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NTP technical report on the toxicity studies of Black Newsprint Inks Administered Topically to F344/N Rats and C3H Mice.

Toxicity studies were conducted by applying black newsprint inks or mineral oils to clipped skin of the dorsal interscapular area of C3H mice and F344/N rats of both sexes, to determine systemic and local effects. Four lots of both letterpress and offset types of newsprint ink were studied, either as composite mixtures or as individual lots. An industrial grade mineral oil, used as an extender for newsprint ink formulation, and USP medicinal grade mineral oil also were studied. Analyses for the presence of polycyclic aromatic hydrocarbons (PAHs) were conducted on composite ink mixtures and mineral oils; letterpress and offset ink mixtures were found to have cumulative concentrations of 206 and 105 ppm, respectively; the concentration of PAHs in the printing ink mineral oil sample was 208 ppm, while none were detected in the USP grade mineral oil. In genetic toxicity studies, letterpress and offset newsprint ink composite mixtures were each mutagenic in Salmonella typhimurium strains TA98 and TA100 when tested in a preincubation protocol with added hamster liver S9. With rat liver S9, results for both inks were positive in strain TA98 and negative in strain TA100. Neither type of ink was mutagenic in the absence of S9 activation. In 30-day studies, 5 rats and mice per sex were given single, daily dermal applications of letterpress or offset newsprint inks, 5 days per week, for a total of 21 - 22 applications. Dose groups for each type of ink received either the neat (undiluted) composite ink mixture, or the 3:1, 1:1, or 1:3 dilutions (ink:USP mineral oil), with a total dose volume of 100 (mice) or 250 (rats) &mgr;l. All animals survived until the end of the studies. Toxicity attributed to ink administration was limited to decreased body weight gains in female rats treated with neat and the 3:1 dilution of letterpress ink, and to scaliness at the site of application in 1 or more mice in each letterpress ink treatment group. As a result of grooming activity and the large amount of test chemical applied, chemicals were spread over the body, and there was evidence that some oral ingestion had occurred. In 13-week studies, various ink and mineral oil formulations were administered dermally to 10 rats and mice per sex. To prevent accumulation of inks and distribution over the body as seen in the 30-day studies, the frequency of application was reduced to twice weekly and the total dose volume was decreased to 20 microliters for mice and 50 microliters for rats. Treatment groups for rats consisted of letterpress ink mixture, offset ink mixture, printing ink mineral oil, USP mineral oil, and clipped, untreated controls. Groups of mice were administered each of the 4 individual lots of both letterpress and offset inks, the composite mixtures of each, and printing ink and USP mineral oils; clipped, untreated groups served as controls. All rats, all male mice, and all female mice except one administered offset ink-lot E survived to the end of the studies. Effects attributable to compound administration in rats were limited to decreased body weight gains in females treated with printing ink mineral oil and letterpress ink mixture, and increased liver and kidney weights in both males and females exposed to USP mineral oil; there were no local toxic effects at the site of application. In mice, there were no body weight effects, but liver weights were increased in most ink and mineral oil treatment groups of both sexes. Dermal toxicity was evidenced in mice by scaliness and irritation at the site of application of both sexes treated with USP mineral oil and letterpress ink-lot C. Microscopically, local toxicity at the site of application was observed in mice of all treatment groups and was characterized by acanthosis and inflammation. In summary, results of these studies indicate that topical administration of black newsprint inks and mineral oils produces local toxicity at the site of application in mice; toxic effects on the skin in this species are consistent with those of a primary cutaneous irritant. In rats, possible evidence for toxicity was limited to decreased body weight gains in females treated with letterpress ink formulations.

Journal Article↗

Simulation of microcalcifications on specimen radiographs of breast biopsies by inks used in marking the surgical resection margins.

