| 摘要 |
<p>A nebuliser assembly (1) for spectroscopic apparatus in which a sample to be analysed is presented in the form of an aerosol. The assembly includes a mounting block (7), preferably a polyethylene, having a through passage (15) within which is mounted a venturi (10), capillary tube (8), capillary guide (16), capillary holder (17) and thimble type adjuster (19). The mounting can include a tubular nut (18) which is in threaded engagement with a liner (18a) which in turn is threaded into passage (15). The tubular nut (18) holds the venturi (10) and capillary guide (16) in place against a shoulder (14) in the passageway (15). Thimble (19) can adjust the position of capillary holder (17), which can slide within tubular nut (18), against spring bias (35). Such adjustment varies the position of the end of capillary tube (8) relative to venturi (10) and thereby the amount of sample aspirated through capillary tube (8) by the action of a pressurised oxidant passing through the venturi. The oxidant is fed via inlet passage (26) in block (7) to chamber (25) and passages (27) provided by the venturi guide (16). The venturi is surrounded by an O-ring seal (24) and this allows the venturi (10) to self-centre within the passageway (15) and improves its concentricity with the capillary tube (8). Also the direct location of the venturi (10) in the passageway (15) of mounting body (7), which provides a wall (34) of a spray chamber, allows a relatively simpler nebuliser construction than in the prior art. The venturi (10) is preferably made from a polyether ether ketone to ensure a smooth surface finish for its bore. </p> |
