Stable isotope analyses of oxygen (¹⁸O:¹⁷O:¹⁶O) and chlorine (³⁷Cl:³⁵Cl) in perchlorate: reference materials, calibrations, methods, and interferences

Abstract

KClO reference materials are available for testing methods and calibrating isotopic data for ClO and other substances with widely varying Cl or O isotopic compositions. Current ClO extraction, purification, and analysis techniques provide relative isotope-ratio measurements with uncertainties much smaller than the range of values in environmental ClO , permitting isotopic evaluation of environmental ClO sources and natural attenuation. Copyright © 2016 John Wiley & Sons, Ltd.

Isotopic Tracing of Perchlorate Sources in the Environment

“…Since 2001, American scholars have analyzed the isotopic composition of various perchlorate reagents (used in laboratories, industry, and military) and products (used in road blasting, fireworks, pesticides, bleaching agents, and propellants). According to reported data [14,31,33,34,42], the synthetic perchlorate δ 37 Cl value is −3.1‰ to + 2.3‰; the δ 18 O value is −24.8‰ to −12.5‰; the Δ 17 O value is 0.0 ± 0.1‰; the ratio of 36 Cl/Cl is ≤2.5 × 10 − 15 -40 × 10 -15; and the average value of δ 37 Cl of synthetic perchlorate is about +0.6‰, which is similar to the δ 37 Cl value of raw material, NaCl (0.0 ± 10-15) 0.9‰) [43]. A similar value indicates that there is almost no fractionation of chlorine isotopes during the process of synthesizing perchlorate by electrolytic oxidation.…”

“…Testing Technology 37 Cl) with relative abundances of 75.77% and 24.23% [28], respectively. 36 Cl is a trace radioisotope produced by cosmic rays in the stratosphere with a half-life of 301,000 years.…”

“…en, it enters the IRMS in a continuous flow mode and is received by a Faraday cup with m/z of 28 and 30 to determine the δ 18 O value. For high-purity ClO 4 − reagents and samples, the yield of O(CO) was usually 100 ± 2%, and the test accuracy of δ 18 O was ±0.3‰ [31,32,35,37]. is method can be used to rapidly and efficiently perform an online test of the perchlorate δ 18 O value, which is especially suitable for batch tests.…”

“…is cracking reaction can be carried out in a sealed quartz tube or Pyrex heat-resistant glass tube. en, the produced O 2 enters the IRMS in a two-way mode after purification and is received by the Faraday cups with m/z of 32, 33, and 34 to simultaneously determine the δ 18 O and δ 17 O values [31,32,37]. For highpurity ClO 4 − reagents and samples, the yield of O(O 2 ) is usually 100 ± 5%, and the test accuracy of Δ 17 O is ±0.1‰.…”

“…To determine the δ 37 Cl value of perchlorate, first, the perchlorate was vacuum decomposed to produce chloride at 600-650 o C. e chloride was dissolved in deionized water, and Cl was precipitated as AgCl by adding AgNO 3 , which reacted with the excess CH 3 I in a sealed glass tube at 300 °C for 2 h to produce CH 3 Cl. e CH 3 Cl purified cryogenically by gas chromatography enters IRMS with continuous flow or dual-inlet mode and is measured at m/z of 50 and 52. e accuracy of the δ 37 Cl analysis was ±0.2‰ [31,32,35,37].…”