title: The effects of isotope-labeled analogs on the LC-IDMS measurement by comparison of ESI responses and matrix effect of melamine,13C3-melamine,13C3+15N3-melamine, and15N3-melamine.
abstract: In this paper, the effect of isotope-labeled analogs on the liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) measurement was evaluated based on the comparison research of electrospray ionization responses (ESI) and matrix effect of melamine,13C3-melamine,13C3+15N3-melamine, and15N3-melamine. The isotope-labeled melamines had similar ionization efficiency with melamine in the electrospray ionization source, but the intensity of corresponding quantitative fragment ions had distinctive differences. Based on the density functional theory at the B3LYP/6-311+G** level, this phenomenon was explained very well. The rare cleavage pathways of melamine, which just could be exactly identified by15N-labeled melamines, resulted in the difference of quantitative fragment ions between15N-labeled melamines and melamine. The interaction of ESI response between melamine and isotope-labeled melamines was investigated using MRM monitor mode.15N-labeled melamine had significant ion inter-suppression effect on melamine, while13C-labeled melamine had little influence on melamine. Finally, the influence of different isotope-labeled melamines on the LC-IDMS result was evaluated using the IDMS correction factor (θ). Taking the determination of melamine in milk powder as an example, the matrix effects of different isotope-labeled melamines and melamine had notable difference and the impact of this difference on the measurement results depended on the concentrations of analyte and matrix solution. It was worth noting that15N3-melamine exhibited significant ion suppression to melamine in matrix solution. The deviation of the results from IDMS method might reach 59% using15N3-melamine as internal standard in special matrix solution. Graphical Abstract The comparison of ESI responses of melamine,13C3-melamine,13C3+15N3-melamine and15N3-melamine.
authors.affiliation: Division of Chemical Metrology and Analytical Science, National Institute of Metrology, No.18, Bei San Huan Dong Lu, Chaoyang District, Beijing, 100029, China.
authors.forename: Xiu Qin
authors.initials: XQ
authors.lastname: Li
authors.affiliation: Division of Chemical Metrology and Analytical Science, National Institute of Metrology, No.18, Bei San Huan Dong Lu, Chaoyang District, Beijing, 100029, China. qhzhang204@163.com.
authors.forename: Qing He
authors.initials: QH
authors.lastname: Zhang
authors.affiliation: Division of Chemical Metrology and Analytical Science, National Institute of Metrology, No.18, Bei San Huan Dong Lu, Chaoyang District, Beijing, 100029, China.
authors.forename: Zong
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Division of Chemical Metrology and Analytical Science, National Institute of Metrology, No.18, Bei San Huan Dong Lu, Chaoyang District, Beijing, 100029, China.
authors.forename: Hong Mei
authors.initials: HM
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Anyang Normal University, Xian'ge Road, Anyang, Henan, 455000, China.
authors.forename: Dong Feng
authors.initials: DF
authors.lastname: Huang
mesh_terms: D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis; D002853:Chromatography, Liquid / Q000379:methods; D007201:Indicator Dilution Techniques; D007553:Isotope Labeling / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods; D014227:Triazines / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014227:Triazines; C011907:melamine
keywords: Comparison; ESI responses; Isotope-labeled melamines; LC-IDMS; Matrix effect; Melamine