Bracketing Technique

The ICP Expert software does not have a bracketing option on the standards page, however, you could try unchecking "Include blank in calibration" and then enter your standards as Calibration Standard 1 and Calibration Standard 2. 

I used bracketing techniques a lot when I worked in a reference method lab in the past, to target Cl, Na, K, ca ...

You need to calculate manually. run a lower std first which is just below your unknown's conc, then run your unknown, then run the higher std which is just above your unknown's conc.

Then enter the three signals and your two std concentrations into excel, then create a correct formula in the cell for unknown's concentration. 

This bracketing technique is the most accurate way to target your unknown as long as your stds are prepared preciously and accurately. It minimizes the effect of fluctuations and drifts of the instrument on your unknowns. 

Once you developed the cal formula in your excel, you can quickly calculate any  unknowns which are tested right between two stds.

It's a technique used in reference labs which are credentialed to assign target values for the manufacturer's calibrators, but slow and "tedious" not applicable for commercial labs.

Here is the calculation examples.

But you need to screen unknown first to get the idea of the general conc. in order to select the best 2 bracketing std.

The cal formular should be: Unknown Conc. = (CPSunknown -CPSstd1)/(CPSstd2-CPSstd1)*(CONC std2-CONCstd1)+CONCstd1

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