Development of Fast Sampling and High Recovery Extraction Method for Stable Isotope Measurement of Gaseous Mercury

• Main Author: Satoshi Irei
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Applied Sciences
• Subjects: total gaseous mercury (TGM); stable mercury isotopes; multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS); sampling technique; acid extraction for gaseous elemental mercury; Minamata Convention on Mercury
• Online Access: https://www.mdpi.com/2076-3417/10/19/6691
• ISSN: 2076-3417

A method involving fast large-volume sampling and bag extraction of total gaseous mercury (TGM) using a 5 mL acid solution was developed for stable mercury isotope ratio measurements. A large gold-coated sand trap (BAuT)—a 45 (i.d.) × 300 mm (length) quartz tube with 131 times more trapping material than a conventional gold trap—was used for the collection of a large amount of TGM. The collected TGM was extracted using 5 mL inversed aqua regia in a 2 L Tedlar bag followed by isotope measurements using a cold vapor generator coupled with a multicollector inductively coupled plasma mass spectrometer. Sampling tests demonstrated that the collection efficiency of the BAuT was 99.9% or higher during the 1–24 h sampling period under the flow rate of 20–100 L min⁻¹. Recovery tests of 24 h bag extraction using 100 ng NIST SRM 8610 exhibited nearly 100% recovery yields. The five measured stable mercury isotope ratios agreed with reference values within 2σ intervals. The overall methodology tested during the pilot field and laboratory studies demonstrated its successful application in analysis, promising highly precise stable mercury isotopic data with a time resolution of less than 24 h.