Part 3: How to Know if Your Calibration Curve is Correct

You’ve bought some standards and you made a multi-point curve.  You might think your work to improve laboratory accuracy is over, but then doubt starts to creep into your mind.  What if something’s gone wrong!?!  What if you run a sample and you expect one answer and your instrument tells you another?!  Is the sample bad, or is there a problem with your calibration curve?  Has something gone wrong somewhere in your plant’s process, or do you have a bad batch of calibration standards!?

The first step in ensuring that your calibration curve is up to par is checking the Correlation Coefficient.  I know, I know….more math….but stick with me here because it’s important!  The R2 value of your calibration curve has a large amount of statistical power.  No one wants to talk about statistics, but it has a lot to do with how well your instrument is calibrated.

In a nutshell, the correlation coefficient gives you an idea of how well the standards relate to each other.  R2 values statistically can range from -1.0 to +1.0, but on your instruments, you should look for a value as close to 1.0 as possible!  Values of R2=0.9987, R2=0.99943, or R2=0.9963 are examples of what you are looking for.  The closer to 1.0 your R2 value is, the stronger the relationship between your standards.  A strong relationship between standards leads to more confidence in the reported results for your samples.  Remember that your standard value points hug your samples, and no one likes crappy, wet noodle armed hugs! It’s listed somewhere in your instrument’s software, you might just have to look around for it.

So you’ve got a strong curve, but calibration curves can be strong….but wrong!  How can you check the accuracy of the standards you used to make the curve?

There is a way to prove that you standards and instrument are operating correctly.  We are going to employ the Dr. Sheldon Cooper of standard….the validation standard!  Just like Dr. Copper, the validation standard knows more than you, and it isn’t afraid to tell you when you’re calibration is wrong!

The validation standard should be a standard SEPARATE from your curve!  Buy it from an alternative supplier, buy a different lot of a standard you use in your curve, or buy 4 standards and just pick one to use only as a validation….just don’t use your validation standard as part of your calibration curve.

If you just analyze one of your calibration standards again as a sample, you will get the right answer 100% of the time….because somewhere in the software you’ve entered those values in as the answer.  This might look promising, but it tells you ZERO useful information about the accuracy and correctness of your calibration curve.  The validation standard’s “job” is essentially to be an unknown sample, that you secretly know the answer to.

A good basic rule of thumb is that the difference between the known value of your validation standard and the instrument’s reported result based on your curve should vary no more than 10%.  We’ll call this “Validation Recovery” for ease of terminology.  For most applications, 10% is much larger than the recovery should be, but if you’re just started down the path of improving your laboratory accuracy….it’s a good basic place to start.

From here we are going to have to dive into a bit more math, and I think we can all agree that one math topic per post is frankly too much math!

Next week I’ll cover the basic statistics of calculating a more precise validation recovery range for your instrument, tracking validation recovery, and how you can use that information to access the performance of your instrument!

New Protein

Duck season is upon us!!

A successful harvest so far this season means that I’ve had a fun chance to do something new with a protein I’ve never used.  I’ve had restaurant duck plenty of times, and it’s always been delicious.  But wild duck is a whole different animal, and it really puts a whole new spin on it when you can take something all the way from harvest to plate.

In addition to eating we also have some wings stashed in the freezer for a taxidermy/biology lab style display I want to do for the upstairs loft.  I’m thinking something along the lines of displaying the wings with little tags and their Latin names.  It’s a nice way to blend hunting with science in a stylized way, and it will feature the prettiest part of the birds….in my opinion.  Using as much of what we bring home as possible is something I really put a lot of focus on, The Engineer might say too much focus….but he usually goes along with my ideas! 🙂

The most shocking part of duck season so far is how strongly Madam Roo has taken to the whole situation.  My usual timid, perpetually nervous girl has taken to charging right through The Engineer when he arrives home that she can go investigate what he’s brought home every morning.  Poor guy just wants to say hello to her, and she can’t even be bothered until she’s accessed the daily harvest.

