When measuring metals by atomic absorption spectrometry, transition metals such as palladium, palladium chloride or transition metal salts are often used as matrix improvers, but heavy metal ions can easily cause environmental hazards and are expensive. Ammonium dihydrogen phosphate as a matrix modifier is effective in eliminating matrix interference, increasing the ashing temperature of the element under test, reducing the ashing loss of the element under analysis, significantly improving measurement accuracy and immunity to interference, while being environmentally friendly and inexpensive when used for the determination of elements such as lead and cadmium by atomic absorption spectrometry. The improvement of matrix modifiers such as NH4H2PO4, (NH4)3PO4, NH4H2PO4+Mg(NO3)2+NH4NO3 and NH4Cl on the determination of Pb in irrigated soil from primary treatment effluent was investigated using the graphite furnace atomic absorption method (GFAAS method), and 40 g/L of NH4H2PO4 was determined as the best modifier, when the ashing and atomisation The RSD was 2.6% and the recovery was above 92.4% using the deuterium lamp corrected background GF-AAS method.
The GF-AAS method was used to determine Cd in fly ash, soil and sediment and to evaluate the effect of different matrix modifiers. The recovery of cadmium was higher with the addition of matrix improvers than without, and by comparing several matrix improvers, the highest recovery of cadmium was obtained with 2% (mass fraction) NH4H2PO4 + 0.4% (mass fraction) Mg(NO3)2 as improver. Both NH4H2PO4 and NH4H2PO4+Mg(NO3)2 were good matrix improvers when using the Seeman effect background correction, with recoveries of 98% or more for all three specimens and optimum ashing temperatures 300-400 °C higher than the other matrix improvers, but NH4H2PO4+Mg(NO3)2 produced stronger background absorption than the transition metals.