Through the refraction of light by a prism or through its diffraction by a diffraction grating, the light from a source is spread out into its different visual wavelengths, from red to blue. Because each element emits or absorbs light only at specific wavelengths, the chemical composition of stars can be determined.

NASA scientists often use a technique called “remote sensing” to study the composition of different elements and structures on planets.

spectrometer

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects.

This type of study is called spectroscopy. The science of spectroscopy is quite sophisticated. From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star. The spectral line also can tell us about any magnetic field of the star.

Spectroscopy is also used in astronomy and remote sensing on Earth. Most research telescopes have spectrographs. The measured spectra are used to determine the chemical composition and physical properties of astronomical objects (such as their temperature and velocity).

Spectroscopy is used as a tool for studying the structures of atoms and molecules. The large number of wavelengths emitted by these systems makes it possible to investigate their structures in detail, including the electron configurations of ground and various excited states.

Spectroscopy also finds uses in astronomy to obtain information about the composition, density, temperature, and other principal physical processes of a certain astronomical object. By measuring red-shift (recession speed), scientists can use spectroscopy to calculate the relative velocities of supernovae and galaxies.

Light source Two kinds of lamps, a Deuterium for measurement in the ultraviolet range and a tungsten lamp for measurement in the visible and near-infrared ranges, are used as the light sources of a spectrophotometer.

Emission instruments use most of the same components as absorption systems. A source of light is not usually required, except in the case of fluorescence spectroscopy. Fluorescence is stimulated in a sample by a beam of radiation which is usually aimed perpendicular to the line of the detector.

Deuterium lamps are always used with a Tungsten halogen lamp to allow measurements to be performed in both the UV and visible regions. Also known as quartz Iodine lamps, these measure most effectively in the visible region from 320 – 1100 nm.

The light source consists of a Xenon flash lamp for the ultraviolet (UV) as well as for the visible (VIS) and near-infrared wavelength regions covering a spectral range from 190 up to 1100 nm.

Determining blank, or zero, values is an important step in all photometric measurements. It serves the calibration of the photometer, which is thus set to “zero”. Blank measurements are carried out in the same instrument, under the same experimental conditions, as the actual sample measurement. …

Historically, reusable quartz cuvettes were required for measurements in the ultraviolet range, because glass and most plastics absorb ultraviolet light, creating interference. Glass, plastic and quartz cuvettes are all suitable for measurements made at longer wavelengths, such as in the visible light range.

The UV range extends from 100–400 nm, and the visible spectrum ranges from 400–700 nm. However, most spectrophotometers do not operate in the deep UV range of 100–200 nm, as light sources in this range are expensive.

The UV region covers the wavelength range 100-400 nm and is divided into three bands: UVA (315-400 nm) UVB (280-315 nm) UVC (100-280 nm).

Absorbance (A) is the flip-side of transmittance and states how much of the light the sample absorbed. It is also referred to as “optical density.” Absorbance is calculated as a logarithmic function of T: A = log10 (1/T) = log10 (Io/I).

Lambda max (λmax): The wavelength at which a substance has its strongest photon absorption (highest point along the spectrum’s y-axis).

As the number of conjugated pi bonds increases, the λmax increases as well! Because longer frequency = smaller energy, this means that the energy gap ΔE between the highest-occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) decreases as the number of conjugated pi bonds increases.

260 nm

The two wavelengths selected for determination were 243 and 374nm, the maximum absorbance wavelength (λmax) of paracetamol and lornoxicam, respectively. Beer’s law was obeyed over the concentration range 4-12 μg/ml at 243 nm by paracetamol and over the concentration range 4-16 μg/mL at 243 and 374 nm by lornoxicam.

Abstract. Acetylsalicylic acid (ASA) was found to be quite soluble and quite stable in a 50/50% volume/volume water–ethanol solution. In this solution, a well-defined spectrum with a maximum absorbance, λmax, of 276 nm of ASA was observed, and a molar absorptivity, ε, of 1.1 × 103 M-cm was determined.

1. A 12.00g sample of a crystallised pharmaceutical product was found to contain 11.57g of the active drug.
2. Calculate the % purity of the sample of the drug.
3. % purity = actual amount of desired material x 100 / total amount of material.
4. % purity = 11.57 x 100 / 12 = 96.4% (to 1dp)
5. –

Like many conjugated organic molecules, caffeine absorbs radiation with a wavelength around 260 nm. A conjugated system is one containing 2 double bonds separated by a single bond. This conjugated pattern may be repeated several times in the molecule.

The UV absorption spectrum (see figure below) of caffeine exhibits a pair of absorption bands peaking at 205 nm and 273 nm with a characteristic absorption shoulder between them. Typically, caffeine content is determined by measuring the absorbance at 275 nm.

Slightly flammable to flammable in presence of open flames and sparks, of heat. Non-flammable in presence of shocks. Explosion Hazards in Presence of Various Substances: Risks of explosion of the product in presence of mechanical impact: Not available.

2 Caffeine does not absorb light in the visible range and therefore has no color. Erythrosine absorbs in the visible range so it has color. Its absorbance maximum can be found at 526 nm so the color it absorbs is green.

If the concentration of solution is increased, then there are more molecules for the light to hit when it passes through. As the concentration increases, there are more molecules in the solution, and more light is blocked. This causes the solution to get darker because less light can get through.

Typical spectra When prepared at a 600 mg/l concentration, a potassium dichromate solution in 0.001 M perchloric acid can be certified at 430 nm for absorbance value.

The Beer-Lambert law states that there is a linear relationship between the concentration and the absorbance of the solution, which enables the concentration of a solution to be calculated by measuring its absorbance.