Greetings. I would like to get opinions from the experts for the improvement and optimization of multiple drug confirmation by LC-MS/MS.
1. One of our method calibration curves follows the sample extraction protocol. The spiking material for the calibration curve was prepared at 0-1000 ng/mL in the urine matrix before extraction. Along the extraction process, the cal/QC/sample is diluted for 10x adding various reagents. However, the curve was projected for 0-1000 ng/mL when the actual amount is 0-100 ng/mL. Is my observation correct? I proposed to adjust the concentration of calibrators to have a final concentration of 0-1000 ng/mL to increase the sensitivity and accuracy of ESI positive mode. Does it dilution trade-off the error since all the samples were prepared in the same manner?
2. The standards used for the calibration curve are parental compounds. Is it necessary to have a 100% matrix match since the addition of beta-glucuronidase will not result in any reaction in parental standard materials?
I would appreciate the input from the experts. Please feel free to comment.
Mrs/Miss Nadarajan,
The employment of the classical approach to quantify analytes by means of the total intensity values (ITOT) of the mass spectrometric (MS) peaks over the whole time of the measurements, very frequently yields to deviation from the linearity-range, due to a set of factors connected with:
(i) The nature of the analytes;
(ii) the type of the matrix,
(iii) the concentration of the analytes, et cetera.
The major reason of this drawback of the classical quantitative concept is that the mass spectrometric phenomena have a random nature and the so-called 'fluctuations' of the experimental measurable variables such as m/z-values and the MS 'intensity' values cannot be accounted for, when there is determined only the ITOT-data. For this reason, the reliability of the standard MS quantitative protocols is only 98 %, despite, the fact that the instrumentation has superior characteristics.
Please, consider in this context, for instance, our study dealing with MS quantification according to this classical analytical approach [1].
[1] Quantitation of Heterogeneous Formulations of Morpholine-Type Fungicides and Surfactants in Polluted Soils
Bojidarka Ivanova, Michael Spiteller
Water, Air, Soil Pollution, 225, Article number: 1918 (2014)
In order to, overcome the aforementioned drawbak of the current classical approache to quantify analytes by mass spectrometry, using, however, the full capability of the analytical instrumentation of exact (or absolute) quantifying, we have developed more recently our own-authored quantitative stochastic dynamic method; and we have introduced innovative formulas, which are capable of precise, selective, sensitive and accurate quantifying of the fluctuations of the experimental variables per different spans of scan time over the whole time of the measurement. Please, consider work [2].
[2] Steroids, 164 (2020) 108750
Stochastic dynamic mass spectrometric quantification of steroids in mixture — Part II; Bojidarka Ivanova, Michael Spiteller
Thus, this innovative method has been tested on analytes in mixture at pg.(mL)-1 and ng.(L)-1 concentration levels, showing an absolute reliability of the method. The coefficients of correlations between our theory and formulas and the experimental data in solution reported, so far, are /r/ = 0.99997 - 1. The method is validated with chromatography, as well.
Consider, as well as, discussion [A]. Therein, have been shown most recent results from our method, as well.
[A] [https://www.researchgate.net/post/VOCs_metabolites_in_Standard_Reference_Material_SRMs]
In other words, the optimization of the analytical procedure according to the current standard method does not make much sense, because of any change of the experimental conditions of the measurements or the chemical functionalization of the analytes should affect on the fluctuations of the measurable variables randomly.
Conversely, there should be used our innovative approach to quantify exactly the fluctuations of the experimental data despite of the type of the analytes; their molecular structures; experimental conditions; complexity of the mixture of the analytes; and more, experimental and molecular factors.
Our method is currently, the best known quantitative approach to study mass spectrometric data, among the known quantitative concepts.
Dhayaalini Nadarajan
Attached is a publication on evaluation of the impact of matrix effects in LC/ MS measurement . I hope this help you
- Badges
- Science topic
- Similar topics
- Analytical Chemistry
- Extraction