Making a tin sample cup for the Flash Analyzer

Tutorial: how to make the tin sample cups

There are many sizes of sample tins available; choose the size that is best for your sample mass.

The easiest way to make the tin sample cups is to buy them pre-formed. They are slightly more expensive but in my opinion it is worth it to not waste your time making them. However, if you want to save the money or have thousands of the un-formed tin slips, you might as well give it a go.

There are two ways to do this, especially if your Flash came with one of these strange metal cylinders that, hopefully, I am using correctly.

Set up, remember to keep space sterile.

Use this other tool to carefully begin forming the capsule.

Carefully form the tin and pull it out.

Finished tin. Awesome! (I'm not impressed)

Step 2: done.

Step 1: fold tin around tool.

 








This is an easier way to make the tins. It's faster and the tin doesn't rip as much.


Now you are ready to make those useless tin slips into useful capsules for your Flash.

Preparing my CN Flash samples

Over the last few weeks, I have been preparing my actual soil samples to run using the CN Flash Analyzer. This involved several steps.

1. thaw the frozen sample
2. homogonize sample
3. mass out about 1 gram of sample
4. dry the sample in a drying oven at 105C for 24hrs
5. sieve sample through 2mm sieve
6. grind sample into a fine consistency
7. mass about 35mg of sample into tin capsule
8. ball capsule using Z technique

To grind the samples, I used a large(ish) mortar and pestle. I tried using several mortar and pestle sets with variable success. The small lab set we had laying around didn't work well at all. Grinding those first few samples took about 10min each! I watched my life slowly tick by. Since then I have used my dad's mortar and pestle from our kitchen. I was shocked at how much better it worked. Each sample was finely ground in about 15 SECONDS!!! I didn't believe it at first. 

A fine soil sample using mortar and pestle.

The four samples in the lower left have been ground compared to the others that are only sieved.

This is my preferred set up to mass out sample and put it in the tin capsules. I've got my samples, ethanol, chem wipes, forceps (2), capsule storage trays, tin capsules, and of course the 5 point balance. Remember to sterilize and wipe your work space after each sample. Also, zero the balance with the tin capsule on it before adding sample.

My prep space, Hands Off!

Keep in mind, accidents and spills happen in the lab, no matter how careful you are. While preping my 40 samples, I spilled, like, 4 soil samples, and a LOT of it. That is why you should start with more sample than you think you are going to use or need. Also, then you have extra prepared sample around in case you need to run more tests.

Sample, I have forsaken thee. (my bad)

My finished samples, Yay!

Filling and balling tin capsules for the Flash CN analyzer

When preparing samples for the Flash CN analyzer, it can be difficult to explain how to use the capsules and use the Z folding technique. Hopefully these videos will help you understand the necessary techniques. It might take many samples before you are comfortable with the techniques, and might be even longer until you can do them without spilling too much. Obviously, I am not there yet. When preparing your final samples, make sure to use gloves and work on a sterilized surface. These videos are just for tutorial purposes (do as I say, not as I do).

This first video shows how to fill the tin capsules. When figuring out how much of sample x is  your target milligrams size, it is helpful to add less than you think it will be. It is hard to remove excess sample once in the tin without spilling it all out. As you can see, the microscoopula is not exactly a precision tool. When massing your samples, use a five decimal point balance. Remember to zero the balance with the empty tin capsule on ti before adding sample.

This second video shows how to fold the tin into a Z, fold the tin over to seal it, and then press it into a ball. It is easiest to do this with a pair of forceps.

Hopefully these videos have been helpful. Good luck and happy analyzing!

 For a laugh, check out how steady my hands are. You defiantly don't want me preforming your surgery, lol.

