Dequenching of infrared luminescence

“Dequenching” has been observed in infrared luminescence as well as ultraviolet fluorescence (Gupta et al., Forensic Sci. Int., 12 (1978) 61 – 64). Thin-layer chromatographic separations of non-luminescing inks can reveal luminescent bands. This dequenched luminescence can also be observed by spot tests with solvents and under transparent adhesive tape.     

Comparison of near infrared light photography and middle infrared light photography for deciphering obliterated writings

There are obliterated writings that are undecipherable by conventional visible and near infrared monochromatic light photography. Some of them could be deciphered undestructively by middle infrared light photography. Characters were written on paper with 101 kinds of pens. Middle infrared light photographs and near infrared light photographs of them were taken and compared to recognize what kinds of inks is transparent at examined wavelength regions. Based on the results obtained, the combination of ink for drawing and obliterating (which is not deciphered by visible and near infrared light photography, but expected to be deciphered with middle infrared light photography) is selected. From the examined photographs, it is demonstrated that there exist obliterated writings which are undecipherable by conventional near infrared light photography, but decipherable by middle infrared light photography.     

Passport examination by polarized infrared spectra

In this study, a new nondestructive technique for passport examination is proposed. In this technique, linearly polarized light is used to measure Fourier transform infrared (FT-IR) reflectance spectra of films on the biographical data page. Thirty genuine and thirty-five counterfeit Japanese passports and five marketed films pasted on name cards were examined. The measured spectra were analyzed as follows. The absorption spectra were obtained by the Kramers-Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1126 and 1263 cm(-1) and dividing the result by the peak area at 1727 cm(-1). When nonpolarized light was used, the samples could not be distinguished by comparing the peak ratios. However, when polarized light was used, they were successfully distinguished by the comparison. Therefore, polarized light is useful for the forensic discrimination of passport films by the measurement of FT-IR spectra.     

Examination of lubricating oils by infrared spectroscopy

Approximately 60 oil samples obtained from the chassis of various motor cars have been examined by infrared spectroscopy. The samples were oils from the engine, gearbox and back-axle. Differences in absorbance of some absorption bands in the infrared spectra (IR) of oil samples were observed. An optimal set of absorption bands was chosen, which was used for quantitative comparison of slightly differing spectra. The significance of differences was tested using Hotelling's T²-test.     

二维相关红外光谱技术鉴别普通办公胶水的应用研究

目的建立一种普通办公胶水的检验鉴定方法。方法采用红外光谱法（FTIR）并结合二维相关光谱分析技术,对不同厂家生产的常用普通办公胶水,以及同一厂家生产的不同批次的胶水进行鉴别分析。结果若胶水的组成成分不同,则一维红外谱图的差异较大,若胶水的组成成分相近,则一维红外谱图的差异就不显著,甚至难以区分,但是以时间为微扰项,进行一系列动态分析,即使用二维红外谱图进行分析,也可轻易的将其区别。结论该方法增加了一维红外光谱的分辨率,可将一维红外光谱不能区分的物质,进行动态分析,由变化过程的差异从而进行区分,拓展了红外光谱的分析能力。     

签字笔水、圆珠笔油红外发光特性的研究

目的记录不同激发光、接收滤光镜下,各种油墨红外发光强弱的程度,为文字检验提供基础性的研究。方法用多波段光源中510~650nm单色光激发各种油墨样本,全波段物证检验CCD系统记录样本在530~950nm接收滤光镜下出现的红外发光图像。结果多数油墨在接收滤光镜到达800~850nm时,呈现出强烈的红外发光状态,并随接收波段的上升而开始衰减。结论可利用某些油墨的发光与否,发光强与弱的特性,检验案件中涂改和涂抹字迹。     

傅立叶变换红外光谱法检验口红的研究

目的建立一种灵敏、准确、无损的口红检验方法。方法利用傅立叶变换红外光谱仪,采用SmartPerformer采样器,对202个不同产地、不同品牌和同一品牌不同牌号的口红样品进行分析检验。结果依据红外光谱图中吸收峰的不同,可以将口红样品加以区分。结论该检验方法不破坏检材,重现性好,可用于鉴定案件现场中提取到的口红物证。     

