1 / 17

Analyses plan Module 19

Analyses plan Module 19. Conductivity and temperature {H + } determined using pH electrode UV/VIS MAS Sample pre-treatment Sample filtration Total organic carbon Major anions and cations to be determined by IC UV oxidation. Conductivity.

zwi
Download Presentation

Analyses plan Module 19

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Analyses planModule 19 • Conductivity and temperature{H+} determined using pH electrode • UV/VIS MAS • Sample pre-treatment • Sample filtration • Total organic carbon • Major anions and cations to be determined by IC • UV oxidation

  2. Conductivity • Ecoscan Con5 (Eutech instruments) conductivity meter. • The instrument is calibrated using 1000 and 1433 µS calibration solutions • The measurements are done for quality control purposes in order to compare measured and calculated conductivity

  3. {H+} determined using pH electrode • Thermo Orion model 720 pH-meter with a Blueline 11-pH electrode. • The pH-meter is calibrated with pH = 4.00 and 7.01 buffer solutions

  4. Major anions and cations to be determined by Ion Chromatograph (IC) • Principle • The sample is injected in a flow of eluent • The analyte ions are separated by different degree of binding to the active sites on the ion exchange material • Ions with opposite charge of the analyte is exchanged with H+ or OH- • The activity of the analyte along with H+ or OH- in the eluent stream are measured by means of a conductometer

  5. Total organic carbon • Analytical chemistry lab Ø 104 • High temperature (680ºC) catalytic combustion analysis on a Shimadzu TOC-5000A instrument • Principle: • The organic carbon is combusted to CO2 by high temperature and catalysis. The amount of CO2 produced is measured using an IR detector • Analytes measured may include: TC, IC, TOC, NPOC, and POC

  6. Al fractionation • Fractionation of monomeric aluminium from polymeric forms is accomplished by 20 sec. complexation with 8-hydroxyquinoline at pH 8.3 with subsequent extraction into MIBK organic phase • Organic bound monomeric aluminium is separated from inorganic aluminium (mainly labile) by trapping the latter fraction on an Amberlight IR-120 ion exchange column • The Al concentrations in the organic extracts are determined photometrically • Download manual from • http://folk.uio.no/rvogt/KJM_MEF_4010/

  7. P fractionation - The oxidation by UV is intended to mimic the photooxidation occurring in the lake during ice free season. - Filtration through 0,45μm filter (or rather 0,2μm) filter removes algae.

  8. P determination • - Orthophosphate reacts with ammoniummolybdate to a yellow-coloured phosphorousmolybdate acid, that is reduced with ascorbic acid in the presence of antimony to a strongly blue coloured complex. This colour is measured photometrically as described in Norwegian Standard (NS 4724).

  9. QC of data • After the analysis the data must be compiled and quality controlled by ion balance and agreement between measured and calculated conductivity • For this purpose you may use the Data compilation and QC worksheet available at http://folk.uio.no/rvogt/KJM_MEF_4010/

  10. Speciesin natural freshwaterCentral equilibriums in natural water samples KJM MEF 4010 Module 19

  11. Inorganic complexes • Major cations in natural waters • H+, Ca2+, Mg2+, Na+, K+ • Common ligands in natural systems: • OH-, HCO3-, CO32-, Cl-, SO42-, F- & organic anions • In anoxic environment: HS- & S2- • Dominating species in aerobic freshwater at pH 8 are:

  12. Hydrolysis • In aqueous systems, hydrolysis reactions are important • Hydrolysis reactions are controlled by {H+} • The higher the pH, the stronger the hydrolysis of metal cations • E.g. Aluminium • Al3+aq denotes Al(H2O)63+

  13. Concentrations of dissolved Fe3+ speciesTwo total Fe concentrations, FeT = 10-4M and FeT = 10-2M

  14. Dissolved Organic Matter • Low molecular weight (LMW) • < 1000Da (e.g. C32H80O33N5P0.3) • E.g.: • High molecular weight • 1000 - > 100 000Da • Humic substance • Very complex and coloured substances • Enhances weathering • The protolyzation of weak organic acids • Complexation of Al and Fe • Total congruent dissolution

  15. Concentrations and activities

  16. Activity • {X} = X · [X] • {X} is the activity to X • [X] is the concentration to X • X is the activity coefficient to X • X are dimensionless • It is determined by: • The diameter (å) of the hydrated X • Its valence (nX) • The ionic strength (I) Not possible to calculate further than I=0.1 n=1 n=2 n=3 n=4 •   when I  0 1 when I<10-5M Anions + cations

  17. Debye Huckel (DH) equation • For ionic strengths (I) < 0.1M the X can be calculated by means of e.g. the Debye Huckel equation: I < 0.1 I < 0.005 because • 0.5 & 0.33 are temperature dependent table values • Presented values are for 25°C • åX is a table value for the specie in question

More Related