Blue Ballpoint Pen Inks Research Articles

Digital color analysis and machine learning for ballpoint pen ink clustering and aging investigation

Fraudulent activities often involve document manipulation, which poses a significant challenge to forensic science. To address this issue, a novel method was developed that combines intended artificial UV pre-degradation, digital color analysis (DCA) of stroke images, and various machine learning (ML) models. This method can cluster blue ballpoint pen inks and predict their photodegradation time. The results of the study indicate that the k-shape clustering method is highly effective in differentiating between inks based on their degradation curve patterns and HSV or RBS color features, aligning well with results from chromatography analyses. Furthermore, the random forest regression model demonstrated superior performance in predicting age, exhibiting the highest coefficients of determination. The DCA-ML method is a straightforward, cost-effective, and highly accurate solution for clustering blue pen inks. Using photodegradation curves to predict document age could eliminate the need for conventional physicochemical analysis techniques.

Rapid analysis and classification of blue ballpoint pen inks using high-performance thin-layer chromatography and digital color analysis

Despite the rise of digitalization, the scrutiny of paper documents with stamps and signatures remains crucial, constituting 55–60 % of document examination court cases. Developing accessible and robust ink analysis techniques is an ongoing challenge for forensic scientists. To tackle issues related to the identification and classification of dye components in blue ballpoint pens, we have proposed an advanced approach that integrates high-performance thin-layer chromatography (HPTLC), digital color analysis (DCA), and hierarchical cluster analysis (HCA) for a simplified yet effective procedure.The method encompasses multiple development of TLC plates. Initial separation employs methanol:ethanol (4:1, v/v), followed by a second separation using methanol:propan-2-ol:formic acid (1:1:0.1, v/v/v) to achieve cationic dye separation. This TLC development enhances separation selectivity, contributing to a more precise clustering of pen inks. Employing advanced DCA as a processing method for HPTLC, the optimal descriptor for ink classification is identified as the difference between red (R) and green (G) color components. The proposed clustering algorithm achieved 8 distinct ink clusters, showing improved discriminative capability and a reduced variable space compared to well-established or state-of-the-art methods.The approach's robustness was demonstrated across different readout devices, including smartphones and scanners. Reproducibility tests yielded consistent clustering results, confirming the method's reliability. Moreover, the method proved effective in clustering pen ink extracts from paper substrates, showcasing its potential for real sample analysis.This HPTLC-DCA approach presents a simple, cost-effective, and high-precision solution for clustering blue pen inks, significantly enhancing accessibility in high-throughput forensic applications.

Application of Raman spectroscopy in relative blue ballpoint pen ink dating for forensic document analysis – a case report

In this case report, blue ballpoint ink on a questioned document was investigated using a newly developed Raman model devoted for dating of documents via writing inks. The majority of blue ballpoint pen inks contain crystal violet - a triarylmethane dye which displays a typical “molecular fingerprint” type of Raman spectrum, of which most intense peaks at 749 cm−1 and 1542 cm−1 (under 785 nm laser excitation) represents the least and the most stable bonds of crystal violet molecules, respectively. The ratios of peak intensities at above mentioned Raman shifts are utilized to estimate the relative dating of the questioned blue ballpoint pen ink in practice, results of which agreed with estimations using other traditional relative dating methods. ® 2023 Journal of Science and Technology - NTTU

Application of Raman spectroscopy in relative blue ballpoint pen ink dating for forensic document analysis – a case report

In this case report, blue ballpoint ink on a questioned document was investigated using a newly developed Raman model devoted for dating of documents via writing inks. The majority of blue ballpoint pen inks contain crystal violet - a triarylmethane dye which displays a typical “molecular fingerprint” type of Raman spectrum, of which most intense peaks at 749 cm−1 and 1542 cm−1 (under 785 nm laser excitation) represents the least and the most stable bonds of crystal violet molecules, respectively. The ratios of peak intensities at above mentioned Raman shifts are utilized to estimate the relative dating of the questioned blue ballpoint pen ink in practice, results of which agreed with estimations using other traditional relative dating methods.
 ® 2023 Journal of Science and Technology - NTTU

Alleviating Luminescence and Quenching toward Discrimination of Ballpoint Pen Inks Using Spectroscopy and Chromatography Techniques

