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Supreme Being
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| one of our laboratory located in Middle East region (where outside temperature usually reached above 45C) is facing problem to maintain the preservation temperature limits of less than 6C in a cool box during transportation of the samples. I am wondering if this temperature limit is practically achievable in a coolbox containing ice or ice packs? I will appreciate if anyone will share his/her experiences or direct me to any study where I will found such data.
sabir |
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Supreme Being
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Last Login: 6/6/2008 4:03:33 PM
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| | Finally, a chance to use all those thermodynamic courses.... The answer is... it depends. It depends on the mass of ice, the ambient temperature, the possibility for convection (is a warm wind blowing?), radiation (is the sun shining directly on the sampler?), conduction (is the sampler well insulated?) and a host of other parameters. You could research this one to death, do all the calculations, and still not really know for sure until you try. And every day the results could be a little different... In Idaho, we had outdoor samplers, with ice in the bottom, sampling during ambient temperatures over 90F and taking warm sewage samples. The samplers were suspended in sewer accesses (i.e. down in a tunnel in the shade with no wind and reasonably good insulation). There was still ice at the end of 24 hours. YMMV (Your Mileage May Vary) but it's certainly worth a try. MLA |
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Supreme Being
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| | The secret is to get the samples cold before you ship them. Ice is better than cool packs because you can surround the samples. Ice the samples after taking them and then change the ice before you ship them -- should be OK. Better yet if you can refrigerate them for several hours before you ship. They will stay cold. |
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Junior Member
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| | I vaguely remember watching an episode of Myth Busters where they were trying to determine the quickest way to cool down a warm beer. If I recall correctly, the quickest method was a mixture of ice, water and salt. Seems like this could apply to sample cooling as well as cooling your favorite beverage. |
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Supreme Being
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| Good idea, but I am not sure if this combination can be used for cooling samples. I suspect that addition of salt over ice lowers the temperature to freezing point. I remember when my grandma, years ago, prepared homemade ice cream by putting the sweetened milk in a metal container and surrounded it by consecutive layers of smashed ice and table salt (without refrigerator), believe me solidified icecream was ready with in 30min.
sabir |
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Junior Member
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| | Sabir We face this problem in Iraq. To work around the temps, we are cooling the samples as soon as we take them, surrounding them in ice and water. Transport with lots of ice, and transport at night, to at least avoid the hottest temperatures and to keep direct sun light effects out of the mix. Because of our transportation problems, we lose a day of holding time to travel, but the lab has a heads up the sample is coming and they are ready to test ASAP. Good luck.
~Joan~ |
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Supreme Being
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Last Login: Today @ 8:41:00 AM
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| I appreciate all valuable suggestions and many inputs but I am still wondering if less than 6°C temperature limit is practically achievable in a coolbox under such severe outside conditions. Because we try this in many ways (it works for the cases when we cooled under refrigerator before transportation) but most of the time we have to collect and transport samples from the far away sites located deep into desert where there is no refrigerator and practically difficult to collect at night. I am going to validate sample transportation for such occasions to ensure sample integrity and I will appreciate if someone will direct me to any similar study.
sabir |
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Supreme Being
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Last Login: 6/6/2008 4:03:33 PM
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| | solar powered refrigerators? |
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Supreme Being
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Last Login: 10/8/2008 8:35:16 AM
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| | Ever think about trying dry ice? Just a thought. Egadz |
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Supreme Being
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| We did not try dry ice but I do not think so if dry ice is recommended for storage of samples meant for Microbiological testing. Dry ice temperature is -78.5C and it will lower the temperature below freezing point that will invalidate the sample and bacteria can not tolerate this shock.
sabir |
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