New Precision Detector Tube for Breath A Icohol Analysis

Transcription

1 New Precision Detector Tube for Breath A Icohol Analysis Tetsuzo Kitagawa3 INTRODUCTION The detector tube method is the simplest procedure for breath alcohol analysis and makes analysis on the spot possible. The writer reported on a study of the detector tube for breath alcohol analysis (Type 104 C) at the Third International Conference on Alcohol and Road Traffic in The detector tube, however, had to be heated to a constant temperature of 50 C during the measurement. Also, the diam eter of the tube was too small (about 2mm) for easy handling and efficient m anufacturing. He has recently developed the new precision detector tube for breath alcohol analysis (Type 104 D) which can be used at ordinary temperatures and has other improvements. The measurable range of alcohol is from 0.10 mg/1 to 1.20 mg/1 with accuracy of less than ± 10% in relative error. The precision detector tube method is now widely used for spot analysis o f breath alcohol o f drivers by the Japanese Police Authority. DETECTOR TUBE FOR ALCOHOL ANALYSIS The detector tube is a glass tube with an inside diam eter of mm and a total length of about 150 mm as shown in Figure 1. A fixed mass of alcohol sensitive reagent particles is filled in the tube. The reagent particles are composed o f porous solid particles (40-60 mesh) coated with acidic chromic trioxide. B A D A. Reagent particles B. Drying particles C. Red glass stains D. Plastic plug Figure 1 Detector tube fo r alcohol analysis (Type 104D) Emeritus Professor of Yokohama National University, President, Komyo Rikagaku Kogyo Co., Tokyo. I l l

2 2 74 T. Kitagawa The mass o f packed reagent particles is 130 mg per tube, and the length of the reagent layer is mm depending on the size of the inside diameter of the tubes. Both ends of the reagent layer are protected by small am ounts o f red glass grains. The original colour of the reagent particles is pink and turns to blue immediately the particles react with alcohol. The chromic trioxide is reduced by ethyl alcohol vapour and a blue chromous salt is formed. In order to remove moisture in breath prior to contact with the reagent, about 200 mg o f drying particles (40-60 mesh) coated with potassium hydroxide are packed in the same tube, being separated from the reagent by red glass grains. PROCEDURE OF MEASUREMENT Both ends o f the detector tube are cut off by cutter and the tube is connected with a metallic aspirating pum p as shown in Figure 2. The volume of the pump is exactly 100 ml. B D E F A. Cylinder C. Handle of piston E. Tube cutter B. Gas inlet D. Release F. Orifice plate Figure 2 Aspirating pump A fter about 3000 ml of breath is sampled into a polyethylene bag, the mouthpiece of the bag is connected with the other end of the detector tube. W hen the piston of the pum p is fully pulled out and turned about 90, it can be fixed in position forming a vacuum of 100 ml in the pump. The breath sample is automatically sucked through the detector tube passing first the drying particles and then the detecting reagent, the flow being controlled by the stainless steel orifice plate provided with a hole o f about 1 mm in diam eter located at the entrance of the pump. One hundred ml of the breath is sucked in after about 90 seconds. This action is repeated twice. Then the bag from the detector tube is removed, and a suction of 100 ml of fresh air is made. The reagent particles in the detector tube change colour on reaction with alcohol vapour, a blue stain of a fixed length being formed after 200 ml of breath and 100 ml of fresh air are sucked through the tube. A mark is made at the pink to blue demarcation line of the tube when sampling is completed, as the stain length has a tendency to lengthen as time passes. The action of the fresh air is to sweep out the absorbed alcohol vapour on the reagent particles, and to increase and stabilise the stain length.

3 New Precision Detector Tube fo r Breath Alcohol Analysis 275 C O N C E N T R A T IO N C H A R T As a constant weight or volume of the reagent particles is packed in each tube, the total length of the reagent layer is an indicator of the inside diameter of the tube.2 The stain length corresponding to a constant alcohol concentration is proportional to the total length of the reagent layer for various detector tubes and the stain length can be corrected for the inside diam eter o f the glass tube by the following simple formula: 10 = 1 + L0 / L, (1) where 1(mm) is measured stain length, 10 (mm) is the corrected stain length, L (mm) is the total length of the reagent particles packed, and L0 (mm) is the standard length which is put as 65 mm. The corrected stain length, 10, of the detector tube and the concentration of alcohol obtained by the FID-type gas chromatography are compared by using the sample gas of alcohol vapour diluted by fresh air. The calibration curve obtained at 20 C is shown in Figure »-.\'(C2H50H m g/i) Figure 3 Calibration curve o f stain length, lo o f detector tube and alcohol concentration measured by gas chromatography. (20 C) The calibration curve in Figure 3 is linear and can be expressed by the following regression formula: 10 = x -1.61, (2) where x (m g/1) is the alcohol concentration obtained by the gas chrom atography. The coefficient o f correlation is r =

4 2 76 T. Kitagawa The concentration chart as shown in Figure 4 can be drawn from the calibration curve in Figure 3. The range of measurement of alcohol concentration is mg/ L 1 I t 1 f O L Alcohol concentration in breath (mg/i) Figure 4 C oncentration chart an d alcohol concentration reading (0.55 m g/1) W hen the detector tube is put on the concentration chart as shown in Figure 4, the length of stain corresponds to the alcohol concentration. The concentration value is read directly on the chart and the correction for the inside diameter of the tube is automatically carried out.2 The tem perature correction table (Table I) must be used for the correction of tem perature of the tube when it is outside of the standard temperature of 20 C and the alcohol concentration is more than 0.50 mg/1. TABLE I. Tem perature correction table Chart Correct concentration (mg/1) reading at temperature of: mg/1) 10 C 15 C 20 C 25 C 30 C 35 C 0.50 No correction for 0.50 or less f Five minutes is sufficient for a whole m easuring procedure. An autom atic sampling device is now under development.