The phenomenon of luminescence and quenching is widely applied in the forensic examination of various ink materials. Here, we introduce a hybrid spectroscopic and chromatography approach to gain insights into the underlying cause of infrared luminescence (IRL) in blue ballpoint (BP) pen inks. A total of thirty BP pen ink samples from the Egyptian market were employed in this study. Insights into the origin of luminescence and quenching in the studied samples were gained based on video spectral comparator (VSC), thin layer chromatography (TLC), ultraviolet–visible (UV–Vis) spectrophotometry, and photoluminescence (PL) spectroscopy. Results showed that some of the studied inks possessed IRL due to the presence of crystal violet and some other triaryl methane dyes. Nevertheless, some ink samples did not possess IRL, despite the presence of the dyes responsible for IRL in their matrix. Interestingly, the inclusion of phthalocyanine dye in those non-luminescent ink matrices resulted in luminescence quenching, mainly due to the overlap between the absorption of phthalocyanine dye and the luminescence of the triarylmethane dyes. The IRL behavior of the ink sample under the first illumination wave band (400–485 nm) exerted control over the IRL activity across subsequent illumination wavebands, and the most effective differentiation was achieved by utilizing the first and second preset filters in VSC. The results revealed the luminescent components present in studied inks and unraveled their distinct luminescence behavior present within the ink matrix. The combination of optical spectroscopy and chromatography techniques could provide a distinctive tool to reveal the luminescence and quenching behaviors of ink dyes for the successful forensic discrimination of several BP writing pens.

Sample preparation of blue ballpoint pen ink for determining the composition of color components by RP HPLC method

The paper presents various theoretical and practical aspects of sample preparation of blue ballpoint pen ink applied on paper for subsequent quantitative analysis using reverse-phase high-performance liquid chromatography (RP HPLC). Estimation of analytical characteristics of a variant of cutting out a paper fragment containing applied ink for reproducibility of analysis results is discussed; composition of the extraction system and extraction conditions were evaluated. Qualitative and quantitative characterization of the extracts was performed by RP HPLC with the diode array detection. Using a scalpel as a tool for cutting out sample fragments and an acidified mixture of solvents as an extractant with performing extraction in an ultrasonic bath at the room temperature for 2 minutes is recommended. It was shown that the influence of different degree of pressure on a ballpoint pen when applying ink to the paper can be minimized by using normalized peak areas of individual dyes. The proposed sample preparation conditions were tested when studying the processes of changes in the composition of applied ink during artificial aging under the influence of constant ultraviolet (UV) irradiation.

Investigation and Discrimination of Ballpoint Pen Inks by Analytical Techniques and Chemometrics.

A population study has been performed for Pakistani ballpoint pen inks of blue, black, red, and green colors (a total of four colors) commercially used in Pakistan. Ballpoint pen inks have been investigated and discriminated by using UV/Vis spectroscopy and FTIR spectroscopy. We have calculated and compared the results in terms of discriminating power (DP). The statistical techniques of principal component analysis and cluster analysis have been applied on obtained data. By visual comparison, the best DP is obtained for green ballpoint pen inks, i.e., 0.866 by using UV/Vis spectroscopy and FTIR techniques. Black and red ballpoint pen inks showed the highest DPs by using UV/Vis spectroscopy; however, blue ballpoint pen inks got the highest DP by using FTIR spectroscopy. DP has been improved by using chemometric techniques and higher DPs are obtained as compared to visual examination.

Classification of ballpoint pen inks based on selective extraction and subsequent digital color and cluster analyses.

Here, we propose a novel approach to the classification of blue ballpoint pen inks based on a combination of selective extraction of coloring components from a paper carrier, digital color analysis (DCA) of the remaining traces, and hierarchical cluster analysis of DCA results. Since most documents of high importance are still produced in hard copies, the proposed method, being highly time- and cost-efficient, could be a significant contribution to forensic science in the field of authenticating handwritten documents. Several commonly used solvents were applied in parallel as extractants to the replicate strokes produced by each pen. It turned out to be possible to limit the number of extractants required for an unambiguous classification to three. We have shown that the optimal descriptor for agglomerative clustering is the colorimetric distance between the original and extracted ink traces in the RGB color space. Five separate clusters of inks that are independent of sample storage temperature were obtained from a set of 16 different pens. This conclusion was further confirmed by the analysis of principal components. The developed DCA-based data processing pipeline outperformed the clustering based on the data of high-performance liquid chromatography in terms of versatility providing a more informative analysis with respect to the inks based on the phthalocyanine dyes.

