How Does Atomic Absorption Spectroscopy Work?

Atomic Absorption Spectroscopy(AAS) is a quantitative analytical elemental technique that provides the total metal content of the sample and is almost independent of the molecular form of metal in the liquid sample. It analyzes the concentration of elements in a liquid sample based on energy absorbed from certain wavelengths of light. Alan Walsh, a Lancashire-born physicist was the one who worked on determining the small concentrations of metallic elements using spectroscopy. He got this idea in the 1950s while working in his garden. He worked on it for several years and finally convinced the manufacturers to use AAS for metallic determination. The first commercial AAS was launched in the 1960s and since then this technique has established a robust place in the field of analytical techniques.  Principle of Atomic Absorption Spectroscopy The AAS technique is based on the absorption of energy by ground-state atoms in the gaseous state. It states […]

Comparison Microscope: Principle, Features & Applications

The invention of the microscope has been a boon in the scientific field which allowed scientists to visualize things or matter or objects which are not visible to the naked eye. The first microscope came into existence with the invention of early microscope, by a Dutch spectacle maker Zacharias Janssen in 16th century. With the passage of time and different needs for visualization, various kinds of microscopes were invented and one of them was the comparison microscope.  The comparison microscope was invented for side-by-side analysis of objects. As the name suggests, it compares two objects simultaneously. It is an instrument that combines two light microscopes side-by-side connected via an optical bridge which facilitates a split view window. It is one of the important instruments used in forensics. Development of Comparison Microscope The comparison microscope was first launched as a prototype in Germany in 1913. However, it was not popularised in […]

Scanning Electron Microscope

Scanning Electron Microscope (SEM) is a type of electron microscope that produces a three-dimensional image of a microscopic object. As the name suggests the microscope forms the images by scanning the surface of the object with the help of a focused beam of electrons. SEM was first developed in 1937 with the contribution of Manfred von Ardenne. However, the first commercial instrument was launched in 1965.  SEM image reveals information like the morphology, crystalline structure, chemical composition, and orientation of materials/components of the sample. SEM requires electrons that have low kinetic energy because the interaction only with the surface up to a few nanometers of depth is required rather than penetrating deep inside the sample. Principle of Scanning Electron Microscope SEM works on the principle that, “When the accelerated electrons with specific amounts of kinetic energy interact with the surface of the sample, the energy is dissipated in the form […]

Famous Scientists of Toxicology

Toxicology is the scientific discipline that deals with the study of poisons or toxic substances and their effects on living organisms. It is a broad field that encloses the application of biology, chemistry, pharmacology, and medicine to study a particular poison and its effects on living beings, especially humans. It is a wide discipline that is being used in many fields such as environmental, clinical, economic, biochemical, regulatory, industrial, genetic, preventive, behavioral, toxinology, wildlife, and forensic toxicology. Forensic toxicology is the discipline that deals with the medicolegal aspect of poison, types of poison, symptoms, and their possible treatment. Section 328 of IPC provides punishment for causing hurt by means of poison or any stupefying, intoxicating or unwholesome drug or other things with the intent to commit an offense (i.e., anything when used in an unwholesome state/composition can act as a poison). Famous Scientists Contributing to Toxicology Toxicology came into existence […]

Age Determination of Ink

Ink is a colored liquid that is used to write or draw on paper. The inks can be in aqueous, powder, or paste form. Inks were first discovered by the Egyptians who used to write and draw things. Another big contribution to ink discoveries and development was the Chinese. In fact, Indian ink was invented in China.  Components of Ink Ink is basically a mixture of various components that have their individual functions. The basic components of the ink are: 1. Pigments   Pigments are the ones that give color to every ink. The pigments can be made up of either organic or inorganic compounds. It is the main component of the ink. 2. Dispersants  Dispersants are used as surfactants and polymers in the ink. 3. Resins or Polymers     Resins and polymers are helpful in improving the binding of the components in ink. 4. Humectants   Humectants are the components that help […]

Column Chromatography: Principle, Types, Working & Applications

Column Chromatography is a chromatographic technique in which the separation of constituents of a substance is carried out in a column packed with an adsorbing material. It is a type of adsorption chromatography in which the constituents separate at differential rates in fractions. It is a technique that uses a solid adsorbent material as its stationary phase which is packed in the column and the mobile phase (gas or liquid) runs through it. The most commonly used stationary phase materials are silica gel or alumina whereas organic solvents are the widely used mobile phase in column chromatography. Principle or Column Chromatography Column chromatography is based on the principles of the rate of adsorption of the analyte on the stationary phase according to its affinity with the adsorbent.  It states that when a sample is loaded at the top of the column along with the mobile phase, the components of the […]

