Matrix effect in LC/ESI/MS analyses – a toolbox for solving problems?

 

Publication

Analytes

Matrixes

Methods, techniques

Results

Available files

Accred Qual Assur 2015, 20, 229–231

Any

Any

LC-MS (and in fact any other techniques)

The issue of LC-ESI-MS matrix effect is put into the broader perspective of metrology and quality assurance of analytical results.

 

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part II. A. Kruve, R. Rebane, K. Kipper, M.-L. Oldekop, H. Evard, K. Herodes, P. Ravio, I. Leito. Anal. Chim. Acta 2015, 870, 8-28

Any

Any

Any LC-MS method

This tutorial review puts the matrix effects into the context of LC-MS method validation.

It gives an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS), especially with electrospray ionisation (LC-ESI-MS), and discuss specific issues that arise with MS (and MS-MS) detection (i.e. LC-MS-MS) in LC (as opposed to the “conventional” detectors), matrix effect being one of them.

 

Anal. Methods, 2013, 5, 3035-3044

Any (examples are given with onion and gatlic)

Any (examples are given with carbendazim, thiabendazole, aldicarb, imazalil and methiocarb)

LC-MS (specifically LC-MS/MS)

The most common methods for overcoming matrix effects in LC/ESI/MS (matrix-matched calibration, standard addition, post-column standard infusion, extrapolative dilution, and postcolumn flow splitting) are compared according to their ability to give both true and accurate results for pesticide determination in complicated matrices such as onion and garlic. Extrapolative dilution and standard addition were found to give results statistically insignificantly different from the correct values. In addition extrapolative dilution – a hybrid approach for both reducing and correcting for matrix effects – was found to result in the highest accuracy of the measurements.

Comparison of the most common approaches of overcoming LC-MS matrix effects (matrix-matched calibration, standard addition, post-column standard infusion, extrapolative dilution, and postcolumn flow splitting) (PDF)

From measuring ionization efficiencies to ion source design – taming the electrospray ionization Presented in Vancouver at 60th ASMS (May 2012)

Different

Fruit and vegetables

LC/ESI/MS

A study of causes of matrix effect is presented. It has been found that processes in both liquid phase (competition for the surface of the droplet) and gas phase (proton transfer) are important and %ME values are in good correlation with the hydrophobicity and gas phase basicity of the analyte and matrix. It has been observed that also compounds with very similar properties – analyte and the corresponding 13C isotope-labeled standard – may suppress each other!

Matrix effect not only influences the accuracy of the analysis results but also reduces sensitivity. Therefore a design of the ESI nebulizer leading to higher sensitivity is presented, which contains an additional nebulizer gas capillary inside the liquid capillary. This nebulizer has been tested for pesticides in fruit and vegetable matrices as well as for pharmaceuticals in serum. This nebulizer enhances sensitivity by 3 to 10 times according to the calibration graph slopes depending on the analyte and matrix. The LoD value observed with the novel nebulizer are by up to 250 times lower compared to the classical ESI nebulizer.

ASMS poster

Rapid Commun Mass 2011, 25, 3252-3258. Study of LC/ESI/MS matrix effect on the example of glyphosate analysis from cereals

Pesticide glyphosate

Wheat and rye

Sample preparation:water extraction;

Determination: LC-ESI-MS

It was found that wheat and rye give very different matrix effect values in analysis of glyphosate using the glyphosate-FMOC derivative. Rye samples tend to undergo stronger ionization suppression than wheat samples. The ionization suppression was found to be dependent on particle size of the grained sample (stronger in case of smaller particles) and analyte concentration (stronger at lower concentrations). It was shown that the isotope labelled standard 13C2-glyphosate undergoes different ionisation suppression than glyphosate and is therefore not efficient in compensating or matrix effect. Also it was found that extrapolative dilution is an adecuate tool to overcome matrix effect even in case of very complicated cerials.

 

Doctoral theses of Anneli Kruve Matrix effects in liquid-chromatography mass-spectrometry, University of Tartu, 2011

Polar pesticides: aldicarb sulphoxide, aldicarb sulphone, demeton-S-methyl sulphoxide, carbendazim, methomyl, thiabendazole, methiocarb sulphoxide, methiocarb sulphone, aldicarb, imazalil, thiodicarb, phorate sulphoxide, phorate sulphone, methiocarb, glyphosate

tomato, sweet pepper, orange, raspberries, banana, cucumber, lemon, blackcurrant, peach, grape, apple, grapefruit, pear, red currant and leek, garlic, onion, wheat, rye

Sample preparation: Luke method (AOAC 985.22), QuEChERS and matrix solid phase dispersion (MSPD)

Determination: LC ESI MS

Data treatment: ANOVA, PCA and PLS regression

Several different methods aiming either to account or overcome matrix effect have been proposed and validated. Also overview and experimental comparison on different approaches to calculate matrix effect are presented.

Defense slides

Rapid Commun. Mass Spectrom. 2011, 25, 1159–1168. Accounting for matrix effects of pesticide residue liquid chromatography/electrospray ionisation mass spectrometric determination by treatment of background mass spectra with chemometric tools

Pesticides: thiabendazole, carbendazime, methomyl, aldicarb, imazalil and methiocarb

garlic and onion

Sample preparation: buffered QuEChERS;

Determination: LC-ESI-MS

Data treatment: PCA and PLS regression

The utility of background ions in MS1 scan spectra was assessed to account for and/or predict matrix effect in LC-ESI-MS analysis using MS2 signals. It was found that a number of ion intensities related to matrix effect are detectable from the MS1 scan spectra and could be used in a partial leastsquares (PLS) model to calculate the actual concentration of the analyte in the sample. The accuracy of the PLS method was considerably higher compared to the classical solvent calibration.

