Problems with the measurement of NH 4 with Ion Chromatography

Transcription

1 Meeting of the heads of the Labs 17./18. September 2015, Vienna (Austria) Problems with the measurement of NH 4 with Ion Chromatography Nils König Northwest, Göttingen a. Instrumentation, software b. Calibration, detection and quantification limit c. Integration of the NH 4 peak d. problems

2 a. Instrumentation, software detectorcontrolling pumps sampler

3 a. Instrumentation, software 6-way velve detectors column oven columns Suppressor

4 waste D-K sampler 6V waste F RP A K Su D-A F F K-El P Dä Degas 6V P A-El P Dä F waste RP H 2 SO 4 H 2 O

5 a. Instrumentation, software instruments: 820 IC Separationscenter 833 IC Liquid Handling Unit Suppressor 819 IC Detector 818 IC Pump 837 IC Degaser 838 Advanced Sample Processor 853 CO 2 Suppressor columns/sample loop: cations: Metrosep C3-250/4.0 with pre-column and guard and 50µl sample loop anions: Metrosep A Supp with pre-column and guard and 20µl sample loop (detector temparture: 35 Grad) Eluents: Eluent cations: 0,005 ml HNO 3 /Liter Eluent anions: 678 mg (3,2mmol/l) Natriumcarbonate + 84 mg (0,5mmol/l ) Natriumhydrogencarbonate /2 Liter Suppressor-Lösung: 6 ml H2SO4 mit 5,04g oxalic acid ( 20 mmol)/ 2 Liter

6 a. instrumentation

7 a. Instrumentation, software 4-chanel - system anions, low range anions, high range cations, high range cations, low range

8 b. Calibration, detection and quantification limit calibration for NH 4 Low range High range Linear regression Linear regression µg/l µg/l

9 b. Calibration, detection and quantification limit Calibration for NO 3 anions, low range anions, high range linear regression quadratic regression

10 b. Calibration, detection and quantification limit cations, 2 ppm

11 b. Calibration, detection and quantification limit cations, 0,1 ppm

12 b. Calibration, detection and quantification limit Element NH4 IC 1 detection limit IC Ordnung ppm Cs Eingabebereich: Blindw.Methode Kalib.Methode Nr. Blindwerte Kalibrierung Signal Konz. µg/l mittl. Blindwertsignal: 0, ,166 0,005 Standardabw 0, ,417 0,01 N 10, ,585 0,015 t(f=n-1,n-2;p=99% einseitig) 2,821 2, ,81 0,02 t(f=n-2, P=99% zweiseitig) 3, ,034 0,025 Nachweiskrit. 0,000 0, ,263 0, ,451 0,035 Detection limit, XN 0,000 0, ,69 0, ,898 0,045 Erfassungsgrenze 0,000 0, ,116 0,05 Quantification limit, XB 0,000 0,007

13 b. Calibration, detection and quantification limit Bestimmungsgrenze Nachweisgrenze Prüfmethode Einheit Prüfmittel 0,004 0,001 ClClIC2.1 mg/l IC2.1 0,007 0,002 FFIC2.1 mg/l IC2.1 0,024 0,007 KKgesIC2.1 mg/l IC2.1 0,007 0,002 NaNagesIC2.1 mg/l IC2.1 0,007 0,002 NNH4IC2.1 mg/l IC2.1 0,004 0,001 NNO2IC2.1 mg/l IC2.1 0,005 0,001 NNO3IC2.1 mg/l IC2.1 0,009 0,003 PPO4IC2.1 mg/l IC2.1 0,007 0,002 SSO4IC2.1 mg/l IC2.1

14 C. Integration of the NH 4 peak problem peak integration Na NH 4

15 d. Problems problem NH 4 : In the smal tubes from the sampler to the column fungi are growing! They eat ammonium! Too low results!!! Cleaning of the tubes with HNO3 and /or H2O2

16 d. Problems b. Pollution of the 6-way velve

17 d. Problems b. Pollution of the 6-way velve

18 F. Probleme, Chemische Störungen b. Pollution of the 6-way velve black: Before cleaning blue: After cleaning

19 d. conclusion: - Ion chromatography is a very sensitive detection method for anions and cations. - The detection limit is lower than with photometric methods. - For good results for NH 4 you need to work very clean (fungi problems).