应用HPLC研究蓝色签字笔迹字迹色痕光老化规律

目的对蓝色签字笔所形成的字迹色痕光老化规律进行研究。方法比对14种蓝色签字笔样品在暗处保存条件下、自然光照射及强灯光照射等老化条件下物理特征变化情况;使用高效液相色谱法,监测蓝色签字笔墨水中色料成分的变化情况,并寻找蓝色签字笔墨水字迹自然光老化规律。结果强灯光照射后出现外观明显的老化现象,暗处存放的样本存在较长的老化时限。在自然光照射下30天内,样品色料成分的相对含量均随时间发生两个阶段的变化。结论样本字迹的外观为鉴定蓝色签字笔墨水字迹的形成时间提供了重要的信息。结合HPLC分析结果,可以确认字迹是否经过光照人工老化,为字迹形成时间鉴定的重要参考依据。     

紫外可见漫反射光谱法无损确证血痕的研究

目的建立一种快速确定血痕的方法。方法将人血、猪血、鸡血、羊血等制成样品纱布,利用紫外可见分光光度计扫描反射光谱进行检测,同时考察了人血的最低检出量。结果血痕的种属与浓度不影响紫外可见反射光谱波峰波谷位置;人血的最低检出量为1.0μL。结论该方法确证血痕具有快速、灵敏、准确、不损坏检材的特点。     

蓝色圆珠笔字迹色痕FT-IR光谱经时变化的研究

笔者曾用FT-IR光谱法对108种不同蓝色圆珠笔油墨进行了系统分析,确定了油墨组成成份,实现了种类认定.在此基础上,选取了二种不同种类的蓝色圆珠笔油墨字迹色痕,在紫外光下定时照射,根据各自光谱特征峰校正峰高的计算,确定相关峰的相对峰高比.根据相对峰高比值随时间变化的规律,进行了曲线拟合和计算机编程.同时,探讨了油墨组份之间随光照时间的变化,其目的是为了推断字迹色痕的“年龄”.     

高效液相色谱法鉴别蓝色签字笔墨水的种类

目的通过对签字笔字迹成分进行检验，达到对签字笔成分进行分离并对签字笔种类进行鉴定的目的。方法使用高效液相色谱法对蓝色签字笔字迹色痕中的色料成分进行分析，并依据分析结果对墨水的种类划分，同时考察了纸张的背景影响、最小用样量以及实验结果的重现性。结果22种蓝色签字笔样品均可以实现区分。结论本研究对实际应用有较大参考价值。     

圆珠笔油墨字迹书写时间鉴别的研究

圆珠笔油墨字迹书写时间的鉴别是摆在文件鉴定人员面前的棘手问题.本文作者借鉴国外的检验方法,经过近十年的探索,考查了各种因素的影响,研究出了适合我国国情的通过圆珠笔字迹油墨被溶解能力测试来确定其书写时间的鉴定技术,并且进一步发展了国外的检验方法,研制出了专用的检验器材,发明了模拟低温操作程序,使这一技术的适用范围更广.在有合适比对样本的情况下,可以准确鉴别落款时间在一年以上、怀疑书写时间在半年以内的可疑文件的真伪.     

LAB图像处理模式区分黑色圆珠笔字迹的方法验证

目的考察验证LAB模式区分黑色圆珠笔字迹的方法,以及油墨浓淡对检验结果的影响。方法采用600dpi分辨率扫描样品并将图像保存成tiff格式,运用PhotoshopCS3图像处理软件中Lab模式进行处理。结果Lab模式无损区分黑色圆珠笔字迹的识别率达到61．67％,且油墨浓淡对实验结果影响不明显。结论此方法可用于黑色圆珠笔字迹的区分检验。     

Differentiation of blue ballpoint pen inks by laser desorption ionization mass spectrometry and high-performance thin-layer chromatography

The differentiation of inks on a questioned document can highlight a fraudulent insertion and is usually carried out by optical comparison and thin-layer chromatography (TLC). Laser desorption ionization mass spectrometry (LDI-MS) may also be used for the analysis of dyes from ink. This analytical technique was compared with a standard method of high-performance TLC (HPTLC) according to their capacity to differentiate blue ballpoint inks. Ink entries on paper from 31 blue ballpoint pens have been analyzed and their dye ink formulations compared. The pens were classified into 26 classes by LDI-MS against 18 for HPTLC. LDI-MS proved to be a more powerful method for differentiating ink formulations because it provides information about dye structures (molecular weights) and relative quantification of dye classes (peak areas). Sample preparation was minimal and analysis time was short in contrast to the more complex extraction, application, and development steps of the HPTLC method. However, only basic dyes and pigments were identified using positive mode LDI-MS, while HPTLC did yield additional information about acid dyes.     

Validation of LAB color mode as a nondestructive method to differentiate black ballpoint pen inks

Nondestructive digital processing methods such as lab color mode (available in Adobe Photoshop) are emerging as alternative methods for forensic document examiners to use when attempting to differentiate writing instrument inks. Although these techniques appear to be viable, little data currently exists regarding the known or potential error rates associated with these techniques. Without adequate data, the validity and reliability of these techniques, including lab color, can not be established. In an attempt to begin to address these issues, 44 black ballpoint ink pens were obtained and used to create 990 pen-pair samples for analysis using established lab color mode techniques. No erroneous findings of "different" were reported following the examination of the known pen-pair combinations in which the same pen was used to create the samples (n = 44). Of the remaining 946 samples, 737 pen-pair samples were differentiated using the lab color mode method, while 209 samples were unable to be differentiated and were recorded as either being "similar" (n = 153) or "unsure" (n = 56). Comparison of the lab color mode results with the results obtained through additional testing using traditional infrared reflectance and infrared luminescence test methods showed that lab color differentiated 102 pen-pair samples (11%; 102/946) that were not differentiated using a VSC-4C.     