I’ve shared this already on Instagram, but it’s just too good and too cute!
“The Stay at Home, Delicate Duck Hunter”

I have grand cooking plans for all sorts of wild game, so I tend to get a bit bossy with home the birds should be cleaned.  Sadly, it’s been a bit too early in the season to pluck a bird for roasting.  They have all been about halfway between their summer feathers and having their dense winter, downy feathers grow in.  This has just led to a mess of plucking, so sadly I haven’t had a bird yet for roasting with my canned apple chutney.  That will come with time I’m sure, but I am antsy to try that and let you know how it goes!

While we patiently wait for the birds to fully plume for winter, and hopefully cleaner plucking, we’ve been breasting out the birds.  I tend to be a bit more skilled than The Engineer in that capacity, so bird cleaning as really become a whole family affair.  We usually try and keep Scout in the house while the knives are flying, but she’s taken to crying like she’s being beaten if we are out with the ducks without her, so we usually cave about halfway through.

Ummm excuse me iz trying to investigate pleez!

Pleez do not mind while I investigate these ducks pleez….

My very first adventure into cooking duck was Spicy Thai Duck Burgers curtesy of From Field to Plate.  I’ve used other From Field to Plate recipes before, and I’ve always had really great results.  I really can’t say enough good things about his lime and tequila turkey marinade!  The burgers were alright, but I would defiantly tweak the spices and flavors next time we make them.

I think I’m just not a huge fan of cinnamon paired with meats.  I know that it’s a normal flavor profile in some Eastern cuisines, but it’s just not my favorite flavor.  Also, I didn’t find it all that spicy, and even The Engineer thought it was too mild.  I will say I did half the jalapeño in the slaw, but usually a single jalapeño is all The Engineer can tolerate spice wise.  It’s so hard to know especially because every pepper is a little different, but it could have used way more oomph.

I would definitely remove the cinnamon and amp up the spice for round two.  Also, I don’t like peanut sauce and it was a Wednesday night, and I was feeling lazy…..so I cheated and bought some peanut sauce for The Engineer.  The From Field to Plate homemade version is probably much better.  If you’re into peanut sauce and give it a try let me know!

High on list of things you don’t want in your burger patty…..

This week we were a bit crunched for time, so instead of trying a new recipe we went to an old fall back.  Friday night duck taco and nacho night with margaritas was exactly what this week called for!  Just treat it exactly the way you’d use regular ground beef, and no one will even know you’re sneaking waterfowl into the dinner rotation!

I do a bit feel like I’m not really using the ducks to their full flavor potential, and it’s making me a little bummed.  I’m not really in love with the texture of ground duck….it’s a bit soft.  More on the side of ground turkey or chicken then say ground beef or deer.  It defiantly goes better, in my opinion, with something crunchy….slaw or tortilla chips.  But, at the end of the day, it’s all getting gobbled up and that’s really what counts.

Meals do really mean more when you know the time and sacrifice that have been put in to make them happen.  So many people have moved so far away from knowing where their food comes from.  Nothing that arrives on your table arrives by magic, and I’m glad that in this house we are active participants in at least some of the meals that arrive on the dining room table.

Bonus points for not having any shot end up in the taco meat!  I’ll take that as my major victory for the week!!

Part 2: What Creates an Accurate Calibration Curve

Welcome back for the second week of Common Calibration Conundrums and Other Laboratory Queries!

Before we get back into the science fun, I have an exciting announcement.  Bion Sciences now has an Instagram account!  Come follow along with us!  There will be blog notifications, access to our website, and photos of the Bion Sciences team in our natural, laboratory habitat!

@bionsciences605

Part 2: What Creates an Accurate Calibration Curve

Now that we’ve covered how often you should calibrate an instrument, we should talk about how you pick standards to use for your curve and how many standards you should be using.

Think back to algebra when we first learned the equation for a line.  If your math teacher was anything like my math teacher, they drilled into your brain that 3 points are needed to accurately verify a line and the corresponding slope.  One point is simply a dot in space, and two points allow for too much swing in the correlation of the line, but three points……three points is really where the magic starts to happen!

Don’t get overwhelmed with the math, I’ll simplify this for you!

The accuracy of your line, and therefore your results, improves dramatically as more data points are added to the line.  Think back to our puppy from last week.  If you only tell the puppy once a day, every day to potty outside, your results might be somewhat….questionable.  Now imagine you tell that puppy 3 times a day, every day, to potty outside.  The chances that puppy is going to catch on greatly improve!  The same goes for your instruments.

