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Topic: What is an instrument blank?  (Read 295 times)

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Offline heyman

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What is an instrument blank?
« on: March 06, 2020, 12:18:27 AM »
I'm having trouble finding a definition for a instrument blank. My assumption is that it is simply running the instrument with no sample at all. Correct me if I'm wrong. Is it similar to an equipment blank?

Offline shchavel

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Re: What is an instrument blank?
« Reply #1 on: March 06, 2020, 08:06:12 AM »
Hello, the principle is right.
What kind of equipment do you use?

Offline heyman

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Re: What is an instrument blank?
« Reply #2 on: March 06, 2020, 09:36:37 AM »
It's just some terminology I'm learning for my analytics class. It's in relation to GC-MS, AES, XRF etc.

Offline Babcock_Hall

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Re: What is an instrument blank?
« Reply #3 on: March 08, 2020, 11:45:45 AM »
I would defer to a card-carrying analytical chemist for what is the correct definition, and my answer is based on how it is used in casual conversation.  In my experience the term blank can have more than one meaning, even just in UV/VIS spectrophotometry (the technique I use most frequently).  It can mean the same thing as a reference, which is a cuvette with just solvent that sets the absorbance to zero.  Or it can mean a solution in which everything is present except the analyte, in which case the absorbance is not necessarily zero.
« Last Edit: March 08, 2020, 12:03:28 PM by Babcock_Hall »

Offline Corribus

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Re: What is an instrument blank?
« Reply #4 on: March 09, 2020, 09:30:16 AM »
When using an instrument to make a measurement, there are basically two sources of uncertainty: those that come from samples and those that come from the instrument itself. An instrument blank is just a blank that is used to determine the noise level of the measurement that is contributed from the instrument. A method blank is usually the same substance as an instrument blank (i.e., just solvent) but it is carried through the entire sample preparatory and possibly experimental process. You might properly call an instrument blank just a blank, and a method blank a negative control, or some such. The reason this is done is to distinguish between the instrument detection limit (IDL, the basic noise level of the instrument) and the method detection limit (MDL, the effective noise level that takes into account contributions not due to the instrument itself - e.g., laboratory contamination). Knowing both of these values can help the analyst track, and find ways to mitigate, different sources of error in their measurement. E.g., if the MDL and IDL are very close, it tells you that your laboratory procedures are very good and your measurement is as close to "perfect" as you can get it without buying a better instrument. On the other hand, if the MDL is considerably higher than the IDL, then you know there are significant sources of error or contamination due to your procedures, and so your method can be improved without investing in newer equipment.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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