Indication with Cu ISE
Approx. 100 mg CaCO3 is weighed out exactly to 0.1 mg into a beaker and is dissolved in a little HCl. The solution is treated with approx. 90 mL dist. H2O, 1 mL Cu-complexing solution and 10 mL buffer solution pH = 10 are added and the solution is titrated with c(Na2EDTA) = 0.1 mol/L (instrument parameters and an example of a curve are given in the appendix).
Calculation
1 mL c(Na2EDTA) = 0.1 mol/L corresponds to 10.09 mg CaCO3 Titer = C00 / C01 / EP1
EP1 = titrant consumption up to the endpoint, in mL C00 = sample weight CaCO3, in mg
C01 = 10.09
– As little HCl as possible should be used for dissolving the CaCO3. After addi- tion of the buffer the pH of the solution must be >8.5.
– The mean value of the titer can be stored in the Titrino as common variable C36.
– Metrohm Application Bulletins Nos. 101, 125, 206 – Metrohm Titration Application Note No. T-52
Method 21 – Titer determination of EDTA solutions
Method parameters & calculations Titration curve Method 21.1
'pa785 DMP Titrino 02287 785.0010 date 2000-11-24 time 08:35 0 MET U M21.1
parameters
>titration parameters
V step 0.10 ml dos.rate max. ml/min signal drift 20 mV/min equilibr.time 38 s start V: OFF pause 0 s meas.input: 1 temperature 25.0 °C
>stop conditions
stop V: abs.
stop V 20 ml stop U OFF mV stop EP 9 filling rate max. ml/min
>statistics
status: ON mean n= 3 res.tab: original
>evaluation
EPC 2 mV EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF
>preselections
req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF ---
'de785 DMP Titrino 02287 785.0010 date 2000-11-24 time 08:35
MET U M21.1 def>formula
Titer=C00/C01/EP1
RS1 text Titer RS1 decimal places 4 RS1 unit:
RS1 limit control: OFF
>silo calculations
match id: OFF
>common variables C36=MN1
>report
report COM1:full;curve;
>mean MN1=RS1
>temporary variables ---
'cf785 DMP Titrino 02287 785.0010 date 2000-11-24 time 08:35
MET U M21.1 C-fmla
C01 2.523 ---
Method parameters & calculation Titration curve Method 21.2
Method 21 – Titer determination of EDTA solutions
'pa785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:38 0
DET U M21.2 parameters >titration parameters meas.pt.density 4
min.incr. 10.0 àl dos.rate max. ml/min signal drift 30 mV/min equilibr.time 32 s start V: OFF pause 0 s meas.input: 1
temperature 25.0 °C >stop conditions stop V: abs. stop V 20 ml stop U OFF mV stop EP 9
filling rate max. ml/min >statistics status: ON mean n= 3
res.tab: original >evaluation EPC 5
EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF >preselections req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF --- 'de785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:38
DET U M21.2
def>formula Titer=C00/C01/EP1 RS1 text Titer RS1 decimal places 4 RS1 unit:
RS1 limit control: OFF
>silo calculations
match id: OFF
>common variables C36=MN1
>report
report COM1:full;curve;
>mean MN1=RS1
>temporary variables ---
'cf785 DMP Titrino 02287 785.0010 date 2000-11-24 time 08:38
DET U M21.2 C-fmla
C01 5.045 ---
Method parameters & calculations Titration curve Method 21.3
Method 21 – Titer determination of EDTA solutions
'pa785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:41 0
DET U M21.3 parameters >titration parameters meas.pt.density 4
min.incr. 10.0 àl dos.rate max. ml/min signal drift 30 mV/min equilibr.time 32 s start V: OFF pause 0 s meas.input: 1
temperature 25.0 °C >stop conditions stop V: abs. stop V 20 ml stop U OFF mV stop EP 9
filling rate max. ml/min >statistics status: ON mean n= 3
res.tab: original >evaluation EPC 5
EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF >preselections req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF --- 'de785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:41
DET U M21.3
def>formula Titer=C00/C01/EP1 RS1 text Titer RS1 decimal places 4 RS1 unit:
RS1 limit control: OFF
>silo calculations
match id: OFF
>common variables C36=MN1
>report
report COM1:full;curve;
>mean MN1=RS1
>temporary variables ---
'cf785 DMP Titrino 02287 785.0010 date 2000-11-24 time 08:41
DET U M21.3 C-fmla
C01 10.09 ---
Method 22 – Total content of Ba, Ca, Mg, Pb and Zn in unused lubricating oils
Recommended accessories
General
Definition
Reagents
Sample preparation
Table, metal content (abs.)
