Column Tubing Materials

Since most anaesthetic mixtures contain at least one volatile liquid component other than the permanent

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Column oven temperature (°C)

Figure 3 Relationship of temperature to flow rate of a porous polymer packing (80/100 mesh). Flow rate = 3.86 x 10~4 T2 -0.283 T+ 59.6.

200 300 400

Filament temperature (°C)

Figure 4 Variation of the hot-wire TCD responses with detector filament temperature. Circles, halothane; squares, nitrous oxide; triangles, carbon dioxide; diamonds, air.

200 300 400

Filament temperature (°C)

Figure 4 Variation of the hot-wire TCD responses with detector filament temperature. Circles, halothane; squares, nitrous oxide; triangles, carbon dioxide; diamonds, air.

gases, operating temperatures with solid adsorbent columns are considerably higher (e.g. 150-220°C) than those required for the separation of the permanent gas alone. Therefore, many of the commonly used tubing materials for permanent gas analysis at lower temperatures may not safely be used in anaesthetic gas analysis. For example, anaesthetic vapours (particularly halothane) tend to decompose in contact with metals (or metal/metal oxide) such as aluminium (& 200°C) and copper (> 250°C) at elevated temperatures, producing a number of halogenated products. Relatively inert materials such as glass and stainless steel may safely be used as column tubing materials for anaesthetic separation purposes at high operating temperatures. Since mixtures contain large amounts of oxygen, heated septum-type injection ports should have a glass liner to prevent metal-liquid anaesthetic contact at higher temperature settings.

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