Rexhaj Arber, Vogeser Michael, Habler Katharina
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich, Germany.
J Mass Spectrom Adv Clin Lab. 2025 Jul 18;37:56-64. doi: 10.1016/j.jmsacl.2025.07.002. eCollection 2025 Aug.
Tandem mass spectrometry (MS/MS) is highly specific in principle, but there is always the possibility of interference due to unexpected substances in the samples that have the identical mass transitions as the target analytes (isomeric/isobaric interferences). By recording the ion ratio (IR), clinical laboratories already widely attempt to identify such interferences in individual cases. To supplement this procedure, differential tuning effects can be assessed. We aimed to evaluate this approach experimentally.
The detuning ratio (DR) is based on the differential influences of MS instrument settings on the ion yield of a respective target analyte; isomeric or isobaric interferences can lead to a shift of the DR for an affected sample. By determining the DR in samples in which known isomeric interference substances have been spiked to the target analyte, the applicability of DR detection was quantitatively investigated.
It was observed in two independent exemplary test systems (Cortisone / Prednisolone and O-Desmethylvenlafaxine / -Tramadol HCl) that a DR can indicate the presence of isomeric interferences.
It was confirmed that a DR can be used as a method to obtain indications of the presence of isomeric or isobaric interferences in individual samples in an analytical LC-MS/MS system; the technique can be used in addition to the established method of IR detection to increase the analytical reliability of clinical MS analyses.Abbreviations: CE, collision energy; CID, collision induced dissociation; CXP, cell exit potential; CLSI, Clinical and Laboratory Standards Institute; DR, detuning ratio; ESI+, positive electrospray ionization; IR, ion ratio; IS, internal standard; LC, liquid chromatographic; LC-MS/MS, liquid chromatography tandem mass spectrometry; ME, matrix effects; MRM, multiple reaction monitoring; MS, mass spectrometry; /, mass-to-charge ratio; TIC, Total ion current.
串联质谱法（MS/MS）原则上具有高度特异性，但由于样品中存在与目标分析物具有相同质量跃迁的意外物质（同分异构体/等压干扰），始终存在干扰的可能性。通过记录离子比率（IR），临床实验室已广泛尝试在个别情况下识别此类干扰。为补充此程序，可以评估差分调谐效应。我们旨在通过实验评估这种方法。
失谐比率（DR）基于质谱仪设置对各个目标分析物离子产率的差异影响；同分异构体或等压干扰可导致受影响样品的DR发生偏移。通过在已向目标分析物中添加已知同分异构体干扰物质的样品中测定DR，定量研究了DR检测的适用性。
在两个独立的示例性测试系统（可的松/泼尼松龙和O-去甲基文拉法辛/盐酸曲马多）中观察到，DR可以指示同分异构体干扰的存在。
证实DR可以用作在分析型液相色谱-串联质谱系统中获取个别样品中同分异构体或等压干扰存在迹象的方法；除了既定的IR检测方法外，该技术还可用于提高临床质谱分析的分析可靠性。缩写：CE，碰撞能量；CID，碰撞诱导解离；CXP，细胞出口电位；CLSI，临床和实验室标准协会；DR，失谐比率；ESI+，正电喷雾电离；IR，离子比率；IS，内标；LC，液相色谱；LC-MS/MS，液相色谱串联质谱；ME，基质效应；MRM，多反应监测；MS，质谱；/，质荷比；TIC，总离子流。