• 6.3014.153 Exchange Unit(s), 5 mL, or 6.3014.213, 10 mL
• Spectrode 610 nm, 6.5501.01X or
• 6.3014.223 Exchange Unit, 20 mL
• 6.0502.140 Cu ISE with 6.2104.020 electrode cable
• 6.0726.017 Ag/AgCl reference electrode with 6.2106.020 electrode cable Apart from other additives, lubricating oils also have metal soaps (e.g. barium arylsulfonates) added to them. Ba, Ca, Mg, Pb and Zn are the metal ions chiefly used. The method is only suitable for unused lubricating oils or the corresponding raw materials. As already explained in Method 21, in the titration with EDTA it is always the total content of the metal ions listed above that is determined – separa- tion is not possible!
Method A describes the determination of the total content of mixtures that may contain Ba, Ca, Mg, Pb and Zn. The metals are complexed with EDTA in semi- aqueous solution and the excess EDTA is photometrically back-titrated with Mg.
Method B is used for mixtures that do not contain Ba and/or Pb. The sample is ashed and Ca, Mg and Zn are titrated potentiometrically with EDTA. Indication is by the Cu ISE.
Total content of the metal ions Ba, Ca, Mg, Pb and Zn in mmol/kg sample.
Method 22.1 – Photometric titration of Ba, Ca, Mg, Pb and Zn
– c(Na2EDTA) = 0.025 mol/L: preparation and titer determination see Method 21 – Buffer solution pH = 10: preparation see Method 21
– Color indicator Eriochrome black T: preparation see Method 21
– Titrant c(MgCl2) = 0.025 mol/L: 5.083 g MgCl2 x 6 H2O, e.g. Merck No. 116102
ôFractopurằ, is dissolved in dist. H2O and then made up to 1 liter.
– Solvents: toluene and isopropanol, analytical grade
The sample weight depends on the metal ion content. It should be selected so that the consumption of c(Na2EDTA) = 0.025 mol/L does not exceed 5 mL. See the following table. The sample is weighed into a 100 mL volumetric flask, dissolved in and made up to the mark with toluene and mixed.
Metal Atomic mass Minimum Maximum
Barium 137.33 g/mol 30 mg 140 mg
Lead 207.2 g/mol 50 mg 200 mg
Calcium 40.08 g/mol 10 mg 40 mg
Magnesium 24.305 g/mol 5 mg 25 mg
Zinc 65.38 g/mol 15 mg 65 mg
Analysis
Calculation
Reagents
Sample preparation
Table, metal content (abs.)
Analysis
Method 22 – Total content of Ba, Ca, Mg, Pb and Zn in unused lubricating oils
The titer of the EDTA solution has already been determined in Method 21 (com- mon variable C36).
10.0 mL prepared sample solution is pipetted into a beaker and treated with 10 mL toluene and 50 mL isopropanol under stirring. Then 5 mL buffer solution pH = 10 and 5.00 mL c(Na2EDTA) = 0.025 mol/L are added. If oil droplets are formed then further toluene is added until they have dissolved. The Spectrode and buret tip are immersed in the solution, 0.5 mL Eriochrome black T is added and the excess EDTA is back-titrated with c(MgCl2) = 0.025 mol/L (instrument parameters and an example of a curve are given in the appendix).
1 mL c(Na2EDTA) = 0.025 mol/L corresponds to 0.025 mmol Me mmol Me / kg = (C01 - EP1) x C36 x C02 x C03 / C00
C00 = 1/10 sample weight in g C01 = 5 (volume of Na2EDTA in mL) C02 = 0.025 (titrant concentration in mol/L) C03 = 1000 (for 1 kg)
C36 = titer of Na2EDTA
Method 22.2 – Potentiometric titration of Ca, Mg and Zn
– Titrant: c(Na2EDTA) = 0.1 mol/L. Preparation and titer determination see Method 21
– Buffer solution pH = 10: preparation see Method 21
– Cu complexing solution: c[Cu(NH4)2EDTA] = 0.1 mol/L; Merck No. 105217 – Hydrochloric acid: w(HCl) = 30...35%, analytical grade
– Sodium hydroxide: c(NaOH) = 2 mol/L
The sample weight depends on the metal ion content. It should be selected so that the consumption of c(Na2EDTA) = 0.1 mol/L is 1...5 mL. See the following table.
The sample is weighed into a platinum crucible and completely ashed at 900 °C in a muffle furnace. After cooling down the white ash is dissolved in a little HCl and rinsed into a beaker with dist. H2O.
