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equired it. For example, there was a 90 second delay in the model we used (Model 207,
Dasabi Corporation), but modification of the circuitry and the sending of the pre-computer
analogue signal directly to the chart recorder (with assistance from the Biomedical
Engineering Department at the Royal Brompton Hospital, London, United Kingdom: Carolyn
Busst and Ron Sinclair) decreased the response time - a factor checked in the first
experiments made to establish the analyser's capability (see Chapter 5). The option of a
reader, chart recorder or an analogue digital computer may seem unusual now in the days of
easy, fast computer access, and the new analysers have these inbuilt for signal display. The
sampling flow of the NO analyser depends on the vacuum pump rate. The NO analysers listed
above at the time that these experiments began sampled at fixed rates between 200 and 800
mls/min. This too was modified for use on the first experiments using this machine (see
Chapter 5). The newer purpose built analysers have a wider range of sampling flow options of
25, 50,100,250 and 5OOmls/min.
Table 4.1: The companies providing chemiluminescence analysers adaptable for nitric oxide
measurement in 1995
ChemLab Instruments Ltd, Hornchurch, United Kingdom
Columbia Scientific Industries Corporation, Austin, Texas,
United States of America.
Dasibi Environmental Corporation, Glendale, Galifornia,
United States of America (Model2107)
Eco Physics, Durnten, Switzerland (CLD 700)
Lear-Seig ler/Mon itor Laboratories, En glewood, Colorado,
United States of America.
Seivers Instruments, Boulder, Colorado,
United States of America. (NOA')
Thermoelectron, Warrington, United Kingdom. (Model 42)
In addition to detecting NO in gas samples, I will mention briefly that the technique can be
used for liquid samples. At room temperature NO has a partition coefficient of 2O; that is in a
sample containing both liquid and gas, there is 20 times more NO in the gas phase than
dissolved in the liquid phase. So if a fluid with no air contact is then injected into a chamber,
the NO quickly escapes into the gas phase and this can be aspirated into the
chemiluminscence analyser. The rest of the NO can then be "stripped" from the solution by
bubbling the solution with an inert gas under vacuum conditions usually at a rate of between
8-10 mls/min driving it into the gas phase which can then be measured (Chung and Fung
1990; Archer, Shultz et al. 1995; Hampl, Walters et al. 1996). However it is vital to avoid
foam or bubbles getting into the reaction chamber as this can then coat the PMT and impair its
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