Metrohm 794 Basic Titrino - Manual (Page 181)

6.3 User methods
794 Basic Titrino
177
6.3.13 "FormolNo""
Determination of the formaldehyde number in fruit juices.
TIP method with the submethods "Form.Pre" and "Form.Det"
Electrode: 6.0232.100 combined pH glass electrode, at measuring input 1.
Additonal instrument: 765 Dosimat, connect to 794 Basic Titrino via Remote line.
Titrant: c(NaOH) = 0.1 mol/L.
Aux. reagent: w(formaldehyde) = 0.35 adjusted to pH 8.5 with NaOH.
Sample: Pipette exactly 25 mL sample into the titration vessel.
Fill the dosimat with the formaldehyde solution and adjust the dosing vol-
ume to 15 mL.
Sequence: FormolNo is started and the submethod Form.Pre titrates the sample to
pH=8.5. An activating pulse starts the Dosimat dispensing the formalde-
hyde solution. After the reaction time of 60 s Form.Det titrates again to
pH = 8.5. The calculation is performed in FormolNo.
Reference: Metrohm Application Bulletin Nr. 180
Form.Pre Preparation of the sample.
'pa
794 Titrino 01102 794.0010
date 2002-01-03 time 09:57 0
SET pH Form.Pre
parameters
>SET1
EP at pH 8.50
dynamics 1.5
max.rate 10.0 ml/min
min.rate 25.0 µl/min
stop crit: drift
stop drift 20 µl/min
>SET2
EP at pH OFF
>titration parameters
titr.direction: +
start V: OFF
pause 0 s
meas.input: 1
temperature 25.0 °C
>stop conditions
stop V: abs.
stop V 99.99 ml
filling rate max. ml/min
>statistics
status: OFF
>preselections
conditioning: OFF
req.ident: OFF
req.smpl size: OFF
activate pulse: OFF
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