Blue Ballpoint Pen Inks Differentiation using Multivariate Image Analysis of Digital Images Captured with PhotoMetrix PRO®

In Forensic Documentoscopy, it is frequently questioned if a particular document was written with one or more pens. Different methods have been developed to distinguish pen inks from each other, but some of these techniques require the ink extraction, destructing the document, and other techniques uses high cost instruments. PhotoMetrix PRO®, an app for mobile devices, is a qualitative and colorimetric analysis tool that applies uni- and multivariate analysis. Amongst them, Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) and Partial Least Squares Discriminant Analysis (PLS-DA) can be obtained from digital images’ decomposing data. It is a non-destructive and a simple method, of easily use and low cost. Chemometric knowledge is important for results interpretation. This study aims to evaluate the PhotoMetrix PRO® capacity on blue ballpoint pens differentiation. Three experiments were performed with different ballpoint pens, including colorful pens as an app functionality control. The results showed appropriate differentiation between colorful ballpoint pens, and there was a satisfactory tendency of separation for different brands of blue ballpoint pens, most used in Brazil. This method is interesting to confirm subjective results, eliminating visual differences, intrinsic for each observer, which can be useful in places with an instrument deficiency, like the Video Spectral Comparator®. New studies to evaluate writing pressure’s influence on data collection and the inks’ age, as well as different mobile’s camera quality, are recommended. This study introduces a new technology that might be further studied for practical application in Forensic Documentoscopy and other Forensic areas.

Discriminating blue ballpoint pens inks in questioned documents by Raman imaging and mean-field approach independent component analysis (MF-ICA)

In the present work, Raman spectroscopy and chemometrics tools were explored as an analytical method to discriminate blue pen strokes on common office paper and bank check paper. The sample set was constituted of blue ballpoint pen inks available on local market and promotional pens as well. The samples were prepared to simulate an adulterated document using different pens. The proposal methodology was based on Raman imaging spectroscopy and Independent Components Analysis algorithm, which were able to recover the original spectrum of each pen, as well as images containing special information about each of the pens used. All recovered spectra could be match with references spectra at least with 0.8572 of correlation coefficient, while recovered images left no doubt about whether a forgery occurred. At the end of analysis, all the examined cases could be solved based on the discrimination between the pens inks, without any prior information.

A microfading survey of the lightfastness of blue, black and red ballpoint pen inks in ambient and modified environments

The lightfastness of approximately 100 randomly selected red, black and blue inks was surveyed using the microfade technique. The inks’ responses were recorded at 55% and at 1% relative humidity (RH) in air, and in a low oxygen environment (<10 ppm O2) at 55% RH. Their light sensitivity in air was highly unpredictable, ranging from the detection limit of the technique to several times greater than the most fugitive ISO Blue Wool Fading Standard (BW1). With very few exceptions, the response of blue and black inks was markedly suppressed in anoxia, and the opposite was true of a significant proportion of red inks tested. The correlation between RH and light-sensitivity in air was weak, with highly variable responses in both directions. The results show that it is not possible to make useful display (light exposure) recommendations for ballpoint pen inks without prior fade-testing.

Direct and comprehensive analysis of dyes based on integrated molecular and structural information via laser desorption laser postionization mass spectrometry

Laser desorption laser postionization time-of-flight mass spectrometry (LDPI-TOFMS) was employed for direct analysis and determination of typical basic dyes. It was also used for the analysis and comprehensive understanding of complex materials such as blue ballpoint pen inks. Simultaneous emergences of fragmental and molecular information largely simplify and facilitate unambiguous identification of dyes via variable energy of 266nm postionization laser. More specifically, by optimizing postionization laser energy with the same energy of desorption laser, the structurally significant results show definite differences in the fragmentation patterns, which offer opportunities for discrimination of isomeric species with identical molecular weight. Moreover, relatively high spectra resolution can be acquired without the expense of sensitivity. In contrast to laser desorption/ionization mass spectrometry (LDI-MS), LDPI-MS simultaneously offers valuable molecular information about dyes in traces, solvents and additives about inks, thereby offering direct determination and comprehensive understanding of blue ballpoint inks and giving a high level of confidence to discriminate the complicated evidentiary samples. In addition, direct analysis of the inks not only allows the avoidance of the tedious sample preparation processes, significantly shortening the overall analysis time and improving throughput, but allows minimized sample consumption which is important for rare and precious samples.

