- Email: [email protected]
Thermal Analysis as an Aid to the Criminalist
References 1. Wynbrandt F and Chisum WJ. Determination of the ABO blood group in hair. Journal of the Forensic Science Society 1971; 11 : 201-204. 2. Mukherjee JB and Chattopadhyay PK. Blood grouping from teeth by the absorptionelution technique and its role in establishing identity. Medicine, Science and the Law 1976; 16: 232-234. 3. Coombs RRA, Bedford D and Rouilland LM. A and B blood group antigens on human epidermal cells demonstrated by mixed agglutination. Lancet 1956; i: 461-466.
(Based on the presentation made to the Ninth Meeting of the International Association of Forensic Sciences, in Bergen, Norway, in June 1981).
Thermal Analysis as an Aid to the Criminalist R. HALONBRENNER Wissenschaftlicher Dienst, Stadtpolizei Zurich, Zurich, Switzerland Most substances undergo physical or chemical changes if they are heated. These changes can be analyzed by a variety of analytical techniques which measure one or more properties of a substance as a function of temperature. Mostly used are thermogravimetry (TG), where weight changes are measured, and differential thermal analysis (DTA) or differential scanning calorimetry, where temperature differences are measured. Thermal analysis has only recently been used in forensic science, probably because large amounts of substance material were required. Now there are a number of instruments which can analyze milligram samples. I n this laboratory the equipment used is the Mettler Thermoanalyzer TA-1 which enables us to combine thermogravimetry and differential scanning calorimetry. Investigations relating to cases of fire damage are in the foreground. While trying to determine the cause of a fire, it is often necessary to find out whether certain materials stocked or deposited in the zone of initial fire have a tendency to self-ignition and might therefore have led to spontaneous ignition. Let me explain this by reference to a group of substances which often play a role when determining the causes of a fire with regard to their possible self-heating or selfigniting properties, namely the so-called drying oils such as linseed oil. To obtain a large surface we apply such substances on kieselguhr, and find a clearly visible peak in the DTA graph which indicates a strong, exothermic heat of reaction, coupled with a weight increase of the sample. This marks the whole process clearly as autoxidation of linseed oil. I n interpreting such a TG/DTA curve, we always speak of "self-heating, possibly with ensuing spontaneous ignition", since firstly the quantitative proportions are not determined by the diagram, and, secondly, specific conditions of the fire site also have to be taken into consideration. Among these other factors there is the distribution of a self-inflammable substance a t the fire site; for instance, a shutter impregnated with linseed oil cannot ignite spontaneously whereas a ball of cotton waste soaked with linseed oil can. The following case illustrates application of the method in fire investigation. There was a fire in a factory of insulation cork slabs. We localized the zone of initial fire in the stock of raw cork. O n the eve of the fire, freshly produced slabs had been deposited there. They were manufactured by heating bitumen with a n oil burner to, allegedly, slightly less than 200°C and mixing it with roasted cork meal. But our measurements showed that temperatures of 220°C could easily be reached not causing an alteration of the end product. Whereas dry cork is not known to self-ignite, freshly processed insulation cork material in blocks is counted among the substances with a tendency to autoxidation. We therefore had to establish the temperature limit above which exothermic
reactions occur in freshly processed material. Thermal analysis showed the critical temperature to be 190°C. This was the first marginal value for the experiments to be carried out in our fire test laboratory. When heating a block of cork to 200°C, we found the dissipation of heat to be sufficient to avoid further heating of the block in spite of the exothermic reactions taking place. If, however, the block of cork was heated beyond 200°C, the exothermic reactions led to ignition even hours after the heating had been turned off. With that the case was closed. Thermal analysis can also be used in soil comparison. After a fire in a garden pavilion, the clothes and shoes of a suspected arsonist were examined. Earth was found clinging to his shoes. The suspect declared that he had been near the grave of his son and that he had not walked on any other ground or meadows. For a comparative analysis of the soil samples we took earth from the area around the grave and from the possible access roads to the fire-site. Twenty milligrammes each of these samples were weighed into crucibles for thermal analysis and heated a t a rate of G°C/min to 900°C. The resulting diagrams were at first only analyzed regarding weight losses in per cent up to 180°C and between 600°C and 800°C, i.e. the moisture contents and carbonate percentages. Furthermore we determined the temperature level at which the separation of carbonates was completed and investigated whether the peak resulting from the conversion of u-quartz into D-quartz at 573°C was evident on the DTA curve or not. Results showed clearly that the soil taken from the shoes was completely different from the soil near the grave. Yet the differences between this soil and the thrcc samples which were taken from the vicinity of the fire area were minimal. Since soil as such is a heterogeneous mixture, analytical tests can generally not prove any identity. But the differences found between the earth on the shoes and the earth from the grave proved that the suspect had not told the truth. For this reason he was sentenced for arson. Thermal analysis is also well-suited to analysis of explosive and incendiary material. Thus, we had to analyze some material that had been found in the possession of a prisoner. I t was a small cardboard box fitted with an electric ignition device and containing red powder. We had to determine whether this device was suitable as an incendiary device. Comparative thermal analysis showed that the red powder was scrapings from the tops of matches. The endothermic DTA-peak a t about 115"C, originating from sulphur, the beginning of an exothermic heat of reaction a t 145°C and the deflagration temperature a t about 162°C were clearly visible. Consequently, the box was well-suited as a n incendiary device. I n conclusion, thermoanalytical tests performed to date have shown that this method provides a valuable addition to the investigation techniques of the criminalist. For further details, a paper in German may be obtained from the author. (Based on the presentation made to the Ninth Meeting of the International Association of Forensic Sciences, in Bergen, Norway, in June 1981).
