KjelFlex K-360:

KjelFlex K-360:
Alcohol determination in spirits according to commission regulation EEC 2870/2000, EEC 2676/1990 and OIV-MAAS312-01A
1. Introduction
3. Results
An accurate and reliable method for the determination of
the alcohol content in mixtures of different ethanol/water
concentrations according to EEC 2870/2000 (spirits),
EEC 2676/1990 (wine) and OIV-MA-AS312-01A (wine)
is introduced. The mixtures are distilled using the
KjelFlex K-360. The alcohol determination is performed
by a digital density meter.
Equipment: KjelFlex K-360 in combination with slim glass
splash protector without alkali inlet, sample tubes
500 mL, beaker filled with water and an ice pack for
cooling, density meter (third party), accuracy:
5∙10-5 g/cm³, relative standard deviation: 10-5 g/cm³,
200 mL volumetric flasks with stopper and thermostated
water bath capable of maintaining 20 ± 0.1 °C
Samples: Four ethanol/water mixtures were prepared in
1 L volumetric flasks. The alcohol content (Table 1) was
determined in the original mixture prior to distillation to
establish the exact concentration.
Table 1: Preparation of ethanol/water mixtures
The special design of the slim splash protector leads to
a lower alcohol loss compared to distillations with the
standard splash protector.
4.99
100
9.92
400
39.83
500
50.04
Slim splash protector Expected impact
No NaOH inlet
Closed inlet avoids loss of alcohol at this
position
Small outer
diameter
Smaller volume from sample tube to
condenser prevents alcohol loss because
of shorter distillation distance
T-shape transfer
piece
Special shape eases the transfer of
alcohol from the splash protector to the
condenser
Direct connection eases the transfer of
Direct connection to
alcohol from the splash protector head to
condenser
the condenser
Firstly, distillation was performed with the standard
splash protector instead of the slim splash protector. The
alcohol loss from undistilled samples compared to
distilled samples was ≤0.2 v/v % (see Table 4). The
regulations require an alcohol loss ≤0.1 v/v %. Distillation
using the slim splash protector improves the results to
achieve the allowed tolerance (see Table 5; mixture 3
and Table 6). Therefore, the slim splash protector is
recommended to fulfill the regulations.
Alcohol determined
[v/v %]
50
Determination:
200 mL sample volumes maintained at 20 °C are distilled
into a 200 mL volumetric flask which is filled with
approximately 10 mL distilled water. The flask is placed
into a beaker filled with cold water and an ice pack.
Distillation parameters are selected as listed in Table 2.
After distillation the volumetric flask, filled with distilled
alcohol, is thermostated at 20 °C and filled up to the mark
with distilled water. The alcohol content is determined by
a digital density meter.
Table 2: Distillation parameters
Ethanol
5 - 40 v/v %
Ethanol
50 v/v %
Volume sample [mL]
200
200
Sample tube [mL]
500
500
Distillation time [sec]
300
260
Steam power [%]
100
100
Sample
In Table 3 the four major charateristcs of the slim splash
protector and its effects are listed.
Table 3: Expected impact of the slim spash protector design with
regard to the alcohol recovery rate
2. Experimental
Volume ethanol ≥ 99.8 v/v %
[mL] per liter solution
3.1 Improved recovery due to slim splash protector
Table 4: Distillation with the standard splash protector:
Comparison of alcohol concentration in undistilled and distilled
solutions measured as dublicate
Standard splash
protector
Alcohol determined
[v/v %]
Alcohol loss after
distillation [v/v %]
Without distillation
39.83
-
After one distillation,
average 1
39.63
-0.20
After one distillation,
average 2
39.64
-0.19
3.2 Recovery of alcohol
Four different concentrations of ethanol/water mixtures
were determined. All following measurements were
performed with the slim splash protector. First, the
alcohol concentration was determined without distillation.
Afterwards, the same mixtures were distilled once (Table
5) or five times in succession (Table 6) and then the
ethanol content was determined with the density meter.
Each sample aliquot was measured three times with the
density meter to exclude variations during density
measurement.
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Table 5: Comparison of alcohol concentration in undistilled and
distilled solutions
Alcohol
Mixture 1
[v/v %]
Mixture 2
[v/v%]
Mixture 3
[v/v %]
Mixture 4
[v/v %]
Without
distillation
4.99
9.92
39.78
50.04
One
distillation
4.95
9.88
39.70
49.94
Difference
-0.04
-0.04
-0.08
-0.10
Table 6: Comparison of alcohol concentrations in undistilled and
five times distilled mixture 2
Alcohol
Mixture 2
[v/v %]
Without distillation
9.92
Five distillations
9.82
Difference
-0.10
5.3 Comparison of the results to the limits mentioned
in the regulations
5. References
Operation Manual for the KjelFlex K-360
[1] Determination of the Alcoholic Strength in Sugar
Containing Water-Ethanol Mixtures (K-360), Application
No. K-355_015 V.1.0 (2009) Büchi Labortechnik AG
[2] Alcohol determination in beverages (K-355), Büchi
Labortechnik AG
No. K355-001, Version A (2005) Büchi Labortechnik AG
[3] Alcohol determinations in beer and wine (K-360),
Application No. K-360-004 V1.0 (2007) Büchi
Labortechnik AG
[4] Alcohol determination in alcopops (K-360),
No. K-360-003 V1.0 (2007) Büchi Labortechnik AG
[5] Alcohol determination in spirits and liquors (K-360),
Büchi Labortechnik AG
Application No. K-360-004 V1.0 (2007) Büchi
Labortechnik AG
[6] Commission regulation EEC 2870/2000
[7] Commission regulation EEC 2676/1990
[8] Compendium of international analysis methods Alcoholic strength by volume – Type I methods, OIV-MAAS312-01A (wine)
Youtube movie about alcohol determination:
BUCHI alcohol determination
All following measurements were performed with the slim
splash protector. According to the regulation EEC
2676/1990 any type of distillation or steam-distillation
apparatus may be used, if it fulfills the following test:
Ethanol-water mixtures with an alcoholic strength of
10.0 % volume are distilled five times in succession. The
distillate should have an alcoholic strength of at least
9.9 % volume after the fifth distillation, i.e. the loss of
alcohol during each distillation should not be more than
0.02 v/v %.
EEC 2676/1990 (wine) [7]
Loss of alcohol must be ≤0.1% when distilling a 10%
ethanol-water mixture five times in succession
OIV-MA-AS312-01A (wine) [8]
Loss of alcohol must be ≤0.1% when distilling a 10%
ethanol-water mixture five times in succession
InTable 6 is shown that both regulations are fulfilled.
EEC 2870/2000 (spirits) [6]
Loss of alcohol must be less than ≤0.1 % when distilling
200 mL ≤50 % ethanol-water mixture
4. Conclusion
The determination of ethanol in ethanol/water mixtures of
different concentrations using the KjelFlex K-360 with the
slim splash protector provides reliable and reproducible
results. The results are in agreement with the following
regulations: EEC 2870/2000 (spirits), EEC 2676/1990
(wine) and OIV-MA-AS312-01A (wine). Using the K-360
for distillation and a density meter with an accuracy of:
5∙10-5 g/cm³ the loss of alcohol was ≤0.1% when
distilling 200 mL of ≤50% ethanol-water mixture and
≤0.1% when distilling a 10% ethanol-water mixture five
times in succession.
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