PRODUCTION OF HUMIC ACID BASED POWDERS FOR LATENT FINGERPRINT DETECTION

Abstract

The invention comprises the production and use of humic acid and its various salts (humate), which have been used even in areas such as food, pharmaceutical, etc., as fingerprint powder, alternatively to fingerprint powders with various compositions used for fingerprint detection, the oldest and most common method for criminal identification at crime scenes.

Claims

1. Use of a powder comprising humic acid or humic acid salts (humate) for fingerprint detection.

2. Use of the powder according to claim 1, wherein said powder further comprises about 10-20% carbon black by weight.

3. Use of the powder according to claim 1, wherein said powder comprises the humic acid salts in the +1 valent of either Na or K salt.

4. Use of the powder according to claim 1, wherein said powder comprises the humic acid salts in the +2 valent of either Ca, Mg or Ba salt.

5. Use of the powder according to claim 1, wherein said powder comprises the humic acid salts in the +3 valent of either Fe or Al salt.

6. Use of the powder according to claim 1, wherein said powder has the average grain size between 10-20 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 Comparative table for detection performances of humic acid fingerprint powder and carbon doped humic acid fingerprint powders on detecting fingerprints left and aged for 1 day on glass, PVC and metal surfaces is given.

[0007] FIG. 2Comparative table for detection performances of Na-humate and K-humate fingerprint powder (+1 valent humates) and carbon doped fingerprint powder left on the glass, PVC and metal surfaces and then 1 day aged is given.

[0008] FIG. 3Comparative table for detection performances of Ca-humate, Mg-humate and Ba-humate fingerprint powder (+2 valent humates) and carbon doped fingerprint powder left on the glass, PVC and metal surfaces and then 1 day aged is given.

[0009] FIG. 4Comparative table for detection performances of Fe-humate and Al-humate fingerprint powder (+3 valent humates) and carbon doped fingerprint powder left on the glass, PVC and metal surfaces and then 1 day aged is given.

DETAILED DESCRIPTION OF THE INVENTION

Application of Humic Acid and its Salts Directly on Latent Fingerprints

[0010] Water-soluble sodium and potassium salts of humic acid are obtained as the result of extraction with various alkalis (KOH, NaOH, etc.) from Lignite or Leonardite based brown coals. Calcium, barium, magnesium, iron and aluminum humates are obtained with the ion-exchange reaction of Na-Humate with various metal salts (CaCl.sub.2), CaCl.sub.2), FeCl.sub.3, etc.). In the present invention, the potassium, sodium, barium, magnesium, calcium, aluminum, iron salts of humic acid and pure humic acid were used as fingerprint powder. Fingerprint powders prepared in the present invention are able to determine traces which aged at various times.

[0011] Potassium, sodium, barium, magnesium, calcium, aluminum, iron salts of humic acid and pure humic acid were grinded separately by using ball mill (Fritsch Planetary Mono Mill Pulverisette) to obtain the particle size of 10-20 m, since the particle size is an important factor for a high quality performance of trace detection in fingerprint powder. According to this, particle sizes of humic acid and its salts were obtained between 10-20 m as the result of grinding operation at 400-600 rpm speed for 40-120 minutes by using appropriate number (40-50 pieces) of grinding balls with appropriate diameter (10 mm).

[0012] Fine brushes, which are made of glass fiber or fine animal hair and do not scratch the traces, and fingerprint powders are used for detection of the latent fingerprints at crime scenes. The application is made by making touch without pressing the brush to fingerprint powder in the powder container and rotating without pressing it on the smooth surface on which have fingerprints. The fingerprints which are left on glass, PVC and metal surfaces and then 1 day aged were detected by dusting with the produced humic acid and humate based powders and comparative tables are given in FIG. 1, FIG. 2, FIG. 3 and FIG. 4.

[0013] Doping Humic Acid and its Salts with Carbon Black and Application to Latent Fingerprints

[0014] There should be a color contrast between the surfaces and the used fingerprint agent for detection of fingerprints at crime scenes. Although the fingerprints detected with powders containing pure humic acid and its salts have adequate qualifications, the color was obtained as light brown; therefore carbon black which is a black colorant agent was added to improve the contrast on light-colored surfaces. Carbon black was added to each type of humic acid and its salts in the ratio of 10-20% and fingerprint powder was prepared by mixing at 400 rpm speed for 20 minutes in ball mill (Fritsch Pulverisette Mill Planetary Mono) without using balls. The preparation conditions of carbon black doped humic acids and its salts are given in Table 1.

[0015] The fingerprints which are left on glass, PVC and metal surfaces and then 1 day aged were detected by dusting with the produced doped humic acid and humate based powders and comparative tables are given in FIG. 1, FIG. 2, FIG. 3 and FIG. 4.

TABLE-US-00001 TABLE 1 Preparation Conditions of Doped Humic Acid and Humate Fingerprint Powders Sample Composition (wt. %) Mixing time 80-90% Humic Acid + 10-20% carbon black 20 min 80-90% Al-humate + 10-20% carbon black 20 min 80-90% Ba-humate + 10-20% carbon black 20 min 80-90% Mg-humate + 10-20% carbon black 20 min 80-90% Fe-humate + 10-20% carbon black 20 min 80-90% Ca-humate + 10-20% carbon black 20 min 80-90% K-humate + 10-20% carbon black 20 min 80-90% Na-humate + 10-20% carbon black 20 min