An online method to determine chlorine stable isotope composition by continuous flow isotope ratio mass spectrometry (CF-IRMS) coupled with a Gasbench Ⅱ

An online method using continuous flow isotope ratio mass spectrometry （CF-IRMS） interfaced with a Gasbench Ⅱ was presented to determine chlorine stable isotope composition. Silver chloride （AgCl） was quantitatively derived from chloride by using silver nitrate （AgNO3）, and then was reacted with iodomethane （CH3Ⅰ） to produce methyl chloride （CH3Cl）. A GasBench Ⅱ equipped with a PoraPlot Q column was used to separate CH3Cl from any other gas species. Finally, chlorine stable isotope analysis was carried out on CH3Cl introduced to the IRMS in a helium stream via an active open split. The minimum amount of Cl used in this method is of the order of 1.4 μmol. Inter-laboratory and inter-technique comparisons show that the total uncertainty incorporating both the precision and accuracy of this method is better than 0.007%. Furthermore, ten seawaters sampled from different locations have a narrow δ37Cl value range from -0.008% to 0.010%, with a mean value of （0.000±0.006）%. This supports the assumption that any seawater can be representative of standard mean ocean chloride （SMOC） and used as an international reference material.

Quantification,morphology and source of humic acid,kerogen and black carbon in offshore marine sediments from Xiamen Gulf,China

Three types of macromolecular organic matters （MOMs）, i.e. humic acid （HA）, kerogen＋black carbon （KB）, and black carbon （BC） were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry （EA/IRMS） and scanning electron microscope （SEM）. The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content （TOC）, while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ 13 C values of the three fractions suggested that materials from terrestrial C 3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ 13 C values of MOMs in the offshore marine sediments.

Developing an authentication approach using SPME-GC-IRMS based on compound-specific δ^(13)C analysis of six typical volatiles in wine

An analytical method using gas chromatography isotope ratio mass spectrometry(GC-IRMS)combined with solid phase micro-extraction(SPME)was developed to measure the 613C values of six typical volatiles commonly occurring in wine(isoamyl acetate,2-octanone,limonene,2-phenylethanol,ethyl octanoate and ethyl decanoate)for the first time.SPME selected with a divinylbenzene/carboxen/polydimethylsiloxane fiber was combined with the GC-IRMS for pretreatment optimization.The optimized SPME parameters of extraction time,extraction temperature and salt concentration were 40 min,40℃ and 10%,respectively.The 613C values measured by SPME-GC-IRMS were in good agreement with those measured via elemental analyzer(EA)-IRMS and GC-IRMS.The differences range from 0.02‰to 0.44‰ with EA-IRMS and from 0 to 0.28‰ with GC-IRMS,indicating the high accuracy of the method.This newly established method measured the precision within 0.30‰ and was successfully validated to discriminate imported real wine samples with identical label but amazing price differences from different importers.