Discrimination of rubber-based pressure sensitive adhesives by size exclusion chromatography

In this report, three pairs of rubber-based pressure sensitive adhesives were analyzed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), attenuated total reflectance Fourier transform infrared spectrometry (ATR/FT-IR) and size exclusion chromatography (SEC). The size exclusion chromatograph was equipped with a refractive index (RI) detector and an ultraviolet (UV) absorption detector set to measure at 254 nm. Both adhesives of each pair revealed indistinguishable pyrograms and IR spectra, however, the SEC chromatograms were able to provide further discrimination. The differences were observed in the range below the polystyrene equivalent molecular weight of 700 Da.     

基体辅助激光解吸电离飞行时间质谱鉴别乌头的研究

目的建立乌头类中药鉴别的基体辅助激光解吸电离飞行时间质谱方法。方法以DHB为基体,优化飞行时间质谱分析条件,对不同种类的乌头类中药进行飞行时间质谱分析,找出乌头类的指纹峰。结果通过比较炮制乌头与生乌头质谱指纹峰的差异,可作出乌头类是否经炮制的判断。结论基体辅助激光解吸电离飞行时间质谱用于乌头类中药的定性鉴别,分析方法灵敏、准确、快速。     

LC-ESI-MS/MS法分析爆炸尘土中的硝化甘油

目的建立了高效液相色谱-质谱/质谱法（LC-ESI-MS/MS）测定尘土中的硝化甘油（NG）的方法,为日后测定爆炸残留物中的NG奠定基础。方法采用液液提取的方式提取样品,考察了前处理条件、色谱条件及质谱参数,最终确定实验方法。结果选择了最佳液相色谱质谱分析方法：固定相为SB C18（4.6×150 mm,5μm）,甲醇—0.05 mmol氯化铵做流动相,甲醇作提取溶剂;该方法在0.25～10 ng/g范围内呈良好线性,相关系数为0.9990;定量下限为0.25 ng/g;加标回收率为90.4%～95.2%。结论本方法操作简单,提取方便,有效避免了尘土复杂基质的干扰,结果准确可靠,灵敏度高,满足对爆炸残留物中硝化甘油的检测要求。     

二氯丙基酯化-气相色谱法分析葡萄叶中3种除草剂

目的建立葡萄叶中2甲4氯、2,4-滴和2,4-滴丙酸3种苯氧羧酸类除草剂的二氯丙基酯化-电子俘获检测气相色谱分析法。方法样品捣碎、添加内标2,4-二氯苯乙酸、酸化、用乙醚提取,提取液用液液分配法净化,净化后挥干有机溶液,用硫酸和1,3-二氯丙-2-醇进行酯化,生成的酯进行气相色谱分析。结果葡萄叶中2甲4氯、2,4-滴和2,4-滴丙酸的检测限分别为20ng/g、20ng/g和30ng/g,葡萄叶中除草剂浓度100~1000 ng/g成线性关系,空白葡萄叶中添加2甲4氯、2,4-滴和2,4-滴丙酸200ng/g的平均回收率分别为98.8%、101.3%和103.1%,回收率的变异系数分别为11.4%、11.0%和9.3%。结论本文方法检测被毒害的葡萄叶中3种除草剂是灵敏和准确的。     

Identification of ascorbic acid and its degradation products in black powder substitutes

Low explosives such as smokeless powder, black powder, and black powder substitutes have been used in illicit pipe bombings throughout the United States. Some of the newer black powder substitutes are formulated with ascorbic acid, which gradually decomposes as the powder ages, making it difficult if not impossible for the forensic chemist to identify it by traditional bulk techniques. A sensitive method for the identification of residual levels of ascorbic acid in black powder substitutes is presented. Powder samples are extracted with a mixture of acetonitrile and bis(trimethylsilyl)acetamide (BSA), which converts carboxylic acid and alcohol functional groups to trimethylsilyl esters and ethers, respectively. Samples are then analyzed by gas chromatography-mass spectrometry (GC-MS). Results have shown that trace amounts of ascorbic acid can be identified at detection limits that are well below those for traditional bulk techniques. Degradation products for ascorbic acid (hydroxylated carboxylic acids, furanones, and lactones) can also be detected.     

