Pierre Negri
Posted by

Take 5 with SCIEX Global Technical Marketing’s Pierre Negri

Share on linkedin
Share on twitter
Share on email

With the rise of Novel Psychoactive Substances (NPS), or designer drugs, in the past decade, forensic toxicologists are being tested like never before. It seems like as soon as one analog is identified, another is synthesized. These new chemicals share structures with certain controlled substances and mimic their effect. When the NPS hit the street, however, they have not yet been fully characterized and are a challenge to analyze by traditional screening methods. Because of this, many designer drugs routinely circumvent laws. Keeping up with new formulations as they emerge is an uphill battle.

“Unleash the power of LC-MS/MS to rapidly identify and quantify NPS in a variety of biological matrices. The various examples shown in this webinar demonstrate how the suite of SCIEX instruments, in combination with novel and intuitive informatics solutions can provide a streamlined and comprehensive solution for the detection of these novel and challenging substances.”

Pierre Negri recently presented a webinar on the potential of LC-MS/MS technology to handle a full range of toxicology applications. He discusses the detection and identification of prescription drugs, over-the-counter drugs and illicit drugs, and their metabolites, with a strong emphasis on NPS.

Here are some additional points from the webinar that Pierre felt were worth sharing.

1. Can confidence criteria be fixed by the software? Can a user modify them as a function of the analysis needs? The confidence criteria are set by the user within SCIEX OS Software and can be modified during the data processing step. Any of the confidence criteria listed in the software (mass error, fragment mass error, error in retention time, % difference isotope ratio, library hit score, formula finder score, and others) can be selected, and each one of them can be assigned an acceptable difference value (green light) and a marginal difference (orange light).

Each one of these criteria can be assigned a user-defined percent weight such that the sum of all the weights selected for each confidence criteria equals 100%.

2. Can you tell me more about the chromatogram shown here? What are the concentrations of the selected compounds? [timestamp: 17:17] If you haven’t caught the webinar just yet, let me give you some background. 

A series of calibrator solutions were prepared and injected into the instrument to build a calibration curve. The calibrators covered concentrations ranging from 1 ng/mL to 100 ng/mL. The chromatogram shown above was generated using the lowest calibrator (1 ng/mL). If you’d like to learn more about chromatography, click here.

3. Are the calibration curves in the matrix? Yes, all three workflows presented in the webinar showed that the calibration curves were generated in the matrix. You can find out more about these studies by downloading the full technical notes:

4. How did you establish the extraction percentage for fentanyl in hair? The extraction recoveries were calculated by dividing the area ratio (analyte area to internal standard area) of a pre-spike sample (depicted as “C”) and the peak area ratio of a post-spike sample (depicted as “B”).

The recovery values for each analyte were calculated as follows: RE (%) = C/B x 100

If you’d like to know more click here.

5. How is the uncertainty determined for the concentration and match score? There is no uncertainty for the concentration. The library match score is calculated by an algorithm that compares the generated MS/MS spectra to the library spectra. The percentage is based on the mirror image similarity between the two MS/MS spectra.

Thank you for reading, and thank you to Pierre! You can check out the webinar here. If you have any questions for Pierre, you can leave a comment or drop him an email at pierre.negri@sciex.com.

Pierre Negri
Posted by
Pierre Negri
As the forensics global technical marketing lead at SCIEX, I collaborate with global key opinion leaders in the criminalistics and forensic toxicology field to build a better understanding of mass spectrometry for forensic research and practice. I also help customers develop and implement new mass spectrometry methods with the main focus of determining emerging forensic trends and market needs for a variety of forensic assays and applications.

Leave a Reply