In routine practice, the evaluation of breast excisional biopsy specimens is assisted by the use of various tissue marking inks to delineate surgical margins and preserve tissue orientation. These inks may simulate microcalcifications in specimen and tissue block radiographs. The magnitude of this problem is studied by systematically identifying the factors leading to the creation of this artifact. Samples of fresh tissue from breast reduction mammaplasties were painted separately with fresh wet ink and ink mixed with dried powdery residue. Black India ink and commercial colored tissue inks (the Davidson Marking System) were tested. The painted tissues were radiographed before and after routine paraffin embedding. Routine histologic sections were obtained from each tissue block for microscopic examination. Compared with unmarked controls, samples inked with blue, green, and red inks containing powdery residues showed radiopaque artifacts on radiographs prior to tissue processing. Only the sample marked with red ink showed residual radiopaque artifacts after processing. Microscopically the dried red ink particles were readily distinguishable from microcalcifications on the tissue sections. On the tissue radiographs, the dried ink artifacts were indistinguishable from true microcalcifications. This study demonstrates that some tissue marking inks used in the pathology laboratory are radiopaque. Inks contaminated with particles of dried residue, often present on ink container lids, may appear as artifacts mimicking microcalcifications on specimen and tissue block radiographs, occasionally complicating the histologic localization of mammographically demonstrated microcalcifications. Tissue marking inks should be tested for radiopacity prior to use on breast biopsies. Ink containers should be checked frequently for buildup of dried residue.

Artifacts↗

Application of tissue-marking ink to prostate biopsy specimens.

BACKGROUND: When sextant prostate biopsy specimens are performed, noting the location from which cancer-containing cores were taken aids in treatment planning. However, many institutions include several cores in a single container, to cut costs. We have tried several methods of ink application and combining ink-labeled biopsy specimens into fewer containers with the goal of maintaining information regarding location while minimizing the expense. METHODS: Several approaches to the application of tissue-marking ink to biopsy cores, core-preparation methods, color combinations, and numbers of cores in each container were assessed. RESULTS: The ink adheres well to dry cores, but these cores often exhibit dehydration artifact. Placing the cores on a wet sponge avoids dehydration but causes ink spread. Excessive ink application occurs with eyedroppers and syringes but is avoided by touching each core with an ink-moistened cotton swab. Application of 1% acetic acid to the inked core promotes congealing of the ink onto the tissue. Yellow, orange, and red ink are more difficult to distinguish than blue, black, or green. Deciphering distinct cores when three or more cores are combined is difficult, especially if cores are fragmented. CONCLUSIONS: With our current protocol, all biopsy specimens are placed on separate moistened gauze sponges. Specimens from the right side of the prostate are marked by green ink, and those from the left side are marked by black ink with a cotton swab. After applying 1% acetic acid to each core, the left and right cores from each location are placed in a single container. This method curbs pathology expenses and maintains tumor location information.

Biopsy, Needle↗

Higher susceptibility of mast-cell-deficient W/WV mutant mice to brain thromboembolism and mortality caused by intravenous injection of India ink.

(WB X C57BL/6)F1-W/WV mice possess a genetic defect in multipotential hematopoietic stem cells; the mice are anemic and lack mast cells. The authors injected diluted India ink intravenously into W/WV mice and congenic normal +/+ mice and searched for genetically determined differences in the development of complications of the injection. In both W/WV and +/+ mice, intravenous ink resulted in thrombocytopenia and markedly prolonged bleeding times, as well as prolonged partial thromboplastin and prothrombin times and reduced fibrinogen concentrations. These effects were similar in W/WV and +/+ mice, although the reduction in platelet counts was greater in W/WV mice. In addition, the mortality associated with ink injection was significantly higher in W/WV mice than in congenic +/+ mice. Most W/WV mice which died first exhibited paralysis, and examination under the dissection microscope revealed that ink injection resulted in significantly more cerebral thromboemboli in W/WV mice than in +/+ controls. Bone marrow transplantation from +/+ mice corrected both the mast cell deficiency and the anemia of W/WV mice and protected the W/WV recipients from the adverse consequences of ink injection. By contrast, +/+ mice rendered as anemic as W/WV mice by breeding did not exhibit increased morbidity and mortality after ink injection. (WC X C57BL/6)F1-Sl/Sld mice, which are anemic and lack mast cells because of a genetic defect different from that of W/WV mice, also exhibited increased morbidity and mortality after intravenous ink. Finally, mixture of ink with commercial heparin prior to intravenous injection markedly reduced the incidence of cerebral thromboembolism and death in W/WV mice. Taken together, these findings suggest that the increased morbidity and mortality exhibited by W/WV and Sl/Sld mice that received injected ink might be related to their mast cell deficiency rather than to their anemia. But measurement of the histamine content of the blood and various tissues of WBB6F1-+/+ mice injected with ink, and examination of their tissues in 1-mu sections, indicated that intravenous ink did not cause substantial mast cell degranulation. As a result, the possibility that mast cells protect +/+ mice from the adverse effects of intravenous ink by a mechanism other than degranulation and release of heparin, or that the differences in the response of W/WV or Sl/Sld mice and their +/+ littermates are due to defects other than their lack of mast cells, cannot be excluded.

