Abstract:
BACKGROUNDReagent purification, sample pretreatment, environmental humidity, reactor cleanliness and experimental quality control are the main influence factors for determination of oxygen isotopic composition of silicates and oxide minerals by BrF5 method.
OBJECTIVESTo determine the optimal experimental conditions and improve the accuracy by selecting silicates and oxide minerals as laboratory raw materials for oxygen isotopic composition analysis. To discuss the influence factors for determination of oxygen isotopic composition of silicates and oxide minerals by BrF5 method.
METHODSUsing BrF5 analysis method and taking standard sample as the reference, oxygen isotopic compositions of silicates and oxide minerals were determined at different calcination temperatures. At the same time, the effects of environmental humidity and reactor cleanliness on the analytical results were also studied.
RESULTSThe results show that 650-750℃ is the best calcination temperature range for removing carbon components during oxygen isotope analysis, which can avoid the isotope fractionation caused by temperature. By reducing the relative environment humidity or the sample loading time within 0.5min, the lower δ18O values caused by vapor was improved. The new reactor, or the reactor with large yellow substance falling off, or the contaminated reactor will reduce the yield of oxygen and cause oxygen isotope fractionation, so the reactors should be fluorinated or purged in time. The sample and standard material is loaded alternately for each reactor to monitor the reliability of the isotopic composition of the sample. The results of oxygen isotopic composition of GBW04409 are consistent with the recommended values. The relative standard deviation is better than 0.1‰ for δ18O under the optimized conditions.
CONCLUSIONSThe proposed method can effectively control oxygen isotope fractionation and improve the applicability of BrF5 oxygen isotope analysis method.
下载: