Inner diameter narrow bore

The internal diameter of a column will affect the sample load, the peak dilution, and the flow rate. The larger the inner diameter, the greater is the loading capacity and the higher is the flow rate. However, peak dilution increases with internal diameter, and therefore mass sensitivity decreases. Most analytical columns range from 2 to 5 mm in diameter. Narrow-bore (or smaller) columns with diameters of 2 mm or less are used for applications where high sensitivity is required, the amount of sample is limited, or solvent purchase and disposal costs are significant. 

Electrophoresis in narrow bore tubes, as performed by Hjerten in 1967, provides a better heat dissipating system. He described an application using glass tubes with an internal diameter (I.D.) of +3 mm. The small volume of the narrow bore tube improves the dissipation of heat due to a lower ratio of the inner volume to the wall surface of a tube (Equation (1)). The better the heat dissipation the higher will be the separation efficiency ... 

Micro-HPLC operation sets special demands on the gradient instrumentation. As the internal column diameter, d, decreases, lower flow rates should be used at comparable mean linear mobile phase velocities, u = 0.2-0.3 mm/s. At a constant operating pressure, the flow rate decreases proportionally to the second power of the column inner diameter, so that narrow-bore LC columns with 1mm i.d. require flow rates in the range of 30-100pL/min, micro-columns with i.d. 0.3-0.5mm, flow rates in between 1 and lOpL/min, and columns with 0.075-0.1 mm i.d. flow rates in the range of hundreds nL/min. Special miniaturized pump systems are required to deliver accurately mobile phase at very low flow rates in isocratic LC. 

Sixty grams of powdered sodium chloride are added to 180g of a 10% aqueous solution of ammonia and the mixture is allowed to stand, with occasional swirling, until almost all the salt has dissolved. The filtered solution is placed in a 1-liter flask fitted with a gas delivery tube leading almost to the bottom of the vessel and an exit tube of narrow-bore glass (3mm inner diameter). A steady stream of car-... 

Ito and Bowman (1970) have described a liquid-liquid partition chromatographic system (without solid support), which involves a long helix of narrow-bore tubing with an inner diameter of less than 0.5 mm. When the coiled tube is filled with one phase of a two-phase system and fed with the other phase, phase interchange takes place in each turn of the coil, leaving a segment of the former phase as the stationary phase. Solutes present in either phase are consequently subjected to a multistep partition process. To demonstrate the capability of the method Ito and Bowman used a two-phase system of chloroform, glacial acetic acid, and 0.1 IV... 

A microreaction system was developed for the carbonylation of nitrobenzene as well [28]. Under lower CO gas pressure [9.5 bar much lower than those in conventional ones (>100 bar)], phenylisocyanate was produced. A gas-liquid slug flow of the reactant mixture was formed in the microchannel for efficient mass transfer across the gas-liquid interfaces. The isocyanate yield of the microflow reaction was shown to be three to six times higher than that of the batch reaction, depending on the inner diameter (i.d.) of the microtube. A higher isocyanate yield was obtained in a narrow-bore tube (0.5 mm i.d.) than in a wide-bore tube (1.0 mm i.d.). The catalyst they applied was Pd(py)2Cl2 and pyridine system. 

Figure 3 Schematic drawing of the interface between HPLC and ESI-MS (LC-MS). The system can be modulated to use 2 either capillary (about o.1-0.5 mm inner diameter) or narrow-bore columns (about 1.6 mm inner diameter) by performing o...

Typical loop sizes for conventional 4.6 mm inner diameter (ID) columns are 10-50 [xl (Figure 3.5). For narrow-bore columns, microinjectors with internal grooves in the rotor down to 20-50 nl are available. For even smaller injection volumes, splitting the fiow entering the column may be required. 

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