Interference Effects in Atomic Absorption

ELEMENT	line nm	INTERFERENCES
Aluminium ¹³Al_26.98	309.27	Enhanced effect caused by ionization. Add an ionization buffer such as 0.1%w/v potassium chloride to both sample and calibration standards
Antimony ¹⁵Sb_121.75	206.83 217.58 231.15	High concentrations of Pb an Cu absorb at 217.58 line. Use line 206.83 or 231.15 if these elements are present. Acids cause depression of the response. Calibration solutions should be matched to the acid concentrations in the sample solutions. Can be determined by a hydride generation or Furnace method.
Arsenic ³³As_74.92	193.70	Flame interferences and scatter effects at arsenic wavelengths. Change to nitrous oxide/acetylene flame. Spike samples and add 1% nickel nitrate solution to digeststes prior to analysis. Can be determined by a hydride generation method.
Barium ⁵⁶Ba_137.34	553.55 455.40	Caused by presence of Ca or Ba ionization. Phosphate, silicon and aluminium cause depression in air/acetylene flame. Use nitrous oxide/acetylene flame and an ionisation buffer 0.1% w/v potassium as chloride. No ionization buffer is needed for determination at line 455.40 since this is the barium ion line.
Beryllium ⁴Be_9.012	234.86	Acids enhances the response. Al, Si, Mg, depresses the response. Add 0.1% hydrofluoric acid to sample and calibration standards. Can use Furnace method.
Bismuth ⁸³Bi_208.98	223.06	No serious interference effects with air/acetylene flame.
Boron ⁵B_10.81	249.77	No serious interference effects using nitrous oxide/acetylene, fuel fich flame.
Cadmium ⁴⁸Cd_112.40	228.80	Adsorption and light scattering. Large excess of silicate depress response. Calibration solutions should be matched with conc.of sample solutions. Can use Furnace method with ammonim phosphate as a matrix modifier.
Caesium ⁵⁵Cs_132.91	852.11	Ionisation effects. Add 0.5% potassium as chloride to both sample and calibration solutions.
Calcium ²⁰Ca_40.08	422.67	Response is depressed by Al, Be,P, Si, Ti, and Zr in air acetylene flame. The addition of releasing agent 0.2% w/v lanthanum to both samples and calibration stds. reduces this effect. The N2O/acetylene flame eliminates many of these problems but an ionisation buffer 0.1% of potassium as chloride must be added to all solutions. Protein in biological samples depress response and 0.5% EDTA should be added to reduce this effect.
Chromium ²⁴Cr₅₂	357.87	Reduced sensitivity with air/acetylene flame. Ca, P, and chloride interference. Phosphate depresses response. Add a 0.25% w/v calcium nitrate to all solns. The N2O flame reduces interference effects with a x2 sensitivity
Cobalt ²⁹Co_26.98	240.73	Large amounts of transition elements affect the response. Calibration stds. should be matched to the concentrations of any of these elements present as major components in the sample soln. Use standard addition. Can use Furnace method.
Copper ²⁹Cu_63.55	324.75	Transition elements and mineral acids depress the response. Adsorption and scatter. Calibration stds.should be matched to the concentrations of any of these elements present as major components in the sample.
Gold ⁷⁹Au_196.97	242.80	Cyanide depresses the response and should be destroyed by fuming with a mix.of sulphuric and perchloric acids.Nitric and HCl give a slight depression, and sulphuric gives a severe depression. Calibration solns. should be matched to the concentrations of these acids in the sample solns. Use ionisation buffer 0.1% w/v of potassium as chloride.
Iron ²⁶Fe_55.85	248.33	Perchloric acid. Nitric acid, Ni and Si depress the response. Add 0.2% w/v calcium chloride to all solns. Citric acid depress response and this effect can be reduced by adding 0.5% v/v phosphoric acid to both sample and standards. Most of these interference effects can be solved by using the hotter N2O/acetylene flame.
Lithium ⁰³Li_6.941	670.78	Ionisation effects. Use ionisation buffer 0.1% w/v potassium as chloride to both samples and calibration stds. Strontium gives enhancement due to absorption by SrOH species. Standards should be matched to concentration of strontium in sample. Can be analysed by Flame photometry.
