Wine Pac: Wine P A C
Wine Pac: Wine P A C
Wine Pac: Wine P A C
WINE PAC
6.6043.003
[
Dear Users,
You have purchased a Metrohm titrator which, with its collection of methods, is specially cus-
tom-made to meet your particular requirements. Metrohm always tries to provide the customer
with as wide a range of application support as possible so that the day-to-day analytical work
is made easier.
In the Application File you will find the descriptions of the corresponding analytical methods,
together with all the necessary remarks and explanations and – very important for you – print-
outs of the instrument parameters and examples of curves.
All these methods are loaded on the Method Memory Card. You only need to «feed» the titrator
with the card, load the required method into the working memory and off you go!!!
You are the specialists in wine production and have to ensure the outstanding quality of this
wonderful drink when it is sold to your customers. Although we at Metrohm do not understand
much about your profession, we have been ion analysis specialists for many years. The combi-
nation of these two elements – and we are convinced of this – will produce optimal results.
For Titrando users: A conversion program ensures that you can adopt the Titrino parameters
in your Titrando without any problems. This conversion program is contained in the PC Control
program.
We wish you pleasure and success in your work,
Your Metrohm
8.110.1793
1
A few additional hints
The methods presented here have been drawn up by taking the relevant methods of the individual coun-
tries into consideration (see literature references). These are methods from the EU, Australia, Israel, Switzer-
land, South Africa, South America and the USA.
All methods have been worked out so that you can use them as so-called SOPs (Standard Operating Pro-
cedures) in your laboratory.
Of course, almost all these methods can be further automated. In the appendix you will find a relevant exam-
ple. For details please contact your local Metrohm distributor, who can also be found on the Internet under:
www.metrohm.com Distributors
The supplied method memory card can be used with the following Titrinos: 798, 799, 785 and 751 (from
program version 20). With VESUV 3.0 Light, which is also supplied (VESUV = Verification Support for Valida-
tion), either you or your Metrohm agency can also transfer the parameter sets to the following Titrinos: 716,
736, 794 or 751 (<program version 20).
Among other things, the supplied CDs contain:
• The VESUV backup file, which allows you to copy the 25 methods into the 716, 736, 751, 785, 794, 798
and 799 Titrinos. For further information please read the Section «Recreating methods» in the VESUV In-
structions for Use, which is also supplied, or contact your local Metrohm agency. If, instead of the printer,
the VESUV software is used for adopting the data, then the «curve» report must be deleted at the Titrino,
which must be set to «mplist» instead (VESUV can only process measuring point lists).
• A conversion program (converter) for adopting the Titrino parameters in the Titrando is contained in the
6.6050.000 PC Control program.
• Acrobat Reader to be installed on your PC so that you can read PDF files.
• Application Bulletins No. 82, 83, 125, 129, 130, 133, 140 and 225.
We recommend that you only load the methods that you require into your instrument.
The method overview can be removed and stored together with the Wine PAC card and the appropriate
instrument.
2
Overview of chapters
A pH value
A1 Calibration of the measuring electrode
A2 pH measurement
B Total titratable acidity
B1 Preparation and titer determination of the titrant
B2 Titration procedures
C Free sulfurous acid (Free SO2)
C1 Preparation and titer determination of the titrant
C2 Orienting Ripper method (CH, SA, USA)
C3 Official reference method (Au, EU, Israel, RSA)
D Total sulfurous acid (Total SO2)
D1 Orienting Ripper method (SA, USA)
D2 Official reference method (Au, CH, EU, Israel, RSA, SA)
E Volatile acids
F Fixed acidity
G Ascorbic acid (vitamin C)
H Reducing sugars
H1 Preparing the solutions and determining the calibration factors
H2 Determining the content of reducing sugars
J Carbon dioxide (CO2)
K Ash and ash alkalinity
L Calcium and magnesium
M Chloride
N Total phosphorus
O Sulfate
P Direct potentiometric measurements with ion selective electrodes (ISE)
P1 Ammonium
P2 Potassium
P3 Sodium
P4 Fluoride
P5 Alcohol content with the fluoride ISE
3
Literature references
– Metrohm Application Bulletins nos. 82, 83, 125, 129, 130, 133, 140, 225
– Metrohm Ti Application Notes nos. T-30, T-72
– OIV Methods: Office International de la Vigne et du Vin, 11 rue Roquépine, F-75008 Paris (1992)
– C.S. Ough, M.A. Amerine
Methods for analysis of musts and wines, 2nd edition
John Wiley & Sons, New York 1988 ISBN 0-471-62757-7
– P. Iland, A. Ewart, J. Sitters, A. Markides, N. Bruer
Techniques for chemical analysis and quality control during winemaking (2000)
Patrick Iland Wine Promotion, Campbelltown, South Australia 5074
ISBN 0646-38435-X
– Edmundo Bordeu S., Juan Scarpa B-B.
