Narrow-bore packed-column HPLC

It Is the purpose of this manuscript to compare four types of mlcrobore columns reported In the literature. The utilization of the narrow-bore packed column HPLC In terms of Instrumentation requirements for Injection valves, pumping systems, and detectors are also discussed. 

Narrow-bore packed-column HPLC, as reported by Yang utilized fused silica columns of OOO pm I.D. packed with 3-, 5- and 10-pm particles. A proprietary packing technique yields high... 

There Is no doubt that narrow-bore packed columns pose very stringent requirements on the design of the liquid chromatograph. Modifications of existing commercial equipment for the practice of narrow-bore packed column HPLC are given below ... 

For high pressure narrow-bore packed column HPLC, a splitter... 

Figure 2. The modified Valeo 0.5 p 1 internal loop sampling valve for split injection in narrow-bore packed column HPLC (Reproduced with permission from Ref. 12, copyright Elsevier Sci. Publ. Co.)...

The design of hydraulic systems for narrow-bore packed column HPLC Is particularly challenging because of the low flow rate used In narrow-bore packed columns. The potential performance of narrow-bore packed columns Is greatly reduced by the constraint of operable constant low flow rates and the operable pressure limit. 

The influence of HPLC on the development of separation media for CEC is rather obvious. For example, HPLC-like hardware , such as frits and packed columns, are employed. A number of various packing technologies have been reported that enable packing particles into narrow bore capillary columns. The solvent slurry packing appears to be the most popular technique that has been transferred di-... 

F.J. Yang, "Narrow-Bore Hlcropartlcle-Packed-Column HPLC,"... 

All three techniques require a column within which the separation of specific chemical compounds can be achieved. For CE, an uncoated narrow-bore cap column for HPLC, a packed column for GC, a coated-cap column or packed column. 

Although HPLC is not fundamentally different from low pressure chromatography, there are specific features of the equipment and column materials that should be noted. The columns are usually supplied ready-packed. For analytical use, column sizes of 4 mm - 125 mm or 4 mm - 250 mm are available, together with narrow bore (2 mm diameter) or microbore (1 mm diameter) columns preparative columns are usually 25 mm 250 mm, or 50 mm 250 mm, or even larger. They are expensive and should be used with care. They should not be subjected to major pressure variations which can lead to compaction of the column bed this can produce high back pressures and a large dead volume at the head of the column. Abrupt changes in solvent should also be avoided, and in particular it is not advisable to... 

The driving forces for the rapid development and growth In mlcrobore column HPLC are (1) savings In solvent consumption a total saving of up to 99.9% can be achieved when narrow-bore microparticle packed columns or open—tubular micro-capillary columns are used (2) the high separation power using long column and small particles (e.g., 3 nm) (3) the compatibility of the column eluent flow rates with a mass spectrometer and flame based detectors and (4) opportunities In new detector development,... 

ELSDs were developed for connection to HPLC with conventional column diameters (Christie, 1992b Upnmoor and Brunner, 1992) but they have also been used for packed column SFC with wide (Carraud et al, 1987 Lafosse, Dreux and Morin-Allory, 1987 Lafosse et al., 1992) and narrow bore colunms (Demirbuker, Andersson and Blomberg 1993 ... 

The need for pure solvents is especially acute with HPLC. The narrow bore of the column and the very small particle size of the column packing require that solvents be particularly pure and free of insoluble residue. In most cases, the solvents must be filtered through ultrafine filters and degassed (have dissolved gases removed) before they can be used. 

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