Animals↗

Does ink age inside of a pen cartridge?

In questioned document examination and ink dating, it has been assumed that the ink inside of a pen cartridge does not begin aging until the ink is dispensed onto paper. Positive ion laser desorption (LD) mass spectra were obtained of ink-on-paper samples containing methyl violet, from new and old pens. Mass spectral studies with methyl violet have established the mechanism for how the dye degrades over time, and have provided structural information concerning the dye's degradation products. This information was used as an indication of the relative age of ink on paper. The LD mass spectrum of the ink from a new pen was indicative of "new" ink, whereas the spectra of the ink found in some older pens may appear to be either new or old. The ink from most of the old pens studied appears not to have aged, supporting the common assumption, whereas other ink samples produced "aged" ink spectra, suggesting otherwise.

Journal Article↗

Colonic tattooing with India ink: benefits, risks, and alternatives.

OBJECTIVE: To provide comprehensive information on key issues concerning colonic tattooing with India ink in reported literature. METHODS: A total of 735 citations on India ink alone were present in the English literature (1966-1995), including 16 on India ink and colonic tattooing. Nine major studies were identified and reviewed for 1) preparation before tattooing (type of ink used, sterilization process, colonic preparation, and antibiotic prophylaxis), 2) the tattooing process (technique and volume injected), 3) success in localization, and 4) complications. RESULTS: A'total of 447 cases of colonic tattooing with India ink have been reported. Major indication was preoperative marking of tumor site. Various India ink preparations were used. Ink was unsterilized in 57% (255/447), autoclaved in 42% (187/447), and gas sterilized in 1% (5/447) of cases. Colonic preparation varied similarly. Prophylactic antibiotics were used in 1% (5/447) of cases. Dilution of India ink varied from undiluted to 1:100 (with 0.9% saline). The volume injected ranged from 0.1 to 2 ml per site injected, commonly with tangential needle insertion and delivery of ink into the submucosa in the majority of the cases. Intraoperative localization was easier with multiple tattoo injections. Five reports of complications have been made. In only one instance did overt clinical complications develop. Risk of a clinical complication with colonic tattooing with India ink is 0.22%. CONCLUSION: Marked variability in technique, as well as potential for reporting bias, limit the quantitative conclusions. In general, colonic tattooing with India ink is a safe, accurate, and inexpensive method for preoperative marking and prospective study of colonic lesions.

Animals↗

The analysis of fountain pen inks by capillary electrophoresis with ultraviolet/visible absorbance and laser-induced fluorescence detection.

Information on the identity of inks adds to the circumstantial evidence in legal cases involving fraudulent documents. In combination with optical methods, multiple thin-layer chromatography (TLC) is currently the analytical tool used by forensic chemists to separate, compare and distinguish inks based on their dye composition. In our studies, capillary electrophoresis (CE) was used for the analysis of water-soluble fountain pen inks. Inks are complex mixtures of synthetic organic and inorganic dyes, surfactants, resins and other components. The investigations included the development of an electrophoretic separation method, the optimization of an extraction procedure for inks from paper as well as the evaluation of ultraviolet/visible (UV/VIS) absorbance and laser-induced fluorescence (LIF) detection for the analysis of inks by CE. Good results for the separation of 17 blue and black inks of different manufacturers and countries of origin were obtained with 100 mM borate buffer, pH 8.0, containing 20% methanol. The electropherograms of the inks and their extracts from paper showed patterns that were in most cases distinctly different from each other. Ultraviolet/visible scans can be used to compare spectra of the separated main and trace components of inks. Fluorescence detection at different excitation and emission wavelengths was more sensitive, but added to the complexity of the electropherograms due to the excitation of coextracted fluorescing paper components. The resolution power of CE combined with the information content provided by the detection modes investigated prove CE to be a powerful tool for the identification of water-soluble inks used on paper documents.

