which combined with the increased thermal conductivity of their non-porous core, gives more efficient heat dissipation. However, the effects of frictional heating for sub-2 μm columns are considerably exaggerated when using pure ACN as mobile phase, as it has a thermal conductivity 3 times less than that of pure water, leading to poorer heat dissipation. Overloading is already problematic for ionised solutes, a group which contains many pharmaceuticals and compounds of clinical relevance, on conventional columns (5 μm porous particles). However, it becomes a more serious issue for both new column types, partially as a result of their very high efficiency, which concentrates the sample as a very narrow band. The sample capacity of one type of shell particle was estimated to be 60% of that of the small totally porous particles, in line with the fraction of the particle volume that is porous. Due to overloading, it is barely possible to achieve perfect peak symmetry for ionised acids or bases with either of these new column types, even by injecting the lowest amounts of sample detectable by UV. While ammonium formate and potassium phosphate buffers gave similar results in overloading studies, use of formic acid as sole mobile phase additive is not recommended for these solutes, as its ionic strength is too low, leading to a catastrophic deterioration in efficiency when sample concentrations of even a few mg/L are injected.     

Gas-liquid chromatography of serum bile acids using glass capillary columns

The proposed combination of a rather simple procedure for sample preparation with capillary gas-liquid chromatography using a barium carbonate/polyethyleneglycol 20,000 column and a Grob-type on-column injector permits measurement of bile acids in serum with high separation efficiency, short analysis time and complete separation of bile acids from cholesterol. The method can be adapted to combined capillary gas-liquid chromatography - mass spectrometry.     

GC Behavior of 3-Ketosteroid Methoximes. Application to GC Studies of Adrenocortical Steroid Hormone MO-TMS Derivatives

Abstract

3-Ketosteroid methoximes (MO derivatives) undergo a degradation when injected into columns that contain acidic materials or supports with acidic sites. Degradation products can usually not be isolated; they result from a Beckmann fission reaction. The extent of sample loss is dependent on the amount of acidic material (pyridine hydrochlo-ride), and decreases with time as the column is “healed” by sweeping or silylation treatment. Lanost-8-ene-3-one MO derivative, where the methoxime group is adjacent to a tertiary carbon atom, gives an unsaturated nitrile by Beckmann fission. An appropriate analytical technique was developed to prevent sample loss. About 1–3 cm of 10% coated support at the head of the column will prevent permanent damage to the column; the solution of the analytical sample should also contain an excess of silylation reagent. When this is done, no sample loss is observed in GC studies of adrenocortical steroid hormones as MO-TMS derivatives.