Packing material, choosing

Select suitable mobile phase condition. Choose a mobile phase that will solubilize the sample and will be compatible with the column packing material. 

Once the analytical scale method conditions are optimized, the next step is to choose a column and scale up the analytical HPLC parameters so that preparative chromatography can be performed and the unknown compound(s) can be isolated for identification by MS and NMR. For ease of transition, a preparative column consisting of the same packing material and particle size should be chosen. The column is the most important component of the process because it determines the amount of material that can be loaded for the desired purity and recovery. An important step in the scale-up procedure is determining the maximum load on the analytical column. The maximum analytical load is essential in determining the loading capacity of the preparative column. When an appropriate column is chosen, the analytical isolation can be scaled up using Eq. (5) 2 ... 

With manufacturer-to-manufacturer variability considerations in mind, a good starting point for late-phase method development studies is to choose a 5- im 250 X 4.6 mm i.d. column with a pore size of 80-100 A and a particle surface area of 150-350 m /g. Ideally, the column should also be available in shorter lengths (3, 5, 7.5, 10, and 15 cm) and with 3- r,m packing material of the same pore size and surface area, such that the separation may be easily optimized following initial runs. 

Some SPE packing materials do not receive endcapping thus, it is important to check for endcapping when choosing an SPE sorbent for a specific analyte. For example, in the case when the R group is C-18, the solute would experience reversed-phase sorption to the C-18 and in some cases sorption to the hydroxyl groups. When the interaction between the two groups is intentional, this is called a mixed-mode application of SPE. More examples of mixed-mode SPE will be shown later in this chapter. 

Here the solid phase could be a catalyst or an inert packing material. If the solid phase is the catalyst, the first question to answer is whether to transport the solids or not the considerations leading to this decision are entirely analogous to those for the gas-catalyst system and relate to the time interval between successive regenerations. If it is decided not to transport the solids i.e., to choose fixed beds, we have the following options (see also Fig. 30) ... 

When choosing the materials of construction, it is apparent that the column shell and its packing must be able to withstand all expected operation temperatures within the CS. In this particular case, the normal boiling points are relatively mUd, between 50 and 80°C. The column shell is basically a pipe containing packing material, and aluminum was used in this case because... 

Choose a column that is compatible with your analyte of interest based on the column selectivity. A 15 cm x 4.6 cm stainless steel column containing 5 pm Cig or Cg packing material is a good place to start. Choose a column with good retention characteristics for your types of analytes. 

There are other factors to consider when choosing a column, especially the particle size of the packing materials, the column dimensions, and the solvent in which the column is packed. For GPC of polymers in organic solvents, columns are commercially available prepacked in some of the most frequently used solvents. Particle size influences the ruggedness and resolving power of the columns, while column length can also affect resolving power and diameter relates directly to solvent consumption. 

One is free to choose which flow will be the continuous and which will be the dispersed phase. When the dispersed phase is lighter than the continuous phase, the separator is in the top of the column, and vice-versa. For a PPC a packing material should be selected that is wetted completely by the continuous phase. 

When choosing an adsorbent for a liquid chromatography separation, whether analytical, preparative or process scale, there are a number of practicalities which need to be considered. The type of packing material must be selected with due consideration to the type of molecule being separated size, shap hydrophobidty and electrostatic characteristics are all important as are the contaminants from which it is to be separated. None of the adsorbents used in liquid chromatography are completely inert in their behaviour towards the sample and mobile phase and therefore the physical and chemical characteristics of the adsorbent must also be related to the sample type for optimised separations with maximum throughput and colurrm lifetime. The required purity of the final product must be considered when devising a... 

Chemical composition of packings. Today, a wider variety of different support materials is available from which to choose. Silica is still widely used, though preparative grades often possess a relatively wide particle size distribution as compared to polymer-based supports. One serious limitation of silica-based supports is the low stability of silicas to alkaline pH conditions, which limits use of caustic solutions in sanitization and depyrogenation. Polymer-based supports, which include poly(styrene-divi-nyl benzene)- or methacrylate-based materials, are widely available and have gained increased acceptance and use. Nonfunctionalized poly(styrene-divinyl... 

The 1938 law states that the label of a medication should contain adequate information regarding its use. However, in practice, it became evident that some pharmaceuticals and medications had to be administered by or under the orientation of a medical practitioner, due to the inability of a layman to diagnose a disease, choose an effective treatment, and recognize the cure or the symptoms. Several products were thus classified, but the prescription concept of a medication was introduced only after Alteration in the Law of Durham-Humphrey s in 1951. Since then, a label had to carry the warring Caution, the Federal Law prohibits dispensation without medical prescription. The use of these medications had to be restricted to prescription by a practitioner and the packing or printed material inside had to contain adequate information so that the practitioner could prescribe them safely. 

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