Fourier transform infrared spectroscopy and high performance thin layer chromatography for characterization and multivariate discrimination of blue ballpoint pen ink for forensic applications

In the present work, fifty seven blue ballpoint pen ink samples were characterized by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy(ATR–FTIR) and discriminated on the basis of high performance thin layer chromatography (HPTLC) and ATR–FTIR spectroscopy coupled with multivariate analysis which otherwise seems to be alike and hence, undifferentiated. The approach of ATR–FTIR has proven out to be an effective tool for characterization of complex ink formulation and hence, ink’s systematic discrimination with the help of multivariate analysis. The overall discrimination for blue ballpoint pen ink with non–destructiveanalysis of ATR–FTIR come out to be 99.69%, which is highly significant in comparison to both visual inspection of the spectra (DP= 97.93%) and destructive HPTLC chromatography (DP=93.80%). The similar methodology can be applied in the real case work of forensic laboratories to check whether two entries of ink on a sheet of questioned document have a common origin or not.

Dating of ballpoint pen writing inks via spectroscopic and multiple linear regression analysis: A novel approach

The dating of questioned document is a firmest problem for forensic experts. The current work is focused on the study of the dating of ink samples by using spectrophotometry technique and multiple regression analysis. A multiple linear regression (MLR) model has been proposed for the estimation of blue ballpoint pen ink dating by measuring the fading of ink with respect to time using UV–Vis spectrophotometer. Before developing the model, the factors like the best solvent for ink extraction and the conditions through which maximum ink is extracted has been determined. All the samples have been treated with the same method to avoid differences caused by the extraction procedure.Cross check of the predicted model has been done by analyzing the known writings. Validation of the equation has been done by calculating the aging of already known values of the same samples. The differences between expected and estimated dating were used to determine the average errors in the dating method. The standard errors have been minimized in case of MLR model significantly.

A novel combined approach of diffuse reflectance UV–Vis-NIR spectroscopy and multivariate analysis for non-destructive examination of blue ballpoint pen inks in forensic application

The present research is focused on the analysis of writing inks using destructive UV–Vis spectroscopy (dissolution of ink by the solvent) and non-destructive diffuse reflectance UV–Vis-NIR spectroscopy along with Chemometrics. Fifty seven samples of blue ballpoint pen inks were analyzed under optimum conditions to determine the differences in spectral features of inks among same and different manufacturers. Normalization was performed on the spectroscopic data before chemometric analysis. Principal Component Analysis (PCA) and K-mean cluster analysis were used on the data to ascertain whether the blue ballpoint pen inks could be differentiated by their UV–Vis/UV–Vis NIR spectra.The discriminating power is calculated by qualitative analysis by the visual comparison of the spectra (absorbance peaks), produced by the destructive and non-destructive methods. In the latter two methods, the pairwise comparison is made by incorporating the clustering method. It is found that chemometric method provides better discriminating power (98.72% and 99.46%, in destructive and non-destructive, respectively) in comparison to the qualitative analysis (69.67%).

Detection and identification of dyes in blue writing inks by LC-DAD-orbitrap MS

In the field of forensic questioned document examination, to identify dyes detected in inks not only provides a solid foundation for ink discrimination in forged contents identification, but also facilitates the investigation of ink origin or the study regarding ink dating. To detect and identify potential acid and basic dyes in blue writing inks, a liquid chromatography-diode array detection-Orbitrap mass spectrometry (LC-DAD-Orbitrap MS) method was established. Three sulfonic acid dyes (Acid blue 1, Acid blue 9 and Acid red 52) and six triphenylmethane basic dyes (Ethyl violet, Crystal violet, Methyl violet 2B, Basic blue 7, Victoria blue B and Victoria blue R) were employed as reference dyes for method development. Determination of the nine dyes was validated to evaluate the instrument performance, and it turned out to be sensitive and stable enough for quantification. The method was then applied in the screening analysis of ten blue roller ball pen inks and twenty blue ballpoint pen inks. As a result, including TPR (a de-methylated product of Crystal violet), ten known dyes and four unknown dyes were detected in the inks. The latter were further identified as a de-methylated product of Victoria blue B, Acid blue 104, Acid violet 49 and Acid blue 90, through analyzing their characteristic precursor and product ions acquired by Orbitrap MS with good mass accuracy. The results showed that the established method is capable of detecting and identifying potential dyes in blue writing inks.

