The Instruments Of Trace Paper Sample Analysis

　　Involved in writing the material in various criminal activities, are closely related with the paper. In the investigation of these criminal activities, the inspection of paper, plays an important role. Forensic Science on the paper test or identification, and Papermaking Industrial sector finished the test paper, there are similarities between the two have differences, because the ultimate focus of its different. As the case is diverse and different nature of the case require different levels of inspection or identification. Forensic Science Laboratory of the paper aims to narrow the scope of investigation, to provide clues for the detection of cases, direction, as confirmed to provide the scientific basis for crime. As provided in the case of paper samples is limited, so the test methods required unconventional micro-analysis. Has developed a number of technical requirements for forensic analysis equipment, such as TLC, HPLC, plasma emission spectrometry, X-ray diffraction and so on.

　　TLC The main component of paper pulp, there is a small amount of plastic materials, pigments and fillers. For the paper in the plastic material, pigment and filler and other components, because the manufacturers use different sources of raw materials, formulation and manufacturing process is also different, so different manufacturers of the same paper, the organic ingredients must exist some differences. This is what we use thin layer chromatography test the theoretical basis of paper evidence.

　　TLC examination paper, the general fluorescence with silica gel GF254 thin-layer plate, select the appropriate extraction solvent extraction (usually ethanol), concentrated extract after TLC analysis. Expand agents commonly used to: V benzene: V methanol = 95:51 or V benzene: V methanol = 90:5

　　If two different patterns of thin layer chromatography, in the case of clean samples can be identified two patterns are different types of paper or different manufacturers of the same kind of paper. If the two patterns of thin-layer chromatography, typically the same kind of paper, whether it is the same paper manufacturers also need to use the thin-layer Scanners . Determination of the relative content of each component pattern, or other methods for further analysis.

　　High performance liquid chromatography Part of the different areas, different manufacturers of the same kind of paper, not only the appearance, physical properties and the same fiber composition, and other organic ingredients are basically the same, with the general identification of thin-layer chromatography is difficult to distinguish. However, the organic components of these papers have some differences in the relative content. Using high performance liquid chromatography to analyze the pigment paper, rubber and other organic components of an effective way to determine the relative intensity of main peaks, to further identify with the different kinds of paper manufacturers and lot numbers.

　　Test using high performance liquid chromatography paper, not only do not need to deal with cracking the samples, and the mobile phase is also a wide range of options. Analysis using C18 reversed phase column, mobile phase using methanol / water or acetonitrile / water detector for the UV detector, detection wavelength of 254nm. Specific methods are as follows: clipping 5cm2 pattern, then cut into pieces, add 1ml anhydrous ethanol, soaked 10h, supernatant chromatography. The results show that: different manufacturers, different batches of the same kind of paper, its relative content of organic components, there are some differences.

　　Atomic emission spectrometry Atomic emission spectrometry to analyze the general elements of paper, especially paper, the type of metal elements and their relative contents were analyzed. In turn, can distinguish between the type and manufacturer of paper. The use of ordinary atomic emission spectrometry need to pattern after mixing ash into the electrode and the toner tank, and then stimulated emission out of the line of determination wavelength and intensity.

　　Q 24 domestic common exchange medium spectrograph and arc voltage.

　　Specific methods of operation, there are two: The first method is to cut thin strips of paper, the spectrum of pure graphite with homemade forceps clamped at one end of paper. Arc formed between the electrode case, the other end of the slow clearance of graphite electrodes sent to spectrography.