Review on in situ Isotopic Analysis by LA-MC-ICP-MS

The method of LA-MC-ICP-MS has become one choice for the analysis of many isotopic systems due to its relatively low cost,high analysis speed,high spatial resolution,and low matrix effect.However,there are still many challenges in the accuracy,precision,and spatial resolution of in situ isotopic composition determination by LA-MC-ICP-MS,which mainly include:(1)how to improve instrument sensitivity,further improve the spatial resolution,and achieve simultaneous determination of isotopes,multiple isotopes,or isotopes with trace elements in low-content samples?(2)how to deduct and correct interference to improve the accuracy of isotopic determination?(3)how to correct isotope fractionation?(4)how to reduce the matrix effect of isotopes?how to develop matrix-matched reference materials?and(5)how to achieve non-matrix-matched correction of isotopes?The high-sensitivity cone combinations,gas mixture,shield torch,and reasonable detector array can be applied to improve the elemental sensitivity.The interferences include the background interference and the interferences from the matrix elements(the isobaric interference,the polyatomic interference,and doubly charged ions interference).To reduce or even eliminate the interference,commonly used methods including interference elimination,background correction,and interference correction by evaluating with an interference-free isotope.Isotopic fractionation correction mainly involves external standard calibration and internal and pseudo-internal standard normalization.For non-matrix matched calibration,many methods can be applied,such as the femtosecond laser,line scan,low laser energy,wet plasma condition,optical setup below the sample surface,and matching the intensity of the sample and standard.In this review,we systematically summarized the above challenges and solutions to promote the study and application of LA-MC-ICP-MS in isotopic determination.