Fourier-transformed infrared breath testing after ingestion of technical alcohol

The study aim was to evaluate the feasibility of a Fourier-transformed infrared (FT-IR) analyzer for out-of-laboratory use by screening the exhalations of inebriated individuals, and to determine analysis quality using common breath components and solvents. Each of the 35 inebriated participants gave an acceptable sample. Because of the metabolism of 2-propanol, the subjects exhaled high concentrations of acetone in addition to ethanol. Other volatile ingredients of technical ethanol products (methyl ethyl ketone, methyl isobutyl ketone, and 2-propanol) were also detected. The lower limits of quantification for the analyzed components ranged from 1.7 to 12 microg/L in simulated breath samples. The bias was +/-2% for ethanol and -11% for methanol. Within-day and between-day coefficients of variation were <1% for ethanol and <4% for methanol. The bias of ethanol and methanol analyses due to coexisting solvents ranged from -0.8 to +2.2% and from -5.6 to +2.9%, respectively. The FT-IR method proved suitable for use outside the laboratory and fulfilled the quality criteria for analysis of solvents in breath.     

应用红外化学成像技术显现潜在的指印

目的应用红外化学（光谱）成像技术显现潜在指纹。方法采用这种新技术进行显现潜在指印的初步实验。结果显示了其对复杂图案背景上指印突出的显现能力。该成像技术具有物质形态特征检验和物质成分检验双重分析能力，在法庭科学领域具有重要的应用价值。     

傅立叶变换红外光谱法检验静电复印墨粉

目的　通过对静电复印墨粉进行检验 ,达到对不同厂家及不同型号墨粉区分的目的。方法　首先利用电熨斗加热提取复印件的墨粉 ,然后利用傅立叶变换红外光谱法对 9个墨粉厂家和 2 4种牌号进行检验。结果可以达到厂家区分和大部分牌号区分 ,区分率达到 95 .7%。结论　本研究对实际应用有较大参考价值。     

Single fiber analysis by internal reflection infrared microspectroscopy.

Attenuated total reflection (ATR) is a convenient mode for single fiber analysis by infrared microspectroscopy, particularly when transmission spectra are difficult to obtain or when surface preferenced sampling is desirable. Textile finishes such as spin finishes, anti-static finishes, and permanent press finishes are revealed by ATR techniques. Bicomponent fibers may be analyzed by a combination of ATR techniques, transmission techniques, and spectral subtraction.     

Bloodstain age estimation through infrared spectroscopy and Chemometric models

The chemical profiling of bloodstains is essential to link the suspect with the crime. The current study proposed a proof-of-concept methodology for the investigation of bloodstains by utilizing advanced ATR-FTIR spectroscopy coupled with new generation chemometric methods. Current study provides encouraging data to allow discrimination between human and animal blood though with small sample size. In this study, different models for the age estimation of human bloodstains are developed from the trained data sets of 1–175 days old bloodstains. The models such as curve estimation (CE), multiple linear regression (MLR), and partial least squares regressions (PLSR) are developed to determine the best prediction model for aged human bloodstains. The obtained results on the dating of bloodstains are very encouraging and also tested for unknown samples. The maximum dating errors are observed in the curve estimation models whereas, the other models MLR, PLSR show excellent age estimation of unknown bloodstains. These models represent an error of ~3 ± 1 days and ~4 ± 1 days in actual and estimated date, respectively, which is lowest ever reported so far. The present methodology is expected to provide a valuable insight into forensic society and hence, to the law enforcement community. The present methodology can further be explored for an ideal model by including all other external variables/factors and for more longer aging time.     

Forensic analysis of bicomponent fibers using infrared chemical imaging

The application of infrared chemical imaging to the analysis of bicomponent fibers was evaluated. Eleven nominally bicomponent fibers were examined either side-on or in cross-section. In six of the 11 samples, infrared chemical imaging was able to spatially resolve two spectroscopically distinct regions when the fibers were examined side-on. As well as yielding characteristic infrared spectra of each component, the technique also provided images that clearly illustrated the side-by-side configuration of these components in the fiber. In one case it was possible to prepare and image a cross-section of the fiber, but in general the preparation of fiber cross-sections proved very difficult. In five of the 11 samples, the infrared spectra could be used to identify the overall chemical composition of the fibers, according to a published classification scheme, but the fiber components could not be spatially resolved. Difficulties that are inherent to conventional "single-point" infrared spectroscopy, such as interference fringing and sloping baselines, particularly when analyzing acrylic type fibers, were also encountered in the infrared chemical image analysis of bicomponent fibers. A number of infrared sampling techniques were investigated to overcome these problems, and recommendations for the best sampling technique are given. Chemical imaging results were compared with those obtained using conventional fiber microscopy techniques.     

Fourier transform infrared analyses of some particulate drug mixtures using a diamond anvil cell with a beam condenser and an infrared microscope.

