RESUMEN
Pulsed glow discharge mass spectrometric(Pulsed-GDMS) method for the measurement of 7 kinds of key elements(Mg,Fe,Cu,La,Ce,Pr and Nd) in rare earth alloys was established. The influence factors of measurement repeatability, such as pulse time, sample homogeneity, anode cap, flow tube, corn, and sample tablet density were systematically studied. The results showed that,for elements with mass fraction of more than mg/g, the parts (anode cap, flow tube and corn) had the largest influence on measurement repeatability. When the new graphitic parts were used and no parts were changed during the whole measurement,the relative standard deviation (RSD) was less than 3%. However, the RSD were 2%-11%and 3%-21% when the new graphitic parts and the reusable parts were used and changed,respectively. The second influence factor of measurement repeatability was the tablet density. The results showed that,the lower the density,the worse the measurement repeatability, and for the dense tablet, the RSD was less than 3%. Key elements in 1# rare earth alloy were measured by high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS), and the analytical results were used as reference values for the calibration of Pulsed-GDMS. The relative sensitivity factors (RSF) were obtained, and the key elements in 2# rare earth alloy were measured by Pulsed-GDMS after calibration. The analytical results of key elements in 2#sample by Pulsed-GDMS and HR-ICP-MS were compared, and the results showed that for the dense sample, the analytical results showed good agreement. Under the optimal conditions, the expanded uncertainty of measurement by Pulsed-GDMS reduced to 3%-10%.
RESUMEN
A direct current glow discharge mass spectrometry ( GD-MS) for the determination of Li, Be, Na, Mg, Si, P, K, Ca, Ti, V, Cr, Mn, Co, Ga, Sr, Mo, Ag, Cd, Sn, Sb, W and Pb in nickel-zinc ferrites was developed. Copper powder as the conductive medium was evenly mixed with nickel-zinc ferrites powder for tableting, and then the impurity elements in nickel-zinc ferrites were determined by GD-MS. The influence of sample preparation and the glow discharge conditions including discharge current, discharge voltage, discharge gas flow rate and pre-sputter time on discharge stability and analysis sensitivity were investigated. The mass spectrometry interferences of analytes were investigated, as well as appropriate isotopes were selected. Most of the mass spectrometry interferences were avoided by measuring in medium resolution mode and high resolution mode. Total signal of Fe, Ni, Zn, O and Cu normalization was adopted, and the impurity elements in nickel-zinc ferrites were calculate in subtraction. The results showed that the detection limits for the investigated elements were in the range of 0. 001-0. 29 μg/g, the relative standard deviations of each element were within 3 . 5%-18 . 6%. The analysis results were consistent with those obtained by inductively coupled plasma mass spectrometry.