Determination in Urine of Meprobamate and the Benzodiazepines Most Commonly Used in Clinical Medicine, by Thin Layer Chromatography ROSA S. G . de KEMPNY and R. M. POMPEI Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, Argentina In this work we describe the technique used for the determination, in urine,
(Based on the presentation made to the Ninth Meeting of the International Association of Forensic Sciences, in Bergen, Norway, in June 1981).
Thermal Analysis as an Aid to the Criminalist R. HALONBRENNER Wissenschaftlicher Dienst, Stadtpolizei Zurich, Zurich, Switzerland Most substances undergo physical or chemical changes if they are heated. These changes can be analyzed by a variety of analytical techniques which measure one or more properties of a substance as a function of temperature. Mostly used are thermogravimetry (TG), where weight changes are measured, and differential thermal analysis (DTA) or differential scanning calorimetry, where temperature differences are measured. Thermal analysis has only recently been used in forensic science, probably because large amounts of substance material were required. Now there are a number of instruments which can analyze milligram samples. I n this laboratory the equipment used is the Mettler Thermoanalyzer TA-1 which enables us to combine thermogravimetry and differential scanning calorimetry. Investigations relating to cases of fire damage are in the foreground. While trying to determine the cause of a fire, it is often necessary to find out whether certain materials stocked or deposited in the zone of initial fire have a tendency to self-ignition and might therefore have led to spontaneous ignition. Let me explain this by reference to a group of substances which often play a role when determining the causes of a fire with regard to their possible self-heating or selfigniting properties, namely the so-called drying oils such as linseed oil. To obtain a large surface we apply such substances on kieselguhr, and find a clearly visible peak in the DTA graph which indicates a strong, exothermic heat of reaction, coupled with a weight increase of the sample. This marks the whole process clearly as autoxidation of linseed oil. I n interpreting such a TG/DTA curve, we always speak of "self-heating, possibly with ensuing spontaneous ignition", since firstly the quantitative proportions are not determined by the diagram, and, secondly, specific conditions of the fire site also have to be taken into consideration. Among these other factors there is the distribution of a self-inflammable substance a t the fire site; for instance, a shutter impregnated with linseed oil cannot ignite spontaneously whereas a ball of cotton waste soaked with linseed oil can. The following case illustrates application of the method in fire investigation. There was a fire in a factory of insulation cork slabs. We localized the zone of initial fire in the stock of raw cork. O n the eve of the fire, freshly produced slabs had been deposited there. They were manufactured by heating bitumen with a n oil burner to, allegedly, slightly less than 200°C and mixing it with roasted cork meal. But our measurements showed that temperatures of 220°C could easily be reached not causing an alteration of the end product. Whereas dry cork is not known to self-ignite, freshly processed insulation cork material in blocks is counted among the substances with a tendency to autoxidation. We therefore had to establish the temperature limit above which exothermic
reactions occur in freshly processed material. Thermal analysis showed the critical temperature to be 190°C. This was the first marginal value for the experiments to be carried out in our fire test laboratory. When heating a block of cork to 200°C, we found the dissipation of heat to be sufficient to avoid further heating of the block in spite of the exothermic reactions taking place. If, however, the block of cork was heated beyond 200°C, the exothermic reactions led to ignition even hours after the heating had been turned off. With that the case was closed. Thermal analysis can also be used in soil comparison. After a fire in a garden pavilion, the clothes and shoes of a suspected arsonist were examined. Earth was found clinging to his shoes. The suspect declared that he had been near the grave of his son and that he had not walked on any other ground or meadows. For a comparative analysis of the soil samples we took earth from the area around the grave and from the possible access roads to the fire-site. Twenty milligrammes each of these samples were weighed into crucibles for thermal analysis and heated a t a rate of G°C/min to 900°C. The resulting diagrams were at first only analyzed regarding weight losses in per cent up to 180°C and between 600°C and 800°C, i.e. the moisture contents and carbonate percentages. Furthermore we determined the temperature level at which the separation of carbonates was completed and investigated whether the peak resulting from the conversion of u-quartz into D-quartz at 573°C was evident on the DTA curve or not. Results showed clearly that the soil taken from the shoes was completely different from the soil near the grave. Yet the differences between this soil and the thrcc samples which were taken from the vicinity of the fire area were minimal. Since soil as such is a heterogeneous mixture, analytical tests can generally not prove any identity. But the differences found between the earth on the shoes and the earth from the grave proved that the suspect had not told the truth. For this reason he was sentenced for arson. Thermal analysis is also well-suited to analysis of explosive and incendiary material. Thus, we had to analyze some material that had been found in the possession of a prisoner. I t was a small cardboard box fitted with an electric ignition device and containing red powder. We had to determine whether this device was suitable as an incendiary device. Comparative thermal analysis showed that the red powder was scrapings from the tops of matches. The endothermic DTA-peak a t about 115"C, originating from sulphur, the beginning of an exothermic heat of reaction a t 145°C and the deflagration temperature a t about 162°C were clearly visible. Consequently, the box was well-suited as a n incendiary device. I n conclusion, thermoanalytical tests performed to date have shown that this method provides a valuable addition to the investigation techniques of the criminalist. For further details, a paper in German may be obtained from the author. (Based on the presentation made to the Ninth Meeting of the International Association of Forensic Sciences, in Bergen, Norway, in June 1981).
Determination in Urine of Meprobamate and the Benzodiazepines Most Commonly Used in Clinical Medicine, by Thin Layer Chromatography ROSA S. G . de KEMPNY and R. M. POMPEI Facultad de Ciencias Exactas y Naturales, University of Buenos Aires, Argentina In this work we describe the technique used for the determination, in urine,