Editor’s Note: We are dedicating each Tuesday in July and August to Copper, number 29 on the periodic table.
My last article talked about identifying impurities in electronic grade copper sulfate as an important step in high-quality electronics manufacturing. Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) was described as an ideal technique for the analysis of impurities in copper sulfate as it enables accurate, high throughput, multi-element analysis with the minimum of sample preparation required. But is it proven?
This technique was tested using a versatile, powerful simultaneous ICP-OES Analyzer spectrometer with solid electronic grade copper sulfate samples.
Sample and standard preparation
We started with solid electronic grade copper sulfate (CuSO4) samples that were dissolved in ultra pure deionzed (DI) water (resistivity >18 MΩ/cm). 5 g of solid sample was dissolved in 50 ml of DI water and made up to a final volume of 250 ml; these samples were then ready for analysis.
Multi-element calibration standards were made at concentrations of 0, 20, 50 and 100 µg/L (ppb) and matrix matched to the samples (2% CuSO4).
A shared software approach was implemented in order to provide control and data processing for a range of elemental and isotopic analysis technologies, including the elements of interest. Instrument calibration plots were created using the calibration standards created (0, 20, 50 and 100 µg/L).
Results and discussion
The method detection limits for this method (MDL) were calculated by analyzing a matrix matched blank with ten repeats, then multiplying the standard deviation (SD) by a factor of 3. The suitability of the analytical method was demonstrated by analyzing a series of matrix spiked samples. 5 electronic grade copper sulfate samples were spiked with 50 µg/L of all the target elements. Both the spiked and unspiked samples were analyzed and their measured concentrations compared. The spike recoveries of all elements, for all samples, are between 92% and 105%.
In order to demonstrate the method and instrument stability, a sample of electronic grade copper sulfate was spiked with all of the target elements at 50 µg/L and then analyzed repeatedly over a period of 60 minutes. The relative standard deviations for all elements were less than 2%, with the exception of lead which was below 4%.
The low relative standard deviations derived from the stability study, combined with the % recovery values of the sample spikes, shows the high level of accuracy and precision of analytical results obtained with the ICP-OES Analyzer spectrometer.
The good method detection limits achieved also show that the ICP-OES Analyzer spectrometer can easily perform the analysis of electronic grade copper sulfate required for electronic factories, semiconductor plants, precious metal technology sites and other electronic grade raw materials testing.
View the Application Note to see additional details, including tables of:
- Elements, analytical wavelengths used and detection limits (DL) achieved
- Measure modes and acquisition parameters
- Sample introduction accessories used
- Spiked and Unspiked sample concentrations and spike recoveries.
- Average, SD and RSD – CuSO4 solution spiked