Electrophoresis, Capillary↗

A GC/MS study of the drying of ballpoint pen ink on paper.

The determination of the age of an ink entry from a questioned document is often an essential problem and a controversial issue in forensic sciences. Therefore, it is important to understand the aging process of the different components found in ink. The aim of this work was to study the drying process of ballpoint ink, characterised by the disappearance of volatile solvents from the ink entry. Phenoxyethanol is of particularly high interest as it is found in more than 80% of the blue ballpoint pens at different concentrations. Liquid extraction followed by splitless gas chromatography/mass spectrometry in the selected ion mode was used to measure the quantitative decrease of solvents from ink entries made with a blue Parker ballpoint pen. Quantities of ethoxyethoxyethanol, dipropylene glycol, phenoxyethanol and phenoxyethoxyethanol were studied in ink entries up to 1.5 years old, thus allowing to calculate aging curves for this particular pen. The low quantities of solvents (in the microgram range for a 1 cm ballpoint entry) were found to decrease quickly after deposition of the ink on paper through the competitive processes of evaporation and diffusion. Losses of up to 75% of solvents were observed after a few seconds. The amount of ethoxyethanol stopped decreasing after about 10 days (quantities reached the nanogram range for a 1 cm ballpoint entry), while the aging curves of dipropylene glycol, phenoxyethanol and phenoxyethoxyethanol level off considerably after 2 weeks. It was observed that ethoxyethanol, dipropylene glycol and phenoxyethanol can also migrate from one sheet of paper to another if placed close enough (e.g. in a book or a stack of papers), therefore contamination from fresh ink strokes from other paper sheets has to be taken into account for those solvents. In this paper we demonstrate that differentiation between fresh ink (<2 weeks) and older inks is possible under laboratory storage conditions. For real cases samples, more parameters have to be studied and other possible pathways have to be considered.

Forensic Sciences↗

Evaluation of desorption/ionization mass spectrometric methods in the forensic applications of the analysis of inks on paper.

Fast atom bombardment and laser desorption mass spectrometry (LDMS) provide molecular level information concerning an ink's composition. Two ink-jet printer inks, Ink A containing the cationic dye Methyl Violet 2B, and Ink B containing the anionic dye, Solvent Black, were studied. Both positive and negative ion detection modes of the mass spectrometer were used. LD may be used for the analysis of inks on paper. Once on paper, the ink's solvent system has evaporated, leaving mainly the dyes behind, which are detected using LDMS. An ink fades with time, indicating that the dyes are degrading. Preliminary results from an accelerated aging study of ballpoint pen ink using UV irradiation confirm that dye degradation products are formed. The degradation chemistry follows an oxidative demethylation process for which all products formed are detected using LDMS. Results suggest that LDMS may be developed to determine the relative age of inks.

Journal Article↗

Differentiation of black gel inks using optical and chemical techniques.

Gel ink pens have become a common writing instrument in the United States. Questioned document examiners often attempt to optically differentiate gel inks from each other and from other non-ballpoint ink writings (e.g., those from roller-ball pens). Since early formulations were primarily pigment-based, they do not elute when analyzed by thin-layer chromatography. However, recent gel ink formulations (i.e., within the past five years) include dye-based inks that can be easily separated. This study differentiates black gel inks using optical and chemical techniques. The techniques include: microscopy, visible and near infrared reflectance, near infrared luminescence, thin-layer chromatography (TLC), spot tests, and gas chromatography/mass spectrometry (GC/MS). As a result of this study a flow chart has been developed allowing for a systematic determination of a questioned ink. In addition, an analysis of volatile compounds found in gel inks revealed that there are some unique ingredients that may be found in gel inks that are not typically found in other non-ballpoint inks.

Journal Article↗

Image-based color ink diffusion rendering.