Although the diamond anvil cell (DAC) has been used in many forensic science laboratories for the analysis of trace evidence, few applications of this technique for the analysis of controlled substances have been reported. This may be due to both an unfamiliarity on the part of forensic drug chemists with this accessory and the nature and quality of spectra that result from use of a DAC on a dispersive instrument. Along with low energy throughput, which results in relatively high noise levels, strong broad diamond absorptions occur. With the use of a Fourier transform infrared instrument, these do not present a problem and nanogram quantities of materials can be analyzed when the DAC is used with an infrared microscope. Since single crystals can be sampled with the DAC, simple physical separations (involving particle-picking) can be used in certain cases to isolate drugs from particulate mixtures for infrared analysis. This method is especially useful for some "difficult" mixtures and residues, and several examples of such analyses involving samples of forensic science interest are presented.     

Forensic applications of infrared chemical imaging: multi-layered paint chips

This paper examines the potential of infrared chemical (hyperspectral) imaging as a technique for the forensic analysis of automotive paint chips in particular, and multicomponent (e.g., layered) samples in general. Improved sample preparation procedures for the infrared analysis of paint chips are detailed, with the recommendation that where mounting resins are chemically incompatible with the sample, it is better to mount and section the sample in a soft wax from which the sections can be removed and pressed into a KBr disk for transmission analysis. Infrared chemical images of multilayered paint chips have been successfully obtained, with the chief advantage over conventional infrared analysis being that thousands of infrared spectra are collected in a few minutes across the whole sample, at a spatial resolution of around 5 microm. As with conventional infrared spectroscopy, chemical species can be identified from their spectra, but the wealth of information available can be also extracted in a number of different ways that make multicomponent spectral (and hence chemical) comparisons between two samples easy to visualize and understand. In one approach, the infrared chemical images of two paint chips being compared side-by-side can be viewed as a "movie," in which each frame is an intensity map of the two samples at a given wavenumber (frequency) value. In another approach, the spectra (pixels) in the image files are classified into chemically similar groups, resulting in a "cluster" image that makes it possible to simultaneously compare all of the layers in two paint chips. These methods are applicable to other multicomponent samples, and also to other chemical imaging techniques.     

红外线照射谷物表面杀菌的研究

利用红外线对小麦和大豆的表面进行照射杀菌,比较不同红外线照射条件对附着生菌数、杀菌效果及对品质的影响。结果表明:红外线照射可在较短时间内杀死对热比较敏感的微生物,照射1s后生存比急剧下降,而接续的照射由于对热抵抗性较强的微生物存在,生存比的下降缓慢。对品质分析和发芽试验也证明:照射后水分含量变化不明显,小麦在2%左右,大豆没有发生变化,对谷物内部品质几乎没有影响。红外线照射引起微生物的死亡不是由谷物表面受热后再向微生物传导加热,而是微生物直接受红外线辐射的热致死的。     

傅里叶红外图像无损检验添改数字的研究

目的建立利用傅里叶红外图像系统无损检验添改数字的检验方法。方法采集同种同品牌、同种不同品牌及不同种书写材料书写的数字1改为4和3添加为8两类样本的红外图像，根据红外吸收的光谱信息对其添改进行检验。结果同种不同品牌及不同种书写材料对红外吸收强弱不同，形成的红外图像有差别；同种同品牌书写材料对红外吸收强弱没有明显差别。结论该检验方法不损坏检材，重现性好，并且纸张成分对其分析结果基本上无干扰。     

Screening experiments of ecstasy street samples using near infrared spectroscopy

Twelve different sets of confiscated ecstasy samples were analysed applying both near infrared spectroscopy in reflectance mode (1100-2500 nm) and high-performance liquid chromatography (HPLC). The sets showed a large variance in composition. A calibration data set was generated based on the theory of factorial designs. It contained 221 N-methyl-3,4-methylenedioxyamphetamine (MDMA) samples, 167 N-ethyl-3,4-methylenedioxyamphetamine (MDE), 111 amphetamine and 106 samples without a controlled substance, which will be called placebo samples thereafter. From this data set, PLS-1 models were calculated and were successfully applied for validation of various external laboratory test sets. The transferability of these results to confiscated tablets is demonstrated here. It is shown that differentiation into placebo, amphetamine and ecstasy samples is possible. Analysis of intact tablets is practicable. However, more reliable results are obtained from pulverised samples. This is due to ill-defined production procedures. The use of mathematically pretreated spectra improves the prediction quality of all the PLS-1 models studied. It is possible to improve discrimination between MDE and MDMA with the help of a second model based on raw spectra. Alternative strategies are briefly discussed.