Plasma background subtraction

Figure 3. Efficiency of plasma background subtraction. Spectra obtained after on-detector integration for 1.6 s. Key a, spectrum of 10 pg/mL Ti b, detector and spectral background and c. net difference spectrum.

The determination of plasma parameters using He-like spectra is based on a self-consistent modeling of the theoretical spectra. The following variables take part in the variation procedure based on least-squares fitting electron and ion temperatures, toroidal plasma velocity, concentrations of H-, He-and Li-like ions. In addition, a background function was used to subtract the plasma background from the experimental spectra. The background consists of continuum radiation from the plasma and detector noise. 

Most recently, Zhang et al. [347] demonstrated the combined use of a novel accurate mass-based background subtraction approach and MDF for detecting and characterizing troglitazone metabolites in rat plasma, bile, and urine. The standard... 

Zhang H, Ma L, He K, Zhu M. An algorithm for thorough background subtraction from high-resolution LC/MS data Application to the detection of troglitazone metabolites in rat plasma, bile, and urine. J Mass Spectrom 2008a 43 l 191-1200. 

Fig. 14.3. Extraction of spectra from chromatographic peak No. 50 in the TIC of a plasma sample spiked with 4-HNE. Left column single scan spectra from scans No. 935, 936, and 937 show changing relative intensities averaging scans 935 937 levels intensity but leaves noise background subtraction reduces noise additionally. (For explication, HC, and RICs see preceding example and Fig. 14.2.)...

Fig. 4.13. An echellogram of iron before the plasma background is subtracted. Long wavelength orders are at the top with wavelength decreasing on each succeeding order. Note the cursor is on the 69th order at 327.2 nm.

Fig. 4.15. (A) Plot of a small section of an echellogram showing analytical lines with background from the plasma (B) plot of the background from the plasma and (C) plot of the background subtracted from the analytical signal. Several low intensity lines are easily observed.

Activity with 1 x S subtract the corresponding blank value (or the individual background value if this is higher than the blank value) from the absorbance values of both reaction tubes with 1 x S (Table 3.7.1 tubes 3 and 4). Divide by the standard factor to obtain nmols/assay. Further divide by 60 min (assay time) to obtain nmol/min/assay. Multiply by 20 (1 ml/0.050 ml) to obtain nmol/min/ml plasma. Calculate the mean value of activity with 1 x S. 

Fundamental requirements for an atomic absorption experiment are shown in Figure 21-2. Principal differences between atomic and ordinary molecular spectroscopy lie in the light source (or lack of a light source in atomic emission), the sample container (the flame, furnace, or plasma), and the need to subtract background emission. 

When the interference is from the plasma emission background, there are background correction options available with most commercial instrumentation. The region adjacent to the line of interest can be monitored and subtracted from the overall intensity of the line. If direct spectral overlap is present, and there are no alternative suitable lines, the interelement equivalent concentration (lEC) correction technique can be employed. This is the intensity observed at an analyte wavelength in the presence of 1000 mg of an interfering species. It is expressed mathematically as ... 

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