Effect of the Dry Ashing Method on Cadmium Isotope Measurements in Soil and Plant Samples

Abstract

A dry ashing method is commonly used to remove organic material from samples prior to geochemical analysis. In the course of this study, the Cd isotope ratios of a series of soil and plant reference materials and samples were studied to evaluate the effect of the dry ashing method on measurement results of Cd isotope ratios. The samples were pre‐treated using the dry ashing method and high‐pressure bomb for comparison. The results show that the digestion using high‐pressure bombs did not lead to Cd loss, but using the dry ashing method would cause different proportions of Cd loss. The whole range of Cd isotope difference between two methods was from −0.07‰ to 3.01‰. There was also an obvious difference in measured Cd isotope ratios from the same leaf sample pre‐treated independently by the dry ashing method, indicating that the amount of Cd loss and the effect on Cd isotope measurement during dry ashing is related to the properties of the samples. Therefore, dry ashing may not be appropriate for the removal of organic material in Cd isotope ratio measurement, especially for samples with high organic contents. The δ114/110Cd values of reference materials NIST SRM 1573a and GSD‐30 are reported for the first time in this study.

Roles of Chloride and Sulfate Ions in Controlling Cadmium Transport in a Soil-Rice System as Evidenced by the Cd Isotope Fingerprint

“…Their δ 114/110 Cd values (relative to NIST SRM 3108) were −1.33‰ ± 0.05‰ (n = 77) and −0.69‰ ± 0.05‰ (n = 91), respectively. These values agree with previously reported data, 37,38 and the measurement precision was better than ±0.05‰ (2SD). The δ 114/110 Cd values (relative to NIST SRM 3108) of four types of soil materials, NIST 2710, NIST 2710a, NIST 2711, and NIST 2711a, also agree with previously published values.…”

“…111 Cd– 113 Cd double spikes were added to the sample solution and heated on a hot plate at 120 °C for 24 h to equilibrate the samples with spikes. Prior to isotopic analysis, chemical purification was performed as previously described. , Briefly, the digested sample dissolved in 6 mol L –1 HCl was loaded into the anion exchange resin AG1-X8 (200–400 meshes, Bio-Rad, USA) in thermoretractable Teflon columns. Next, 6 mol L –1 HCl, 0.3 mol L –1 HCl, and the mixture of 0.5 mol L –1 HNO 3 and 0.1 mol L –1 HBr were sequentially used to elute matrix elements, and finally, Cd was obtained with 2 mol L –1 HNO 3 .…”

“…The δ 114/110 Cd values (relative to NIST SRM 3108) of four types of soil materials, NIST 2710, NIST 2710a, NIST 2711, and NIST 2711a, also agree with previously published values. 37,38 Calculations of the Cd isotopic compositions and fractionation between the two pools are provided in SI.…”

Atomic spectrometry update – a review of advances in environmental analysis

“…Various digestion methods for the determination of Cd isotope ratios in a range of soil and plant materials were studied. 119 High pressure bomb digestion at 195 C for 72 h with a 1 + 3 mixture of HNO 3 and HF did not lead to Cd loss and d 114/110 Cd values for the four soil and two plant RMs tested gave reproducible results within reported values. On the other hand, dry ashing, performed at 550 C for between 12 and 24 h with 25-700 mg sample, followed by heating at 120 C for 24 h with a 1 + 3 v/v mixture of HNO 3 and HF, resulted in Cd loss and perturbation of Cd isotope ratios to varying degrees in all sample types.…”

δ238U of Coal Reference Materials Determined by MC‐ICP‐MS

“…The dry ashing procedure can efficiently and quickly remove organic matter but may also result in elemental loss and potential isotopic fractionation (Li et al 2011, Lv et al 2020, Zhang et al 2018. In contrast, using the highpressure bomb has been considered as a robust procedure that does not affect U isotope measurements of geological and environmental samples (Zhang and Hu 2019).…”