Matrix effect assessment

Matrix effect assessment Six replicates of ribavirin neat solutions (30, 500, and 3760 ng/mL) are spiked into extracted blank plasma samples. The matrix effect is estimated by comparing the mean peak area of ribavirin in the above sample extract with the mean peak area of the corresponding neat solution with ribavirin concentrations the same as the above. 

The issue of selectivity is one that is often difficult to address. Initial method development is invariably carried out by using standards made up with pure solvents, i.e. free from any matrix effects. It is often only when real samples are analysed that the true extent of interference becomes apparent and the value of the method can be properly assessed. An added complication is that interferences , by their very nature, are not constant and a number of samples may have a combination of interferences that defy analysis by a method that is otherwise successful on a routine basis (another example of Murphy s law ). 

In their broadest application, CRMs are used as controls to verify in a direct comparison the accuracy of the results of a particular measurement parallel with this verification, traceability may be demonstrated. Under conditions demonstrated to be equal for sample and CRM, agreement of results, e.g. as defined above, is proof. Since such possibilities for a direct comparison between samples and a CRM are rare, the user s claims for accuracy and traceability have to be made by inference. Naturally, the use of several CRMs of similar matrix but different analyte content will strengthen the user s inference. Even so, the user stiU has to assess and account for all uncertainties in this comparison of results. These imcertainty calculations must include beyond the common analytical uncertainty budget (i) a component that reflects material matrix effects, (2) a component that reflects differences in the amount of substance determined, (3) the uncertainty of the certified or reference value(s) used, and 4) the uncertainty of the comparison itself AU this information certainly supports the assertion of accuracy in relation to the CRM. However, the requirement of the imbroken chain of comparisons wiU not be formally fulfilled. 

The effect of co-extracted matrix components on the analyte response in the final determination step should be assessed. Normally, this is done by comparing the response of standards in solvent with matrix-matched standards, i.e., standards prepared in the extract of a control sample without residues. Because matrix effects tend to be inconsistent, the guidelines propose the general use of matrix-matched calibration unless it is demonstrated to be unnecessary. 

HPLC/MS and HPLC/MS/MS analyses are susceptible to matrix effects, either signal enhancement or suppression, and are often encountered when the cleanup process is not sufficient. To assess whether matrix effects influence the recovery of analytes, a post-extraction fortified sample (fortified extract of control sample that is purified and prepared in the same manner as with the other samples) should be included in each analytical set. The response of the post-extraction fortified sample is assessed against that of standards and samples. Matrix effects can be reduced or corrected for by dilution of samples, additional cleanup, or using calibration standards in the sample matrix for quantitation. 

All available methods (TG-MS, PyGC-MS and LDI-MS) suffer from difficult quantitation, although for different reasons. In TG-MS, selective volatilisation may not reflect the composition in the solid the quantitation problem of PyGC-MS requires assessment of the importance of matrix effects. Laser ablation methods cannot easily be calibrated. Quantitation is simplified in case of dual detection (MS for identification, FID for quantitation). A general drawback of many direct methods, which allow only small sampling volumes, is granule-to-granule variations. 

JPT). The transfer of processing equipment, manufacturing systems and analytical methodology was initiated. The initial process characterisation and trial batches were executed at receiving site and effectiveness assessed again using the comparability matrix and the demonstration batches were successfully completed, versus pre-defined acceptance criteria, within a predefined 12-month time frame. 

Matuszewski, B. K. Constanzer, M. L. Chavez-Eng, C. M. Strategies for the assessment of matrix effect in quantitative bioanalytical methods based on HPLC-MS/MS. Anal. Chem. 2003, 75, 3019-3030. 

It is eoncluded that the determination of dioxin-like activity in cleaned sediment extracts using the DR-Luc bioassay has a consistent reproducibility, and can be used as a reliable and robust tool in the hazard assessment of dredged materials in a licensing system. Its advantage over ehemical analysis is that it also detects the effects of combined exposure as well as the effect of unidentified congeners or chemicals present in concentrations below the limit of detection of chemical analysis with a similar mode of action. In addition the use of cleaned sediment extracts circumvents the problem of disturbing sediment matrix effects. 

It may be important to consider the variability of the matrix due to the physiological nature of the sample. In the case of LC-M/MS-based procedures, appropriate steps should be taken to ensure the lack of matrix effects throughout application of the method, especially if the nature of the matrix changes from the matrix used during method validation. For Microbiological and immunoassay, if separation is used prior to assay for study samples but not for standards, it is important to establish recovery and use it in determining results. In this case, possible approaches to assess efficiency and reproducibility of recovery are ... 

Munakata, N., Roberts, P. V., Reinhard, M., and McNab, W. W. J. (1998). Catalytic Dechlorination of Halogenated Hydrocarbon Compounds Using Supported Palladium A Preliminary Assessment of Matrix Effects. IAHS Publication(250), 491-496. 

Onorati, F., Pellegrini, D. and Ausili, A. (1998) Sediment toxicity assessment with Photobacterium phosphoreum a preliminary evaluation of natural matrix effect, Fresenius Environmental Bulletin 7 (Special), 596-604. 

A common way to assess the matrix bias is to analyse a drinking water (therefore containing a matrix) in the proficiency testing. For this analysis, laboratories calibrate their instruments using standard, commercial or in-house solutions. If a CRM is available, a possible matrix effect can be corrected by adjusting operational instrument parameters to match the certified value. 

In order to assess matrix effects, spike-recovery experiments were performed on samples from 10 individual human and six monkey matrix lots. Human samples were spiked with concentrations at the LLOQ and 10-fold the LLOQ. Monkey samples were spiked with concentrations at the LLOQ, two- and 400-fold the LLOQ. The results of the spike-recovery experiments are shown in Table 6.2. Some unspiked human samples showed a substantial amount of X, and their values were subtracted from the spiked sample results before calculating the spike recovery. For samples from monkey plasma samples, all samples were blank and no correc-... 

---