Technical Summary: Methanol Analysis (Bulletin ref. TB019944B)
 

A rapid high performance methanol analysis based on the direct reaction with the enzyme Alcohol Oxidase (AOD). Intended for a range of industrial applications including the monitoring of dimethyl dicarbonate (DMDC) dosage as preservative in the soft drinks industry.
 

Name:
 

Methanol
 

Codes:

GMRD-125
GMRD-125J
GMRD-125SJ
 

50ml
8 x 50ml
4 x 175ml
 

70 cycles
560 cycles
1000 cycles
 

Instruments:
 

AM5/GL6/GM8 Series analyzers
 

Principle:

Dimethyl dicarbonate hydrolyzes after a few hours to breakdown products carbon dioxide and methanol. The methanol concentration is determined by enzymatic oxidation with buffered alcohol oxidase according to the equation:
 

Under controlled conditions, the rate of oxygen uptake from the buffer is directly proportional to methanol concentration.
 

Samples:
Sample volume:

Soft drinks, colas and other aqueous products, still or carbonated.
Typically 10 µl, variable 3 - 25 µl
 

Analysis time:
Analytical Range:
Precision:
 

20 seconds (sample to sample time, approx. 60 seconds)
ca 0 - 500ppm (500 mg/L); Range adjustable with sample size
C.V. typically = 1 - 2 % @ 100 mg/L
 

Selectivity:

Alcohol oxidase also measures ethanol, so alcoholic soft drinks should not be analysed.
 

Reagent Stability:

Shelf-life 6 months unopened when stored at 0-5°C. After reconstitution,
ca 5 days for AOD/buffer reagent if stored at 0 - 5°C between use.  Fresh aliquots may be frozen for several weeks at -20°C or lower to extend life.
 

Note:

i) Some juices and other beverages contain a low background level of methanol which can be determined before dosage with DMDC.
ii) No sample pre-treatment is normally necessary except carbonated products which should be degassed in the normal way.
iii) The assay can also be applied to monitoring methanol as a carbon source in culture fermentation processes, contact Analox for details.