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- Posts: 1
- Joined: Tue Jun 21, 2016 10:04 am
I am a new user to IC and I'm currently trying to commission a metrohm 930 IC compact. Using a Metrosep A Supp 5 - 150/4.0 with guard & suppression & ultrafiltration.
I have had a bespoke mix made by two different manufacturers which contain 1000ppm of F, Cl, NO2, Br, NO3, PO3 & SO4.
I have created a Hi-lo cal the lo range comprises 0.1, 0.25, 0.5, 0.75 & 1pmm stds.
The hi range comprises 1, 5, 15, 30 & 50 ppm stds.
All are made up to 100ml in grade a volumetrics.
For the 50ppm std l take 5ml of the 1000ppm mix upto 100ml for my 50ppm using a calibrated 5ml rainin electronic pipette, the 3ml for the 30ppm std, 1.5ml for the 15ppm std etc.
For my lo range I take appropriate dilutions upto 100ml in grade A volumetrics using my 50ppm std prepared earlier.
I repeat this for my std checks.
I can get what I have been told are good calibration slope. RSD 0.5-2% with an r value of 0.9999
The issue is the accuracy I see on the std checks is poor 80-120%. PO3 NO2 & NO3 being the worst.
Can anyone advise if this is normal. Am I expecting too much. Is my cal range to wide, too many points, too many analytes?
I use fresh demin water each preparation and I'm following metrohms mainatenance schedule closely.
Any help gratefully received.