External Calibration, Internal Calibration, Spike

Basic questions from students; resources for projects and reports.

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What is the difference between external and internal calibration. How would i perform these with soils containing hydrocarbons.

How would i spike a soil sample containing hydrocarbons. Do i use my calibration standards to spike it. Or its a different solution. Thank you
Your question implies GC, but these articles (links) will answer most of your questions.

External (ESTD) vs. Internal Standard (ISTD) Calibration in HPLC [ https://hplctips.blogspot.com/2014/03/e ... ndard.html ]

Internal Standard (ISTD) HPLC Calculation Notes
[ https://hplctips.blogspot.com/2016/02/i ... ation.html ]
For spiking your soils, spike with your standard so you know the mass of analyte you spike and the mass of the sample. Such that 0.1ml of 10ug/ml standard would be 1ug of analyte, spiked into soil of 30g would give you a soil concentration of 1ug/30g or 33.3ug/kg of soil. (values are examples, just use whatever your actual values are for the process)

When you do the analysis you subtract any concentration found in the sample from the concentration found in the spiked sample, then compare it to what the known value should be and you have percent recovery.

The difference in external standard and internal standard is whether or not you are comparing the concentration/area of the analyte to that of another spiked internal standard analyte. The links in the last post will explain it in detail.
The past is there to guide us into the future, not to dwell in.
Thank you for all your help

For spike do you mean spike it with the stock calibration solution or make a new spike solution out of stock solution? I am just so confuse of what should i spike my soil with. Thank you
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