Analyses plan Module 19

1
Analyses planModule 19

• Major base cations to be determined by ICP-AES
• Conductivity and temperature
• H determined using pH electrode
• Al fractionation
• Major anions to be determined by IC
• Use of auto-pipettes
• Total organic carbon
• UV and Vis absorption

2
Conductivity

• Master student lab V160
• 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

• Analytical Chemistry lab Ø109
• 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 base cations to be determined by ICP-AES

• Ca2, Mg2, Na, K
• Method will be demonstrated in Module 24
• Appropriate calibration solutions are prepared by
  Masha
• Conducted by Anne-Marie Skramstad

5
Major anions to be determined by Ion
Chromathograph (IC)

• Analytical Chemistry lab Ø109
• Tot-F, Cl-, NO3-, SO42-
• 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 is and accompanied H
  or OH- in the eluent stream is measured by means
  of a conductometer
• Presented by Hege Lynne et al

6
Total organic carbon

• Analytical chemistry lab Ø 104
• High temperature (680C) 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 av IR detector
• Presented by Hege Lynne et al.
• Analytes measured may include TC, IC, TOC, NPOC,
  and POC

7
Al fractionation

• Master student lab V160
• Method presented as example in Lecture 1 (slide
  15)
• Download manual from
• http//folk.uio.no/rvogt/KJM_MEF_4010/

8
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/

9
Speciesin natural freshwater Central
equilibriums in natural water samples

• KJM MEF 4010
• Module 19

10
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

11
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
• Al3aq denotes Al(H2O)63

12
Concentrations of dissolved Fe3 speciesTwo
total Fe concentrations, FeT 10-4M and FeT
10-2M
13
Dissolved Organic Matter

• Low molecular weight (LMW)
• lt 1000Da (e.g. C32H80O33N5P0.3)
• E.g.
• High molecular weight
• 1000 - gt 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

14
Concentrations and activities
15
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 I0.1
n1
n2
n3
n4

• ? ?? when I ? 0 ? ? 1 when Ilt10-5M

Anions cations
16
Debye Huckel (DH) equation

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