Background correctors

Nakahara and Chakrabarti [137] showed that the seawater salt matrix can be removed from the sample by selective volatilisation at 1700-1850 °C, but the presence of sodium chloride, sodium sulfate, and potassium chloride causes a considerable decrease in molybdenum absorbance, and magnesium chloride and calcium chloride cause a pronounced enhancement. The presence of magnesium chloride prevents the depressive effects. Samples of less than 50 pi can be analysed directly without using a background corrector with a precision of 10%. 

Practical system for flame atomic absorption spectrometry including a deuterium background corrector. 

Lead line, 217nm lamp current, 8mA spectral band width, 0.7nm scale expansion 4x (0.25A full scale) furnace gas, 135ml H min 1. The deuterium background corrector was used. 2... 

Solvents such as chloroform, carbon tetrachloride, hexane and benzene gave absorption signals because of their non-specific absorption at the lead resonance line. Although these solvent peaks generally emerged well before the lead compounds, the use of the background corrector is recommended to eliminate these potential interferences. 

The three methods for lead in air are essentially identical however, one should use S-341 because this method has been validated unlike P CAM 155 or P CAM 173. Although all the methods recommend 2-3 ml of nitric acid for wet ashing, the final solutions differ in that P CAM 155 recommends 1% nitric, P CAM 173 recommends 1% HC1, and S-341 recommends 10% nitric with EDTA 0.1 M to suppress phosphate, carbonate, iodide, fluoride, and acetate ion that cause flame suppression. EDTA is suggested in P CAM 173 where interferences are anticipated. Both S-341 and P CAM 173 use the 217.0 nm line which is twice as sensitive as the 283.3 nm line. Strong nonatomic absorption found when high concentrations of dissolved solid are present requires use of the background corrector. These two methods differ from P CAM 155 and those for biological analysis,... 

Procedure Use a Perkin-Elmer 403 atomic absorption spectrophotometer equipped with a deuterium arc background corrector, a digital readout device, and a burner head capable of handling 20% solids content. Blank the instrument with water following the manufacturer s operating instructions. Aspirate a portion of the Standard Preparation, and record the absorbance as As then aspirate a portion of the Sample Preparation, and record the absorbance as Av. Calculate the lead content, in milligrams per kilogram, of the sample taken by the formula... 

An alternative procedure for the Zeeman background corrector is to operate the hollow cathode continuously but to expose the sample to an alternating magnetic field. The sample atoms absorb at the resonance line when not exposed to the magnetic field, but develop hyperfine structure and do not absorb the resonance line when the magnet is turned on. With the magnetic field on, absorption of the resonance line is a measure of molecular background. From the combined data, the net atomic absorption can be measured. 

Fig. 4. Chart trace illustrating dry, ash and atomise events with background corrector off.

It is standard practice to use method (b) when determining metals with absorbing wavelengths below 300 nm. A deuterium background corrector is standard equipment and is commercially available on all modern atomic... 

Operating conditions. AAS-device with graphite tube furnace and deuterium background corrector. Wave-length, 228.8nm EDL, Cd (6 W). 

Operating conditions. AAS device with background corrector, absorption cuvette open (15 cm length, 15 mm diameter) and closed system with crystal windows circulating pump, 2.51 min-1 pressure fusion vessel. Wavelength, 253.7 nm EDL, Hg (5 W) deuterium compensator. 

Simple procedures that require only a dilution of serum or urine have been reported by Schattenkirchner and Grobenski [95], and by Ward et al. [96]. The former diluted samples of sera 1 + 4 with 0.1% Triton X 100 and urine samples 1 + 9 with 0.01 M HC1 and the latter used a 1 + 9 dilution of serum in water. In both cases calibration was by standard additions to compensate for the considerable matrix interferences. Ward et al. [96] demonstrated an excellent correlation (r = 0.98) between neutron activation analysis (NAA) and ETA—AAS analysis of the total plasma Au and albumin bound Au, which contains up to 90% of the total. There was however, a bias towards higher values (10%) by NAA. This difference did not appear to be pre-atomisation losses during ETA—AAS, the recoveries of added Au ranged from 90—105%, nor over-correction by continuum source background corrector. 

Spectral slit-width Wavelength Background corrector Gas flow ... 

Instrumental Conditions. FAA analyses for Ba, Fe, and Mn were done on a Perkin Elmer model 560 atomic absorption spectrophotometer with an air-acetylene flame for Fe and Mn and a nitrous oxide-acetylene flame for Ba (38, 39), The remaining elements were determined by ETAA with the conditions listed in the appendix (Table A-l) with a Perkin Elmer model 5000 atomic absorption spectrophotometer equipped with a model HGA-400 graphite furnace and a deuterium background corrector. The precision of FAA was 1.0% and the precision of ETAA was 10%. Absorbance readings for FAA were converted directly to concentrations by comparison with absorbance readings for standards that had been previously stored in the instrument s computer. 

FIGURE 13. Comparison of pulsed GC-AA output continuous UV detection output. The pulsed output was obtained using a 0.85 ml injection at 382-ppm trimethylarsine. The power supply dial was set at 2000 °C and the pulse program was set to give a 7-s pulse on a 30-s interval. The background corrector of the detector was not employed and, as indicated by the arrow, molecular absorption of the 193,7-nm EDL-As can be detected. The continuous output was obtained using 0.20 ml of 2536-p.p.m. trimethylarsine with the furnace at ambient temperature and very low attenuation of signal to the recorder... 

Of the three chromatograms (B, , D) determined under atomization conditions (1800 ° dial, Dj background corrector on) with the respective EDL sources (As, Se, Sn) operating in their recommended modes, only the selenium chromatogram looks like the chromatograms obtained without other compounds present. In the cases of arsenic (B),... 

Sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), concentrations were measured by atomic absorption spectrophotometry (Perkin Elmer 2380 equipped with deuterium background corrector). Cd, Zr, and Cu concentrations were obtained in a quartz cell, by differential pulse anodic stripping voltammetry (DPASV) with a assy carbon thin-film mercury covered electrode (Tacussel polarographic equipment fitted with a Tacussel EDI type electrode). Pure water was produced by a Milli. Q water purification system (Millipore). Chlorate, sulfate and carbonate were measured using classical methods. 

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