So I have a question on determining the expiration date of latent print reagents.
Do you shorten the expiration date of a prepared reagent if one of its components is set to expire sooner?
Ie. R6G expiration is 6 months but the Pet ether ingredient will expire in 4 months. Do you use a 6 month expiration for the R6G or set it to 4 months?
And why do you use one expiration over the other (6 or 4 months)
Thank You
Expiration date of in-house reagents
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SConner
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Re: Expiration date of in-house reagents
In general, I don't think you can have a reagent comprised of several chemicals with an expiration date beyond that of the chemical ingredient with the soonest expiration. Kind of like, your section can have stricter policy than what's specified in the quality manual but not looser.
What pet ether only has a 4 month shelf life? That seems really short.
What pet ether only has a 4 month shelf life? That seems really short.
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josher89
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Re: Expiration date of in-house reagents
We have a policy where we don't consider our reagents to expire. We test them prior to any casework (the day of) to ensure they are working properly. This gets you away completely from tracking expirations on individual chemicals or prepared reagents.
"...he wrapped himself in quotations—as a beggar would enfold himself in the purple of emperors." - R. Kipling, 1893
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NRivera
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Re: Expiration date of in-house reagents
I am most definitely NOT a chemist. That being said, I think it depends on the specific reagent and the component solvents. I'm not familiar with an expiration date on properly stored Pet Ether. I don't know what would cause it to degrade in a bottle. The same could not be said for a bottle of silver nitrate left out in sunlight for example.
Standards and controls are essential, but what do you do when a control fails? Do you wait for the results of your control before you process evidence or do you process your evidence with a test strip at the same time? It would stand to reason that a procedure involving a potentially destructive process would require previous confirmation of a standard and/or control before it is used on evidence, but that's not how it's done in a lot of places.
There's really not a one-size-fits-all answer to that question. In our lab, solvents (Pet ether, hexane, isopropanol, etc.) don't generally have an expiration date. Some reagents do (i.e. DFO and IND). For R6G, the Pet ether flavor has a 6-month shelf life but the methanol one is indefinite. You should consider each one individually based on its components. It seems reasonable to me that if you have a component that expires in 4 months, whatever reagent you use it in should not go past that date. /2cents.
Standards and controls are essential, but what do you do when a control fails? Do you wait for the results of your control before you process evidence or do you process your evidence with a test strip at the same time? It would stand to reason that a procedure involving a potentially destructive process would require previous confirmation of a standard and/or control before it is used on evidence, but that's not how it's done in a lot of places.
There's really not a one-size-fits-all answer to that question. In our lab, solvents (Pet ether, hexane, isopropanol, etc.) don't generally have an expiration date. Some reagents do (i.e. DFO and IND). For R6G, the Pet ether flavor has a 6-month shelf life but the methanol one is indefinite. You should consider each one individually based on its components. It seems reasonable to me that if you have a component that expires in 4 months, whatever reagent you use it in should not go past that date. /2cents.
"If at first you don't succeed, skydiving was not for you."
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josher89
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Re: Expiration date of in-house reagents
We throw in a test strip with the rest of our evidence. That strip is laden with a print prior to placing it in the fuming chamber. We look at the polymer crusty development first then it will get processed with a dye stain prior to the evidence to confirm development.
If it's porous, we apply a test print on a sheet of paper and process it. If development occurs, we're good to go.
We've been using prepared dye stains from 2016 and AA stains from 2017 with no issues although generally we are only making what we can use up within a few months.
If it's porous, we apply a test print on a sheet of paper and process it. If development occurs, we're good to go.
We've been using prepared dye stains from 2016 and AA stains from 2017 with no issues although generally we are only making what we can use up within a few months.
"...he wrapped himself in quotations—as a beggar would enfold himself in the purple of emperors." - R. Kipling, 1893
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g.
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Re: Expiration date of in-house reagents
Oooooooh! A rare chance to actually use my chemistry.
Two things. Some solvents, like PetEther or various solvents that can oxidize or form peroxidizers can actually degrade over time into potentially explosive bombs. Pet Ether will probably be fine if you have normal, lab, flammable storage containment cabinets.
The bigger concern is many solvents can absorb moisture from the air over time. The more polar the solvent, the more capacity to absorb water. The more humid the environment, the longer you open the jar, leave it uncapped, etc. gives it a chance to absorb water. It won't make it dangerous, but will reduce its effectiveness, change its polarity, possibly affect its solubility etc.
So worst case, over time, you might see a decline in performance.
Josher89's suggestion is the best one, confirm the performance prior to use. Although I recommend using the German BKA approach with standard strips of amino acids (make them yourself or commercially available) so you can monitor the chemical's sensitivity down to an appropriate level.
https://www.ncbi.nlm.nih.gov/pubmed/19804528
Two cents, what it's worth and all.
g.
Two things. Some solvents, like PetEther or various solvents that can oxidize or form peroxidizers can actually degrade over time into potentially explosive bombs. Pet Ether will probably be fine if you have normal, lab, flammable storage containment cabinets.