This paper proposes an image-based painterly rendering algorithm for automatically synthesizing an image with color ink diffusion. We suggest a mathematical model with a physical base to simulate the phenomenon of color colloidal ink diffusing into absorbent paper. Our algorithm contains three main parts: a feature extraction phase, a Kubelka-Munk (KM) color mixing phase, and a color ink diffusion synthesis phase. In the feature extraction phase, the information of the reference image is simplified by luminance division and color segmentation. In the color mixing phase, the KM theory is employed to approximate the result when one pigment is painted upon another pigment layer. Then, in the color ink diffusion synthesis phase, the physically-based model that we propose is employed to simulate the result of color ink diffusion in absorbent paper using a texture synthesis technique. Our image-based ink diffusing rendering (IBCIDR) algorithm eliminates the drawback of conventional Chinese ink simulations, which are limited to the black ink domain, and our approach demonstrates that, without using any strokes, a color image can be automatically converted to the diffused ink style with a visually pleasing appearance.

Algorithms↗

Flow and distribution of India ink in microvessels of the frog.

Velocities of an India ink front and of RBCs moving ahead of it were studied by intravital microscopy in capillaries of frog mesentery and skeletal muscle. Measurements were made during microperfusion of single vessels or groups of connected vessels in mesentery, and following intravenous ink injection in both tissues. The presence of ink did not appear to interfere with microvascular flow or vasomotion during the period of observation. On the average, the ink spearhead moved only slightly faster than the RBCs. There was substantial variation in relative velocities of RBCs in the same vessel and in the relative velocities of ink front and RBCs. The time course of ink filling showed substantial heterogeneity of flow in mesentery, more nearly uniform flow in skeletal muscle. Comparison of the measured velocity ratios of ink to RBCs with published observations on relative velocities of RBC to blood suggest that the advancing, apparently parabolic front of ink moves at less than twice the mean blood velocity. This is due in small part to diffusive dispersion of the ink particles in the laminar flow gradient, but more largely to stochastic dispersion of the front by interaction with RBCs and by displacement at branches.

Animals↗

Safety and efficacy of India ink and indocyanine green as colonic tattooing agents.

BACKGROUND: Controversy exists concerning the safety and efficacy of colonic tattooing for the intraoperative identification of polypectomy sites. The purpose of this study was to determine (1) the concentrations of India ink and indocyanine green that resulted in high-visibility tattoos without significant tissue inflammation and (2) the India ink injection volume that produces best visibility at colonoscopy, laparoscopy, and laparotomy. METHODS: Twenty-two New Zealand white rabbits (2 kg) were anesthetized and injected with India ink (undiluted 1:10, 1:50, 1:100, 1:1000, 1:10,000) and indocyanine green as an undiluted, concentrated formulation (25 mL/2 mL solvent) or in a diluted form (25 mg/5 mL solvent) at various concentrations (1:10, 1:50, 1:100). Tuberculin syringes were used to create a 0.1 mL serosal bleb at two injection sites 2 cm apart. Laparotomy was repeated at days 1, 3, and 7 after injection. Additionally, 16 rabbits were injected with India ink at laparotomy and re-explored at 1 and 5 months. Twelve mongrel dogs (20 kg) were injected with 1.0 mL volumes. Re-exploration by colonoscopy, laparoscopy, and laparotomy was done at 7 days and 1 month. Tattoo visibility at re-exploration in both animal models was graded on a scale (0 = agent not seen, 1 = seen with difficulty, 2 = easily seen). Histology in the rabbit was judged by degrees of inflammation (0 = no inflammation, 2 = mild inflammation, 4 = moderate inflammation, 6 = severe inflammation). RESULTS: The concentrated indocyanine green solution was easily visible only on day 1 in the rabbit. Injections of both concentrated and diluted indocyanine green caused mucosal ulceration and moderate to severe inflammation. India ink studied at 7 days, 1 month, and 5 months after injection in the rabbit model was visible at all concentrations. The undiluted and 1:10 concentrations were easily seen and showed evidence of mucosal ulceration. Tattoos produced with all other India ink concentrations were visible without gross inflammation. India ink was also studied at 7 days and 1 month in dogs. The tattoo with the 1:100 concentration at 0.5 mL was seen consistently at colonoscopy, laparoscopy, and laparotomy with only a mild submucosal reaction at 7 days. The tattoos produced with the 1:100 and 1:1000 concentrations at 0.5 mL and 1.0 mL injection volumes were easily seen by all methods of intraabdominal visualization at 1 month with similar histology. CONCLUSION: Indocyanine green was an ineffective colonic tattooing agent. India ink was an effective colonic tattooing agent. Dilute concentrations that caused little to no inflammation could be visualized at 7 days and 1 month in rabbits and dogs and at 5 months in rabbits. India ink, at appropriated concentrations, appears to be a safe short- and long-term colonic tattooing agent.

