HPLC columns types

Table 3.1. HPLC Column Types Based on Inner Diameters (i.d.)...

A sophisticated commercial HPLC or GC instrument now costs many thousands of dollars and requires a dedicated and skilled operator. It generally has very different applications with GC now generally rarely used in drug analysis but much more in environmental analysis (there are important exceptions). The analytical instruments are very different, employing very different carrier fluids (a carrier gas such as helium in GC versus a mobile phase such as a defined water/methanol mixture in HPLC), column types (packed columns in HPLC versus unpacked in GC), and different and distinct injection and detection methods. 

Table 6.4 Percent Carbon Loading Values for Some ODS (Cig) RP-HPLC Column Types...

Structural formulae (up to too in a file) Starting conditions for RP HPLC (column type, eluent)... 

Hplc techniques are used to routinely separate and quantify less volatile compounds. The hplc columns used to affect this separation are selected based on the constituents of interest. They are typically reverse phase or anion exchange in nature. The constituents routinely assayed in this type of analysis are those high in molecular weight or low in volatility. Specific compounds of interest include wood sugars, vanillin, and tannin complexes. The most common types of hplc detectors employed in the analysis of distilled spirits are the refractive index detector and the ultraviolet detector. Additionally, the recent introduction of the photodiode array detector is making a significant impact in the analysis of distilled spirits. 

Additional factors influencing column performance are the type and quality of the packing process, which mainly determines the theoretical plate count (N) of the column. In contrast to HPLC columns the efficiency of the separation itself is determined predominantly by the quality of the sorbent alone (pore... 

It is not unexpected that the choice of the type of HPLC column, the temperature at which it is maintained and the choice of buffer added to the mobile phase are likely to have an effect on the separation obtained, even for a simple mixture as in this case. 

The most common and diverse approach to cleanup (and extraction of water samples) in pesticide residue analysis is SPE. Over the last 20 years, improvements and diversifications in SPE formats, sorbent types, and apparatus have made SPE a widely used approach for a variety of applications, including the analysis of pesticide residues. SPE cartridges or disks can be likened to low-resolution HPLC columns in that similar stationary and mobile phases are used. A typical particle size in SPE is 40 pm, and the plastic cartridges are generally packed with 0.1-1 g of sorbent in plastic tubes. The choice of reversed-phase, normal-phase, and ion-exchange media in SPE is very diverse, and Table 2 lists some of the more popular SPE applications for the cleanup of pesticides. 

Small bore or microbore is a term used for hplc columns that have diameters less than about 2 mm. Columns of this type were first used as long ago as 1967, but at that time the influence of extra-column dispersion was not appreciated, so that the columns were not used in chromatographs of appropriate design. In 1977 there was a renewal of interest in the properties of small bore columns, but it is only in the last few years that systems have become commercially available that allow the potential of small bore columns to be realised. Several manufacturers are now marketing a range of small bore columns, and a number of recent hplc instruments are claimed to be compatible with them. 

A number of specialised stationary phases have been developed for the separation of chiral compounds. They are known as chiral stationary phases (CSPs) and consist of chiral molecules, usually bonded to microparticulate silica. The mechanism by which such CSPs discriminate between enantiomers (their chiral recognition, or enantioselectivity) is a matter of some debate, but it is known that a number of competing interactions can be involved. Columns packed with CSPs have recently become available commercially. They are some three to five times more expensive than conventional hplc columns, and some types can be used only with a restricted range of mobile phases. Some examples of CSPs are given below ... 

A chiral GC column is able to separate enantiomers of epoxy pheromones in the Type II class, but the applications are very limited as follows a custom-made column packed with a p-cyclodextrin derivative as a liquid phase for the stereochemical identification of natural 3,4- and 6,7-epoxydienes [73, 74] and a commercialized column of an a-cyclodextrin type (Chiraldex A-PH) for the 3,4-epoxydiene [71] (See Table 3). The resolution abilities of chiral HPLC columns have been examined in detail, as shown in Table 7 and Fig. 14 [75,76, 179]. The Chiralpak AD column operated under a normal-phase condition separates well two enantiomers of 9,10-epoxydienes, 6,7-epoxymonoenes and 9,10-epoxymonoenes. Another normal-phase column, the Chiralpak AS column, is suitable for the resolution of the 3,4-epoxydienes. The Chiralcel OJ-R column operated under a reversed-phase condition sufficiently accomplishes enantiomeric separation of the 6,7-epoxydienes and 6,7-epoxymonoenes. 

The most common packing material in HPLC columns (Figure 13.4, C) is a solid with an organic group attached to it. For instance, the solid may have a hydrocarbon chain containing 18 carbons attached to it, making it hydrophobic. This type of column is called a C18 column or a reverse-phase column. Columns can be made with varying polarities and functionalities and thus can be used to carry out a wide variety of separations. 

Name two types of HPLC columns that might be used to separate nucleotides. 

Cabrera K. Lubda D. Eggenweiler H. Minakuchi H. Nakanishi K. A new monolithic-type HPLC column for fast separations. Journal of High Resolution Chromatography, 2000, 23, 93-99. 

Cabrera, K., Lubda, D., Eggenweiler, H.-M., Minakuchi, H. and Nakanishi, K., A New Monolithic-type HPLC Column for Fast Separations, J. High Resolut. Chromatogr., 23 93-99, 2000. 

HPLC column Different batches for same column type ... 

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