Interference-free determination of arsenic in urine by atomic absorption using two-stage probe atomization in a graphite furnace

Inductively coupled plasma mass spectrometry, hydride generation atomic absorption spectrometry and graphite furnace atomic absorption spectrometry are presently used to determine total arsenic in urine, but after labor consuming sample pretreatment. Therefore, we proposed a new approach to solve this problem using two-stage probe atomization. High-resolution continuum source graphite furnace atomic absorption spectrometer was equipped with the probe accessory for that. The sample consisting of 15 mu L urine and 20 mu g Pd-modifier was dried on the furnace bottom at smooth heating up to 120 degrees C and atomized at 2300 degrees C with internal Ar flow. The resulting vapors of As condensed on a tungsten probe installed above the dosing hole. At the same time, Ar flow removed an essential part of the matrix components without condensation. At the second atomization stage at 2300 degrees C and interrupted internal gas flow, the probe was lowered into the furnace and heated by electric current to accelerate condensate evaporation. This procedure fully separates the analytical signal from the finely structured molecular background. Matrix interference disappears due to significantly different rates of As and urinary phosphates binding with Pd at temperature of 120 degrees C and distillation on the probe. The limit of As detection in urine is 1.5 mu g L-1 and quantification range is 50-1000 mu g L-1 that almost covers the entire patients' urine concentration range of interest for environmentalists and physicians.

Automated summary

A new two-stage probe atomization method was proposed for determining total arsenic in urine, using a high-resolution continuum source graphite furnace atomic absorption spectrometer. This method effectively separates arsenic from matrix components, with a low detection limit and a wide quantification range.