We are trying to detect elemental impurities such as Sb, As, Ba, Pb in TiO2.
the method we are using is strong acid digestion: 4.5mL H2O, 4 mL HNO3, 0.5 mL HCL and 1 mL H2O2 for detecting of As, Ba and Pb.
and same acid digestion for Sb+ adding of Tartaric acid to samples and standards after digestion. We are trying to avoid HF for digestion.
However, we dont get good recovery in some samples.
we getting low or high recovery for Ba, As and Sb in Spiked samples and even in some standards.
only Pb shows good recovery.
any suggestions for that please?
The recovery percentage in Inductively Coupled Plasma (ICP) analysis, whether exhibiting low recovery (110%), stems from a complex interplay of factors spanning sample preparation, instrumental parameters, and matrix effects. Low recoveries typically occur due to incomplete sample digestion where undissolved particles or organic residues prevent full elemental release, particularly problematic with refractory matrices like silicates unless proper acid mixtures (e.g., HNO₃/HF) and microwave digestion are employed. Volatilization losses affect elements like mercury or arsenic during open-vessel digestion when temperatures exceed their boiling points, necessitating cold-vapor techniques or closed digestion systems. Adsorption of trace metals onto container walls, especially in low-pH conditions, or precipitation as fluorides can be mitigated through silanized vials or chelating agents like EDTA. Ionization suppression from high matrix concentrations reduces plasma efficiency and can be addressed by sample dilution or matrix-matched calibration, while polyatomic interferences in ICP-MS require collision/reaction cells or high-resolution instruments. Conversely, high recoveries often result from spectral interferences where overlapping masses falsely elevate signals, demanding mathematical corrections or alternative isotopes for analysis. Contamination from impure reagents, labware, or environmental sources introduces artificially high readings, preventable through ultrapure acids and proper lab protocols. Calibration errors from incorrect standard preparation or memory effects from previous samples require rigorous quality control including certified reference materials and extended rinse cycles. Hydride-forming elements may show artificially enhanced signals requiring careful optimization of reduction conditions. Optimal recovery requires method-specific validation through spiked samples and reference materials, with acceptable ranges typically 85-115% depending on regulatory requirements, while persistent issues may necessitate advanced techniques like isotope dilution or sector-field ICP-MS for accurate quantification in complex matrices.
- Badges
- Science topic
- Similar topics
- Instrumentation Engineering
- Instruments