Knowing the correct location to dig is one of the biggest challenges in the mining sector. To achieve this, an area must be first mapped by drilling exploratory holes and measuring the elements of interest from each.
Based on the size of different mines, a large number of drill holes may be required for analysis prior to the determination of the ore quality. This results in the generation of different samples that can be analyzed to determine the feasibility of digging. Hence, there is a need for a fast, precise and repeatable analysis.
This article focuses on the assessment of copper ore samples collected from different drill patterns to fulfill these requirements.
Using a proprietary sample preparation method, copper ore samples were prepared in solutions containing 10-15% acids with up to 4000mg/L of dissolved solid contents. The digested samples were evaluated using a PerkinElmer AAnalyst™ 400 atomic absorption spectrometer.
The spectrometer was operated in flame mode and was used in conjunction with a PerkinElmer FAST Flame 2 sample automation accessory consisting of a 1 mL sample loop, dual peristaltic pumps and an SC-4 autosampler.
Table 1 shows the operating conditions of the AAnalyst 400. The FAST Flame 2 accessory enables rapid sample washout, in-line dilution and high sample throughput, while analyzing samples in large quantities.
Table 1. AAnalyst 400 Operating Conditions for Cu
||10 cm titanium
||Air (10.00 L/min) / Acetylene (2.50 L/min)
||Cu Hollow Cathode Lamp (Part Number N3050121)
The accuracy and stability of the analyses were monitored using a geological reference material, SU-1b Nickel-Copper-Cobalt Ore (National Resources Canada, Ottawa, Ontario, Canada) as a QC check.
This reference material was analyzed once per analytical run, which includes digested copper ore samples, calibration verification solutions, and calibration blank and standards.
The measurements were performed over external calibration curves with a blank of 1, 6, 20, 30, and 40 mg/L Cu in 15% acid. The correlation coefficients of all calibrations were 0.999 or more. An independent calibration verification solution (30 mg/L Cu) was carried out for every 12 samples, while calibrations were repeated following every 60 samples.
Results and Discussion
The SU-1b reference material containing 1.185% copper was evaluated during analytical runs to determine the accuracy of the method. The concentration of copper (Cu) observed in the reference material, after sample preparation, was 47.4 mg/L. The Cu recoveries in SU-1b obtained from 16 individual analytical runs for over seven days are shown in Figure 1, for both diluted and undiluted samples.
Figure 1. Copper recoveries in SU-1b from 16 runs over seven days, both with and without autodilution
Most of the recoveries were found to be within 10% of the certified value, corroborating both accuracy and stability of the methodology. Further, the agreement between the recoveries of the diluted and undiluted samples ensures robust and accurate auto-dilution capability of the FAST Flame 2 accessory.
Besides performing in-line sample dilution, the FAST Flame 2 accessory facilitates improved sample throughput in combination with an autosampler to evaluate samples in large batches.
In this experiment, the sample-to-sample time including sample uptake, in-line dilution, and sample washout was 28 seconds. Within a given time period, five times more samples were analyzed using this procedure compared to the conventional sample uptake by using an autosampler.
Figure 2 shows a stability plot of the SU-1b reference material analyzed for 45 times continuously, with the recovery of each sample normalized to the first sample. System stability is demonstrated with all recoveries being within 10% of the original reading, with the exception of the second sample which recovered at 113%. The recoveries were within 10% of the certified value for all samples.
Figure 2. Stability plot for copper in SU-1b measured 45 consecutive times, with in-line dilution.
This article showed that the FAST Flame 2 sample automation accessory combined with the AAnalyst 400 flame atomic absorption spectrometer is ideal for a rapid and accurate copper analysis.
When coupled with an autosampler, the FAST Flame 2 accessory increases sample throughput along with fast washout, in-line dilutions, and avoiding the need to manually dilute samples before analysis.
The improved sample throughput does not compromise stability and accuracy. Therefore, it has been proven that the combination of FAST Flame 2 and the AAnalyst 400 is useful for the mining industry.
This information has been sourced, reviewed and adapted from materials provided by PerkinElmer.
For more information on this source, please visit PerkinElmer.