Quantifying indium with ion chromatography in hydro- and biohydrometallurgical leaching solutions

Quantitative native speciation of ppb-level metals in semiconductor-manufacturing-used strong acids and a base

The presence of metal species in solvents significantly impacts production yields in the semiconductor industry, particularly as the dimensions of integrated circuits continue to decrease. Therefore, it is imperative to control metal concentrations in solvents to levels as low as a few parts per billion (ppb) throughout fabrication processes. Effective purification methods are essential for removing various levels of contamination, and understanding the speciation of metals is crucial for achieving efficient purification. Conventional methods for the speciation of solution-phase metals include ion chromatography (IC) and ultraviolet-visible (UV-Vis) absorption spectroscopy. However, these techniques present limitations; for instance, IC can inadvertently alter species during the elution process, while the requirement for high-purity parts per million (ppm) concentrations of metals obscures the speciation of trace mixed samples using UV-Vis absorption spectroscopy. In this study, we present a quantitative speciation method for metals in their native states within strong acids and a base, utilizing the breakthrough curve (BTC) theory in conjunction with inductively coupled plasma-mass spectrometry (ICP-MS). Sodium, potassium, magnesium, calcium, iron, and copper serve as model systems for our investigations. The combination of BTC and ICP-MS provides insights into the species present and their respective abundances. Our findings indicate that breakthrough time (tBT) is predominantly influenced by the charge states and binding selectivity of the metal species and the concentrations of competing binding species. For scenarios where the product of the adsorption equilibrium constant (K) and the concentrations of a species at equilibrium (C) is significantly less than one (KC ≪ 1), tBT serves as a critical metric for assessing metal species at trace levels. Taking sodium (I) and potassium (I) at 10 ppb as representative examples, we discovered that tBT was accelerated by a factor of 5.7 when the concentration of the competing binding species ([H]+ in this study) was increased five-fold from 0.02 M to 0.1 M nitric acid (HNO3). Specifically, the tBT for sodium (I) decreased from 23 min to 4 min, while for potassium (I), it dropped from 114 min to 20 min. Furthermore, in the cases of magnesium (II) and copper (II) at 10 ppb, tBT was expedited by a factor of approximately 25; the tBT for magnesium (II) fell from 100 min to 4 min, and for copper (II), it decreased from 157 min to 6 min when the [H]+ concentration was increased five-fold from 0.1 M to 0.5 M HNO3. Additionally, we observed distinct species transformations for iron and copper, evidenced by markedly altered tBT in 0.1 M choline hydroxide solutions, which was observed to be less than 10 min. Anionic iron complexes and neutral copper particles were inferred, supported by ion exchange and UV-Vis absorption spectroscopic measurements. Furthermore, copper particles, potentially identified as copper (II) hydroxide or copper (II) oxide, exhibited a size distribution ranging from 200 to 400 nm with a peak at 300 nm, as characterized using particle analyzers. The advantages of the BTC theory-facilitated native quantitative speciation are anticipated to enhance informed decision-making for optimizing purification processes within the semiconductor industry.

A Fast and Efficient Procedure of Iron Species Determination Based on HPLC with a Short Column and Detection in High Resolution ICP OES

The optimization and application of a new hyphenated procedure for iron ionic speciation, i.e., high performance liquid chromatography (HPLC) with short cation-exchange column (50 mm × 4 mm) coupled to high resolution inductively coupled plasma optical emission spectrometry (ICP hrOES), is presented in this paper. Fe(III) and Fe(II) species were separated on the column with the mobile phase containing pyridine-2,6-dicarboxylic acid (PDCA). The total time of the analysis was approx. 5 min, with a significantly low eluent flow rate (0.5 mL min^-1) compared to the literature. Additionally, a long cation-exchange column (250 mm × 4.0 mm) was used as reference. Depending on the total iron content in the sample, two plasma views were chosen, e.g., an attenuated axial (<2 g kg^-1) and an attenuated radial. The standard addition method was performed for the method's accuracy studies, and the applicability was presented on three types of samples: sediments, soils, and archaeological pottery. This study introduces a fast, efficient, and green method for leachable iron speciation in both geological and pottery samples.

Iron species determination by high performance liquid chromatography with plasma based optical emission detectors: HPLC-MIP OES and HPLC-ICP OES

The paper presents an independent application of two hyphenated techniques, wherein an identical chromatographic system i.e. high performance liquid chromatography (HPLC) was coupled to microwave induced plasma optical emission spectrometry (MIP OES) or inductively coupled plasma optical emission spectrometry (ICP OES). A cation-exchange column and a mobile phase based on pyridine-2,6-dicarboxylic acid (PDCA) were employed to separate Fe(II) and Fe(III) within 300 s. Additionally, two methods of sample preparation were employed. Optimization and validation of both methods were conducted parallel. The applicability was presented with different sample matrix types: post-glacial sediments, archaeological pottery, soils located in the proximity of industry wastes disposal site, river sediments and yerba mate (Ilex paraguariensis). Obtained results were compared in terms of the excitation source (microwave induced or inductively coupled) and supplied gas (nitrogen or argon). The research introduces HPLC-MIP OES for iron speciation analysis and its applicability were critically evaluated with HPLC-ICP OES.