When trying to develop a new method, how do I do a literature search?

Previously, I spoke about the sources of information available for method development. We discussed some of the resources we could use to figure out how to build a method for the detection of naloxone, buprenorphine, norfentanyl, and methadone in urine. For this post, we’ll go through the search process with these analytes using urine as our matrix of focus. For this assay we’re running a Sciex 5500 triple quadrupole mass spectrometer with a Shimadzu NexeraX2 UHPLC. Since we’re not out to reinvent the wheel here, let’s assume this assay, in some form, has already been done. It’s likely Sciex has an application note with these analytes detected in urine. Perhaps all of them in are in a large, complex urine panel or they’re located in various other app notes with other vendors? Either way, the easiest approach is the simplest: first look for an application note from Sciex or other vendors that have as much similarity to our assay as possible.  Continue reading When trying to develop a new method, how do I do a literature search?

What are some good sources of reference for sample prep method development?

In my previous post, I briefly mentioned the process of method development. Today, I’ll go into a bit more detail and will explain how to start the process so we can get a global view of what we’re doing, and more importantly, why we do it. The why: the sole purpose for method development is to construct a robust and analytically sound method that will not just pass the barriers of validation, but provide physicians and patients with sound and reliable results. Continue reading What are some good sources of reference for sample prep method development?

How to Monitor and Prevent Sample Carryover during Method Development

When running through the exhaustive process of method development, most of us put the majority of our focus on validation and how to complete our crazy validation checklists. Throughout this process, the last thing we want to see is some random hiccup in our workflow. But a whole validation without a hiccup is just wishful thinking, right? Whether your analytes are on back order or you have the misfortune of catastrophic instrument failure, we all experience some type of complication or mishap. One in particular, sample carryover, seems rather innocuous, but without some type of preventive action, it can really ruin a good method. Nonetheless, if you have preventative measures in place, this can be easily preventable.

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How to calculate percent recovery and matrix effects for your analytical assays

For many of us developing an analytical assay requires numerous experiments in addition to lots of data review, and yet despite the feeling of confidence in our success, how reliable is our assay really? How do we measure reliability of our assay? Well, there are many ways but here I’ll explain the most common approach using a theoretical analyte called compound X, which, in this case, is readily prescribed for arthritis. And like many drugs, compound X is excreted in large quantities, unmodified, in human urine. So, for arguments sake, let’s say we’ve already defined our LC/MS-MS method and we’ve ironed out an extraction method using SLE+ (Thanks Bruce!)

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