A local variance based approach to alleviate the scene content interference for source camera identification

Identifying the source camera of images is becoming increasingly important nowadays. A popular approach is to use a type of pattern noise called photo-response non-uniformity (PRNU). The noise of image contains the patterns which can be used as a fingerprint. Despite that, the PRNU-based approach is sensitive towards scene content and image intensity. The identification is poor in areas having low or saturated intensity, or in areas with complicated texture. The reliability of different regions is difficult to model in that it depends on the interaction of scene content and the characteristics of the denoising filter used to extract the noise. In this paper, we showed that the local variance of the noise residual can measure the reliability of the pixel for PRNU-based source camera identification. Hence, we proposed to use local variance to characterize the severeness of the scene content artifacts. The local variance is then incorporated to the general matched filter and peak to correlation energy (PCE) detector to provide an optimal framework for signal detection. The proposed method is tested against several state-of-art methods. The experimental results show that the local variance based approach outperformed other state-of-the-art methods in terms of identification accuracy.     

Hair analysis and detectability of single dose administration of androgenic steroid esters

Detection of anabolic steroids in hair samples has been possible only in fatal cases or in cases of high-continuous dosages. In order to verify the possibility of detecting an acute administration, a sensitive and specific assay has been developed for the simultaneous determination of testosterone, nandrolone and some of their esters in hair. The analytes were extracted from finely cut hair with methanol-trifluoroacetic acid overnight. After the incubation, the mixture was evaporated to dryness, redissolved and extracted with hexane. The dried organic layer was silanised and analysed by GC-MS and GC-MS-MS. A sensitivity of at least 20 pg injected was obtained for all the analytes. In guinea pigs treated with a single intramuscular dose of 10 mg/kg nandrolone decanoate, neither nandrolone decanoate nor nandrolone were found in hair collected after 13 days, while both compounds were clearly detectable after four repeated doses (each dose every 3-4 days) of 20 mg/kg nandrolone decanoate. Neither nandrolone decanoate nor nandrolone could be detected in hair from a male healthy volunteer 1 month after treatment with 50 mg nandrolone decanoate, while his urine still tested highly positive for the main nandrolone metabolite (> 100 ng/ml). Testosterone esters could not be detected in hair of healthy subjects collected respectively 3, 2 and 1 month after a single intramuscular administration of 250 mg testosterone enanthate (five subjects), a single intramuscular coadministration of 25 mg testosterone propionate plus 110 mg testosterone enanthate (one subject), or a single oral administration of 120 mg testosterone undecanoate (three subjects). Otherwise, hair analysis revealed an increase of testosterone concentration corresponding to the period of treatment. Analysis of blood and urine samples confirmed the absorption of those compounds. At the sensitivity achieved by the present method, no detection of nandrolone, nandrolone decanoate nor testosteron esters in hair seems to be obvious after a single dose administration.     

Characterization of children's latent fingerprint residues by infrared microspectroscopy: forensic implications

The chemistry of children's latent fingerprint residues was investigated as a function of time and temperature by non-destructive spectrochemical analysis. Latent fingerprints from children, ranging in age from 2 to 11 years, were deposited onto aluminum-coated glass slides and were analyzed by Fourier-Transform Infrared Microspectroscopy. The results revealed that there are three major classes of compounds present in children's latent fingerprints: carboxylic acid salts, proteins, and esters. By studying the changes in the fingerprint residues as a function of time and at elevated temperatures, we discovered that the salts in the fingerprint residues are stable relative to the esters. These findings have relevant forensic implications; by targeting the acid salts instead of the esters or proteins, children's latent fingerprints may be recovered after extended periods of time have elapsed.     

