Tuesday, May 12, 2009

Which electrode for which titration

Which electrode for which titration?

Titrant Specifics Electrode description* Order No. Reference Electrolyte Remarks

Aqueous acid/bases


Ecotrode Plus 6.0262.100 c(KCl) = 3 mol/L 6.2308.020
alkaline samples Unitrode6.0259.100

c(KCl) = 3 mol/L
6.2308.020


titrations performed at high temperatures Unitrode 6.0259.100

Idrolyte
6.2308.040


titrations with small sample volumes Combined LL micro pH glass electrode
OR
Combined flat membrane pH glass electrode

6.0234.100


6.0227.100

c(KCl) = 3 mol/L

6.2308.020

Shaft diameter 6.4 mm, minimal immersion depth; 10 mm

Shaft diameter 12 mm, minimal immersion depth; 1–2 mm

titrations in water with low conductivity

Aquatrode plus 6.0257.000

c(KCl) = 3 mol/L

6.2308.020

Typical application: water analysis - p&m value etc.

Perchloric acid

See AB 80 and Monograph"Non-aqueous titration of acids and bases with potentiometric endpoint indication" Solvotrode - combined LL pH glass electrode, ground-joint diaphragm (PCTFE) 6.0229.100 c(LiCl) = 2 mol/L in ethanol 6.2312.010

easy to clean sleeve diaphragm

IMPORTANT: When not in daily use, store in LiCI sat. in ethanol and soak membrane in distilled water before use. However, when in daily use, store in distilled water, so that only the membrane is immersed, not the diaphragm. Before the measurement lift the diaphragm sleeve slightly and allow a small amount of electrolyte to flow out. Rinse the electrode with distilled water, replenish the reference electrolyte and start the titration (see bottom of chart).

IMPORTANT: Never fill the Solvotrode with LiCIO4 in glacial acetic acid!

TBAOH

See AB 80 and Monograph"Non-aqueous titration of acids and bases with potentiometric endpoint indication" Solvotrode - combined LL pH glass electrode, ground-joint diaphragm (PCTFE)
6.0229.100

c(TEABr) = 0.4 mol/L in ethylen glycol1

6.2320.000

Potassium methylate


Solvotrode - combined LL pH glass electrode, ground-joint diaphragm (PCTFE)

6.0229.100

c(TEABr) = 0.4 mol/L in ethylen glycol1
6.2320.000

Cyclohexyl-amine


Solvotrode - combined LL pH glass electrode, ground-joint diaphragm (PCTFE)
6.0229.100

c(LiCl) = 2 mol/L in ethanol 6.2312.010


Silver nitrate

AB 25

Ag-Titrode, possibly Ag2S coated

6.0430.100



arsenite, cerium sulphate, iron (III), iodine, potassium bromate, sodium nitrite, sodium thiosulphate, oxalic acid, permanganate, titanium

For titrations where the pH value during the titration doesn't change. Pt-Titrode
6.0431.100

Electrode is also available with a plug-in head S (6.0431.500 )
For titrations during which the pH value changes. Combined LL Pt-ring electrode 6.0451.100

c(KCl) = 3 mol/L

6.2308.020



Karl Fisher reagent


Double Pt-wire electrode

6.0338.100



Cr3+ , Fe2+,

Also for COD titrations Micro Au-Titrode 6.0435.110

L = 160 mm, Loger version available: (6.9904.023), L= 250 mm


EDTA

Back-titration of the BaCl2 excess. For sulphate determination see AB 140.

Polymer membrane electrode, Ca2+
6.0508.110

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order no: 6.0750.100

EDTA

Complexon® III and IV

Determination of Al, Ba, Ca, Cd, Bi, Co, Fe, Mg, Ni, Pb, Zn. See AB 125

Ion selective electrode Cu2+

6.0502.140

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order no: 6.0750.100
Determination of Ca, Mg, See AB 125

Polymer membrane electrode, Ca2+

6.0508.110



Surfactants in aqueous media

Tego® trant A 100,2
see AB 233

Ionic surfactant electrode
6.0507.120

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order No: 6.0726.100

sodium lauryl sulphate, see AB 233

«Cationic surfactant» electrode
6.0507.150

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order No: 6.0726.100

Sodium tetra phenyl borate, see AB 230, AB 263

NIO surfactant electrode
6.0507.010

Inner chamber of the reference electrode:
c(KCI) = 3 mol/L (6.2308.020)
Outer chamber: c(NaCL) = 1 mol/L

a separate reference electrode is needed.
Order No: 6.0726.107


Non aqueous surfactants

Nonaqueous media, solvents as Chloroform, MIKB, see AB 269

Surfactrode resistant
6.0507.130

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order No: 6.0726.107

electrode not suitable for high salt concentrations and pH > 10

Nonaqueous media, solvents as MIKB

Two phase titration, see AB 269

Surfactrode refill
6.0507.140

c(KCl) = 3 mol/L

6.2308.020

a separate reference electrode is needed.
Order No: 6.0726.107

electrode not suitable for Chloroform


AB = Application Bulletin

* All these electodes are equipped with a Metrohm plub-in head G3

1) TEABr 0.4 mol/L tetra ethyl ammonium bromide in ethylene glycol (6.2320.000) is an electrolyte solution for non-aqueous titrations. It is very useful when titrating low acid contents with TBAOH. In such cases the LiCI sat. in ethanol (6.2312.000) would cause an alkali error during the measurement. The Solvotrode is a combined pH glass electrode specially designed for non-aqueous titrations. This electrode is normally filled with LiCI sat. in ethanol. However, when titrating with TBAOH we strongly recommend replacing the CiCI electrolyte with 0.4 mol/L TEABr in ethylene glycol. This electrolyte can of course also be used for all other non-aqueous titrations with various titrants.

2) TEGO trant A 100
6.2317.000 (6 g)
6.2317.010 (60 g)
Available on request 6.2317.020 (500 g)

3 To connect an electrode with plug-in head G to a Titrino or 726/796 Titroprocessor, use one of the following cables: 6.2104.020 (1 m), 6.2104.030 (2 m) or 6.2104.040 (3 m); to connect an electrode an electrode with plug-in head S to the above instruments, use cable 6.2104.510 (1 m). See Metrosensor Electrode Catalog for additional information.

Storage of the Solvotrode when not in daily use: Store the Solvotrode in LiCI sat. in ethanol. Use a normal electrode holder.

More information on Electrodes

> See also: which electrode for which application?
> Metrosensor On-line Catalog
> Metrosensor Electrodes Catalog for download (Info Center -> Products)

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