Preparing Soil Samples for the Flash CN Analyzer

How to Prepare Your Soil Samples for the Flash CN Analyzer
a Tutorial by Sarah A-J

So, you have just collected your samples, good job! Now, the lab work. First you will want to sieve and grind your samples.  You probably will want a total of around 3-5mL of sieved, dry, ground soil to work with. Depending on how rocky your soil is, you might have to sieve more or less soil. For me, to get around 5mL, I had to start with around 20mL of soil. I used a 2mm sieve.
After sieving I proceeded to dry my samples at 65 degrees Celcius for 2 days.
Post drying, I ground my samples twice using a mortar and pestle. Twice because I was unhappy with how fine the sample was after the first grinding. Because the final sample size that I will use in the Flash CN analyzer is only about 5-15mg, I think the sample has to be very fine and homogenized.

 

From upper right to lower left, you can really see the difference between unsieved, sieved, ground once, and ground twice. 

Once your soil is all ready, you have to prepare them to drop into the Flash analyzer. Make sure you have all the nessicary equipment and stuff before you begin. Also, it's most time efficient if you plan to prep a large batch at a time. Don't prep the samples and then store them for a few days. Try to prep them and then put them in the analyzer soon after. 

You will need tin sheets or pre-made tins, two tweezers, ethanol (for cleaning), a scupula, a high precision balance (preferably to 6 decimal places).

R.I.P. Beloved Muffle Furnace

It's a sad time here in the third floor lab. Dr. Chaudhary's long term lab companion is being moved to lab equipment hospice care: the Thermolyne 62700 Muffle Furnace. Right when I need to use it, too! Grrrr, lab equipment. First I can't get the Flash CN analyzer to work, and now our muffle furnace is on the fritz.

 

 

This is not what you want to see when you are planing to run your samples. So, we have a second, larger furnace in the downstairs lab, but it is also in a bad way. This second furnace is "new to us" and, as such, is missing quite a few parts, including internal shelves and a plug. A freaking plug! The back of the machine looks pretty naked without a plug to hook up to an outlet.

I've contacted ThemoScientific and they said that the thermal control panel needs to be replaced. Unfortunately, this part costs 640$, and that's uninstalled. I'm like, "Okay, where's that money ganna come from?" Dr. Chaudhary said, "No way. That's not ganna happen."

Oh, well. I guess I'll be putting all my eggs in the lets-just-get-a-new-plug-for-the-other-furnace basket. That or I'll have to face the Flash again (ugh *shiver*). I'm really not as upset as I may sound. It's just that I was hoping to run my soil samples back in October, and it is now half way through November, but all you can do is go with the flow.

Presentation to Senn High School Students

This last Monday, Susanna and I presented about green roofs and our experiment to three groups of ecologically minded Senn High School students.

We prepared our talk for two weeks before hand and were rewarded with three great sessions. Of course there were a few students who were falling asleep (tip: if you're going to sleep, don't sit in the front row), but most of the students seemed interested and engaged. I was nervous before hand, and at times the talk got a little bumpy, but over all it was really rewarding when I could catch someone's eye and they were like, "hey, I'm listening to what you're saying, and I like what I hear."
Here are some of my favorite slides:

Thermochron Replacement and Soil Sample Collection

Two weeks ago, Susanna and I made our way back to the green-roof after an unintentional hiatus. The time had come to change out the thermochron ibuttons. They can hold 2048 temperature readings meaning we could leave them out for about 12 weeks before needing to retrieve the data by connecting them to the computer. After downloading the data and starting new missions for each thermochron, we replaced them into their respective trays.

Susanna replanting the thermochrons.

Because we were both out there, we decided it was the best time to collect the soil samples that we both will need for our lab tests. Susanna will be testing the water retention capacity and I will be measuring soil carbon and nitrogen levels. We collected 100 mL of soil from each of 40 trays, giving us more than enough lab work to grind through in the coming weeks.

Me, posing while collecting soil samples.

The plants are looking pretty good:

Green-roof trays of prairie plants.

 Here are some action shots from the afternoon.

Planting thermochrons

Thermochrons and soil collection

Soil collection