Metal Atomic mass mg metal / sample
Calcium 40.08 g/mol 4...20
Magnesium 24.305 g/mol 2...12
Zinc 65.38 g/mol 6...33
The titer of the EDTA solution has already been determined in Method 21 (com- mon variable C36).
The acidic sample solution in the beaker is made up to approx. 50 mL with dist.
H2O and the pH adjusted to 6...8 with NaOH. After the addition of 5 mL buffer solution pH = 10 and 1 mL Cu complexing solution the electrodes (Cu ISE and
Calculation
Remarks
Method 22 – Total content of Ba, Ca, Mg, Pb and Zn in unused lubricating oils
1 mL c(Na2EDTA) = 0.1 mol/L corresponds to 0.1 mmol Me mmol Me / kg sample = EP1 x C36 x C01 x C02 / C00 C00 = sample weight in g
C01 = 0.1 (titrant concentration in mol/L) C02 = 1000 (for 1 kg sample)
C36 = titer of titrant
This method is not suitable for the determination of Ba and/or Pb, as insoluble sulfates (from the sulfonates) are formed during the ashing process.
Method 22 – Total content of Ba, Ca, Mg, Pb and Zn in unused lubricating oils
Method parameters & calculation Titrations curve Method 22.1
'pa785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:55 0
MET U M22.1 parameters >titration parameters V step 0.10 ml dos.rate max. ml/min signal drift 30 mV/min equilibr.time 32 s start V: OFF pause 0 s meas.input: 1
temperature 25.0 °C >stop conditions stop V: abs. stop V 20 ml stop U OFF mV stop EP 9
filling rate max. ml/min >statistics status: OFF >evaluation EPC 30 mV EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF >preselections req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF --- 'de785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:55
MET U M22.1
def>formula mmol/kg=(C01-EP1)*C36*C02*C03/C00 RS1 text mmol/kg RS1 decimal places 2
RS1 unit: Me RS1 limit control: OFF >silo calculations match id: OFF >common variables >report report COM1:full;curve; >mean MN1=RS1 >temporary variables --- 'cf785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:55
MET U M22.1 C-fmla C01 5
C02 0.025 C03 1000 ---
Method parameters & calculation Titration curve Method 22.2
Method 22 – Total content of Ba, Ca, Mg, Pb and Zn in unused lubricating oils
‘pa785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:59 0
DET U M22.2 parameters >titration parameters meas.pt.density 4
min.incr. 10.0 àl dos.rate max. ml/min signal drift 20 mV/min equilibr.time 38 s start V: OFF pause 0 s meas.input: 1
temperature 25.0 °C >stop conditions stop V: abs. stop V 10 ml stop U OFF mV stop EP 9
filling rate max. ml/min >statistics status: OFF >evaluation EPC 5
EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF >preselections req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF —————— ‘de785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:59
DET U M22.2
def>formula mmol/kg=EP1*C36*C01*C02/C00 RS1 text mmol/kg RS1 decimal places 2
RS1 unit: Me RS1 limit control: OFF >silo calculations match id: OFF >common variables >report report COM1:full;curve; >mean MN1=RS1 >temporary variables —————— ‘cf785 DMP Titrino 02287 785.0010
date 2000-11-24 time 08:59
DET U M22.2 C-fmla C01 0.1 C02 1000 ——————
Method 23 – Ca and Mg in water (water hardness)
Recommended accessories
General
Definition Reagents
Analysis
Calculations
Remarks
• 6.3014.223 Exchange Unit, 20 mL
• 6.0504.100 Ca ISE with 6.2104.020 electrode cable
• 6.0726.107 Ag/AgCl reference electrode with 6.2106.020 electrode cable The determination of the Ca, Mg and total hardness in water is carried out very frequently throughout the world (also in oil industry laboratories).
The method described below allows the simultaneous determination of Ca and Mg by a potentiometric titration using the Ca ISE. This is made possible by adding an auxiliary complexing agent (acetylacetone) to the sample. This additive also has the advantage that it masks Al, Fe and Mn ions so that they do not interfere.
The titration is carried out with EDTA in an alkaline sample solution buffered with TRIS.
Ca and Mg and total hardness in process and drinking water in mmol/L.
– Titrant: c(Na2EDTA) = 0.05 mol/L. Preparation and titer determination see Method 21.2.
– Auxiliary complexing solution: 10 g acetylacetone (e.g. Merck No. 109600) and 12.1 g tris-(hydroxymethyl)aminomethane (e.g. Merck No. 108387) are dissolved in dist. H2O and then made up to 1 liter.
100 mL water sample is measured out into a beaker and treated with 15 mL aux- iliary complexing solution. The electrodes and buret tip are immersed and the solution is titrated with c(Na2EDTA) = 0.05 mol/L. Two endpoints are obtained.