微波衍生化和GC/MS/MS技术分析血、尿中的吗啡

目的建立了血、尿等生物检材中海洛因代谢产物吗啡的定性分析方法。方法以丙酸酐为衍生化剂,采用微波衍生化技术结合GC/MS/MS进行分析。结果当CID电压为0.9V时,衍生化物的母离子与子离子碎片信息丰富,碎片为m/e268、324、342。结论此方法科学、准确,灵敏度高,能满足吸食海洛因类、吗啡类毒品人员的生物检材的检验要求。     

Run-specific limits of detection and quantitation for STR-based DNA testing

STR-based DNA profiling is an exceptionally sensitive analytical technique that is often used to obtain results at the very limits of its sensitivity. The challenge of reliably distinguishing between signal and noise in such situations is one that has been rigorously addressed in numerous other analytical disciplines. However, an inability to determine accurately the height of electropherogram baselines has caused forensic DNA profiling laboratories to utilize alternative approaches. Minimum thresholds established during laboratory validation studies have become the de facto standard for distinguishing between reliable signal and noise/technical artifacts. These minimum peak height thresholds generally fail to consider variability in the sensitivity of instruments, reagents, and the skill of human analysts involved in the DNA profiling process over the course of time. Software (BatchExtract) made publicly available by the National Center for Biotechnology Information now provides an alternative means of establishing limits of detection and quantitation that is more consistent with those used in other analytical disciplines. We have used that software to determine the height of each data collection point for each dye along a control sample's electropherogram trace. These values were then used to determine a limit of detection (the average amount of background noise plus three standard deviations) and a limit of quantitation (the average amount of background noise plus 10 standard deviations) for each control sample. Analyses of the electropherogram data associated with the positive, negative, and reagent blank controls included in 50 different capillary electrophoresis runs validate that this approach could be used to determine run-specific thresholds objectively for use in forensic DNA casework.     

Methadone extraction from minimal amounts of biological fluids

A new solid phase extraction method was studied to extract methadone from small amounts of biological samples, by using little disposable columns prepacked with reverse phase sorbents. Two different commercial kinds of reversed phase columns prepacked with octadecylsilane (ODS) were tested; the results were compared to those obtained by a direct liquid/liquid extraction method. Gas chromatograms of extracts obtained by means of ODS reversed phase columns showed a good signal/noise ratio resulting in higher sensitivity (20 ng/ml as detection limit), in comparison with the liquid/liquid extraction method.     

溴甲酚绿与溴甲酚蓝显现液显现潜血印痕的比较

目的 探索一种犯罪现场上潜血印痕新型显现技术；方法 利用溴甲酚绿、溴甲酚蓝、四丁基碘化铵与酒精溶液作为新型潜血印痕显现液,研究该技术显现潜血印痕的效果,并与国内外最常用的四甲基联苯胺显现技术进行交叉比较；结果 新型溴甲酚绿和溴甲酚蓝酒精显现液对稀释浓度到为1/1000的潜血印痕的极其敏感,显现出的手印纹线清晰连贯、反差明显,无颜色背景,且能够有效增强四甲基联苯胺处理后潜血印痕；结论 新型潜血印痕显现技术反应灵敏、反差明显,能作为四甲基联苯胺的后处理试剂,若得到推广应用,将能够有效提高犯罪现场上潜血印痕的发现率、提取率和利用率.     

An Amino Acid Model for Latent Fingerprints on Porous Surfaces*

Abstract: Analytical standards are needed in latent fingerprint detection for research and development as well as for quality control in routine work because normal fingerprints are too varied for comparison studies and tests. One way is to create latent fingerprints. For the amino acid sensitive detection method this can be achieved by coating test items with an amino acid solution using a modified commercial office bubble jet printer. Besides low costs, fast and easy preparation, the main advantage of a bubble jet printer is that the amino acid loading per area on the test item can be calculated by weighing the cartridge on a balance. This opens the possibility to determine the deviation for every printing series. The reproducibility of prints in a printing series made by one cartridge has a deviation of 2–16% and of prints made by different cartridges 20–25%.     

A new staining method for constriction marks in skin

A modified Poley's acid fuchsin-methyl green stain was used to demonstrate ligature marks in tissues taken at autopsy. This stain was compared in 30 cases with haematoxylin-eosin, Mallory's trichrome and Ogata's picro-indigocarmine stains. Using the modified Poley method, it was possible to demonstrate the compression mark in corpses even when post-mortem changes were advanced. The method was found useful in evaluating the cases when the force used was minimal or when the mark was atypical using the usual haematoxylin-eosin method.     

A new staining method for constriction marks in skin.

