Column particle size

TSK-GEL column Particle size (/tm) Average pore size (A) Polyethylene oxides/glycols Molecular weight of sample Dextrans Globular proteins ... 

Column Particle size ( lm) Length (mm) ID (mm) Pore size (A) Surface area (mVg) Carbon load (%) End capping pH range... 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

In addition to the above-discussed parameters, other factors such as dimension of the column, particle size of the silica gel, and mobile phase additives may be considered for the optimization of chiral resolution on these CSPs. Metal ions often are important structural components in some proteins to organize conformation [112]. Therefore, the effect of metal ions as mobile phase additives may be useful. Oda et al. [74] used zinc ions as the mobile phase additive on avidin CSP to improve the chiral resolution of ibuprofen, chlormezanone, and other drugs. The results are summarized in Table 5, which indicates that the addition of zinc ions in the mobile phase has resulted into an improved resolution of some... 

To achieve the optimum reversed-phase LC separation, one needs to explore variables such as the analyte chemistry, mobile-phase composition (solvent type, solvent composition, pH, and additives), column composition, column particle size, and column temperature. For pharmaceutical analysis using mass spectrometry, the chemistry of an analyte is rarely changed beyond manipulation of the mobile phase pH, and even there options are limited. Volatile pH modifiers (buffers) are still preferred for LC-MS, and concentrations of these modifiers are kept low. Relatively simply mobile phases consisting of water, acetonitrile, and either formic acid (0.1% v/v), ammonium acetate (1-20 mM), or both have been common. 

Matrix (volume) Analytes Internal standard LOQ (ng/ml) Sample preparation Column (particle size, dimensions) Ionization and detection mode Reference... 

The column efficiency, backpressure and lifetime should be taken into account and compromised when selecting the best column particle size. Most often, porous particles with diameters of 5 pm are used in conventional analytical columns and 3 pm (exceptionally 2 pm) porous particles are usually used in short high-speed columns for... 

Reducing particle size of the SEC column packings reduces the time requirements in SEC because of the increased mass transfer and resultant separation efficiency. Hence, columns can become smaller in dimensions while maintaining resolution. This approach has been used for many years. Column bank lengths dropped from several meters to now typically 60 cm with current SEC column particle sizes of 5 pm as compared with about 100 pm in the early 1960s. During the same period, time requirements dropped from about 6 hr to less than 1 hr. 

Column particle size too small (for example, 3 pm) Use larger particle size (for example, 5 pm). 

The value of S is directly proportional to the column particle size, dp. Noting that and substituting Equations (11.25) and (11.26) into H = l n/L from the Summary Equation Series we find that... 

HPLC measurements were performed on a Waters radial-compression system with a CN column (particle size 5 xm, cartridge 8-mm i.d.). The HPLC apparatus consisted of an ERC-3110 degasser (Erma Optical Works), a Waters U6K injection system, a filter and a precolumn (CN), and a Beckman 160 UV detector with a zinc lamp at a wavelength of 214 nm. The liquid phase was a mixture of 50 vol % acetonitrile and 50 vol % water that contained 0.005 M dibutylamine phosphate. The flow rate was 2.0 mL min" ... 

The nitrobenzene oxidation mixture was analyzed using the HPLC method. 0.2 mL of the stock solution was pipetted into a 25 mL volumetric flask and acetonitril-water (1 2 v/v) was added to it. About 20 pL of the sample solution was next injected into the HPLC systan (Shimatzu) equipped with a Hypersil bond C,j column (particle size 5 pL, 25 x 4.6 mm i.d.) to quantitatively determine the vanillin component while another component was determined qualitatively. Acetonitril-water (1 8) containing 1% acetic acid was used as an eluent with a flow rate of 2 mL/min. The eluent was then monitored with an UV (ultraviolet) detector at 280 mn [6]. 

Table 10 Purity and Recovery of EHoramycin by Column Particle Size...

As noted in Chapter 3, narrow ranges of small particles produce more efficient columns. Particle size is usually given according to mesh range, determined by the pore sizes of the sieves used for screening (see Table 5.2). Common choices for GC are 80/100 or 100/120 mesh. 

Table 2.8 Columns, particle sizes and their operational conditions.

Gravitational, as opposed to centrifugal, sedimentometers are also used to measure particle size distributions. In these, an initially homogeneous suspension is allowed to settle under the influence of gravity in a column. Particle sizes are determined either by sampling or by optical detection. 

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