Análisis químico del vino
Ediciones Universidad Católica de Chile (1998)
ISBN 956-14-0516-4
– Vorschriften zur Weinanalytik. Bundesamt für Weinbau, Eisenstadt (Austria)
– Jornal Oficial das Comunidades Europeias, Portugal
– Gazzetta Ufficiale della Repubblica Italiana, 2a Serie speciale N. 90 (1990)
– The Israeli Standard for Wine Determination, No. 1318
– Schweizerisches Lebensmittelbuch, Kapitel 30 + 30A, Wein aus Trauben
– Jakob, L.
Taschenbuch der Kellerwirtschaft
Fachverlag Dr. Fraund GmbH, Wiesbaden (Germany) 1984
– West, S.J., Frant, M.S., Anderson, M.G., Chandler, L.L.
A simple, accurate method for determining alcohol in wine using a fluoride ion-selective electrode
Thermo Orion (1999)
4
Method 1 –
A 1 Calibrating the measuring electrode
Recommended • 6.0258.000 Unitrode (comb. pH glass electrode with built-in Pt 1000 tem-
accessories perature sensor)
• Alternatively: 6.0259.100 Unitrode (comb. pH glass electrode) with 6.2104.020
electrode cable and separate thermometer
A pH value
General The pH value is defined as the negative logarithm of the concentration of free,
dissociated hydrogen ions in mol/L: pH = –log[H+]
The pH scale ranges from 0 to.14 and the neutral point is at pH = 7.0, where H+-
und OH – ions are present in equilibrium. pH values <7 result from an excess of
H+, pH values >7 from an excess of OH –. The more acidic a solution, the lower
its pH; the more alkaline a solution, the higher its pH.
Weak acids, e.g. tartaric acid, do not dissociate completely, i.e. only a small
fraction (2...3%) of the H+ ions are released:
This also means that only on very rare occasions can the concentration of acids
or alkalis be inferred from the pH value.
As the pH scale is logarithmic, this also means that small differences in pH cor-
respond to large differences in the H+ concentrations. For example, at pH = 3.0
there are ten times as many H+ ions present than at pH = 4.0, and at pH = 3.1
there are twice as many H+ ions present that at pH = 3.4. The pH is measured
potentiometrically – i.e. by currentless potential measurements. Apart from the
measuring instrument (pH meter or titrator), a pH glass electrode and a refer-
ence electrode are required. For practical reasons these two electrodes are
usually contained in a single combined electrode.
According to Nernst (we will not go into any details here) the theoretical slope
of such electrodes is 59.2 mV / pH at 25 °C or 58.2 mV / pH at 20 °C. The elec-
trode zero point (0 mV) normally lies at pH = 7.0, but can vary within certain
limits without the measuring accuracy being affected. This variation called pHas
(asymmetry) should not exceed ±0.25 pH units. As a result of aging processes
the electrode slope diminishes with time. If it becomes lower than 92% of the
theoretical slope, i.e. 54.5 mV / pH at 25 °C or 53.5 mV / pH at 20 °C then the
electrode must be regenerated (send it to your local Metrohm agency).
1
Method 1 –
A 1 Calibrating the measuring electrode
In order to check the condition of the electrode and to set the electrode data on
the measuring instrument, the electrode is calibrated with pH buffer solutions.
Buffer solutions are standards that have a defined pH value. This pH value is
also temperature-dependent and this temperature dependency is given on the
label of commercial buffer solutions. The relationship can be seen in the plot of
«mV against pH»:
--- Theoretical values
0 mV at pH = 7.00 and T = 25 °C
Slope = 59.2 mV / pH (100%)
+177.6 mV at pH = 4.00 and
+414.4 mV at pH = 0.00
–177.6 mV at pH = 10.00 and
–414.4 mV at pH = 14.00
the buffer solution pH = 7.00; a second buffer solution is used to determine the
slope of the pH electrode. It is important that at least one buffer value is located
close to that expected for the sample. From the asymmetry potential and slope
the pH meter determines the calibration line for the pH electrode and uses it to
convert the measured mV values into pH values.
2
Method 1 –
A 1 Calibrating the measuring electrode
Practical work Always use fresh buffer solutions – after use these should be discarded and not
returned to the bottle!
We recommend the use of a pH electrode with built-in temperature sensor
– 6.0258.000 Unitrode.
A) According to Au/CH/
RSA/SA (two-point cali- tCR
'0$ 4ITRINO
bration) DATE
TIME
Connect the electrode to MEASINPUT #!, -
CALDATE
the Titrino, rinse it with P( 5M6
dist. H2O and dab it dry BUFFER
with a soft paper tissue. BUFFER
CAL4EMP #
Immerse the electrode SLOPEREL P(AS
in the first Metrohm
buffer solution, switch tPA
on the stirrer, select '0$ 4ITRINO
<CAL> mode and press DATE
TIME
CAL P( -
<START>. Enter the set PARAMETERS
A pH value
value of the first buffer CALIBRATION PARAMETERS
solution, e.g. 7.00 at 25 MEASINPUT
CALTEMP #
°C (7.02 at 20 °C) and BUFFER P(
accept the value with BUFFER P(
<ENTER>. The buffer BUFFER P( /&&
is measured. Rinse the SIGNAL DRIFT M6MIN
EQUILIBRTIME S
electrode with dist. H2O, ELECTRID
dab it dry, immerse it in SAMPLE CHANGER CAL /&&
the second buffer solu- ACTIVATE PULSE /&&
LIMIT SMPL SIZE /&&
tion, stir, enter the set STATISTICS
value for the second buf- STATUS /&&
fer solution, e.g. 4.00 at
25 °C (3.99 at 20 °C) and
accept the value with
<ENTER>. The second
buffer solution is mea-
sured. Exit the calibration
mode with <STOP>.