LC-MS/MS法检测圆珠笔墨迹中碱性蓝7及其去乙基产物的降解变化

目的考察圆珠笔墨迹中碱性蓝7及其去乙基产物的降解变化,为圆珠笔墨迹书写时间的研究提供基础数据。方法用氙灯老化碱性蓝7以生成其5个去乙基产物。建立LC-MS/MS检测碱性蓝7及其去乙基产物的方法。制作圆珠笔墨迹样本,在室内自然光照条件下老化3个月,同时进行控制实验条件的氙灯老化和高温老化实验。结果碱性蓝7的相对含量持续下降,其第一、第二级去乙基产物E4、E3的相对含量相继达到最大值,剩余三个去乙基产物E2、E1和E0的相对含量在三个月内持续增加。结论碱性蓝7的相对含量与光的辐照能量呈指数函数关系,其去乙基产物E4、E3的相对含量与光的辐照能量呈二次函数关系。不同油墨中碱性蓝7的老化曲线不同。温度对碱性蓝7的降解基本没有影响。     

Differentiation of blue ballpoint pen inks by positive and negative mode LDI-MS

Usually, the differentiation of inks on questioned documents is carried out by optical methods and thin layer chromatography (TLC). Therefore, spectrometric methods were also proposed in forensic literature for the analysis of dyes. Between these techniques, laser desorption/ionization mass spectrometry (LDI-MS) has demonstrated a great versatility thanks to its sensitivity to blue ballpoint ink dyes and minimal sample destruction. Previous researches concentrated mostly on the LDI-MS positive mode and have shown that this analytical tool offers higher discrimination power than high performance TLC (HPTLC) for the differentiation of blue ballpoint inks. Although LDI-MS negative mode has already been applied in numerous forensic domains like the studies of works of art, automotive paints or rollerball pens, its potential for the discrimination of ballpoint pens was never studied before. The aim of the present paper is therefore to evaluate its potential for the discrimination of blue ballpoint inks. After optimization of the method, ink entries from 33 blue ballpoint pens were analyzed directly on paper in both positive and negative modes by LDI-MS. Several cationic and anionic ink components were identified in inks; therefore, pens were classified and compared according to their formulations. Results show that additional information provided by anionic dyes and pigments significantly increases the discrimination power of positive mode. In fact, it was demonstrated that classifications obtained by the two modes were, to some extent, complementary (i.e., inks with specific cationic dyes not necessarily contained the same anionic components).     

Ballpoint pen inks: the quantitative analysis of ink solvents on paper by solid-phase microextraction

We wish to describe further developments to a method previously reported on the detection of 2-phenoxyethanol in ink. The solid-phase microextraction (SPME) sampling technique, together with gas chromatography-mass spectrometry (GC-MS), has been used to quantify solvents in writing ink. In conventional approaches, the analysis of ink on documents requires some degree of destructive sampling. The methods commonly used remove ink samples from paper using a scalpel or a paper punch. To avoid document destruction, a sampling cell was constructed that allows solvents to be adsorbed directly onto the SPME fiber from the headspace above the document surface. Analytes (ink volatiles) are then desorbed from the SPME fiber on a gas chromatograph equipped with a mass selective detector (GC-MSD). With this method, it was possible to detect the presence of ink solvents on documents for a period lasting up to c. 2 years.     

Dynamic of the ageing of ballpoint pen inks: quantification of phenoxyethanol by GC-MS.

The ageing process of some inks were studied to evaluate whether it is possible to date them. We used gas chromatography coupled with mass spectrometry to measure the evaporation of volatile components. The selected approach thus follows the disappearance of one ink volatile component (phenoxyethanol) as a function of time. The ink ageing curve represents the ratio of an evaporating compound to a stable compound of ink according to time. The results obtained are thus independent of the quantity of ink sampled for analysis. We obtained for two pens, containing two different inks, a curve highlighting an exponential decrease of the evaporating compound. By fitting these curves we determined the limitations of dating a ballpoint pen ink. Two distinct behaviours were observed in two distinct modes, the first called 'fast mode' and the second called 'slow mode'. In order to try to explain the phenomenon, the studies were based on solvent diffusion theory in complex matrix (such as polymer on varnish). Calculations from certain parameters showed an extremely fast evaporation of ink solvents, as well as varying behaviour depending on the paper used. The results showed that it is not possible to date ballpoint pen inks with this method in document examination casework.     

Forensic discrimination of blue ballpoint pen inks based on thin layer chromatography and image analysis

This article aims to provide a new and fast method for differentiation of inks on a questioned document. The data acquisition was carried out by designing specific image analysis software for evaluating thin layer chromatograms (TLC-IA). The ink spot was extracted from the document using methanol and separated by TLC using plastic sheet silica gel 60 without fluorescent indicator, and a mixture of ethyl acetate, ethanol, and water (70:35:30, v/v/v) as mobile phase. To discriminate between different pen inks, new software was designed on the basis of intensity profile of red, green, and blue (RGB) characteristic. In practice, after development of chromatogram, the chromatograms were scanned by ordinary office scanner, intensity profiles of RGB characteristics on the development straight of each sample were produced and compared with the mentioned software. RGB profiles of ballpoint inks from various manufacturers showed that the patterns in most cases were distinctly different from each other. This new method allowed discriminating among different pen inks with a high reliability and the discriminating power of 92.8%. Blue ballpoint pen inks of 41 different samples available on the local market were successfully analyzed and discriminated.