====== ICP-OES Analysis ====== ===== Overview ===== Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) is the main elemental analysis technique used in the naKnow experimental campaign carried out with TND. Its purpose is to determine the elemental composition of representative electronic components and to provide quantitative data that can be used to test material-content hypotheses and improve modelling assumptions. In this work, ICP-OES is mainly used for metals and other inorganic elements. The analytical result is not produced directly from an intact product. The component is first dismantled and homogenised, the organic fraction is reduced by thermal treatment, and the remaining solid fraction is mineralised so that the elements of interest are transferred into a liquid solution. The prepared solution is then introduced into the ICP-OES instrument for elemental screening or quantitative measurement.
{{ :agilent_icp_oes_5100.jpeg?650 |Agilent ICP-OES 5100}} Agilent ICP-OES 5100 used for the analytical measurements.
===== Principle of ICP-OES ===== The prepared liquid sample is introduced into an argon plasma. The liquid is nebulised and exposed to the very high temperature of the plasma, which produces characteristic elemental signals at specific wavelengths. The instrument measures these signals and uses them to identify the elements present. When a calibration curve is available, the measured signal intensity can be converted into an elemental concentration. The analytical logic used in the project can therefore be described as a sequence from a heterogeneous solid product to an interpretable elemental concentration: ^ Analytical stage ^ Function in the analysis ^ | Sample separation and homogenisation | Reduces the heterogeneity of the original component and produces a representative fraction for analysis. | | Thermal treatment | Reduces organic material and leaves a solid residue containing the inorganic fraction of interest. | | Mineralisation | Transfers metals and other target elements from the solid residue into a liquid solution. | | Plasma introduction | Nebulises the prepared liquid into an argon plasma and produces element-specific signals. | | Detection and interpretation | Identifies elements from their characteristic wavelengths and, where calibrated, calculates their concentrations from signal intensity. | ICP-OES therefore provides an elemental composition rather than a complete description of material structure. It can show how much of an element such as copper, aluminium, indium, gallium, silver or gold is present in the analysed fraction, but it does not by itself identify the original physical layer, component function or manufacturing history responsible for that element. ===== Sample preparation and representativeness ===== Electronic products are heterogeneous. A screen, PCB or other electronic assembly may contain plastics, metallic supports, conductive layers, connectors and several functional sub-components. For this reason, the preparation stage is essential to the interpretation of ICP-OES results. TND dismantles the waste item into separate fractions and prepares a mass balance so that the analysed material can be related back to the original product. For screens, dismantling can isolate sub-components such as the LED backlight strips shown below. Separating these fractions before analysis helps distinguish the material contribution of a specific part from the composition of the complete screen assembly.
{{ :screen_led_backlight_strips.png?520 |LED backlight strips separated during screen dismantling}} LED backlight strips separated from a screen during sample preparation.
After dismantling, the material is progressively reduced in size and homogenised. Sample preparation uses successive grinding and quartering stages, followed by preparation of a fine powder. This progression is important because a coarse or poorly mixed sample can contain local concentrations of metals that are not representative of the whole fraction.
{{ :retsch_sm300.jpeg?300 |RETSCH SM 300 cutting mill}} {{ :retsch_rs200.jpeg?330 |RETSCH RS 200 grinder}} Equipment used for progressive sample-size reduction: RETSCH SM 300 cutting mill and RETSCH RS 200 grinder.
Thermal treatment is applied to the prepared material before mineralisation. Its purpose is to reduce the organic fraction and recover a solid residue that can subsequently be dissolved. Operational conditions must follow the laboratory's current approved procedure. ===== Mineralisation ===== Mineralisation converts the prepared solid residue into a liquid solution suitable for ICP-OES. This is performed in a closed high-pressure microwave mineralisation system. The acid system is selected according to the sample composition and the elements that must be quantified. Two mineralisation routes are used: an aqua-regia-based route and an alternative fluoride/nitric-acid route for difficult matrices.
{{ :sample_weighing.png?300 |Prepared sample fraction before mineralisation}} {{ :anton_paar_multiwave_pro.jpeg?430 |ANTON PAAR Multiwave Pro mineralisation system}} Prepared sample fraction and the ANTON PAAR Multiwave Pro used for mineralisation.