The calibration data can
be viewed with <CAL:
DATA>. The key se-
quence <PRINT><CAL:
DATA><ENTER> is
used to print out the cali-
bration report.
3
Method 1 –
A 1 Calibrating the measuring electrode
B) According to the EU
tCR (two-point calibration)
'0$ 4ITRINO
DATE
TIME Same procedure as for
MEASINPUT #!, - A). However, the DIN
CALDATE
P( 5M6 buffer pH = 6.865 at 25
BUFFER °C (6.881 at 20 °C) and
BUFFER the buffer solution pH =
CALTEMP #
SLOPEREL P(AS 3.557 at 25 °C (3.57 at 20
°C) are used.
tPA
'0$ 4ITRINO
DATE
TIME
#!, P( -
PARAMETERS
CALIBRATION PARAMETERS
MEASINPUT
CALTEMP #
BUFFER P(
BUFFER P(
BUFFER P( /&&
SIGNAL DRIFT M6MIN
A pH value
EQUILIBRTIME S
ELECTRID
SAMPLE CHANGER CAL /&&
ACTIVATE PULSE /&&
LIMIT SMPL SIZE /&&
STATISTICS
STATUS /&&
4
Method 2 –
A 2 Measuring the pH value
Rinse the electrode with dist. H2O and dab it dry with a soft paper tissue. Im-
merse the electrode in the undiluted wine sample and measure the pH under
stirring. When the drift criterion has been achieved, the pH value will be shown
on the instrument or printed out. The measured pH is stored in the Titrino as the
constant C40.
Remarks The pH value is of great importance for biological systems. In wines it plays
a larger role than the titratable total acidity. The pH influences the growth of
microorganisms, the color and shade, taste, redox potential, the ratio of free to
A pH value
bound SO2, the stability, the possibility of forming or preventing iron phosphate
turbidity, etc. There is no direct relationship between the pH value and the
content of titratable total acidity; in contrast, there is an (empirical) relationship
between the pH value and the potassium hydrogen tartrate / tartaric acid ratio.
The pH of a solution (wine) is also temperature-dependent. This temperature
dependency cannot be compensated by the instrument, which only adjusts the
electrode slope! This means that, when giving the pH value, it is essential that
the temperature at which the pH was measured is also mentioned. Example:
pH = 3.52 at 18.2 °C.
The pH value of wines is normally in the range 3.3 to 3.8:
Table wines 3.1...3.6; sparkling wines 3.0...3.6; dessert wines and late-vintage
wines 3.4...3.8.
1
Method 3 –
B 1 Preparation and titer determination of the
titrant
Recommended acces- • 6.3014.223 or 6.3026.220 Exchange Unit (possibly with 6.1608.040 PE bot-
sories tle)
• 6.0258.000 Unitrode (comb. pH glass electrode with built-in Pt 1000 tem-
perature sensor)
• Alternatively: 6.0259.100 Unitrode (comb. pH glass electrode) with 6.2104.020
electrode cable and separate thermometer
Reagents • Titrant: c(NaOH) = 0.1 mol/L, e.g. Merck no. 109141, or dissolve 4.0 g NaOH
in CO2-free dist. H2O, make up to 1000 mL and mix.
• Standard substance: potassium hydrogen phthalate, e.g. Merck no. 102400
Titer determination Potassium hydrogen phthalate is dried overnight in a drying oven at 105 °C and
allowed to cool down in a desiccator for at least 1 h. Care should be taken that
the titrations are carried out at a constant temperature.
The titer determination is normally carried out three times and the mean value is
used. The mean value of the titer is stored in the Titrino, e.g. as Common Vari-
able C30.
Approx. 200 mg KH phthalate is weighed out into the titration beaker with an
accuracy of 0.1 mg and dissolved in approx. 50 mL dist. H2O. The solution is im-
mediately titrated against c(NaOH) = 0.1 mol/L until after the first endpoint.
1 mL c(NaOH) = 0.1 mol/L corresponds to 20.423 mg KH phthalate
1
Method 3 –
B 1 Preparation and titer determination of the
titrant
tPA
'0$ 4ITRINO
DATE
TIME
$%4 5 -
PARAMETERS
TITRATION PARAMETERS
MEASPTDENSITY
MININCR ±L
DOSRATE MAX MLMIN
B Total titratable acidity
SIGNAL DRIFT M6MIN
EQUILIBRTIME S
START 6 /&&
PAUSE S
DOSELEMENT INTERNAL $
MEASINPUT
TEMPERATURE #
STOP CONDITIONS
STOP 6 ABS
STOP 6 ML
STOP 5 /&&