High Precision Zinc Stable Isotope Measurement of Certified Biological Reference Materials Using the Double Spike Technique and Multiple Collector-ICP-MS

Abstract

Biological reference materials with well-characterised stable isotope compositions are lacking in the field of ‘isotope biochemistry’, which seeks to understand bodily processes that rely on essential metals by determining metal stable isotope ratios. Here, we present Zn stable isotope data for six biological reference materials with certified trace metal concentrations: fish muscle, bovine muscle, pig kidney, human hair, human blood serum and human urine. Replicate analyses of multiple aliquots of each material achieved reproducibilities (2sd) of 0.04–0.13‰ for δ66/64Zn (which denotes the deviation of the 66Zn/64Zn ratio of a sample from a pure Zn reference material in parts per 1000). This implies only very minor isotopic heterogeneities within the samples, rendering them suitable as quality control materials for Zn isotope analyses. This endorsement is reinforced by (i) the close agreement of our Zn isotope data for two of the samples (bovine muscle and human blood serum) to previously published results for different batches of the same material and (ii) the similarity of the isotopic data for the samples (δ66/64Zn ≈ –0.8 to 0.0‰) to previously published Zn isotope results for similar biological materials. Further tests revealed that the applied Zn separation procedure is sufficiently effective to enable accurate data acquisition even at low mass resolving power (M/ΔM ≈ 400), as measurements and analyses conducted at much higher mass resolution (M/ΔM ≈ 8500) delivered essentially identical results.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-017-0240-y) contains supplementary material, which is available to authorized users.

Inter-comparison of stable iron, copper and zinc isotopic compositions in six reference materials of biological origin

“…between − 0.4‰ and 1.1‰ (Table S1). BCR-639 exhibits a very negative value (~-3‰ [42,52] , Table S1), which is unusual regarding the known Zn isotopic variability. The BCR-639 reference material is a "high-level" serum that has been doped with trace elements, and we think that it contains added Zn, probably highly purified Zn, with a negative δ 66 Zn value (Rehkämper M., Pers.…”

“…To that end, the scientific community devoted to the study of metal isotopic compositions in living systems has reported isotopic values for reference biological materials. A list of the published values is given in Table S1 for Fe, Cu and Zn isotopic compositions [39,[45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]. Several observations can be drawn from that compilation.…”

Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi

“…We report urine Zn concentration data adjusted for hydration status using the specific gravity (sg) method, as in Phiri et al ( 2020 ) where sg was a suitable adjustment method for urine Se concentration for both WRA and SAC. Other studies have also used sg to adjust urine Zn concentration (Moore et al 2017 , 2019 ; Middleton et al 2019 ). The sg was measured using a handheld temperature-corrected refractometer (PAL-10S, Atago, Japan), on 1 to 2 drops of urine.…”

Assessment of coupled Zn concentration and natural stable isotope analyses of urine as a novel probe of Zn status

“…To this end, a 64 Zn-67 Zn double spike solution was added to sample solution aliquots with 50 to 125 ng Zn, such that the mixtures had a ratio of sample-to spike-derived Zn (S/N) of 1 ± 0.1. 36 The mixtures were equilibrated overnight at 130 °C and pure Zn fractions were then separated by anion exchange chromatography 36 . After drying and converting to the nitrate form, the Zn separates were dissolved in 0.1 M HNO3 to obtain Zn solutions with concentrations of 50 to 100 ng ml -1 for isotopic analysis.…”