EP1 corresponds to Ca, the difference between EP1 and EP2 to Mg (instrument parameters and an example of a curve are given in the appendix).
Ca hardness in mmol/L = EP1 x C01 x C36 x C02 / C00
Mg hardness in mmol/L = (EP2 - EP1) x C01 x C36 x C02 / C00 Total hardness in mmol/L = EP2 x C01 x C36 x C02 / C00
C00 = 100 (sample volume in mL)
C01 = 0.05 (concentration Na2EDTA in mol/L) C02 = 1000 (for 1 liter)
C36 = titer c(Na2EDTA) = 0.05 mol/L
– Ca ISEs that have been stored dry are conditioned for about 10 min in c(CaCl2)
= 0.01 mol/L before the determination.
– The Ca ISE should not be allowed to stand for a long time in a sample that has already been titrated as this shortens its working life.
– Samples that contain a lot of Ca but only a little Mg produce only one EP for the sum of the two ions. In such cases an Mg standard is added to the auxiliary complexing solution, which is then added to the sample. This addition must be subtracted again in the calculations.
Method parameters & calculation Titration curve Method 23
'pa785 DMP Titrino 02287 785.0010
date 2000-11-24 time 10:40 0
DET U M23 parameters >titration parameters meas.pt.density 4
min.incr. 10.0 àl dos.rate max. ml/min signal drift 10 mV/min equilibr.time 52 s start V: OFF pause 0 s meas.input: 1
temperature 25.0 °C >stop conditions stop V: abs. stop V 10 ml stop U OFF mV stop EP 9
filling rate max. ml/min >statistics status: OFF >evaluation EPC 5
EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF >preselections req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF --- 'de785 DMP Titrino 02287 785.0010
date 2000-11-24 time 10:40
DET U M23
def>formula Ca=EP1*C01*C02*C36/C00 RS1 text Ca RS1 decimal places 2
RS1 unit: mmol/L RS1 limit control: OFF Mg=(EP2-EP1)*C01*C02*C36/C00 RS2 text Mg RS2 decimal places 2
RS2 unit: mmol/L RS2 limit control: OFF Total=EP2*C01*C02*C36/C00 RS3 text Total RS3 decimal places 2
RS3 unit: mmol/L RS3 limit control: OFF >silo calculations match id: OFF >common variables >report report COM1:full;curve; >mean MN1=RS1 >temporary variables --- 'cf785 DMP Titrino 02287 785.0010
date 2000-11-24 time 10:40
DET U M23 C-fmla C01 0.05 C02 1000 ---
Method 23 – Ca and Mg in water (water hardness)
Method 24 – Pb in leaded gasoline
Recommended accessories
General
Definition Reagents
• 6.3014.223 Exchange Unit, 20 mL
• 6.5501.01X Spectrode 610 nm
• Separating funnel 250 mL
Leaded gasoline is decreasing in importance as a fuel for motor engines as most vehicles are now equipped with catalytic converters. It is nevertheless important to be able to determine the lead content of ôredằ gasolines. The Pb content of leaded gasoline is normally 0.026...1.3 g/L.
The method described is based on the following principle:
A known volume of sample is diluted with lead-free ôheavy distillateằ and the tetraalkyllead converted with iodine monochloride. Dialkyllead and the conversion products are extracted with water and any organic constituents in the aqueous extract are oxidized with nitric acid. At the same time the lead compounds are converted to Pb(NO3)2. The lead nitrate is then titrated photometrically with EDTA.
Lead content in g/L Pb at 15 °C (60 °F). Can also be given in g/US gal. or g/UK gal.
– Titrant: c(Na2EDTA) = 0.005 mol/L. 1.865 g Na2EDTA x 2 H2O (e.g. Merck No.
108418, Titriplex III) is dissolved in dist. H2O, treated with 1 mL c(NaOH) = 1 mol/L and made up to 1 liter with dist. H2O.
– Lead standard: c(Pb) = 0.005 mol/L. 1.656 g Pb(NO3)2 analytical grade (e.g.
Merck No. 107398) is treated with 10 mL conc. HNO3, dissolved in dist. H2O and then made up to 1 liter.
– Acetate buffer: 23 g anhydrous sodium acetate is dissolved in dist. H2O. After the addition of 7.2 mL glacial acetic acid the solution is made up to 1 liter with dist. H2O.
– Color indicator (xylenol orange): 0.2 g xylenol orange tetrasodium salt is dis- solved in dist. H2O, treated with 0.5 mL c(HCl) = 1 mol/L and made up to 100 mL with dist. H2O. The solution can be kept for approx. 1 week.
