K. W. Smalldon

Otimum use of paper, thin-layer and gas-liquid chromatography for the identification of basic drugs. I. Determination of effectiveness for a series of chromatographic systems.

Abstract A method is described for the determination of effectiveness for a series of chromatographic systems which uses the concept of discriminating power. The discriminating power for a series of chromatographic systems is defined as the probability that two drugs selected at random from a large population would be discriminated in at least one of the systems. The series of systems with the highest discriminating power is shown to produce the best overall separations for a large specified drug population and therefore leads to the identification of an unknown drug using a minimum number of systems. The conditions for maximum discriminating power are described and discussed.

The Characterization of Dyestuffs on Wool Fibers with Special Reference to Microspectrophotometry

Although synthetic fibers have achieved much greater importance in the textile industry over the years, wool still remains the fiber type most frequently encountered in Home Office forensic science laboratories.

Optimum use of paper, thin-layer and gas-liquid chromatography for the identification of basic drugs : II. Paper and thin-layer chromatography

Abstract The concept of discriminating power has been applied to the paper and thin-layer chromatography of 100 basic drugs in eight systems which are representative of the systems in current use. The design of the most effective series of chromatographic systems for the separation and identification of a large drug population is discussed in terms of the individual discriminating powers of the systems and inter-system correlation. It is shown that both the substrate and solvent may have to be changed to obtain significantly different systems.

Optimum use of paper, thin-layer and gas-liquid chromatography for the identification of basic drugs. 3. Gas-liquid chromatography.

Abstract The concept of discriminating power has been applied to the gas-liquid chromatogaphy of 62 basic drugs using eight stationary phases which show a wide range of polarity and are representative of those in current use. The SE-30 and OV-17 columns possessed the highest discriminating powers and SE-30 was the only phase which eluted all the drugs studied. More polar columns not only failed to elute many drugs altogether but the retention indices of those that were eluted also showed high correlation with all the other columns. A single low-polarity phase, such as SE-30 or OV-17, is recommended as the “preferred liquid phase” for the identification of basic drugs. If only low-molecular-weight drugs are considered, DEGS/KOH is recommended as the second “preferred liquid phase”. The use of derivatisation for the identification of basic drugs by gas-liquid chromatography is briefly discussed.

The Extraction of Dyestuffs from Single Wool Fibers

The most important techniques of those currently used in Home Office forensic science laboratories for the analysis of fiber dyestuffs are thin-layer chromatography and visible absorption spectroscopy of dye solutions. To obtain useful discrimination 20 to 50 ng of each dye component must be extracted. In most fiber examinations the recovered fibers are between 2 and 10 mm in length and contain between 2 and 200 ng of dye, depending on the depth of dyeing. Consequently, dye extraction must be efficient if the techniques are to be applied in a reasonable proportion of cases involving fiber comparisons. This paper is concerned with the extraction of dyes from wool fibers.

Transfer of Nitroglycerine to Hands during Contact with Commercial Explosives

The techniques of thin-layer chromatography, gas chromatography with electron capture detection, and gas chromatography/mass spectrometry were used to analyze hand swab extracts for the presence of nitroglycerine. Both the amount of nitroglycerine transferred to the hands after handling commercial explosives and its persistence were measured. Gas chromatography-electron capture detection was found to be the most accurate and sensitive technique for making such determinations, especially if the extract was partially purified by thin-layer chromatography prior to analysis. The lowest limit of detection was 10 ng of nitroglycerine, and residues could be detected over 20 h after handling the raw explosive.

Assessment of Solvents for the Recovery of Nitroglycerine from Hands Using Cotton Swabs

Eight solvents were compared for their relative efficiency in removing nitroglycerine from the hands of persons handling explosives. The amount of interfering material also removed from the hands by the cotton swabs and the stability of the nitroglycerine in the solvent used were also investigated. Aqueous solvents yielded the best recoveries, when the extracts were partially purified by thin-layer chromatography before analysis, but the explosive was degraded rapidly by microorganisms that grew in the solutions. Of the aqueous, organic, and polar solvents tested, ethanol was found to offer the most complete, consistent, and stable recovery.

The Identification of Acrylic Fibers by Polymer Composition as Determined by Infared Spectroscopy and Physical Characteristics

Acrylic fibers are now regularly encountered in the investigation of crime mainly due to their widespread use in the manufacture of outer clothing and carpets. Although acrylic fibers are easily recognized as a group, making a specific identification is particularly difficult. The sample available for identification and comparison in forensic science laboratories may be restricted to a few single fibers, a condition which imposes severe limitations on the value of existing identification schemes for acrylic fibers.

A Comparison of the Relative Sensitivities of the Adsorption Wire and Other Methods for the Detection of Accelerant Residues in Fire Debris

Abstract The relative sensitivities of steam distillation, hot headspace and adsorption wire techniques for fire accelerant recovery were compared under conditions designed to simulate the more extreme casework conditions of tenacious adsorption of accelerant to fire debris. Hot headspace performed least well, requiring between twenty and a hundred times more accelerant for detection than the adsorption wire method. Steam distillation was of intermediate sensitivity. Confirmatory tests were devised to allow the adsorption wire method to be used without recourse to other techniques in case work. A case example is given.

The Persistence of Military Explosives on Hands

Amounts of military explosives that were transferred to hands on contact have been quantified. Factors affecting the persistence of these residues were studied and it was found that about 90% was removed by a single wash. Subsequent washes were however progressively less efficient. Although cyclonite (RDX) and trinitrotoluene (TNT) could be detected easily after 24 h, their presence could not be established after 48 h on the hands of volunteers who had washed about twelve times.