top of page
Choosing a Method
CDI's clientele have diverse backgrounds in both content and purpose. Therefore, not everyone who visits this site will know the exact procedure they might request to best serve their purpose. For clientele collecting data for regulatory purposes and subsequent submission for compliance, please start at our Regulatory Services. For clientele who are research based and require an analytical service that can be tailored for their project, please begin navigating at Research Services. It is encouraged to contact our office to speak with a professional when selecting a service so that an appropriate analytical solution may be chosen. However, we have provided a few commonly asked questions that will help when selecting what method is right for you.
What is the nature of my molecule?
If you know the molecular mass and polarity of your compound(s), the above chart can be used as a guide to select the inlet and ionization technique that may work best. If you already have data that has been generated for your compound(s), there may be an advantage to look at alternative methods since technology advancements are continuing to offer new applications.
What is the difference between unit and high resolution mass spectrometry?
A) A unit resolution mass analyzer can distinguish a mass within ± 0.1 – 0.5 Da as compared to B) a high resolution mass analyzer that provides a 1000x increase in mass distinction. C) An overlay of the two spectra reveals the challenge using URMS. The shaded inset is magnified in D) to reveal that at high resolution, one compound that is identified in URMS may be as many as ten distinct compounds when viewed by HRMS. This could effectively yield a false positive in MS analysis.
What is my matrix and does that effect what analytical approach I request?
The answer to this question is yes. Matrix effect can be a substantial obstacle to overcome when performing mass spectrometry analyses. The matrix is the overall composition of your sample, e.g. plasma or tissue, less the analyte(s) of interest. Analytical methods are initially developed to maximize the detectivity of an analyte, e.g. a steroid. The more complex the matrix, the more the method is compromised due to issues like ion suppression or interfering isobaric masses. Oftentimes, sample preparations need to be carefully developed to remove matrix effects, while retaining the quality and presence of an analyte of interest. When thinking about what method to request, please contact our offices to discuss your project. If we do not already have a validated method to achieve your analytical goals, CDI will amend or develop a standard operating procedure to ensure the data quality required for your project is attained and that your analyte is unequivocal from the presence of components like impurities, degradants and matrix.
How much sample do I need to supply?
The advancements that have been made in analytical equipment have significantly altered the amount of sample needed for analyte determinations. The sensitivity of a method is dependent on the sample matrix and subsequent preparation as well as the instrument chosen for analysis. Please contact CDI to discuss what level of detection may be required for your project. We will work with the client to choose a method that minimizes the amount of sample required. This is especially important in proteomic investigations where the project is usually sample limited.
What if I am working with a controlled substance?
If you are working with a drug and are unsure if it is regulated as a controlled substance, please visit The Controlled Substances Act (dea.gov). CDI is a DEA Controlled Substance facility (Schedule 1-5) and will require a completed Form 225 along with any narcotics received.
bottom of page