Background correction continuum

Zeeman background correction. Continuum source (D2) may be applied for plasma/ serum matrices... 

Background correction continuum source Furnace program... 

Deuterium arc background correction. This system uses two lamps, a high-intensity deuterium arc lamp producing an emission continuum over a wide wavelength range and the hollow cathode lamp of the element to be determined. 

Define background absorption and background correction. How does the use of a continuum fight source help with background correction ... 

A spectrometer with rapid response electronics should be used for electrothermal atomization, as it must follow the transient absorption event in the tube. Automatic simultaneous background correction (see Section 2.2.5.2) is virtually essential, as non-specific absorption problems are very severe. It is important that the continuum light follows exactly the same path through the furnace as the radiation from the line source (assuming a deuterium lamp is being used rather than Smith-Hieftje or Zeeman effect). The time interval between the two source pulses should be as short as possible (a chopping frequency of at least 50 Hz) because of the transient nature of the signal. 

Figure 14.12 —Schematic of an instrument showing deuterium lamp background correction. Perkin Elmer, model 3300 with a Littrow-type monochromator. This double beam assembly includes a deuterium lamp whose continuum spectrum is superimposed, with the aid of semitransparent mirrors, on the lines emitted by the hollow cathode lamp. One beam path goes through the flame while the other is a reference path. The instrument measures the ratio of transmitted intensities from both beams. The correction domain is limited to the spectral range of the deuterium lamp, which is from 200-350 nm. (Reproduced by permission of Perkin Elmer.)...

Background correction is carried out with a continuum source, e.g. a hydrogen hollow-cathode lamp or a deuterium-arc lamp. 

Bismuth 223.1 air/acetylene Sample preparation. Dissolve 2.000 g of sample in 12 ml of hydrochloric acid, 6 ml of nitric acid and 20 ml of water in a PTFE beaker. Evaporate the solution to 10- 12 ml, cool, add 1 ml of hydrofluoric acid dropwise and boil for five minutes. Cool, add 5 ml of 1% boric acid solution and dilute to 50 ml. Background correction using a UV continuum source is advisable for bismuth... 

When determining those elements which absorb in the UV portion of the spectrum, corrections for nonatomic absorption are almost essential. This is especially true for solutions of high solids content, such as those which result from fusion techniques. This correction is generally made by using a hydrogen continuum lamp. Some of the newer instruments have provisions for automatic and continuous background correction. A field installable kit is available to retrofit the model 1200 now used. 

One of the main practical problems with the use of AAS is the occurrence of molecular species that coincide with the atomic signal. One approach to remove this molecular absorbance is by the use of background correction methods. Several approaches are possible, but the most common is based on the use of a continuum source, D2. In the atomization cell (e.g. flame) absorption is possible from both atomic species and from molecular species (unwanted interference). By measuring the absorption that occurs from the radiation source (HCL) and comparing it with the absorbance that occurs from the continuum source (D2) a corrected absorption signal can be obtained. This is because the atomic species of interest absorb the specific radiation associated with the HCL source, whereas the absorption of radiation by the continuum source for the same atomic species will be negligible. 

Continuum source background correction uses a deuterium lamp to obtain an estimate of the background absorbance. A hollow-cathode lamp obtains the total absorbance. The corrected absorbance is then obtained by calculating the difference between the two. 

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