Method of dating manuscripts

FIELD: physics.

SUBSTANCE: three samples of a letter are obtained and analysed, one of which is extracted with a solvent and subjected to UV spectrophotometry right away; the second is analysed 30 days layer; the third is analysed 60 days after analysing the first sample; the second and third samples are extracted and subjected to UV spectrophotometry in the same conditions as the first sample; quantitative comparison of the results of UV spectrophotometry of the three samples is carried out based on the ratio of optical densities in the region of peaks (330-1100 nm) of dyes per unit length of the line of each sample in intervals of 1 and 2 months to obtain the behaviour of ageing of the manuscript, wherein ageing takes place in "natural" conditions with optimally permissible temperature, relative humidity and air speed in accordance with GOST 30494-96.

EFFECT: simplicity, high accuracy, guaranteed reproducibility and high reliability of determining ageing.

1 dwg

 

The invention relates to the technical examination of documents and can be used to determine the authenticity and age of different types of documents, made pastes ballpoint pens, prints and other materials letters in judiciary practice, working with documents of historical value.

The known method of determining the limitation of the execution of manuscripts Aginsky V.N. "Dating and Characterizing Writing, Stamp Pad'an Jet Printer Inks by Gas Chromatography / Mass Spectrometry", International Journal of Forensic Document Examiners Vol.2 No.3. July/Sept. 1996, pp.103-116 by using the method of gas (gas-liquid) chromatography and mass spectrometry, using the existing correlation between the age of strokes and concentration colorless components, "high-boiling organic solvents (phenylglycol, benzyl alcohol etc) before and after their "artificial aging" (by heating at elevated temperature), and Vice versa. This method uses the change in the concentration colorless components through evaporation and polymerization over time and does not take into account changes of the dye ink. The method of determining the age of the documents used in this method consists in determining the existence of phenylglycol paste strokes researched account using gas-liquid chromatography-mass spectrometry, extraction phenylglycol of p is ordinary investigated first stroke of the "weak" (carbon tetrachloride), then the "strong" (chloroform) with an organic solvent. Followed by quantitative determination of the degree of extraction of phenylglycol (SEF), which decreases with age, pasta stroke testing of resin paste analyzed stroke on the ability to polymerization. This is accelerated artificial ageing of samples analyzed stroke (heat) and determine the degree of extraction phenylglycol from this sample - militia(1). The difference in the SEF and SEF (t) gives the initial criterion for determining the age of the studied material.

The disadvantage of this technical solution is the inability to determine whether "artificial aging", low accuracy and the time interval determining the age of the documents (from 1-2 months to fifteen years), the need to determine the chemical composition (identification phenylglycol or other substances) ink, the use of complex sample preparation and special equipment, gas-liquid chromatograph with a mass selective detector.

The known method of determining the limitation of the execution of manuscripts and other materials letters EN 2296 315, IPC G01N 21/31 (prototype), lies in the fact that you get two of the sample material letters, one of which is extracted by solvent, the other is first subjected to heating with microwave radiation and so on), and the ZAT is extracted under the same conditions with the same solvent, the first sample, then make a quantitative comparison of the results of the extraction. Before a quantitative comparison of both samples subjected to UV spectrometrically. Get the ratio of optical densities in the area of the peak maxima of the dyes per unit length of the stroke of each sample, they expect the ratio of optical densities in the range from 400 to 1100 nm, and determining the limitation of the analyzed document is carried out by comparing these values with the same parameters of documents with known date of execution presented in graphical or tabular form.

This method allows you to determine the duration of execution of manuscripts or documents, using the existing correlation between the age of strokes and concentration as a colourless volatile components of the organic solvents and the concentration of the dye before and after artificial aging": the longer the stroke, the less the difference in concentration before and after artificial aging, and Vice versa.

The disadvantage of this technical solution is used in the method of "artificial aging" of the sample (heating by means of microwave radiation and so on)that greatly raises doubts about the validity of the results, despite the advantage of low cost is time.

The objective of the proposed technical solution is to achieve a high detection accuracy of the prescription period of handwritten texts, good reproducibility and high accuracy aging. In addition, there is no need to determine the chemical composition (identification of phenylglycol or other substances) ink, the use of complex sample preparation and special equipment (gas-liquid chromatograph with mass selective detector), comparing the changes in volatile components and dye ink.

The problem is solved using three samples, rather than two (as in the prototype). 1st sample of the material of the letter is extracted with a solvent. Then subjected to UV spectrophotometrically, 2nd study sample letters examined 30 days after the study 1 sample, and the 3rd sample is examined after 60 days of study 1st. The 2nd and 3rd samples extracted in the same conditions as the 1st sample, and then in the same conditions UV spectrophotometery. Next, perform a quantitative comparison of the results of UV spectrophotometrically three samples between a relative optical densities in the area of the peak maxima (330-1100 nm) of the dye per unit length of the stroke of each sample in the range of 1 and 2 months, the obtained relationship of optical densities to the stroke length (S) is the initial value is to determine the age of the studied material, and the presence and character of the dynamics in the results spectrophotometrically is established by calculating the transmittance of the sample 2 and sample 3 to the transmittance of the sample 1, and the aging occurs in a "natural" conditions at optimum allowable temperature, relative humidity and speed of air movement in public areas.

