Analyser format for the specific assay of acetic acid (acetate) in beverages and food products. On calibration, the prepared reagent is linear to > 28 micrograms of acetic acid per mL of assay solution.
INTRODUCTION:
The most widely used method for enzymatic quantification of acetic
acid is that employing acetyl-coenzyme A synthetase (ACS). However,
this method is based on the use of an indicator reaction catalysed by
L-malate dehydrogenase that is in permanent equilibrium, and therefore
a non-stoichiometric increase in absorbance is observed from the
acetate present in the sample. Thus, a slightly non-linear response
to increasing acetate concentration is observed upon calibration,
resulting in poor R2 values. In addition (depending on the supplier)
reagents prepared for auto-analyser applications can have very limited
on-machine stability, due to rapidly increasing blank absorbance values.
To overcome these issues, Megazyme developed this alternative acetic
acid kit, based on the enzyme acetate kinase (AK; see equations 1-3
below), especially for the auto-analyser user. This reagent has improved
on-machine stability, gives excellent linear calibration curves, and results
in a stoichiometric change in absorbance due to the acetic acid present
in the sample.
KITS:
Kits suitable for performing a minimum of 550 assays in auto-analyser
format are available from Megazyme.
The kits contain the full assay method plus:
Bottle 1: Buffer (11 mL, pH 7.4) plus sodium azide (0.02% w/v ) as a
preservative. Stable for > 2 years at 4°C.
Bottle 2: NADH plus ATP, PEP and PVP.
Stable for > 2 years at either 4°C or -20°C.
Bottle 3: Acetate kinase plus pyruvate kinase and D-lactate
dehydrogenase suspension, 4.1 mL.
Stable for > 2 years at 4°C.