Development of Reference Materials for the Analysis of Inorganic Trace Impurities in Cadmium Telluride Solutions

A series of matrix reference materials for 21 inorganic trace impurities in 2 mg/g cadmium telluride (CdTe) solution with five impurity concentration levels (0, 1, 2, 4, 8 ng/g) were developed. High purity (>99.999%) CdTe was used as raw materials and dissolved using HCl-HNO₃ mixed acid, and then was doped with multi-elements solutions to prepare the candidate reference materials (RMs). Matrix-matched ICP-MS with internal standard calibration was established for certification, homogeneity test and stability test. Mass spectrum interferences of ¹⁰⁶Cd¹H on ¹⁰⁷Ag and ¹¹⁴In¹H on ¹¹⁵In could be effectively removed by optimizing argon gas flow parameters coupled with mathematical correction. The matrix suppressed effect was effectively corrected about 20%-60% by using matrix-matched method. The precision of consecutive analysis expressed as RSD (n=22) was reduced to approximately 1% by using internal standard calibration. The linearly correlation coefficient factors (R) of standard curves were greater than 0.999 for all elements. The limits of detection (LODs) ranged from 0.001 ng/g to 0.35 ng/g, and the spike recoveries ranged from 89.2% to 106.5%. The established method was further validated by using CRM EB507. The dissolution of packaging containers was investigated and the results showed that the impurity dissolution from HDPE (high density polyethylene) bottle was lower than that from PP (polypropylene) plastic bottle. Except for Ca and Se, the dissolution of elements of concern in 4 months was less than 0.2 ng/g, which met the requirement. All elements were tested by the established method, and the results showed that the homogeneity, long-term and short-term stability of RMs were satisfactory and the validity period was 12 months. The mass fractions of 21 elements were certified by using a collaborative characterization program with eight sophisticated participating laboratories and using HR-ICP-MS and Q-ICP-MS methods. The arithmetic mean values were taken as the certified values, and the uncertainty was systematically and comprehensively evaluated. The measured results ranged from 3.5 ng/g to 4.5 ng/g, and the RSD ranged from 1.2% to 8.5% from 8 labs. The average value was about 4.0 ng/g, which was consistent with the target values and the relative expanded uncertainty was about 7%. This series of matrix RMs fills the blank of relevant RMs at home and abroad, and it plays an important role in verifying the reliability of measurement methods and ensuring the consistency and traceability of measurement results.