The Determination of Signs of Accelerated Ageing of Records made with Ballpoint Pen Inks by Using Chromatography Methods

A study of four different ballpoint pen inks was carried out using methods of HPLC and solid-phase micro extraction and gas chromatography mass spectrometry. Inks of different ballpoint pen manufacturers-two blue ones and two purple ones were chosen for the research. Naturally aged ink samples on paper were stored under various conditions, and the comparative samples were exposed to aggressive influence of light, temperature and ozone. During the study of artificially and naturally aged samples differences in chemical composition of ink were identified-possible signs of accelerated ageing were detected in records and signatures that were made with blue and purple ballpoint pen inks.

Forensic Discrimination Potential of Video Spectral Comparator and Micro Spectrophotometer in Analyzing Question Document and Fraud Cases in India

The aim of the study was to evaluate the discriminating power of non-destructive methods, including optical methods likes the Video spectral comparator method (VSC) and Micro spectrophotometer (MSP) used to differentiate ballpoint pen ink which is commonly used in question document and fraud cases in India. Documents have been investigated to determine the feasibility of utilizing the Video spectral comparator method (VSC) and Micro spectrophotometer (MSP) for the differentiation and comparison of inks on paper. The work focused on how to develop the most effective procedure to ensure quality, when Micro spectrophotometer is used to differentiate writing materials by characteristics color scan of each ink. Six different commercially available blue ballpoint pen inks produced from most popular pens in Indian Market which were used as research material. We have studied most selling pens in Indian market (Reynolds, Parker, and Lexis 2 types, Cello griper and local made pen) for overwriting, alternation and modification of ballpoint pen ink on documents. These pens are generally used on questioned document in forensic discrimination cases and these questioned documents cases received by forensic science laboratories regularly. In forensic discrimination cases generally initial writing is overwritten by using other ink and to identify which ink was used to overwrite is challenging task in field of forensic science. The present study highlighted that the Video Spectral Comparator method (VSC) and Micro spectrophotometer (MSP) can be used routinely in such types of document cases and it has demonstrated to be an excellent analytical method for the forensic analysis of inks on a questioned document.

Use of Raman spectroscopy and chemometrics to distinguish blue ballpoint pen inks

The objective of this work is assessing whether the combination of Raman spectroscopy and chemometric tools is appropriate to differentiate blue ballpoint pen inks. Fourteen commercial blue ballpoint pen inks from different brands and models were studied and Raman spectra were obtained on ink lines written on A4 sulfite paper. First, a study of the best Raman configurations, in terms of laser intensity used and acquisition mode, was carried out to ensure sufficient spectroscopic quality without damaging the sample. Chemometric methods were applied first to improve the definition of spectral bands and to suppress fluorescence contributions from the signal. Once the spectra were suitably preprocessed, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to explore whether the different inks could be distinguished from their Raman spectra. Almost all inks could be gradually differentiated, through successive PCA analyses or looking at the different levels of the dendrogram structure provided by HCA. From these exploratory results, a tree structure was constructed based on PCA and HCA results in order to reflect the degree of similarity among ink classes. This tree structure was used as the basis to develop hierarchical classification models based on partial least squares-discriminant analysis (PLS-DA). Correct classification of inks was achieved by these PLS-DA models built and the most important regions to identify the ink classes were detected using the variable importance in projection plots (VIPs). The combination of Raman spectroscopy and chemometrics has been proven to be a promising fast non-destructive tool to differentiate among very similar ink types in documents.

Statistical Discrimination of Blue Ballpoint Pen Inks by Infrared (IR) Spectroscopy

Statistical chemometric method was used in discriminating 24 blue ballpoint pen inks from six different brands (Pilot, Carera, Stabilo, Faber-Castle, G-soft and Papermate) available in Malaysian market. Discrimination method was developed based on the combination of infrared spectra (IR) and chemometric technique which comprise of principal component analysis (PCA) and Agglomerative Hierarchical Clustering (AHC). The chemometric software used was XLSTAT 2011. The spectral region 4000–400 cm-1 was used to ‘fingerprint’ each ink from the 24 samples. PCA was used to detect any outliers whereas AHC was used to separate the ballpoint pen inks into their own class. This study showed that acceptable statistical discrimination (70.92% correct classification of the ballpoint pen dataset) between these 24 samples. FTIR-PCA and FTIR-AHC were successfully discriminate three different brands which were Carera, Pilot and g-soft. While, the other three brands, Papermate, Fabercastle and Stabilo could not be discriminated perfectly. The results of this study indicate that Transmission FTIR Spectroscopy coupled with chemometrics is useful discriminating tool for forensic studies involving inks.