 

Rapid Commun Mass 2010, 24, 919-926. Optimization of electrospray interface and quadrupole ion trap mass spectrometer parameters in pesticide liquid chromatography/electrospray ionization mass spectrometry analysis.

Pesticides: aldicarb, imazalil and methiocarb

garlic

Sample preparation: buffered QuEChERS;

Determination: LC-ESI-MS

Data treatment: ANOVA

Optimization tools: software based and two-level full factorial design

Four different strategies for optimization of ESI and MS parameters were studied on the example of LC-ESI-MS analysis of three pesticides. It was found that the true optima from the sensitivity point of view are found only when the standard and eluent are mixed before infusion to the ionization source.

Also it was found that moving away from the optimal ESI and MS parameter values giving highest sensitivity decreases the influence of matrix effect (ME values shift closer to 100%). Therefore there is a conflict between the optimum from the sensitivity’s and the matrix effect’s point of view. Which optimum is used in the final method depends on the situation: if the analyte concentrations to be detected (for example the pesticide residues) are higher than the detection limit, then the optima can be chosen aiming at minimal matrix effect. On the other hand when the concentration range to be determined is close to detection limit parameters leading to the lowest detection limit should be chosen and other means for combating the matrix effect should be used.

 

 

J. AOAC Intl. 2010, 93, 306-314. Electrospray Ionization Matrix Effect as an Uncertainty Source in HPLC/ESI-MS Pesticide Residue Analysis

Pesticides: thiabendazole, aldicarb, imazalil and methiocarb

Tomato, cucumber and sweet corn

Sample preparation: buffered QuEChERS;

Determination: LC-ESI-MS

This work presents an empirical approach—the matrix effect graph approach—for estimating the uncertainty due to the matrix effect in HPLC/ESI-MS analysis of pesticide residues in fruits and vegetables. The root mean square of the relative residuals on the matrix effect graph are used as the estimate of relative uncertainty of the sample peak areas caused by the matrix effect. The approach was validated with tomato, cucumber, and sweet corn matrixes at the 0.5 mg/kg concentration level.

 

Anal. Chim. Acta 2009, 651, 75-80. Combating matrix effects in LC/ESI/MS: The extrapolative dilution approach

Pesticides: methomyl, thiabendazole, aldicarb, imazalil and methiocarb

tomato, cucumber, apple, rye, garlic

Sample preparation: QuEChERS

Determination: LC-ESI-MS

Matrix effect is investigated as the function of dilution. It is demonstrated that in some cases dilution can eliminate matrix effect, but often it is just reduced. A new quantitation method based on consecutive dilutions of the sample and extrapolation of the analyte content to the infinite dilution, i.e. to matrix-free solution (where ionization suppression is absent) was proposed.

 

The method was validated for LC/ESI/MS analysis of five pesticides in five matrices at two concentration levels (0.5 and 5.0 mg kg−1).

 

J. Chrom. A 2008, 1187, 58-66. Matrix effects in pesticide multi-residue analysis by liquid chromatography-mass spectrometry

Polar pesticides: aldicarb sulphoxide, aldicarb sulphone, demeton-S-methyl sulphoxide, carbendazim, methomyl, thiabendazole, methiocarb sulphoxide, methiocarb sulphone, aldicarb, imazalil, thiodicarb, phorate sulphoxide, phorate sulphone, methiocarb

15 different fruits and vegetables: tomato, sweet pepper, orange, raspberries, banana, cucumber, lemon, blackcurrant, peach, grape, apple, grapefruit, pear, red currant and leek

Sample preparation: Luke method (AOAC 985.22), QuEChERS and matrix solid phase dispersion (MSPD)

Determination: LC ESI MS

Three sample preparation methods: Luke method (AOAC 985.22), QuEChERS (quick, easy, cheap, effective, rugged and safe) and matrix solid phase dispersion (MSPD) were applied to different fruits and vegetables for analysis of 14 pesticide residues by high-performance liquid chromatography with electrospray ionization – mass spectrometry (HPLC/ESI/MS). Matrix effect, recovery and process efficiency of the sample preparation methods applied to different fruits and vegetables were compared. The Luke method was found to produce least matrix effect. On an average the best recoveries were obtained with the QuEChERS method. MSPD gave unsatisfactory recoveries for some basic pesticide residues. Comparison of matrix effects for different apple varieties showed high variability for some residues. It was demonstrated that the amount of co-extracting compounds that cause ionization suppression of aldicarb depends on the apple variety as well as on the sample preparation method employed.

 

 

Comments

Should you have any questions regarding the data, the used experimental, data treatment or computational methods, etc, please do not hesitate to contact Anneli Kruve (e-mail: anneli.kruvebwut.ee)!     Proposals for collaboration are also most welcome!

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See also other research topics at UT Chair of Analytical chemistry

  

University of Tartu

 

Last edited:  Saturday, 02-Jan-2016 11:48:50 EET