Feb/March_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 2 1 2 7 H ighly sought after for use in the electronics industry, rare earth el- ements (REEs) and their alloys are critical to the functionality of awide range of devices, from smartphones to medical imaging equipment and wind turbines. Global demand for REEs has exploded in recent decades, a trend that shows no sign of abating. A recent Adamas Intelli- gence report predicts a five-fold increase in demand for REEs in the magnet indus- try alone by 2030 [1] , a growth that the or- ganization describes as unfathomable. REEs, unlike the name suggests, are not rare in nature; however, they are a finite resource and hard to locate in economically extractable formats. Moreover, REE mining is fraught with high costs, geopolitical conflict, and en- vironmental damage. Add to this the rise in electronics waste (e-waste) and pollution from the disposal of obsolete technology, and the result is an attitudi- nal shift around how REEs are extract- ed, but more importantly, how they are recovered and recycled back into the manufacturing process. To support global demand for REE recycling and reuse, laboratories require solutions that can detect and characterize trace and ultra-trace quan- tities of REEs in e-waste. Reliable and robust technology is needed to gener- ate the high throughputs required to make the process both practical and profitable. For many years, inductively coupled plasma mass spectrometry (ICP-MS) has been used to detect REEs. This highly sensitive technology can deliver outstanding results, but the methods can be time-consuming and require stringent cleanroom condi- tions. With restricted matrix robustness and manual workflows, the through- put achievable using this technique has limitations. New advances in inductively cou- pled plasma optical emission spec- trometry (ICP-OES) are now challenging the status quo when it comes to analyz- ing REEs, even in ultra-trace quantities. With advanced ICP-OES systems able to achieve the same sensitivity as ICP-MS, ICP-OES also offers improved matrix ro- bustness, simpler operation, and high- er sample throughputs. The accelerated detection provided by ICP-OES allows laboratories to more efficiently char- acterize REEs in e-waste and environ- mental samples. This shift supports the sustainability ambitions of an industry working to change an age-old linear economy to a circular manufacturing model, recycling e-waste and reducing its dependency on natural resources. CHALLENGES IN RARE EARTH ELEMENT DETECTION The REEs are classified as the 15 ele- ments in the lanthanide series, lantha- num (La) to lutecium (Lu), plus scan- dium (Sc) and yttrium (Y), which have close geological occurrence with the lanthanides. The high demand for these elements, added to extraction issues and limited accessibility, makes them a highly valued commodity. The en- vironmental impact of extracting and processing REE ores, coupled with the damaging effects of e-waste, has led the electronics industry to evaluate its entire manufacturing supply chain. A major challenge to widespread REE reuse and recycling has been limita- tions in the accurate and efficient detec- tion and extraction of these elements. Samples often contain multiple REEs, and the interelement spectral interfer- ence mounts a significant challenge be- cause REEs emit similar spectral lines (see Fig. 1). In complex matrices, such as those seen in e-waste, further inter- ference can also be generated from oth- er metals, especially base metals such as iron and nickel. Techniques must be selective and sensitive enough to de- tect trace amounts in complex matrices while accounting for the interference generated by overlapping wavelengths. REEs are usually analyzed using techniques such as x-ray fluorescence spectrometry, ICP-MS, and ICP-OES. ICP-MS has long been the method of choice due to the high levels of sen- sitivity that can be achieved. For this technique, samples must be prepared in a liquid form, usually through diges- tion to produce an aqueous solution in an acidified matrix. The sample is then ionized to reduce it to its constituent elements and the elements are then separated and detected based on mass- to-charge ratio. The required dynamic range of linearity is captured effectively by ICP-MS but interference is difficult to elucidate during analysis. For this rea- son, ICP-MS is commonly used for dis- crete mass detection, to analyze each element in isolation from the others; the more complex the matrix becomes, ADVANCED ICP-OES LEADS THE WAY TO FAST AND EFFICIENT RARE EARTH ELEMENT DETECTION The latest advancements in ICP-OES systems are changing the landscape for rare earth element analysis. TECHNICAL SPOTLIGHT