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Feb. 23rd, 2005 07:00 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ladynox25
So, last Friday we had a huge number of samples come in at once. A gignormous number of samples, in fact. Something like 90 samples. Wait, I hear you say, 90 is not big. No, not until you factor in that 90 samples works out to something like 240 BOD bottles--every one of which has to be set up by hand. What does this involve, you ask? I'll tell you.
First of all, it involves setting up the sets in the computer. We run BOD and BODc as two different sets so almost every day we have 2 sets to run. This means 1) picking duplicates to representatiely cover 10% of the # of samples. This means 2) picking at least two dilutions for each sample. For samples where we need to ensure precise values, for samples which we have no prior data from, and for samples with a wide enough spread of previous results, we have to pick four dilutions. This means 3) setting up the QC date and time accurately in the system. Then, after all this is done, we can go *get* the samples.
Before we get the samples, however, we have to make up the seed and standard. The seed is a harmless strain of bacteria that has to be activated with water and is added to all samples. The standard is a solution of glucose and glutamic acid. Both of these are made fresh every day. Oh, and before we can read anything with the probes, we have to do the Winkler titration, which uses a color-based endpoint to determine the volume of oxygen dissolved in the water we will be using later to fill the bottles with. We do this twice, and fill a third bottle to calibrate the probes with.
Once we have the samples, we have to determine if any of them have chlorine added, because chlorine will interfere with the results. So we test all the samples for chlorine and dechlorinate those samples which have chlorine. This is maybe 75% of the samples. This sounds easy, doesn't it? The testing for chlorine and dechlorination typically takes 30-45 minutes for an average batch (say 40-60) of samples. Once the samples are dechlorinated, we refine the dilutions. Maybe sample X has a strong smell today so we want to add an additional dilution to it. Once that is done, we have to pH the samples. This means we take a reading, and if the pH is not within range (6.5-7.5) we adjust it until it is. Which can be very frustrating for a sample with buffer in it which absolutely refuses to move that extra .1 pH, or equally, for a sample that is so sensitive that it goes from 7.6 to 6.4 with *one* drop of very weak acid. Once all the samples are pH'd, then they are ready to pour. But wait a minute, because the *bottles* aren't ready yet.
First, we number the bottles. Then we seed the bottles. Then we add standard to the standard bottles. *Then* we can pour the samples into the bottles. 75 mL for a 4 dilution. 50 mL for a 6 dilution. Using pipettes, 3 mL for a 100 dilution or 0.2 mL for a 1500 dilution. And whatever you do, *don't* pour the wrong sample into the wrong bottle! Okay, that takes at least an hour, are we done yet? No, because we get the joyful task of filling up the bottles. Grab the nalgene tube and bend over the cart full of little bottles and try, with a cramping hand, to control the flow of water so that you fill the bottles fast without overflowing. 240 bottles is two large cartfuls, almost (a large cart has 146 bottles on it).
Now, calibrate the probes, stick them in the first set of blanks, and start recording values. Oh, for the BODc bottles, don't forget to add a scoop of nitration inhibitor after you read. Then stopper the bottles and cap them. One the cart is done, cover it with a black plastic cover with the dates on it so you know when to read off. Then trundle the cart into the incubator and wait 5 days. Enter the data into the computer, clean up, go home.
So, Paul (who is my labmate and nominal supervisor, until I become fully qualified on this test) and I did this on Friday for 90 samples, aka 240 bottles. Which is an extremely large setup. *Then*, when we were done with that, *I* had to set up my check sets so that I can be fully qualified to do this test on my own. This was 60-some additional bottles, almost a full small cartload (small carts hold 76 bottles), in two sets, both of which had to be set up and run separate from the other Friday sets. And, by the nature of the check set, I could not get help from anyone. Despite the fact that I hurt all over. Well, I managed somehow, came home and took a nice long hot shower and some naproxen and went to bed.
Fast forward to today. Remember how I said up above about how you wait five days and then read off? The gignormous set that we read on Friday was set to read off today. And Paul called in sick. Thank Diety that reading off is not so bad as reading on, as you just read the values, do some calculations, empty the bottles and dispose of them, clean up the carts, and enter the data. Except while I was doing that I was *also* setting up today's set. Which wasn't gignormous, but still respectable (138 bottles, maybe 40 samples). Which, altogether, wasn't done until more than two hours *after* the time I was supposed to be reading off the check sets that I had set up on Friday. Thank goodness that hours don't matter so much in this test. Otherwise I would have been royally screwed. As it was, I managed to get everything read off, set up and read on (despite the people from login handing me three samples to set up when I was almost 90% done with this step) and read off again. Altogether, I spent as much time in the lab today as I did on Friday and I hurt.
Still, I suppose if I can handle something like that on my own, that means I really am ready to take this job on.
Oh, and I almost forgot to mention that since I only read off my check sets today, I still am not officially qualified to do this test on my own. Which means that in addition to everything else, this morning I was running around trying to find someone who could at least nominally supervise me. What that boiled down to in the event was someone from the office who is trained on BOD coming down for a few minutes to check my dilutions, since they are the trickiest part of setup.
