Multiple reaction monitoring matrix effects

The method for chloroacetanilide soil metabolites in water determines concentrations of ethanesulfonic acid (ESA) and oxanilic acid (OXA) metabolites of alachlor, acetochlor, and metolachlor in surface water and groundwater samples by direct aqueous injection LC/MS/MS. After injection, compounds are separated by reversed-phase HPLC and introduced into the mass spectrometer with a TurboIonSpray atmospheric pressure ionization (API) interface. Using direct aqueous injection without prior SPE and/or concentration minimizes losses and greatly simplifies the analytical procedure. Standard addition experiments can be used to check for matrix effects. With multiple-reaction monitoring in the negative electrospray ionization mode, LC/MS/MS provides superior specificity and sensitivity compared with conventional liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/ultraviolet detection (LC/UV), and the need for a confirmatory method is eliminated. In summary,... 

Quality control methods for each protocol are also presented. Applications and representative data are presented for the sensor controlled aerosol and matrix microinjection, whereas representative data for matrix solution fixation are reported elsewhere (8). Sensor controlled aerosol is applied to multimodal cell tracking by fluorescence and multiple reaction monitoring (MS/MS) of a fluorescent dye incorporated into stem cells and tumor cells surgically implanted into a mouse brain. This protocol enables validation of MSI using confocal microscopy for the tracking of implanted cells, and potentially the effect of a given cell s microenvironment upon its molecular composition. Matrix microinjection is used to acquire a MALDI mass spectrum of a single motor neuron from layer V of a mouse motor cortex. 

The standard addition procedure is another method for recognising and overcoming potential matrix effects in quantification. Both alternatives, FIA—MS or FIA—MS—MS, can be performed using this procedure. Despite the increased expenditure because of a multiplication in analyses, the FIA approach combined with standard addition remains the faster technique even with the application of specific analytical MS—MS techniques such as product-, parent- or neutral loss scans applying selected reaction monitoring (SRM). The greatest drawback of this technique is that the compounds to be quantified must... 

Phospholipids exist in high abundance in plasma and are believed to be one of the major causes of matrix effect. Individual types of phospholipids can be monitored using SRM transitions specific for their molecular ions, and the product ions produced via CID. An in-source multiple reaction... 

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