Mineralisation is a critical analytical stage because ICP-OES measures the elements that reach the liquid phase. Incomplete dissolution can therefore lead to an incomplete representation of the solid sample. Replicate preparation and separation of remaining solids allow the mineralised fraction to be checked and, when required, treated further under the laboratory SOP. **Safety note:** Mineralisation involves corrosive reagents and pressurised microwave equipment. This page describes the analytical principle and project workflow only; laboratory operation must follow TND's approved procedures and be performed by trained personnel. ===== Analytical modes used in the project ===== Two complementary ICP-OES approaches are used. The first is an IntelliQuant screening step. It is semi-quantitative and is used to identify the metals present and estimate their approximate concentration ranges. This first view supports decisions on dilution and on the calibration range required for a more precise analysis. The second approach is a quantitative calibrated analysis. The unknown sample signal is compared with a calibration curve, allowing the concentration to be calculated more accurately. The project protocol applies quantitative calibration to elements present above the selected screening threshold and to precious metals such as gold and silver. Palladium and platinum are also quantified when they are detected during screening. Multiple wavelengths are examined for each element to help identify spectral interference. ^ Mode ^ Main purpose ^ Interpretation ^ | IntelliQuant screening | Rapid identification of the elements present and estimation of concentration ranges. | Semi-quantitative. The method provides an approximate error below 10%, while spectral interference can affect some elements. | | Quantitative calibration | More precise concentration determination for selected elements. | Signal intensity is interpreted through an element-specific calibration curve and checked across several wavelengths. | One example of spectral interference concerns strontium in the presence of iron, where nearby wavelengths can lead to a false or uncertain response. This is why the initial screen is not treated as the final quantitative result and why calibrated measurements use several wavelengths as a verification step. ===== Interpretation of results ===== In the result sheets, the suffix attached to an element indicates how the value was obtained. An **''i''** identifies a result produced with the Intelligent/IntelliQuant semi-quantitative mode, while an **''e''** identifies a value obtained using the calibrated quantitative mode. This distinction should be preserved when laboratory results are imported into modelling or comparison tables because the two values do not have the same analytical precision. ICP-OES results are most useful when they are interpreted together with sample metadata. For PCBs, relevant parameters include board area, copper layer count, copper thickness, stack-up, surface finish, PCB technology, assembly state and connector presence. For screens, the project considers parameters such as display technology, transistor technology, electrode material, rigidity and functional-layer structure. The elemental result can then be tested against these parameters to determine whether a model assumption is supported by laboratory data. ===== Application to screens and other electronic components ===== The screen campaign illustrates the role of ICP-OES in material modelling. Screen technologies contain several functional layers and sub-components, and the expected elemental profile can vary with the display architecture. Elements of interest include those associated with transparent electrodes, backplanes, contacts and conductive layers, including indium, gallium, aluminium, copper and silver. ICP-OES is therefore used as a bridge between an observable product parameter and a measured elemental quantity. For example, a difference in electrode or transistor technology may be tested by comparing the concentrations of elements expected in those functional layers. The same principle is applied to PCBs, where measured copper and finish metals can be compared with geometric and technological parameters. For wafers, an important limitation is that ICP-OES can provide elemental composition, while several modelling parameters relate to process history, device architecture or encapsulation. These characteristics may therefore require complementary information or analytical methods. ===== Practical analytical planning ===== ICP analysis continuously consumes high-purity argon. For this reason, samples are preferably prepared and analysed in batches rather than as isolated measurements. Batch organisation also reduces the time that mineralised solutions remain in storage. Mineralised samples should be analysed within a maximum of one week in order to limit problems such as metal precipitation during storage. The screening stage supports four practical decisions before quantitative calibration: which metals are present, their approximate concentration ranges, the dilution required for measurement, and the calibration range that should be selected. This makes the semi-quantitative analysis an analytical planning step as well as a preliminary result. ===== Conclusion ===== ICP-OES in the naKnow experimental campaign is a quantitative link between physical electronic samples and material-composition models. Reliable interpretation depends on three connected elements: representative sample preparation, effective transfer of the inorganic fraction into solution, and a measurement strategy that distinguishes preliminary screening from calibrated quantification. The method is particularly useful for testing hypotheses about metal content in PCBs and screens, while its elemental nature also defines its limits for parameters that describe structure, processing history or material form rather than chemical composition. ===== Source ===== **TND** & Deliverable **L1.6i – Résultats intermédiaires d’analyses en laboratoire**.