论文部分内容阅读
Introduction The use of organic compounds leads to contamination of water resources worldwide.Therefore,monitoring these compounds is important.But due to coeluting matrix components,a reliable quantification is critical.With online solidphase extraction(SPE),matrix effects are reduced because the matrix is not retained on the SPE cartridge.In this work,tap,ground,river,and ultrapure water were spiked with pesticides and analyzed with a fast and automated online SPE method coupled to a triple quadrupole mass spectrometry system.For the evaluation of a 75-ng/L spike in river water,a standard addition calibration and external calibration were prepared.With online SPE we show that matrix effects are reduced and,therefore,an external calibration is sufficient to quantify compounds in environmental water.Methods Tap,river and ground water were first centrifuged and then spiked with different concentrations of pesticides.These water samples were directly injected into the LC system without further sample preparation.The system enables two configurations without re-plumbing the system: direct injection and online SPE.For the online SPE mode,two trapping columns are alternately in use for time saving and higher sample throughput.The analysis of pesticides in ground and river water was performed with direct injection and online SPE to compare and determine the matrix effects.Results It is important to quantify matrix effects when using LC/MS with electrospray ionization.Therefore,a calibration in ultrapure water and a matrix matched calibration in river and ground water were prepared and the slopes of both calibration curves were compared.It was assumed that in ultrapure water no matrix effects were present.Matrix effects were observed for both environmental(river and ground water)waters and for most compounds,which is illustrated by comparing matrix matched standards to a calibration in ultrapure water.On the example of aminocarb,the matrix effects led to overall ion suppression in river water of 27%for direct injection and just 16%for online SPE.For ground water,direct injection showed 22%ion suppression and online SPE 7%ion enhancement.This shows that with the enrichment process parts of the matrix,such as salts and minerals,are flushed out and matrix components cannot interfere with the analyte.For most compounds,less matrix effects were detected with online SPE measurements compared to direct injections.In summary,with online SPE,standard addition calibration is not necessary,and an external calibration is sufficient to quantify organic compounds in environmental water,which saves time and labor.Novel Aspects With online SPE matrix effects are reduced and,therefore,an external calibration is sufficient to quantify compounds in environmental water.