What is cold Vapour Atomic Absorption Spectroscopy?
Definition: A type of atomic absorption spectrometry where no vaporisation step is required because the sample is a volatile heavy metal such as mercury, which is a vapour at room temperature.
Why we require cold Vapour AAS for the analysis of Hg and metalloids?
The cold vapor atomic absorption technique is widely used for mercury trace analysis because of its simplicity, robustness, and relative freedom from interferences. Excellent detection limits can be achieved with our modern instruments.
What is the principle of atomic fluorescence spectroscopy?
Atomic fluorescence spectrometry (AFS) is an analytical method used to determine the concentration of elements in samples. The sample is converted to gaseous atoms, and the element of interest is excited to a higher electronic energy level by a light source.
What technique can be used to determine the mercury?
In many parts of the world, cold vapor atomic absorption spectroscopy (CVAAS) is still the most commonly used technique for the determination of mercury.
Which of the following elements is determined by the cold vapor method?
The cold vapor technique is the only EPA approved method for determining mercury at this level [4].
What is hollow cathode lamp in AAS?
A hollow cathode lamp is used as a spectral line source for Atomic Absorption (AA) instruments. AAS lamps utilize the hollow cathode effect to generate light at wavelengths for the element of interest. The emission line selected must avoid wavelength overlaps, and have good intensity with low noise.
What is the difference between AAS and AFS?
Atomic Spectrometry
Both in AAS and AFS, a light source is used for excitation of analyte atoms. However, in AAS this light source is in a straight-line optical axis configuration, but in AFS the light source is rotated 90° (see Figure 2).
What are the advantages and disadvantages of atomic fluorescence spectroscopy?
As it was already pointed, one of the most important advantages of this technique is due to its high sensitivity and specifity. Another is its fast and rapid diagnosis ability. The main disadvantage is that not all compounds fluoresce.
What is cold vapor technique?
Cold Vapor Atomic Absorption Spectroscopy or CVAAS is one of the primary techniques for mercury analysis. Introduced in 1968 by Hatch and Ott, CVAAS is now the reference method for drinking water monitoring under the Safe Drinking Water Act passed in 1974, and amended in 1986 and 1996.
Which technique is better for analysis of mercury from drinking water?
Mercury in waste water can be determined by Flameless Atomic Absorption Spectroscopy. It is a cold vapour technique with very good sensitivity.
Why acetylene gas is used in AAS?
Because it gives a very high temperature: 2200-2400 ∘C. This is due to its high heat of combustion, around 1300 kJ/ mol. If still higher temperatures are required, as for Al, Si, Ti, etc., a combination of acetylene and N2O is used, which reaches 2600-2800 ∘C.
Which is the cold cathode lamp?
Cold-cathode lamps include cold-cathode fluorescent lamps (CCFLs) and neon lamps. Neon lamps primarily rely on excitation of gas molecules to emit light; CCFLs use a discharge in mercury vapor to develop ultraviolet light, which in turn causes a fluorescent coating on the inside of the lamp to emit visible light.
Why AES is better than AAS?
In AAS, when monochromatic light is bombarded through the sample the atoms absorb energy, and the extent of absorption is recorded. In AES, the sample which gets atomised in the flame then absorbs the energy through the electrons which get excited.
What are the main differences between AAS and AES?
While AAS quantifies the absorption of electromagnetic radiation by well-separated neutral atoms, AES measures emission of radiation from atoms in excited states.
What are different applications of atomic fluorescence spectrometry?
These findings could have future applications in forensic sciences and toxicology. Another important application of AFS is in studying the speciation of metals within samples. For certain metals, including mercury and arsenic, the compound that the metal is in determines whether it is toxic or (relatively) benign.
What are the applications of fluorescence spectroscopy?
Applications. Fluorescence spectroscopy is used in, among others, biochemical, medical, and chemical research fields for analyzing organic compounds. There has also been a report of its use in differentiating malignant skin tumors from benign.
What is atomic emission analysis?
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample.
How would you test for the presence of mercury in water?
The simple test uses a sheet that changes color when inserted into mercury-contaminated water, with results visible to the naked eye. The membrane uses a dye called rhodamine, a florescent organic compound, to indicate the presence of mercury.
Why is a hollow cathode lamp used in AAS?
Which flame is used in AAS?
air-acetylene flame
1.1 Flame atomic absorption spectrometry. Chromium is typically determined by flame AAS using an air-acetylene flame or a nitrous oxide-acetylene flame.
What is the difference between hot and cold cathode?
Two types exist: In the hot cathode gauge (HCG) the source of the ionizing electrons is a thermionic cathode. In the cold cathode gauge (CCG) it is a circulating space charge current of electrons trapped in crossed electric and magnetic fields.
Which coating is used in CCFL?
Introduction. Cold Cathode Fluorescent Lamps (CCFLs) are sealed glass tubes filled with inert gases. When a high voltage is placed across the tube, the gases ionize creating ultraviolet (UV) light. The UV light, in turn, excites an inner coating of phosphor, creating visible light.
What is the main difference between AES and AAS?
AAS and AES differ in their operating principle where AAS employs the method of absorption of light by the atoms and, in AES, the light emitted by the atoms is what is taken into consideration.
Is AAS and AES same?
AES is similar to AAS in many regards, except that the emission of the heated gaseous metallic atoms is measured. The primary advantages of AAS and AES for the forensic scientist are unsurpassed limits of detection, accuracy, and precision for elemental analysis.
What are the applications of AAS?
Atomic absorption spectroscopy is utilized across many industries and is instrumental in the detection of metals within a sample. As such, this process is commonly utilized in pharmacology, archaeology, manufacturing, mining, and forensics.