– Nitric acid: w(HNO3) = 65%, analytical grade
– Ammonia: w(NH3) = 25%, analytical grade, diluted 1:1 with dist. H2O.
– Iodine monochloride: 111.0 g potassium iodide is dissolved in approx. 400 mL dist. H2O in a 1000 mL volumetric flask and mixed with 445 mL conc. HCl. The mixture is allowed to cool down to room temperature and then 75.0 g KIO3 is slowly added under stirring. Stirring is continued until a clear orange-red liquid is obtained. The solution is made up to the mark with dist. H2O.
– ôHeavy Distillateằ: Petroleum distillate with a low bromine number (fraction of approx. 10% of 205 °C and approx. 90% of 240 °C distillates).
Method 24 – Pb in leaded gasoline
Sample preparation
Analysis
Calculations
Literature 50 mL iodine monochloride and 25 mL ôHeavy Distillateằ are placed in the separat-
ing funnel. The temperature of the sample is measured to 0.5 °C and then 25.0 mL sample is added to the separating funnel. This is sealed immediately and shaken for 60 s. The phases are then allowed to separate for a few minutes. The lower aqueous phase is run off into an Erlenmeyer flask and the organic phase extracted a further three times with portions of 20 mL dist. H2O (these aqueous extracts are also run off into the Erlenmeyer flask). A few glass boiling beads are added to the Erlenmeyer flask and its contents are heated and boiled off until a volume of 15...20 mL remains. 5 mL HNO3 are run into the boiling solution down the inner wall of the flask and heating is continued to virtual dryness. The addition of HNO3 and heating to dryness are continued until a white deposit remains.
The titer of the EDTA solution is determined first. 10.00 mL lead standard is added to a beaker and diluted to approx. 70 mL with dist. H2O. 10 mL acetate buffer and 5 drops of xylenol orange are then added and the solution is titrated with c(Na2EDTA)
= 0.005 mol/L (instrument parameters and an example of a curve are given in the appendix).
Calculation of the titer:
Titer = C00 / EP1
C00 = 10 (added lead standard in mL)
The titer is stored in the Titrino as common variable C37.
Sample
After cooling down, the deposit is dissolved in approx. 200 mL dist. H2O by heating and swirling it around. It is allowed to cool down and the pH is adjusted to 5...6 with NH3 solution. 10 mL acetate buffer and 5 drops of xylenol orange are then added and the solution is titrated with c(Na2EDTA) = 0.005 mol/L.
1 mL c(Na2EDTA) = 0.005 mol/L corresponds to 1.036 mg Pb g/L Pb = EP1 x C01 x C37 / C00
C00 = sample volume in mL***
C01 = 1.036 C37 = titer of titrant
*** The sample volume must be converted to 15 °C. The coefficient of expansion for gasoline is assumed to be 0.00065 / °C. For conversion to a sample volume at 15 °C the result obtained above is multiplied by the following expression:
1 + 0.00065 (t - 15)
Example: the sample was measured at 22.5 °C and a content of 1.55 g Pb / L was obtained.
1 + 0.00065 (22.5 - 15) = 1.005 1.005 x 1.55 = 1.558 g/L Pb at 15 °C – ASTM D 3341-91
Standard Test Method for Lead in Gasoline – Iodine Monochloride Method
Method parameters & calculation Titration curve
Method 24
Method 24 – Pb in leaded gasoline
'pa785 DMP Titrino 02287 785.0010 date 2000-11-24 time 11:02 0 MET U M24
parameters
>titration parameters
V step 0.10 ml dos.rate max. ml/min signal drift 30 mV/min equilibr.time 32 s start V: OFF pause 0 s meas.input: 1 temperature 25.0 °C
>stop conditions
stop V: abs.
stop V 20 ml stop U OFF mV stop EP 9 filling rate max. ml/min
>statistics
status: OFF
>evaluation
EPC 30 mV EP recognition: all fix EP1 at U OFF mV pK/HNP: OFF
>preselections
req.ident: id1 req.smpl size: all limit smpl size: OFF activate pulse: OFF ---
'de785 DMP Titrino 02287 785.0010 date 2000-11-24 time 11:02
MET U M24 def>formula
Pb=EP1*C01*C37/C00
RS1 text Pb RS1 decimal places 2 RS1 unit: g/L RS1 limit control: OFF
>silo calculations
match id: OFF
>common variables
>report
report COM1:full;curve;
>mean MN1=RS1
>temporary variables ---
'cf785 DMP Titrino 02287 785.0010 date 2000-11-24 time 11:02
MET U M24 C-fmla
C01 1.036 ---