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Pesticides Are Like Siblings, They Don’t Always Get Along, Part 3 - Opened Ampul Stability

14 Mar 2021

Two of my RESTEK colleagues, Landon Wiest and Jana Hepner, have posted parts one Pesticides are like Siblings – some get along well and some don’t – No. . .Really? and two Pesticides are like Siblings, They Don’t Always Get Along part 2 – now with the GC mix! on this topic showing what happens to the 200+ pesticides in our LC and GC multiresidue CRM kits when the mixes are all combined together into a single mixture then used to detect pesticides in celery matrix. Both confirmed with their study results that once pesticides ampules are mixed together and stored for a number of days some pesticides degraded immediately while others degraded over a longer timeframe. 

This wasn’t surprising to us knowing many of these pesticides were designed to degrade and because of that we segregated them into different ampules during manufacture based on their chemical properties in order to keep them stable once packaged.  Both also offered the same guidance: it’s best to prepare your calibration stock solutions by combining multiple ampule contents into a single mix daily to ensure the best stability.  Landon further clarified this doesn’t mean opening new ampules each day, but rather properly storing each mix separately under the proper storage conditions until combining into a stock mix for calibration.

a box of blue and white cubes box
LC Kit Cat.# 31971 GC Kit Cat. #32562

Landon also noted the expiration date on the CRM product label applies only until the ampule is opened.  The ISO 17034 standard requires the CRM manufacturer, or producer, to characterize starting materials to confirm purity, identity and traceability, then measure stability and assign a stated uncertainty value for each compound contained up until the stated expiration date.   Producers perform these measurements during manufacturing and conduct both short-term and long-term stability studies to measure the stability of the packaged contents to determine the expiration date on the label. 

It’s not uncommon for our customers to ask: how long are the contents stable after opening the ampule when stored and handled properly?  This blog post answers this question.  Requiring data to support our answer we designed an open ampule stability study to determine how long the pesticides in our LC and GC multiresidue kits remain stable after opening.

Click here to play a video clip describing our study and results we obtained (open ampule stability study link to video clip:


In summary, the data obtained from our open ampule stability study revealed when properly stored using the deactivated amber screw cap storage vials provided in the kit and kept under either refrigerator, or freezer conditions both the LC and GC multiresidue pesticide kits remained stable after opening for up to 31 days.  The results of this study confirmed these multiresidue mixes will remain stable for at least a month after opening, however we recommend you conduct your own stability studies to meet the goals and requirements of your lab’s quality assurance program plan. 

Once again National Brothers and Sisters Day is right around the corner on May 2, 2021!... so don’t forget to tease, annoy, irritate, or maybe just hug or thank that special sibling of yours.