Age Determination of Paper

Paper is one of the pieces of evidence encountered in a criminal case including murder, forgery, fraud, or suicide since it is one of the common writing surfaces for any person. Therefore, its examination is important to provide accurate data after analysis. Paper is a thin sheet made from wood pulp or other lignocellulosic materials such as cotton, rice, or wheat straw for writing, printing, and packaging purposes. It is believed that it was originated in China in the 2nd century as an alternative writing material to silk. Almost 200 years of its mechanized production resulted in significant changes in information networking all over the world. Steps of Paper Manufacturing 1. Pulping The wood is cut into small wood chips which are mixed with water and finely ground to form a pulp. This step helps in cleaning and separating fibers of wood. 2. Bleaching The raw pulp contains an appreciable […]

Gas Chromatography: Principle, Working & Uses

Gas chromatography (GC) is a widely used instrumental method for analytical purposes. GC is an analytical separation and purification technique used to analyze a volatile compound in the gaseous phase. This technique is based on the principles of column chromatography where gas is used as the mobile phase. The stationary phase in GC can be a liquid or solid and based on this the GC can be categorized as Gas-Liquid Chromatography (GLC) or Gas-Solid Chromatography (GSC). The separation in GLC is based on the principle of partition of the analyte into liquid and gas whereas in GSC the separation is based on the adsorption of the analyte on the solid stationary phase. GC was first developed by APJ Martin and Anthony T James in 1951 and it was gas-liquid chromatography based on the principle of partition chromatography. The first gas-solid chromatography was developed by Erika Cremer (German Physical chemist) and […]

Gas Chromatography Mass Spectrometry

GC-MS or Gas Chromatography Mass Spectrometry is a hybrid analytical technique that is used to perform the separation, purification, and identification of a substance simultaneously. The Gas Chromatography component is used to perform the separation and purification of the sample whereas Mass Spectrometry helps in the identification of the substance. In GC-MS two different individual techniques are coupled together to analyze a single substance. Earlier the two techniques were used individually for analysis purposes. In 1950, Fred McLafferty and Roland Gohlke, two Dow Co. researchers, dramatically enhanced the analytical power of GC by coupling it with MS.  Adding MS allowed each component exiting the gas chromatograph to be analyzed separately. When taken together, the mass spectra and the chromatographic peaks allowed unambiguous identification of each component. Principle of Gas Chromatography Mass Spectrometry GC-MS uses the principles of both instruments and consolidates them to give a single analytical result of the […]

Types of Microscopes

There are a lot of things, both living and non-living, on this earth and not everything is visible to the naked eye. Therefore, an instrument called a ‘microscope’ was developed to enter the world of those tiny things.  The word ‘microscope’ is derived from the Greek words ‘mikros’ which means “small” and ‘skopein’ which means “to examine or look“. The first microscope developed was a simple microscope in 1590. It has been said that the first compound microscope was developed in 1620 in Europe but the founder is unknown. Galileo Galilei discovered in 1610 that a telescope can also focus on small objects. He worked on it and his work was appreciated by Giovanni Faber, who named Galilei’s instrument a microscope in 1625.  Since the variety of microscopic organisms or things is vast and they cannot be viewed by a single microscope. Therefore with the difference in the need for […]

How is Forensic Taphonomy Useful in Investigations?

Forensic taphonomy is the post-mortem transformations or changes that occur in the dead remains of a corpse since the death and its discovery. The word Taphonomy is derived from the Greek words- ‘taphos’ which means “burial“, and ‘nomos’ which means ‘law“. The term taphonomy was first defined by Russian geologist Efremov(1940) to encompass studies in what he referred to as the “transition of animal remains from the biosphere into the lithosphere”. The use of taphonomy in forensics was first described by Dirkmaat and colleagues (2008) as “the most significant development to alter the field of forensic anthropology.” What is Forensic Taphonomy?  Forensic taphonomy involves the investigation of soft tissue changes, decomposition rates and patterns, the dispersion of body parts, and the modifications that occur to both soft tissues and bones. The effect of the environment on the decomposition of a dead corpse is an important factor. As per Casper’s dictum, […]