Lanthanum ⁵⁷La_138.91	550.13	Ionisation effects. Use ionisation buffer 0.1% w/v potassium as chloride to both samples and calibration stds. Use the N2O/acetyleny fuel rich flame.
Lead ⁸²Pb_207.20	217.00	The 283.31 line is preferred for routine analysis because of better S/N ratio and lower background interference effects.
Magnesium ¹²Mg_24.31	285.21 279.55	Al and Si depress the response in the air/acetylene flame. Add 0.1% La or Sr as chloride to both sample and calibration stds. These effects are reduced in the hotter N2O/acetylene flame with addition of ionisation buffer 0.1% w/v potassium as chloride to all solns. Determination at the 279.55 line however, is the magnesium ion line and requires no KCl buffer with the hotter flame.
Manganese ²⁵Mn_54.94	279.48	Si depresses the response. Add 0.2% w/v calcium chloride to both samples and calibration stds. Mo and W depress response when acetylene pressure drops below 100 lb. (7Kg cm^-2 or 100 lb in ^-2) Change to a full acetylene cylinder.
Mercury ⁸⁰Hg_200.59	253.65	Large amounts of Cobalt enhance response. Reducing agents (SnCl2) should be added in xs to all solutions. The cold vapour flameless method is recommended.
Molybdenum ⁴²Mo_95.94	313.26	Ca, Fe, Mn, Sulphate, and Sr depress response in air/acetylene flame. Add 0.5% w/v aluminium chloride or 2% w/v NH4Cl to both samples and calibration stds. or use the N2O/acetylene flame which gives a x2 increase in sensitivity. The presence of calcium and iron in the hotter flame may cause depressed response which can be reduced by adding 0.5% w/v aluminium or 1% w/v sodium sulphate to both sample and standards. Change acetylene cylinder when pressure falls below 100 lb (7Kg cm^-2 or 100 lb in ^-2)
Nickel ²⁸Ni_58.71	341.48 232.00	Nickel line interference. Use line at 341.48 for routine work. A large excess of iron causes enhancement and calibration stds. should be matched to the concentration of this element in the sample solutions.
Potassium ¹⁹K_39.10	766.49	Ionisation effects. Add 0.1% w/v sodium or caesium to both sample and calibration solns. High conc. of mineral acids depress response. Calibration stds. should contain the same conc. of acids. Usually analysed by Flame photometry.
Silicon ¹⁴Si_28.09	251.61	Ionisation effects depress response. Use the N2O/acetylene fuel rich flame. Add ionisation buffer 0.1% w/v of an alkali metal as chloride.
Silver ⁴⁷Ag_107.87	328.07	Al, Zn, Th, KmnO4, iodate and tungstate depress the response. Do not use hydrochloric acid unless silver is in solution as a chloride complex. Calibration stds. should match the conc. of any of these present as major components in the sample.
Sodium ¹¹Na_22.99	589.00 589.59	Ionisation effects. Add ionisation buffer 0.1% w/v potassium or caesium chloride to sample and calibration stds. Can be determined by Flame photometry.
Strontium ³⁸Sr_87.62	460.73	Phosphate, Al, Si, depress response. Add 0.5% w/v lanthanum or calcium chloride to all solutions or use the N2O/acetylene flame
Tin ⁵⁰Sn_118.69	224.61	The N2O / acetylene flame should be used for routine determinations in anything but aqueous solutions.
Uranium ⁹²U_238.01	358.49 356.66	CN in the flame gives a high noise level at 358.49nm. For this reason, the 356.66nm line is used for most determinatios. Use ionisation buffer 0.1% alkali metal as chloride.
Vanadium ²³V_50.94	318.54	Al and Ti enhances the response. Add 0.5% aluminium to all solutions. Ionisation effects can be eliminated by addition of 0.1% alkali metal as chloride to all solns.
Zinc ³⁰Zn_65.37	213.86	Response is depressed with large excess of silicon. The calibration solns. should be matched to the conc. of the element in the sample solns. Strontium removes Cu and phosphate contamination.
Zirconium ⁴⁰Zr_91.22	360.12	The response is enhanced in the presence of ammonium ions, chloride, fluoride and iron. Response is depressed by nickel (NiBr ), nitrate and sulphate. The addition of 0.2% m/v of ammonium fluoride to both sample and standard helps reduce interference effects.

Reference: Pye Unicam "Atomic Absorption Data Book".

INERFERENCES IN ANALYSIS BY ATOMIC ABSORPTION

Interference Effects in Atomic Absorption