The Lion Intoxilyzer 6000 and Lion Intoximeter 3000: comparison of response to Methyl Tertiary Butyl Ether

Transcription

1 The Lion Intoxilyzer 6000 and Lion Intoximeter 3000: comparison of response to Methyl Tertiary Butyl Ether David S JOSTY Lion Laboratories pic, Barry, W ales CF63 2BE United Kingdom INTRODUCTION In various countries an alkyl ether known as Methyl Tertiary Butyl Ether (MTBE) is added to unleaded petroleum fuel products in order to raise their octane levels. It has been suggested individuals who occupationally are exposed to such fuels (and therefore this compound) might have high levels of MTBE in their exhaled breath, (possibly through passive or direct inhalation or through dermal exposure) such that might falsely elevate a breath alcohol reading, as measured by a substantive breath alcohol testing device. Due to this concern it was decided to test the effects of this alkyl ether on the Lion Intoximeter' 3000 and the lion intoxilyzer 6000UK. [The Lion Intoximeter 3000 evidential breath alcohol analyser has been an approved instrument used in the detection and measurement of breath alcohol in the United Kingdom since 1983, whilst the lion intoxilyzer 6000UK evidential breath alcohol analyser is scheduled for introduction into Police in the United Kingdom during 1997], The reason for this is that until now, most of the documented work in this area has been performed in conjunction with the Breathalyzer a device not used by Police in law enforcement within the United Kingdom. MTBE, alternatively known as 2-Methoxy-2-Methyl Propane, is a moderately soluble and highly flammable butyl ether and has been reported to be a slight inhalation hazard, causing irritation to mucous membranes lining the respiratory passage. As well as this it is a slight eye and skin irritant and has been reported to be a slight ingestion hazard. The chemical structure of MTBE is shown below: -299-

2 M ethyl Tertiary Butyl Ether CH, h 3c o c c h 3 I c h 3 It has been reported [Hartle, 1993] that at two sampled service stations which use only minimal amounts of MTBE within their petroleum products (less than 1%), only 1 o f 32 breath samples from attendants contained a concentration of MTBE which was above the analytical limit of detection, reported at 0.16ppm. In a further study [Moolenaar et al., 1994] it was found that the median post-shift blood concentration of M TBE in occupationally exposed workers was 0.24pg/l (range, pg/l; p = ). EXPERIM ENTAL It was decided to assess the response of both the Lion Intoximeter 3000 and the lion intoxilyzer 6000UK to different concentrations of MTBE, particularly at the concentrations described above, in order to obtain an indication as to whether a blood M TBE concentration of 37pg/l results in a vapour concentration of MTBE which is significant enough to artificially elevate breath alcohol readings as reported by these devices. Different concentrations of aqueous MTBE solutions were added to a certified Smith and Wesson Breath Simulator. After the solution had reached a stable temperature of 34 C ± 0.1 C, vapour samples were generated and were presented to both evidential instruments. The table below displays the results from these tests and any messages generated by the devices. The table also includes the equivalent vapour MTBE concentrations for each solution concentration; [the MTBE solution/air partition coefficient was determined by gas chromatographic method and found to be approximately 200:1 at 34 C]. The above procedure was repeated using whole human blood obtained from the British Blood Transfusion Service. The results from those particular tests are also discussed

3 Finally, dry MTBE gases of various concentrations were prepared [nitrogen was used as the diluent gas] and presented to the two evidential breath testing devices. The results are discussed below and compared with the results obtained using the wet vapour samples containing MTBE. RESULTS AND DISCUSSION The results obtained using the aqueous solutions of MTBE clearly indicate that the vapour concentration generated above an aqueous solution of MTBE at a concentration of 37.0 ig/l [at a temperature o f 34"C ± 0. T'C] would not be sufficient to produce a falsely elevated reading on either the Lion Intoximeter 3000 or the lion intoxilyzer 6000UK. [Although they are not displayed here, the results obtained using the whole blood mentioned above correlated well with those obtained using the aqueous MTBE solution]

4 Table 1 : The Effects of Various Concentrations of W et M TBE Vapour on Results Obtained Using the Lion Intoximeter 3000 and the lion intoxilyzer 6000UK. A queous M TBE V apour M TBE Response by Evidential Breath Testing Device Solution Concentration (pg/l) C oncentration (m g/l) Lion Intoximeter 3000 lion intoxilyzer 6000UK Any other Reading reported Reading %RSD* (pg/ 100ml) message (fig/ 100ml) No No No No No No No No No No Large Acetone Interferent Detected In fact, as Table 1 indicates, a solution/blood concentration several hundred times greater than those which already have been reported would be necessary to cause an elevation in a breath alcohol reading as reported by the Lion Intoximeter W ith regard to the lion intoxilyzer 6000UK it should be noted that due to the nature of its 3pm infrared multi-channel system which incorporates one ethanol sample filter and three interference filters, the interfering species (in this instance, MTBE) absorbs to different extents at the four different filter wavelengths. The lion intoxilyzer 6000UK measures the extent of the interference by calculating the percentage relative standard deviation (%RSD) produced by the four channels and, if the %RSD deviates appreciably from zero then a significant degree of interference is detected. In the United Kingdom if the %RSD exceeds a certain pre-set value and the combined alcohol/interferent reading exceeds 37pg/100ml, the

5 Interferent Detection M essage will be displayed both on the screen and on the Printout. If this occurs the procedure is aborted. Table 2 below displays the results obtained using the dry MTBE vapour and, as may be seen from the table, the concentration of MTBE required in the form of a dry gas in order to cause an elevated reading using the Lion Intoximeter 3000 far exceeds those concentrations already reported. Further to this, due its interferent detection system described above, the lion intoxilyzer 6000UK would abort any evidential breath test if the breath supplied contained MTBE at any of the concentrations described below (provided a combined alcohol /interferent value of 37 o.g/100ml is exceeded). Table 2 : The Effects of Various Concentrations of Dry M TBE Vapour on Results Obtained Using the Lion Intoximeter 3000 and the lion intoxilyzer 6000UK. D ry Gas Vapour Response by E vidential B reath Testing Device C oncentration (g/l) Lion Intoximeter 3000 lion intoxilyzer 6000UK Reading (pg/100ml) Reading (pg/100ml) %RSD* 3.19 x x x x

6 CONCLUSIONS It has been demonstrated that MTBE vapours (both w et and dry ) at the concentrations reported by a number of authors will not cause an elevation in an alcohol reading as measured and reported by the Lion Intoximeter 3000 and the lion intoxilyzer 6000UK, the existing and most recently approved evidential breath alcohol analysers in the United Kingdom respectively. Further to this, when unrealistically high vapour concentrations of M TBE are presented to the lion intoxilyzer 6000UK, the evidential breath testing procedure will abort if the combined value obtained due to alcohol and chemically interfering species exceeds a pre-determ ined value - thus preventing unlawful prosecutions. REFERENCES Hartle R (1993). Exposure to methyl tert-butyl ether and benzene among service station attendants and operators. Environmental Health Perspectives, 101 Suppl 6:23-6. M oolenaar RL, Hefflin BJ, Ashley DL, Middaugh JP and Etzel RA (1994). Methyl Tertiary butyl ether in human blood after exposure to oxygenated fuel in Fairbanks, Alaska, Archives o f Environmental Health, 49(5):