Animals↗

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.

Journal Article↗

Characterization of ballpoint pen inks by thermal and desorption and gas chromatography-mass spectrometry.

The characterization of ink on paper is of importance for dating and comparing questioned ink entries in forensic document examination. Inks are commonly characterized by their colorant profile that is identified by well-established analytical methods. Numerous ink formulations show identical colorant profiles, though. In order to differentiate inks that are not distinguishable by colorant analysis, a method for the characterization of colorless ink ingredients, namely binders, solvents and additives is necessary. In this paper, we propose a technique for the analysis of colorless compounds in ballpoint inks using direct thermal desorption of the ink on paper followed by chemical analysis of the desorbed volatile compounds by gas chromatography-mass spectrometry. As compared to liquid extraction and subsequent analysis of the extracts, the technique avoids possible contamination risks. Sensitivity is very high due to the enrichment of volatile components by thermal desorption. Even from old samples, the chromatograms obtained by the method enable the determination of binder polymers, solvents and additives. Pure binders as used by ink manufacturers were analyzed for unambiguous assignment of analytical results to specific polymers. To prove the practical applicability, we analyzed 121 ballpoint pens, not all having the same colorant profile, and grouped the pens into resin and solvent categories.

Journal Article↗

Evaluation of the image quality of ink-jet printed paper copies of digital chest radiographs as compared with film: a receiver operating characteristic study.

Paper copies of digital radiographs printed with the continuous ink-jet technique have proved to be of a high enough quality for demonstration purposes. We present a study on the image quality of ink-jet printed paper copies of digital chest radiographs, based on receiver operating characteristic (ROC) analysis. Eighty-three digital radiographs of a chest phantom with simulated tumors in the mediastinum and right lung, derived from a computed radiography (CR) system were presented in two series of hard copies as ink-jet printed paper copies and as laser recorded film. The images, with a matrix of 1,760 x 2,140 pixels, were printed with a spatial resolution of 10 pixels/mm in the CR film recorder as well as in the ink-jet printer. On film, every image was recorded in two versions, one optimized for the mediastinum and one for the lungs. On paper, only one image was printed; this constituted an effort to optimize both the mediastinum and the lungs. The ink-jet printed images, printed on a matt coated paper, were viewed as on-sight images with reflected light. The examinations were reviewed by six radiologists, and ROC curves were constructed. No significant difference was found between the performance of film and that of ink-jet paper prints. Because the cost for a paper copy is only a tenth of that of film, remarkable cost reductions can be achieved by using the ink jet technique instead. Our results show that further quality studies of ink-jet printed images are worthwhile.

Copying Processes↗

Classification and dating of black gel pen ink by ion-pairing high-performance liquid chromatography.

A novel approach for classification and dating of the black gel pen ink entries on document was developed based on ion-pairing high-performance liquid chromatography (IP-HPLC). Ninety-three black gel pens were collected and divided into two groups, dye-based and pigment-based, by preliminary solubility test. The chromatographic conditions for separation of the dye-based black gel pen inks were optimized and the dye components in inks were satisfactorily separated by using 40 mmol/L tetrabutylammonium bromide as ion-pairing reagent. According to the number and the chromatographic retention times of the main dye components, the 50 dye-based inks were categorized into four classes. The inks within a class can be further identified by the percentage of each dye component. The compositional changes of the dye components in the black gel pen ink entries on paper were investigated in light and natural aging conditions and it has been found that the dye components in the ink entries underwent obvious decomposition, and the decomposing extent of the dye components was related to the aging time. The results can provide scientific evidences for dating of the suspicious black gel pen ink entries on documents.

Chromatography, High Pressure Liquid↗