An example of execution

The method of determining the age of the documents used in this method consists in the following:

from the investigated material letters get 3 samples with a period of 30 days, each sample is obtained by a cut of a small segment of the strokes of the material of the letter. Samples are subjected to extraction with an organic solvent;

- the extract is quantitatively spectrophotometric using a UV spectrometer, or other device that determines the quantitative characteristics of the UV spectra in the regions of wavelengths from 330 to 1100 nm;

- obtain quantitative differences in the area of the maxima of the UV-spectra of sample 1, sample 2, sample 3 compared between them. UV spectra were obtained for the ink strokes made with a ballpoint pen blue color using a standard spectrophotometer "Specord M-40" (manufactured by Carl Zeiss Jena, Germany).

Samples are cut strokes of the signature length of 20 mm in the uniform field h is carrying a dye, without dirt and intersections with other materials, letters and selected the same length and size. Each of the obtained samples treated individually in a clean glass container 2.0 ml of organic solvent acetonitrile qualification OFS (high purity). The extraction time of 10 minutes the Examination is conducted in the time period of examination is 2 months.

The sample 1 is obtained by extraction with acetonitrile cut stroke. Sample 2 is obtained by extraction with acetonitrile cut stroke within 1 month from the start of the study. Sample 3 is obtained by extraction with acetonitrile cut stroke within 2 months from the start of the study. To address the issue of the limitation period run of the investigated materials letters, get UV spectrometric data on the spectrophotometer "Specord M-40" and compare them quantitatively. To do this, the wavelength of the peak corresponding to the absorption peaks of the dye cut investigated, comparing the magnitude of the changes in the optical densities of the samples 1, 2, 3, and find quantitative criterion S (%/cm stroke), which characterizes the change in the number of substances that have fallen into solution per unit length of bar:

S1={(1-D2/D1)·100%}/L1, S2={(1-D3/D2)·100%}/L2,

S3={(1-D3/D1)·100%}/L3where

S1, S2, S3 - change the number of substances that have fallen into solution per unit length of the stroke of the investigated neckline [%/cm];

D1- the optical density of the solution on the length of the maximum peak of the substances of the sample 1;

D2- the optical density of the solution on the length of the maximum peak of the substance sample 2;

D3- the optical density of the solution on the length of the maximum peak of the substance sample 3;

L1, L2, L3 is the length of the strokes of the investigated cut [cm].

On the basis of the received wavelengths in the regions of maxima in the UV-spectra for a particular investigated material letters established the presence and character of the dynamics in the results spectrophotometrically for each sample by calculating the relationship of the transmittance in the region of maximum UV spectrum of the Sample 2 and Sample 3 to the transmittance in the region of maximum UV spectrum of the Sample 1. The obtained values of the relationship of optical densities to the length of the strokes are initial value to determine the age of the studied material letters.

The results of the study materials strokes by this method are shown in table:

The number of investigated sampleThe optical density-D, Rel. unitsLength of cut, mmSpectral Cree is ERI - S, %/cm of neck
Sample 1
λ - 570,1 nmD1- 0,03320S1- 18,2
Sample 2
λ - 570,3 nmD2- 0,02120S2- 19,1
Sample 3
λ - 570,1 nmD3- 0,01320S3- 30,3

Age determination of the investigated document is provided by comparison of the quantitative indicators transmittance of the material researched emails with the same settings for documents (or any of the materials letters)made pasta ballpoint pens, with a predictable deadlines, previously obtained by experiment, are presented in the calibration graph to determine the age of the studied material letters (the m the drawing).

The technical result is to increase the reproducibility and reliability of determining the age of materials letters using "natural aging" in intervals 1 and 2 months.

Sources of information

1. Sapronenko TI, Agin, VN, Viktorova LN. and other age Determination strokes of handwritten texts, executed in ink. - M, VNII MVD of the USSR, 1987

2. AGINSKY NR. The establishment of complete strokes of handwritten texts. - M, RF Ministry of internal Affairs, 1997

3. Aginsky V.N. "Dating and Characterizing Writing. Stamp Pad and Jet Printer Inks by Gas Chromatography/Mass Spectrometry", International Journal of Forensic Document Examiners, Vol.2, No.3, July/Sept / 1996, pp.103-106.

4. Interstate standard GOST 30494-96. "Residential buildings and public. The parameters of the microclimate in the premises".

5. EN 2296315, IPC G01N21/31 (prototype).

1. The method of determining the limitation of the execution of manuscripts and other materials letters, namely, that receive the samples of the studied material letters, which are extracted by the solvent, is subjected to UV spectrophotometrically produce quantitative comparison of the extraction results, calculate the ratio of optical densities of the samples, compare these values with documents with a known date of execution, wherein the receive and examine three sample letters, one of which is extracted with a solvent and subjected to UV-Spa is trophotometer immediately, the second examined 30 days after study of the first sample, the third sample examined after 60 days after the study of the first sample, the second and third samples are extracted and UV spectrophotometery in the same conditions as the first sample, then conduct a quantitative comparison of the results of UV spectrophotometrically three samples between a relative optical densities in the area of the peak maxima (330-1100 nm) of the dye per unit length of the stroke of each sample at intervals of 1 and 2 months, the obtained relationship of optical densities to the stroke length (S) serve as an initial value to determine the age of the studied material, and the presence and the character of the dynamics in the results spectrophotometrically are established by calculating the relationship of the transmittance of the sample 2 and sample 3 to the transmittance of the sample 1, and the aging occurs in a "natural" conditions at optimum allowable temperature, relative humidity and speed of air movement in public areas.

2. The method of determining the limitation of the execution of manuscripts according to claim 1, characterized in that the optimal parameters must conform to the requirements of GOST 30494-96.



 

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