High Concentration calculations on Na when the signal intensity for the sample is higher than the blank?

Hi all -

 

I am very new the ICP-OES analysis and I am very confused by the values that the Agilent software is calculating. I prepare samples with a 100 fold dilution (I am running in organic solvent not aqueous) and for my samples I am getting signal intensities that are smaller than the blank or any of the calibration standards, but then it is calculating my final concentration as really high. I do not understand how this can be. Any advise would be appreciated. Thank you!

  • On the sequence tab, did you put a dilution factor in the table? If so, then your values are getting multipled. What instrument do you have?

  • It sounds like sodium contamination from maybe the acids or something in your prep maybe?  Are you storing your solutions in HDPE, Teflon, or borosilicate glass? What acids are you using in your digestion?  Have you checked the cooled cone interface and injector tube to make sure there is no sample residue?

  • I understand that the values are getting multiplied - I deal with dilution factors on a daily basis with the chromatography work I do. What I do not understand is why my Na intensities in my samples are falling well below the Na intensity of my blank or lowest concentration standard how to troubleshoot  why this is happening. From what I have been able to diagnose is that the blank Na intensities have gone from close to 0 to 10,000 in the course of a month. I have been systematically going through the system and cleaning and replacing items as needed.

  • This question has been marked as assumed answered.

  • Is your sample uptake time, peristaltic tubing and pump speed the same for your standards as it is for your samples? Are they diluted into the same matrix? These need to be uniform across all - perhaps check in your method that everything is consistent. Also be wary of which Na wavelength you are using - some are more temperamental than others. Run a few together to see if one is more suited to the samples and standards you are using. 

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