Bepaling van het zuur- of baseverbruik en van de alkaliniteit met Titrino 736
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Open Access
Type
Report
Language
nl
Date
2002-10-31
Research Projects
Organizational Units
Journal Issue
Title
Bepaling van het zuur- of baseverbruik en van de
alkaliniteit met Titrino 736
Translated Title
Validation of a titrator for the determination of
acidity in rainwater and alkalinity in groundwater
Published in
Abstract
Het doel van deze rapport is het valideren van een
titratie-systeem (736ohm Metrohm) door het vaststellen van de
prestatiekenmerken met betrekking tot twee bepalingsmethoden, namelijk de
potentiometrische bepaling van de pH en zuur- of baseverbruik van
regenwater, en de potentiometrische bepaling van het gehalte aan carbonaat,
waterstofcarbonaat en hydroxide in grondwater. Voor elk van de methoden
zijn aantoonbaarheidsgrens, reproduceerbaarheid, robuustheid en (voor
carbonaat/ waterstofcarbonaat) het meetbereik vastgesteld. Onderzocht is of
de reproduceerbaarheid, bepaald met standaard-oplossingen ook in de matrix
van toepassing is. Voor beide nieuwe methoden zijn de bepaalde
prestatiekenmerken vergelijkbaar met de prestatiekenmerken van huidige
methoden. Voor de bepaling van het zuur- of baseverbruik van regen water is
de aantoonbaarheidsgrens 5 mumol/l hydroxylionen (OH-) dan wel
hydroniumionen (H3O+). De RSD voor de reproduceerbaarheid van het zuur-of
baseverbruik is beter dan 4% bij 100 mumol/l H3O+, en die van de pH-bepaling
is beter dan 0.09 pH -eenheden. De analysetijd is 8 minuten, bij 100
mumol/l H3O+. Bepaling van het carbonaat en waterstofcarbonaat gehalte in
grondwater: De aantoonbaarheidsgrens is voor zowel carbonaat als
waterstofcarbonaat 0.02 mmol/l. Het meetbereik voor waterstofcarbonaat is
0.02 tot 60 mmol/l.eter dan 5% bij een waterstofcarbonaatconcentratie van
25 mmol/l. De analysetijd is ca. 10 minuten, bij 60 mmol/l
waterstofcarbonaat.
A 736ohm Metrohm titrator has been validated for determination of acidity in rainwater and alkalinity in groundwater. The performance characteristics have been determined in terms of reproducibilities and detection limits, and appeared to be comparable to those of the previously applied methods. The determination starts with reading of the pH and sample temperature. The determination of the acidity is carried out by gradually adding a 0.002 mol/l H2SO4 standard as titrant to the sample up to a fixed end-point of pH 4, and subsequently the sample is titrated back with 0.002 mol/l NaOH standard. The addition is stopped when a fixed end-point of pH 5.6.is reached. The reproducibility, in terms of the relative standard deviation, of the acidity determination is better than 4% at 100 mumol/l H3O-. The detection limit is 5 mumol/l for both hydroxide and hydronium. Acidity determination takes place in 8 minutes. The determination of the alkalinity (interpreted as the sum of the concentrations of bicarbonate, carbonate and hydroxide) is carried out by gradually adding a 0.05 mol/l HCl standard to the sample up to fixed end point of pH 8.3 (if the pH of the sample is higher than 8.3) and then up to end point of pH 4.5. The reproducibility, in terms of the relative standard deviation, of the alkalinity determination is 5% by 25 mmol/l (bi)carbonate. The detection limit for bicarbonate is 0.02 mmol/l. The applicable concentration range is 0.02 - 60 mmol/l. A typical alkalinity determination takes place in 10 minutes.
A 736ohm Metrohm titrator has been validated for determination of acidity in rainwater and alkalinity in groundwater. The performance characteristics have been determined in terms of reproducibilities and detection limits, and appeared to be comparable to those of the previously applied methods. The determination starts with reading of the pH and sample temperature. The determination of the acidity is carried out by gradually adding a 0.002 mol/l H2SO4 standard as titrant to the sample up to a fixed end-point of pH 4, and subsequently the sample is titrated back with 0.002 mol/l NaOH standard. The addition is stopped when a fixed end-point of pH 5.6.is reached. The reproducibility, in terms of the relative standard deviation, of the acidity determination is better than 4% at 100 mumol/l H3O-. The detection limit is 5 mumol/l for both hydroxide and hydronium. Acidity determination takes place in 8 minutes. The determination of the alkalinity (interpreted as the sum of the concentrations of bicarbonate, carbonate and hydroxide) is carried out by gradually adding a 0.05 mol/l HCl standard to the sample up to fixed end point of pH 8.3 (if the pH of the sample is higher than 8.3) and then up to end point of pH 4.5. The reproducibility, in terms of the relative standard deviation, of the alkalinity determination is 5% by 25 mmol/l (bi)carbonate. The detection limit for bicarbonate is 0.02 mmol/l. The applicable concentration range is 0.02 - 60 mmol/l. A typical alkalinity determination takes place in 10 minutes.
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