Automatic Calibration of Analytes using a Combination of Inline Dilution and Subsequent Inline Ultrafiltration

Metrohm inline sample preparation (MISP) is a versatile collection of cost and time-effective techniques that reduce manual sample preparation. This article discusses a combination of inline dilution and subsequent inline ultrafiltration which allows automatic dilution and subsequent filtration of samples before injection.

MagIC Net allows intelligent dilution to be run by checking results and the sample to be re-diluted if the result is not within the calibration range. In addition, the stock standard solution is automatically diluted for multipoint calibration. As a result, each analyte can be automatically calibrated effectively.

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Mixed standard stock solution (1000 mg/L of each anion)

Sample preparation

Metrohm inline dilution technique (MIDT) followed by Metrohm inline ultrafiltration.


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Metrosep A Supp 5 - 100/4.0 6.1006.510
Metrosep A Supp 5 Guard/4.0 6.1006.500


Eluent 3.2 mmol/L sodium carbonate
1.0 mmol/L sodium hydrogen carbonate
Suppressor regenerant 100 mmol/L sulfuric acid
Rinsing solution STREAM


Conductivity detection following the sequential suppression.


930 Compact IC Flex Oven/SeS/PP/Deg 2.930.2560
IC Conductivity Detector 2.850.9010
858 Professional Sample Processor 2.858.0020
800 Dosino 2.800.0010
741 Magnetic Stirrer 2.741.0010
IC equipment: Inline Dilution 6.5330.120
IC equipment: Inline Ultrafiltration 6.5330.130
MSM Rotor A 6.2832.000
Adapter sleeve for Suppressor Vario 6.2842.020


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Flow rate 0.7 mL/minutes
Injection volume 20 μL
Pmax 15 MPa
Recording time 11.5 minutes
Column temperature 45 °C
Final dilution volume 7 mL


Stock standard solution 50.0 mg/L of chloride, nitrate, and sulfate each
Dilution factor Calibration level
Calibration level Dilution factor Concentration
Level 1 1 50.0 mg/L
Level 2 2 25.0 mg/L
Level 5 5 10.0 mg/L
Level 10 10 5.00 mg/L
Level 20 20 2.50 mg/L
Level 50 50 1.00 mg/L

Setup Scheme

The installation is carried out in accordance with the AB 376 ProfIC Vario 6 Anion.


Anion Calibration
RSD [%]
Corr. Coeff.
Dilution 1:50
RSD [n = 10, %]
Dilution 1:50
Recovery [%]
1 Chloride 1.423 0.99996 2.18 101.1
2 Nitrate 2.128 0.99992 1.88 102.5
3 Sulfate 1.536 0.99995 1.42 100.6

This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.

For more information on this source, please visit Metrohm AG.

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