When it comes to calibration points, more is always better.  Again, there is no such thing as over calibrating an instrument!

The more data points you provide the instrument, the accuracy of the answers the instrument provides you will also improve.  The only issue that arises from more calibration standards is the time it takes to analyze each standard.  It’s important to find a balance between the most accurate curve you can produce and managing the time restrictions inside your lab.

To deal with time restrictions and busy schedules, sometimes improving your accuracy might involve decreasing the number of calibration points.  (Cue massive shock and awe as I appear to contradict everything I’ve said up to this point! 😊)

Let me give you an example.  Suppose you run 10 calibration standards….but because it takes several hours to build that impressive calibration curve you only calibrate your instrument every other month.  By the end of the second month, how true do you think those 10 data points are….I would argue they probably aren’t accurate anymore.  Instead, what if you ran 5 points once a week, or 3 points every day??  A smaller, more current curve will almost certainly produce more accurate data.  In the world of the laboratory, accuracy is the name of the game!

So, you’re staring at a list of calibration standards and you find yourself wondering, “How do I figure out what to order?!”

A good rule of thumb is that your calibration standards should “hug” your expected value.  For example, if your anticipated answer is 3ppm, you wouldn’t want to make a curve using points 0.5ppm, 1.0 ppm, and 1.5 ppm.  You also wouldn’t want to use standards that all have values above your expected answer….meaning that 5.0ppm, 8.5ppm, and 12.25ppm also wouldn’t make a good curve for a value of 3ppm.

For an expected answer is 3ppm, I might select standards with values of 1.0 ppm, 2.5ppm, and 5.0ppm.  Typically, the wider the range of expected answers, the larger the range of standards should be.  Remember, your values need to be hugged by calibration points, not left to fend for themselves on the outskirts of your curve.  Every once in a while you might have a stray value that exceeds the boundaries of your calibration points, and that’s fine….every once in a while!  On the day-to-day and with your typical samples though, your results will be most correct if they are contained within the confines of your calibration data points!

Next week will be, Part 3: How to Know if Your Calibration Curve is Correct.  It’s Big Bang  Theory-themed so be sure to keep your eyes peeled for that!  In the meantime, if you have any questions about this week’s post or any ideas for future posts but sure to leave a comment and let me know!

Sore Fingers and Stocked Freezers

The flip flops have been exchanged for Ugg boots, and cold weather is here to stay for the next several months.  As much as I’ve complained about the looming cold weather’s effects on my Summer garden, the dip in temperatures has given me an opportunity to practice one of my favorite Fall activities…..

Squirreling everything possible away like a crazy and deranged food hoarder!

I have no idea why, but I love getting everything squared away for winter.  I guess it’s just nice to make the best use of everything.  Somewhere between Labor Day and Halloween I start to act like an old time-y prairie grandma, and I feel an overwhelming responsibility to “put everything up” for the winter…..and I don’t feel bad about that at all!

One of my least favorite tasks of pre-winter hoarding is sorting out all the herbs.  It’s easy, and so important because I do cook with them all winter long, but it does lead to cold, damp, and slightly sore fingers.  My preferred way of preserving my herbs is to freeze them.  It works quite well, and is faster than drying I think.  Plus, I have a secret tip that really saves a ton of prep work time when you need to use the herbs.

First, you’ll need to gather up all your herbs.  I had thyme, oregano, and cilantro that needed to be dealt with this year.  The cilantro was the easiest.  Just cut off near the soil, wash well, and freeze on a cookie sheet.  Once the cilantro is frozen, transfer to a freezer bag and try and remove as much air as possible.  Pull out as needed for Mexican nights or game day guacamole.  I find the beauty of freezing them is that they tend to behave very similar to fresh once you add them into recipes.

The thyme and oregano takes a bit more work, but it isn’t hard.  If you have a delicate, wispy thyme plant you might be able to get away with freezing everything whole.  I am apparently some sort of thyme miracle worker and managed to grow a small herb tree.  No one wants twigs in their tomato sauce, so I have to pluck all the leaves off the stalks.

