what is a chemistry standard?

Question

I am trying to understand the difference between standards and controls that are used in a chem lab

Answer 1

A standard solution is one that has been very carefully analyzed and characterized, usually by means traceable to a central standards bureau, such as NIST, so that the value is well known and can be trusted for instrument calibrations and methods development.

A control sample uses known quantities of an analyte (it may be a standard, but does not have to be) so that analytical chemists can confirm that their processes are accurate and precise.

For example, I might have a standard buffer solution that I use to calibrate a pH meter on a regular basis, say daily. Then, during each day, as I run dozens or hundreds of pH readings, I will periodically (say, once ever 20 tests), run a control sample through to make sure my readings are still in line with what I'd expect. This gives the customer more confidence that the readings really match the real world situation.

Hope that helps.

Answer 2

In our lab a standard is a purified known compound we use to compare and relate to a substance found in a sample. For instance we would record data for standard (ie UV-VIS) and compare that data against data recorded for a sample. Say we were looking for acetominophen in a blood sample, we would first analyze pure acetominophen (which you can buy from chemical companies. Aldrich, etc) and then analyze the sample and compare the data.

We use controls, ie negative controls, positive controls to test our methods. For instance if we are looking for acetominophen in a blood sample, there is usually some sort of extraction that is associated with the procedure to isolate the drug. We would use a control sample in which we follow the exact procedure as we would to the live sample to verify that none of the chemicals (extraction agent, buffers, etc) contained any drug. Controls are just a way to validate the work done on a sample.

Positive controls are also used quite often. Usually when someone is looking for a particular drug they also want to know how much is in there. So, a calibration curve is created in which a standard in a spiked in blank blood at different levels. The signal response is assumed linear and the concentration of the drug that is being tested can be calculated. Positive control samples are samples in which you spike a known amount of drug ie 5mg and then calculate that amount based on your calibration curve to verify that you can calculate a known amount of drug correctly.

Sorry this is so long, but i think I covered most of the question.

Its true you can't calibrate a standard...standards are used to calibrate instruments or measuring devices.

Answer 3

standards are run lots and lots of times and are calibrated.

controls are run normally with the sample so you have an idea of how the process went. ie if you're testing for inhibition you test something that will have none so you know how good your compound functions.

Answer 4

Shiara is incorrect. Technically speaking, you cannot calibrate a standard. I agree with all other comments, though.