UGC NTA NET/JRF Exam, Forensic Science, August-2024

Capillary Zone Electrophoresis (CZE) can serve as a complementary technique to Ion Exchange Chromatography (IEC). Both are used to separate ionic species, but they operate on different principles.

While IEC separates analytes based on their interaction with charged stationary phases, CZE separates ions by their electrophoretic mobility in a capillary filled with a buffer.

CZE offers high resolution, speed, and low sample consumption, and can be especially useful for resolving complex mixtures of proteins, peptides, and small ions that may not be well separated in IEC.

The process of interpreting or recovering illegible, obliterated, or effaced writing is known as decipherment. This term is used in forensic document examination when original content has been intentionally removed or has faded due to time or damage.

Techniques used in decipherment include UV/IR photography, oblique lighting, digital enhancement, and chemical reagents, depending on the nature of the substrate and ink. The goal is to restore or read the hidden or unclear text without further damaging the document.

Urobilinoids, including urobilin and stercobilin, are metabolic products derived from the degradation of heme, particularly from the breakdown of red blood cells. The pathway begins in the liver, where bilirubin is formed and excreted into the bile, entering the intestines.

There, bacterial action converts it into urobilinogen, which is further oxidized into stercobilin and urobilin.

These are primarily excreted in feces, giving them their characteristic brown color. A small portion may be reabsorbed and excreted in urine, but the main excretion route is fecal.

In handwriting analysis, shading refers to the variation in line width caused by pressure applied through a flexible split nib or other writing instruments.

This is a deliberate stylistic trait where thicker and thinner lines alternate, contributing to the individual's handwriting characteristics.

Shading is different from pressure variation that occurs unconsciously or from hesitation. It can be a distinguishing feature in signature verification or authorship determination.

Duolite C 225, Amberlite 120, Dowex 50, and AG50W are trade names for strong acid cation exchange resins.

These resins typically contain sulfonic acid groups (-SO,H) bonded to a polymer matrix, which can exchange hydrogen ions (H+) with other cations in solution. They are used in water softening, metal ion separation, and protein purification.

Their strength lies in their ability to function over a wide pH range and maintain high capacity for cation binding.

P-dimethylaminocinnamaldehyde (DMAC) is a reagent used in colorimetric tests for detecting urea in biological fluids such as urine.

When DMAC reacts with urea, especially in acidic conditions, it forms a colored complex, typically yielding a yellow to orange color, which is indicative of the presence of urea.

This test is used in clinical and forensic toxicology to estimate renal function or verify the presence of urine on evidence materials.

Urea is a major nitrogenous waste product in urine and its detection can also help confirm sample authenticity in various investigations.

In chromatography, resolution is the quantitative measure of how well two analytes are separated by a chromatographic column. It is calculated using the formula:where tᵣ₁ and tᵣ₂ are the retention times of the two compounds, and W₁, and W₂, are the widths of their respective peaks.

A resolution value (R₅) of 1.5 or more typically indicates baseline separation. High resolution is essential in both qualitative and quantitative analysis for accurate identification and measurement of components in mixtures.

Alkenes, when reacted with water in the presence of an acid catalyst (usually H₂SO₄) undergo acid-catalyzed hydration to form alcohols. For example:
This reaction follows Markovnikov's rule, meaning the hydrogen attaches to teh carbon with more hydrogen atoms, and the OH group goes to the carbon with fewer hydrogens.

This process is widely used in the industrial synthesis of alcohols, respecially ethanol and propanol, from ethene and propene respectively.

During ethanol synthesis from starch-based materials (like grains or potatoes), fermentation not only produces ethanol but also results in the formation of small quantities of higher alcohols, collectively referred to as fusel oil.

Fusel oil contains compounds like amyl alcohol, isobutanol, and isoamyl alcohol, which are more oily and pungent than ethanol and can impart undesirable flavors or toxic effects.

It is considered an inferior liquor and is often removed during distillation. However, in some distilled spirits, trace amounts may remain to add character.

A dum-dum bullet has a lead core enclosed in a metallic jacket where the tip of the jacket is deliberately made thin or exposed. Upon impact, this causes the bullet to expand or mushroom, inflicting greater tissue damage than a fully jacketed bullet.

Originally developed in Dum Dum Arsenal, India, such bullets were designed to maximize stopping power.

Their use in warfare is banned under the Hague Convention due to the excessive injury they cause, but they may still be used in some law enforcement or selfdefense contexts.