I like to place a freezer bag into a quart sized, wide mouth canning jar, and then just strip the leaves off directly into the bag.  Pinch the base of each twig and gently pull towards the thinner end.  For large, multi branched stems you will need to probably pluck each stem singularly.  With a little practice and patience you should end up with a bunch of tiny thyme leaves in the bag and a garbage can full of naked….or nearly naked mini trees.  Close the bag, leaving some air in, and toss in the freezer.  Once the leaves have frozen, crumple them slightly to break them up and remove the air from the bag.

Follow the same process for the oregano as you do for the thyme.  Here comes the time saving secret!  Once the leaves have frozen…..give them a really good crumpling and crunching.  Ta da…..instant chopped oregano leaves!  Thyme is so small it doesn’t matter, but basil and oregano leaves can get quite large and in charge.  The post freeze crumple is much faster than chopping everything before freezing!

If you’re looking for a tasty and filling way to use up some of your frozen herbs, might I suggest Chicken Pot Pie Soup!  I made it this week and it was a massive success….AND I DON’T EVEN LKE POT PIES!

Soup is one of The Engineer’s favorites, and even though he would eat soup when it’s 100 degrees outside, I refuse to make it.  This chicken pot pie soup will certainly become a standard in our winter rotation, and it’s easy enough to whip up quickly on a school night!

Chicken Pot Pie Soup

• 8 oz butter
• 3 garlic cloves, minced
• 1 medium onion, chopped
• 1 cup flour
• 6 cups chicken stock
• 2 tbsp fresh frozen thyme
• 2 tbsp fresh frozen oregano
• 1/2 tsp cayenne pepper
• 1 pinch of ground nutmeg
• 1 large potato, diced
• 3 carrots, diced
• 2 cups half and half or milk
• 1 cup frozen peas
• 3 cups rotisserie chicken meat, cubed
• 1/4 pound deli ham. sliced
• salt and pepper to taste

In a large stock pot, melt the butter over medium heat.  Once melted, add the garlic and onion, cooking until fragrant and translucent.  Slowly add in the flour, whisking vigorously to form a smooth rue.  Cook the flour for a few minutes being careful to stir so the mixture doesn’t burn.  We need to cook out the raw flour taste, so just keep an eye on it and let it go a bit golden brown. Whisk the chicken stock into the rue being sure to get out any lumps.  Add the potato, carrots, and spices and cook until the veggies are tender.

Once you potato and carrot are tender, add the peas, ham, chicken, and half and half.  Drop the temperature to simmer, and just let everything warm through.

Serve up hearty bowls of this you’re sure to keep the chilly temps at bay.  For regular nights I would serve it up with a nice loaf of crusty bread for dipping.  Or, if you’re feeling extra fancy….or like me, you have some spare pie crust sitting in the freezer…..you can make some crust crisps to give it a more traditional “pot pie” feeling.

I just rolled my dough into a large rectangle, cut thin strips, and twisted into fun little pie sticks.  I topped with a bit of sea salt and baked at 375 for 20 minutes.  Some of them did come untwisted in the oven, but they were still flakey and delish!

Herby, warm, and delicious!

Changing of the Season

Here’s to hoping your shift into the Fall season has been less abrupt than ours.  It felt like we went from glorious, sunshiny days to sad, deary, and cold all overnight.  Such is life in the Midwest I suppose.  You’d think I would be used to it by now.  This week we are due to have a weather swing of more than 30 degrees!  It’s been chilly but since there is still tank top weather visible in the forecast I’m refusing to turn on the heat.

I’m honestly most upset about the toll the abrupt cold temperature swing is having on my garden.  My poor pepper plants all still have flowers on them!  I have little baby poblano peppers that almost certainly aren’t going to achieve their maximum potential….it’s so annoying!  Gardening season is over I suppose….time to harvest what I can salvage, dry all my herbs, and nestle in for winter!

This is so true….us Midwesterners know what’s up!

With the changing of the seasons comes a shift in activities.  Twice now I have insisted that The Engineer go apple picking with me!  Additionally, I’ve forced him to stand in front of many a pile of pumpkins while I attempt to select just the right shaped pumpkin for the front porch!  I don’t even generally decorate for fall….why do fall when you can skip straight to Christmas right?!  Something just has me in the mood to switch it up this year I guess.

