Method for Nitrate Determination by Cadmium Reduction, Version 2.3

Transcription

1 Methd fr Nitrate Determinatin by Cadmium Reductin, Versin 2.3 PRINCIPLE This methd is designed fr the determinatin f nitrate in sil, water, and ther frms f samples. The sample is prepared ffline if necessary and then intrduced t the FIAlab analyzer. Nitrate is reduced t nitrite via a cadmium clumn placed n the instrument. The nitrite is then reacted with sulfanilamide and cupled with N- (1-Naphthyl) ethylenediamine dihydrchlride t frm a magenta clred az dye. This methd is designed t be run n the FIAlyzer-1000 r the FIAlyzer-FLEX. SUMMARY This methd is designed fr the determinatin f nitrate in samples f varius matrices. The methd is capable f detecting nitrate in the range f mg N-NO 3 / L. Fr mre infrmatin, see the sectin n perfrmance metrics. SAFETY The txicity r carcingenicity f all reagents used in this methd must be taken int accunt and therefre each chemical listed belw shuld be handled accrdingly. Each labratry is respnsible fr maintaining cmpliance with OSHA regulatins regarding the safe handling f the chemicals specified in this methd. Material Safety Data Sheets (MSDS) shuld be made available t all persnnel using the methd. All waste materials shuld be dispsed f in a respnsible manner, in accrdance with federal, state, lcal, and any ther applicable regulatins. The fllwing chemicals have the ptential t be highly txic r highly hazardus; fr detailed explanatins cnsult the MSDS: Phsphric Acid Cadmium Sdium Hydrxide Cpper (II) Sulfate Page 1

2 EQUIPMENT AND SUPPLIES Equipment: Balance, analytical, with a 0.01 g reslutin ph meter, accurate t 0.1 ph Pipettes fr making standards Glassware: Class A vlumetric flask, 1L, QTY 2 Graduated cylinder, 100mL, QTY 1 Glass strage cntainer, 1L, clear, QTY 2 Glass strage cntainer, 1L, brwn tinted, QTY 1 Autsampler (fr high sample lads): Cetac ASX-280/560 (recmmended) r AIM-3200/3300 Page 2

3 REAGENTS AND STANDARDS Chemical part numbers refer t Sigma-Aldrich unless nted therwise. Chemical Chem. Frmula CAS# Supplier PN Deinized Water H 2O Ammnium Chlride NH 4Cl EDTA, disdium frm C 10H 14N 2Na 2O 8 2H 2O E4884 Sdium hydrxide NaOH Brij L23 Slutin (30%) C 12E B4184 Sulfanilamide H 2NC 6H 4SO 2NH S % Phsphric acid H 3PO N-1-Naphthylethylene diamine C 10H 7NHCH 2CH 2NH 2 2HCl dihydrchlride Cpper (II) sulfate pendahydrate CuSO 4 5H 2O C7631 Preparatin f Reagents Carrier: Matrix match carrier t samples. Salt slutin t seawater samples, extractin slutin fr sil samples, etc. Reagent 1: Ammnium Chlride Buffer (1 L) Disslve 86g f ammnium chlride in 800 ml f deinized water. Add 1.0g f disdium EDTA. Adjust the ph f this slutin t 8.5 +/ using sdium hydrxide pellets as needed (apprximately 3.5 g). Add 0.5mL f 30% Brij L23. Mix until disslved. Fill cntainer t 1 L mark using deinized water. Mix well and stre in a glass bttle. The reagent shuld be clear with n particles in it. Reagent 2: Sulfanilamide Slutin (1 L) Mix 100ml f 85% phsphric acid int 800 ml f deinized water. Disslve 40g f sulfanilamide and 1.0 g N-1-Naphthylethylene diamine dihydrchlride t this slutin. Add deinized water t a ttal vlume f 1 L. Mix well and stre in a dark glass bttle. The reagent shuld be clear r very faintly pink with n particles in it. Prbe Wash Slutin: Water with 0.1% Brij L23 (1L) Add 3.3mL Brij L23 t 800mL f deinized water, dilute t 1L. Mix well and stre in a plyethylene bttle. The wash slutin shuld be clear with n particles in it. Page 3