A modified Poley's acid fuchsin-methyl green stain was used to demonstrate ligature marks in tissues taken at autopsy. This stain was compared in 30 cases with haematoxylin-eosin, Mallory's trichrome and Ogata's picro-indigocarmine stains. Using the modified Poley method, it was possible to demonstrate the compression mark in corpses even when post-mortem changes were advanced. The method was found useful in evaluating the cases when the force used was minimal or when the mark was atypical using the usual haematoxylin-eosin method.     

Direct carboxyhemoglobin determination by derivative spectroscopy

A fast and sensitive method for the determination of carboxyhemoglobin (COHb) in blood using derivative spectroscopy is described. The addition of sodium dithionite as a reducing agent is not required. The concentration interval studied was from 0.5% to 100% COHb.     

Determination of the severity of endogenous intoxication at the level of average molecular peptides

A possibility was demonstrated of using the method related with determination of the level of average-weight molecules or average molecules (AM) for the diagnosis of sudden death in forensic medical expertise of cadaver. Blood plasma was investigated according to the method of M.I. Gabriekyan modified by Yu. V. Pervushin, which involves deproteinization of samples with subsequent spectrophotometry at 254 and 280 nm. The AM levels were studied in different pathologies including cardiovascular diseases, alcoholic and narcotic intoxications and pneumonia, caused by a variety of agents, as well as the syndrome of sudden children's death. An analysis of the obtained results denotes a possibility of using the postmortem determination of the AM level concurrently with determination of an endogenous intoxication degree in the forensic medical practice for establishing the cause and mechanisms of nonviolent death.     

高效液相色谱法鉴别指甲油的种类

目的建立一种简便快速、灵敏准确的鉴别指甲油样品的方法。方法以乙腈为提取剂,在乙腈/水（80∶20）,检测波长为UV-220nm的色谱条件下,对22种不同产地、不同品牌的指甲油样品进行HPLC分析。结果依据指甲油中组分的不同,可将其分为5大类,每类中各个样品又可根据其色谱峰峰面积比的不同,进一步进行种类的鉴别。结论该方法是一种简便、快速、准确的鉴别指甲油的方法。     

一种制备酶标记抗体的新技术及在血痕种属鉴定的应用

本实验建立了一种过碘酸钠氧化法为基础、制备ＨＲＰ标记的免抗人ＩｇＧ抗体的新技术。首先以己二酰二肼作为肼化剂，在ＩｇＧ分子上接上肼基，然后以过碘酸钠作为氧化剂，使ＨＲＰ分子上的糖基氧化为醛基，进而使醛基与联结在ＩｇＧ分子上的肼基形成Ｓｃｉｆｆ氏碱而达到酶与抗体的联接。在用斑点ＥＬＩＳＡ方法鉴别血痕种属的研究中，该法制各的酶标记抗体具有高效价，高敏感度，高特异性等优点。     

Use of gold nanoparticles as molecular intermediates for the detection of fingermarks

Among the numerous methods dedicated to the detection of latent fingermarks, the MultiMetal Deposition (MMD) offers, as a main advantage, the ability to be applied on a great number of porous and non-porous surfaces, e.g., paper, plastic, glass, latex, and polystyrene, even if wetted. While considered as a powerful and sensitive technique, MMD is often neglected, mainly because of operational limitations (siliconized vessels, restrictive pH domain, numerous immersion baths, ...). In this contribution, we propose a modification of the standard MMD method so that the procedure is simplified with a number of baths reduced to a minimum. To reach this goal, it was necessary to obtain a fully operable solution which could detect fingermarks in a single step. We chose to take advantage of the molecular recognition mechanisms by functionalizing the gold nanoparticles with a molecular host able to bind itself to gold while keeping the ability to trap molecules in solution. Cyclodextrins were chosen as they can be easily chemically modified to offer gold-binding abilities. Moreover, they are widely used as hosts for various molecular guests (dyes, luminescent molecules, ...). This new formulation has been tested on three different surfaces to attest the feasibility of this strategy. Successful results were obtained with detailed fingermarks offering a good contrast to allow their identification without the need to enhance the results (such as with a physical developer). If the new formulation behaves very similarly to the old one, in terms of experimental conditions, it offers the additional advantage to develop fingermarks after immersing them in only one bath. The goal is thus reached.