Would you just look at that?!  Perfectly picked pumpkins, squash, and corn cobs! 🙂

If you pick the apples, you’ll need to do something with the apples.  Nothing will make your house seem warm and cozy….even if the heat isn’t on yet…..than making apple butter!  I hadn’t ever tried my hand at apple butter previously, but I’ve whipped of several of these batches, and I’ve even had it taste tested by several friends and coworkers.  The results have been an overwhelming success, and it honestly doesn’t get much easier than this recipe!

This first batch of apples was a variety called Cortland…I’m not sure why my bag says mix.

Before I get into the recipe I have an important public service announcement to make!

In case you find yourself preparing to go apple picking and looking up recipes wondering, “How many apples do I need for all this festive, fall fun-ness!?”  Well let me give you a list of what 1 peck of apples will get you.  For those of you not super up on your apple picking terms and quantities….1 peck is roundabout 10 pounds!

From my first peck of apples I made:

• Nearly 2 full batches of apple butter….the second batch was maybe 5 apples short of full
• 12 caramel apple and pecan pasties
• 2 quarts of apple pie filling
• Random apples for raw eating throughout the weekend

I now return you to your regularly scheduled recipe post!

Apple Butter

Ingredients

• Apples
• Brown Sugar
• Cinnamon
• Nutmeg

Supplies

• Crock Pot
• Immersion Blender — if a smoother texture is desired

Directions

Wash, core, and simply rough chop your apples into bite sized pieces.  Fill your crock pot until the very top and you can just get the lid on.  We have a two crock pots, but I used our smaller 4 quart sized pot.  The measurements are relative to that, but feel free to make more or less to suit your needs.

Place the lid on your crock pot and let cook on Low for about 12 hours.  I started mine in the evening and just let it go to town all night long.  There’s no need to add any liquid to the apples!

After 12 hours, stir your apple mixture.  It will be very soft and broken down on the bottom, the top apples might still be a bit firm, depending on how large a batch you’re working on.  To you apple mush add 1 cup loosely packed Brown Sugar, 1 tbsp Cinnamon, and 1/4 tsp Nutmeg.  Again, this is for 4 quarts of fairly tangy apples.  I like to taste the tang in the finished product, but if you like it sweeter feel free to adjust to your own personal tastes.

Recover you crock and let everything stew and simmer together for another 3-5 hours.

After this second cooking, if the mixture is still looking chunkier than you’d like, use an immersion blender, or regular blender, to make a smoother texture.  If you don’t mind it a bit chunky, just skip that step.  I’ve done both and it all comes out just fine, just what you prefer.

If canning, place your mixture into clean, half pint jars.  Process in a water bath for 10 minutes and let rest over night to seal.

4 quarts of apples gave me 4 half pint jars plus a few extra tablespoons to enjoy on the fly!

I didn’t freeze any myself, but my coworker always freezes her.  Bag or place in portioned containers to freeze and enjoy at a later date!

I’ve Got A Brand New Blog

I was asked to start writing a science blog for work.  I’m not sure how much interest there will be, or how interested any of my current readers might be in this info, but I thought I might start sharing them here as well.

A few fun facts and some science knowledge never hurt anyone after all!  Currently, the plan is that I’ll post for work weekly.  That might taper off, but we have some events coming up and we wanted to drum up some interest and talking points with some customers before the events.  I will also be keeping up on my “personal” blog posts….which I have been bad about but hopefully all of this extra blogging will keep me on a schedule!

So….without further ado….I present my new blogging topic–

Common Calibration Conundrums and Other Laboratory Queries

Hey!

I’m coming at you to discuss some common science questions and issues I get asked in the lab frequently.  I thought I would start with a little mini-series on calibration issues, and then hopefully we can move on to other issues and questions you face in the lab on a daily basis.

If there is a specific topic or question you liked me to address, just leave a comment on this post and I’ll get back to you!

Part 1: When to Calibrate

You should calibrate as often as practically feasible for your laboratory process and timelines!  It will not hurt your instruments to calibrate them too often, but it will hurt your results if you do not calibrate often enough.

I know you might think that calibrating often is a waste of time…….and you’re busy…and the plant operators want their results…and the results seem fine so you’ll just ignore recalibrating your instruments until something bad happens.

Just take a minute and think about all the parameters around your instruments that change….even weekly.

Did you consider factors like-

• Did you change mobile phase?