BORON DETERMINATION IN STEELS BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY - COMPARATIVE-STUDY OF SPARK ABLATION AND PNEUMATIC NEBULIZATION SAMPLING SYSTEMS

An experimental study for the determination of boron in steels by inductively coupled plasma atomic emission spectrometry is presented. A comparison is made of spark ablation and pneumatic nebulization (after microwave digestion) sampling systems. A one-step microwave digestion procedure for total boron content using diluted aqua regia (HCl+HNO3, 3+1) and high pressure vessels was developed. The influence of microwave power and time on the dissolution of boron compounds is discussed. The strongest available conditions (0 OMEGA, 600 V, 600 Hz) were required for spark ablation sampling. The stability of spark sampling during the spark ablation-ICP process was tested by plotting iron and boron emission versus sparking time. The iron content of collected and dissolved spark-produced particles was analysed and showed that the amounts of aerosol from different boron steels samples during 90 s sparking processes were fairly similar. The analytical performance of both systems was evaluated. Using pneumatic nebulization, after microwave digestion of the sample, a detection limit for boron of 2.6 mug g-1 and overall relative standard deviation (RSD) values of 1-3.5% were found. For spark ablation the detection limit for boron was 0.65 mug g-1, the overall RSD ranging from 0.5 to 1.5%. A comparison of the data for British Chemical Standards (BCS) Certified Reference Materials (CRMs) Carbon Steel Residual Series (Group B) and Spectroscopic Standard (SS) 456/1 to 460/1, indicated that the accuracy of both methods was satisfactory.