First of all, it involves setting up the sets in the computer. We run BOD and BODc as two different sets so almost every day we have 2 sets to run. This means 1) picking duplicates to representatiely cover 10% of the # of samples. This means 2) picking at least two dilutions for each sample. For samples where we need to ensure precise values, for samples which we have no prior data from, and for samples with a wide enough spread of previous results, we have to pick four dilutions. This means 3) setting up the QC date and time accurately in the system. Then, after all this is done, we can go *get* the samples.
Before we get the samples, however, we have to make up the seed and standard. The seed is a harmless strain of bacteria that has to be activated with water and is added to all samples. The standard is a solution of glucose and glutamic acid. Both of these are made fresh every day. Oh, and before we can read anything with the probes, we have to do the Winkler titration, which uses a color-based endpoint to determine the volume of oxygen dissolved in the water we will be using later to fill the bottles with. We do this twice, and fill a third bottle to calibrate the probes with.
Once we have the samples, we have to determine if any of them have chlorine added, because chlorine will interfere with the results. So we test all the samples for chlorine and dechlorinate those samples which have chlorine. This is maybe 75% of the samples. This sounds easy, doesn't it? The testing for chlorine and dechlorination typically takes 30-45 minutes for an average batch (say 40-60) of samples. Once the samples are dechlorinated, we refine the dilutions. Maybe sample X has a strong smell today so we want to add an additional dilution to it. Once that is done, we have to pH the samples. This means we take a reading, and if the pH is not within range (6.5-7.5) we adjust it until it is. Which can be very frustrating for a sample with buffer in it which absolutely refuses to move that extra .1 pH, or equally, for a sample that is so sensitive that it goes from 7.6 to 6.4 with *one* drop of very weak acid. Once all the samples are pH'd, then they are ready to pour. But wait a minute, because the *bottles* aren't ready yet.
First, we number the bottles. Then we seed the bottles. Then we add standard to the standard bottles. *Then* we can pour the samples into the bottles. 75 mL for a 4 dilution. 50 mL for a 6 dilution. Using pipettes, 3 mL for a 100 dilution or 0.2 mL for a 1500 dilution. And whatever you do, *don't* pour the wrong sample into the wrong bottle! Okay, that takes at least an hour, are we done yet? No, because we get the joyful task of filling up the bottles. Grab the nalgene tube and bend over the cart full of little bottles and try, with a cramping hand, to control the flow of water so that you fill the bottles fast without overflowing. 240 bottles is two large cartfuls, almost (a large cart has 146 bottles on it).
Now, calibrate the probes, stick them in the first set of blanks, and start recording values. Oh, for the BODc bottles, don't forget to add a scoop of nitration inhibitor after you read. Then stopper the bottles and cap them. One the cart is done, cover it with a black plastic cover with the dates on it so you know when to read off. Then trundle the cart into the incubator and wait 5 days. Enter the data into the computer, clean up, go home.
So, Paul (who is my labmate and nominal supervisor, until I become fully qualified on this test) and I did this on Friday for 90 samples, aka 240 bottles. Which is an extremely large setup. *Then*, when we were done with that, *I* had to set up my check sets so that I can be fully qualified to do this test on my own. This was 60-some additional bottles, almost a full small cartload (small carts hold 76 bottles), in two sets, both of which had to be set up and run separate from the other Friday sets. And, by the nature of the check set, I could not get help from anyone. Despite the fact that I hurt all over. Well, I managed somehow, came home and took a nice long hot shower and some naproxen and went to bed.
Fast forward to today. Remember how I said up above about how you wait five days and then read off? The gignormous set that we read on Friday was set to read off today. And Paul called in sick. Thank Diety that reading off is not so bad as reading on, as you just read the values, do some calculations, empty the bottles and dispose of them, clean up the carts, and enter the data. Except while I was doing that I was *also* setting up today's set. Which wasn't gignormous, but still respectable (138 bottles, maybe 40 samples). Which, altogether, wasn't done until more than two hours *after* the time I was supposed to be reading off the check sets that I had set up on Friday. Thank goodness that hours don't matter so much in this test. Otherwise I would have been royally screwed. As it was, I managed to get everything read off, set up and read on (despite the people from login handing me three samples to set up when I was almost 90% done with this step) and read off again. Altogether, I spent as much time in the lab today as I did on Friday and I hurt.
Still, I suppose if I can handle something like that on my own, that means I really am ready to take this job on.
Oh, and I almost forgot to mention that since I only read off my check sets today, I still am not officially qualified to do this test on my own. Which means that in addition to everything else, this morning I was running around trying to find someone who could at least nominally supervise me. What that boiled down to in the event was someone from the office who is trained on BOD coming down for a few minutes to check my dilutions, since they are the trickiest part of setup.
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Date: 2005-02-24 08:49 am (UTC)Well, at least the hump's over for now...