The bigger concern is many solvents can absorb moisture from the air over time. The more polar the solvent, the more capacity to absorb water. The more humid the environment, the longer you open the jar, leave it uncapped, etc. gives it a chance to absorb water. It won't make it dangerous, but will reduce its effectiveness, change its polarity, possibly affect its solubility etc.
So worst case, over time, you might see a decline in performance.
Josher89's suggestion is the best one, confirm the performance prior to use. Although I recommend using the German BKA approach with standard strips of amino acids (make them yourself or commercially available) so you can monitor the chemical's sensitivity down to an appropriate level.
https://www.ncbi.nlm.nih.gov/pubmed/19804528
Two cents, what it's worth and all.
g.
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4n6Dave
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Re: Expiration date of in-house reagents
g.
I don't know that answered my question though.
So if you have pet ether that has an expiration date of 10/30/2019 (Presumably due to the factors you mentioned but the primary one is moisture or contamination) and I make R6G today. Does the R6G expire on 10/30/2019.
Or are you assuming that the Pet Ether was good on 9/30. Therefore the solution of R6G will be good for its normal life span (6 months?).
We run positive controls with each test just wondering how other labs are setting the expiration dates. Before our LIMS we wouldn't consider the expiration of the components but the LIMS will flag a chemical now if any of its components are expired.
I don't know that answered my question though.
So if you have pet ether that has an expiration date of 10/30/2019 (Presumably due to the factors you mentioned but the primary one is moisture or contamination) and I make R6G today. Does the R6G expire on 10/30/2019.
Or are you assuming that the Pet Ether was good on 9/30. Therefore the solution of R6G will be good for its normal life span (6 months?).
We run positive controls with each test just wondering how other labs are setting the expiration dates. Before our LIMS we wouldn't consider the expiration of the components but the LIMS will flag a chemical now if any of its components are expired.
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g.
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- Location: St. Paul, MN
Re: Expiration date of in-house reagents
I see.
Well, it's similar to what happens in DNA, Drug Chemistry, etc. then yes, like SCONNER said, you are limited by the expiration date in the mixture by the first one that expires. This is one reason DNA for example, tracks all of their expiration dates and when a solution, buffer, reagent, etc. has an outdated component, the whole reagent is deemed to expire.
So the answer to your question in the strictest sense is "it would expire when the pet ether expires".
That said, one can have a process for VERIFICATION of chemicals if written that when a solvent/chemical hits the expiration date, that for the months or years after, you will verify the performance of the chemical. So just because something hits an expiration date, you don't have to throw it out, as long as you verify it is still working properly and this is written into your procedures. We did this for extremely expensive standards/reference materials in drug chem. They had a year expiration date, but prior to use, we tested them to show there was no breakdown, contamination, and we verified the standard against the original verification work/performance when we received it into the lab. i.e. we had objective evidence that the material was performing exactly as it did when received, and then later, past an expiration date, and each time we used it, afterwards, until it no longer was performing as expected.
In other words, if your procedures note that your positive controls test the effectiveness of the chemical each time prior to use, then you are ok.
But I would make sure that your positive controls actually DO test the effectiveness (especially the SENSITIVITY) of the reagent by using a depletion series from a standard control/commercial product, and ensuring that it doesn't just react with with a great, loaded test latent print on a surface, but can detect latent prints with reduced residue and low concentration of target reactants. Otherwise you do run the risk of missing borderline latent prints. Ninhydrin is a great example of a reagent that really decreases its sensitivity performance after a few months on a shelf. It might still "appear to work" with a test strip, but fresh ninhydrin and old ninhydrin have very different sensitivities. From my observations.
g.
Well, it's similar to what happens in DNA, Drug Chemistry, etc. then yes, like SCONNER said, you are limited by the expiration date in the mixture by the first one that expires. This is one reason DNA for example, tracks all of their expiration dates and when a solution, buffer, reagent, etc. has an outdated component, the whole reagent is deemed to expire.
So the answer to your question in the strictest sense is "it would expire when the pet ether expires".
That said, one can have a process for VERIFICATION of chemicals if written that when a solvent/chemical hits the expiration date, that for the months or years after, you will verify the performance of the chemical. So just because something hits an expiration date, you don't have to throw it out, as long as you verify it is still working properly and this is written into your procedures. We did this for extremely expensive standards/reference materials in drug chem. They had a year expiration date, but prior to use, we tested them to show there was no breakdown, contamination, and we verified the standard against the original verification work/performance when we received it into the lab. i.e. we had objective evidence that the material was performing exactly as it did when received, and then later, past an expiration date, and each time we used it, afterwards, until it no longer was performing as expected.
In other words, if your procedures note that your positive controls test the effectiveness of the chemical each time prior to use, then you are ok.
But I would make sure that your positive controls actually DO test the effectiveness (especially the SENSITIVITY) of the reagent by using a depletion series from a standard control/commercial product, and ensuring that it doesn't just react with with a great, loaded test latent print on a surface, but can detect latent prints with reduced residue and low concentration of target reactants. Otherwise you do run the risk of missing borderline latent prints. Ninhydrin is a great example of a reagent that really decreases its sensitivity performance after a few months on a shelf. It might still "appear to work" with a test strip, but fresh ninhydrin and old ninhydrin have very different sensitivities. From my observations.
g.