5 New Precision Detnctor Tube for'breath Alcohol Analysis 2 f7 ACCURACY * The alcohol vapour was diluted by the hum an breath to constant concentrations o f 0.16, 0.45, 0.65 and 0.98 mg/1. The sample gas was repeatedly measured every eleven times by means of the detector tube method. The coefficient of variation (looo /x, x is sample mean) in the detector tube m ethod o f 3.16, 3.07, 2.84 and 2.15 % were respectively obtained. TABLE II. C om parison between detector tube m eth od an d g a s chrom atography. No. Alcohol concentration (mg/1) Cdt ^ gc Cdt Cgc Cdt Q?e ^ dt Cgc LOO a Mean (x) Corrected sum of squares (S) (xlo-4) The sample gas of alcohol concentrations of 0.26, 0.45, 0.76 and 0.98 mg/1 was repeatedly measured every seven times by means of the detector tube method (C DT) and the gas chrom a tography (Coc) as shown in Table II. The results of comparison of both methods are shown in Figure 5. The correlation coefficient is and the regression form ula is as follows: CDT = CGC (3) There is good correlation between the two methods. The ratio variances (FQ) of 3.78, 1.41, 1.00 and 2.53 respectively in the F-test are all smaller than the limit value of F = 4.28 at the 95% reliability level. Also the difference between mean values(t0) of 1.22, 1.11, 0.67 and 0.21 respectively in the t-test are all smaller than the limit value o f t = at the 95% reliability. Therefore, any significant deviation could not be found at the 95% reliability level between the detector tube m ethod and the gas chrom atography. Good correlation was also found among the different lots of detector tubes. The shelf life of the detector tube is estimated as about 10 months when stored in a cold, dark place. EFFECT OF OTHER GASES Carbon monoxide, carbon dioxide, w ater vapour, and saturated and unsaturated hydrocarbons have no effect on the colouration o f detector tube. Acetone vapour less than about 7 mg/1 also has no effect.

6 75 T..Kitagawa Figure 5 Comparison o f detector tube method and gas chromatography in breath alcohol analysis. BREATH SAMPLING Jones, Wright and Jones1proved that the alcohol concentration in the rebreathed air-coincides well with the blood alcohol level obtained by equilibriation in vitro. In order that the blood alcohol level may be represented by the alcohol concentration o f breath, the alveolar air m ust be sam pled into the sampling bag. W hen the breath is sampled into a single-type bag of about 3000 ml in volume, the concentration of alcohol in the breath sample may be smaller than that of the alveolar air because of dilution by the dead space in the mouth and condensation of alcohol vapour on the surface of bronchi. The writer has developed the double-type bag for sampling the breath as shown in Figure 6. The bag is composed of two parts, A and B. When breath is blown into the mouthpiece attached at the entrance of the cylindrical A bag, the diluted part of the breath is firstly purged into the B bag of ml through the A bag and the concentrated breath from alveoli is effectively sam pled in the A bag o f ml. After the pipe between A and B is intercepted by means of a pinch-cock, the mouthpiece o f the A bag is connected with the end o f the detector tube for measurement. The A bag must be made of polyester film laminated with polyethylene to prevent transmission of alcohol vapour through the film when the breath sample is kept for several days and the bag must be warm ed to about C before the contents are analysed. Within minutes after sampling the breath, however, the alcohol concentration in the breath sample is not altered at a tem perature above 10 C.

7 New Precision Detector Tube fo r Breath Alcohol Analysis 279 Figure 6 Double-type bag fo r sampling breath. HUM AN TESTS Beer, whisky, Japanese Sake or shochu were ingested by volunteers and breath samples were taken at 20 minute intervals and analysed by both the detector tube method and by gas chromatography. The typical breath alcohol curves with peaks at about 60 minutes after drinking were obtained. The results showed good correlation between the two methods. No difference was found in the results am ong the different kinds o f alcoholic beverage. PRESENT STATUS OF JAPANESE REGULATIONS According to the Japanese Regulations, the limit of alcohol concentration in the driver s breath is less than 0.25 mg/1. Considering the error of measurement, the scales of the concentration chart officially used by the Police Authority are graduated with three s less than the actual alcohol concentrations. Therefore, there is no possibility of high readings due to measurement error alone. Since 1973 the Japanese Police Authority has officially adopted the above-m entioned precision detector tube method (Type 104 D) with successful results for determining driver alcohol levels. The former type of colorimetric detector tube for breath alcohol detection (Type 104 B) had been used, however, by the Police Authority since While the num ber of automobiles has been increasing very rapidly in Japan in recent years, the num ber of deaths caused by automobile traffic accidents has decreased after the peak value in The num ber of (feaths attributable to the effect of alcohol on the contrary, has been gradually increasing. The importance o f spot analysis of breath alcohol of drivers should be again recognised. % t a* < * REFERENCES 1. Jones, A. W., Wright, B. M., and Jones, T. P., An Historical and Experimental Study of the Breath/Blood Alcohol Ratio, Proceedings of the Sixth International Conference on Alcohol, Drugs and Traffic Safety, Addiction Research Foundation, Toronto, Canada, Kitagawa, T., The Rapid Measurement of Toxic Gases and Vapours Proceedings of the Thirteenth International Congress on Occupational Health, New York Kitagawa, T., Detector Tubes for Analysis of Alcohol in Breath, Proceedings o f the Third International Conference on Alcohol and Road Traffic, British Medical.Association, London, Kitagawa, T., and Wright, B. M., A Quantitative Detection-tube Method For Breath-alcohol Estimation, British Medical Journal, 2: 652, 1962