4 Tips n Prlnging Cd Clumn Life [Optinal] CuSO 4 t Reagent 1: Prepare 2% CuSO 4 slutin by additin f 10 g CuSO 4 5H 2O t 500 ml DI water. Add 2 ml f 2% w/v CuSO 4 slutin per 1 L f R1 slutin. Degassing Carrier and Reagent 1: Degas Carrier and Reagent 1 daily. If helium is available, sparge the slutins fr ne minute (apprx. 20 psi sparging pressure). If helium is nt available, apply vacuum until slutin bubbles fr ne minute. Nte that plastic bttles are gas permeable. Use glass cntainers. Ntes n reagent shelf life: Use f high quality labratry glass bttles is imprtant. Reagent 1 shuld be prepared every twelve weeks. Reagent 2 shuld be prepared every fur weeks. CuSO 4 slutin, if used, shuld be prepared every twelve weeks. Preparatin f Standards Dilute 1000 mg/l N-(NO 3) stck slutin with carrier t the desired range f nitrate standards. SAMPLE COLLECTION AND PRETREATMENT This prtcl nly cvers the analysis prcess. Sample cllectin and pretreatment depends n the type f sample and will have t be determined separately. Page 4

5 INSTRUMENT SETUP MID-RANGE Flw injectin analysis apparatus parameters: Cmpnent Specificatins FIAlab PN Analyzer FIAlyzer-1000 r FIAlyzer-FLEX flw injectin analyzer *Inquire Spectrmeter FLAME-T-VIS-NIR Spectrmeter nm Light Surce HL-2000-LL. Tungsten-halgen, nm Peristaltic Pump Tubing 1.02mm ID (white/white) *Inquire Sample Injectin Lp 35µL 3.0in/7.6cm f Tefln capillary tubing with *Inquire 0.03in/0.71mm ID Reactin cil 1 Cadmium clumn Reactin cil 2 750µL 65in/165cm f Tefln capillary tubing with in/0.76mm ID SMA-Z Flw Cell 10mm light path Sftware parameters: Parameter Value Pump Speed 60% Primary Spectrmeter Wavelength 540nm Secndary Wavelength (ptinal fr extended upper range) 600nm Reference Wavelength 650nm Fig. 1- Flw schematic fr nitrate determinatin. Page 5

6 FIASOFT METHOD The prgram script using an autsampler is shwn belw. Fr manual sample intrductin see the FIAsft manual. Nitrate Methd Script FIAlab Injectin Valve Sample Lad Message Turn On Cadmium Clumn FIAlab Peristaltic Pump CunterClckwise(%) 60 Autsampler Wash Next Sample Delay (sec) 60 Lp Start Autsampler Wash Analyte New Sample Next Sample FIAlab Injectin Valve Sample Inject Delay (sec) 3 FIAlab Injectin Valve Sample Lad Spectrmeter Reference Scan Spectrmeter Absrbance Scanning Delay (sec) 30 Spectrmeter Stp Scanning Lp End Autsampler Rinse Delay (sec) 60 Autsampler Wash Delay (sec) 30 Autsave Data C:\Users\FIAlab\Desktp\Autsave Data\DateTime FIAlab Peristaltic Pump Off Page 6

7 PERFORMANCE METRICS Fig. 2 Example plt and calibratin data fr nitrate. Lwer limit f detectin: 0.003mg N-NO 3 / L 4.84*10-8 ml N / L Lwer limit f quantificatin: 0.008mg N-NO 3 / L 1.29*10-7 ml N / L Upper limit f detectin: 25.0mg N-NO 3 / L 4.03*10-4 ml N / L Sample thrughput: 100 samples / hur Startup + Calibratin: 10 minutes Shutdwn: 5 minutes Page 7

8 ALTERNATE CONFIGURATIONS Lw-Range Setup Cmpnent Specificatins FIAlab PN Sample Injectin Lp 140µL 12.0in/30cm f Tefln capillary tubing with in/0.71mm ID SMA-Z Flw Cell 100mm light path Lwer limit f detectin: 0.001mg N-NO 3 / L 1.61*10-8 ml N / L Lwer limit f quantificatin: 0.003mg N-NO 3 / L 4.84*10-8 ml N / L Upper limit f detectin: 1.0mg N-NO 3 / L 1.61*10-8 ml N / L Sample thrughput: 100 samples / hur Startup + Calibratin: 10 minutes Shutdwn: 5 minutes Page 8