Microwave hydrolysis

Choline Biosensor Rapid assay using microwave hydrolysis and a choline biosensor Panfili et al. (2000)... 

PANFILI G, MANZI P, COMPAGNONE D, SCARCIGLIA L and PALLESCHI G (2000), Rapid assay of chohne in foods using microwave hydrolysis and a choline biosensor , J Agric Food Chem, 48, 3403-7. pant I and trennery v c (1995), The determination of sorbic acid and benzoic acid in a variety of beverages and foods by micellar electrokinetic capillary chromatography , Food Chem, 53(2), 219-26. pare j r j and Belanger j m r (1997), Instrumental Methods in Food Analysis. Series Techniques and instrumentation in analytical chemistry - Vol. 18, Amsterdam, Elsevier. 

E Tatar, M Khalifa, G Zaray, I Molnar-Perl. Comparison of the recovery of amino acids in vapor-phase hydrolysates of proteins performed in a Pico Tag work station and in a microwave hydrolysis system. J Chromatogr A 672 109-115, 1994. 

WG Engelhart. Microwave hydrolysis of peptides and proteins for amino acid analysis. Am Biotech Lab 8(15) 30-35, 1990. 

Early studies in microwave-assisted hydrolysis of proteins showed the recoveries of amino acids after microwave hydrolysis to be quite consistent with the results provided by conventional hydrolysis [293,294]. Engelhardt et al. used on-line microwave hydrolysis in an HPLC system followed by derivatization with OPA to improve the detection sensitivity for proteins [295]. 

The initial work on microwave-assisted hydrolysis of proteins was conducted using commercial domestic microwave devices. Different laboratory microwave ovens featuring various methods of operation are now commercially available as well. The microwave-assisted hydrolysis of proteins or peptides is usually performed in sealed containers [296] where the sample is in direct contact with the concentrated acid used for hydrolysis. In vapour-gas microwave hydrolysis [297], the acid is evaporated and only the vapour contacts the sample, which prevents contamination of the samples by small amounts of amino acids potentially present in the acid used for analysis. 

Microwave-assisted hydrolysis systems equipped with temperature regulators suitable for quality control of protein products are now available. In fact, microwave hydrolysis is the sole technique in which the acid temperature and vapour pressure are measured directly, in situ. Other devices measure the temperature of a heating unit such as metal heating block or oven surrounding a hydrolysis chamber. 

The reaction rate doubles with every 10°C increase, so that hydrolysis at 145°C for 4 h gives results comparable to the conventional method. Microwave hydrolysis reduces analysis time to 30-45 min. Alternative hydrolysis agents include sulfonic acid, which often gives better recovery but is nonvolatile, and alkaline hydrolysis, used in the analysis of tryptophan, proteoglycans, and proteolipids. 

Hydrolysis itself accelerates racemization. Shorter acid exposure at higher temperatures, such as 160°C for 1 hr, decreases racemization by about 50% compared to conventional hydrolysis. Liquid-phase methanesulfonic acid, gas-phase microwave, conventional, and gas-phase micro-wave hydrolysis produce progressively higher rates of racemization. Additional phenol, however, significantly reduces racemization during microwave hydrolysis. " ... 

Under strictly controlled conditions, amino acids have also been shown to be at least as stable under microwave hydrolysis as with conventional hydrolysis. Degradation of amino acids during microwave hydrolysis appears to be equivalent to that which occurs during conventional hydrolysis. The degree of racemization seems to be significantly less with microwave hydrolysis. 

In wet hydrolysis, specialized reaction vessels are required for microwave hydrolysis. The material used to construct these vessels must (1) be transparent to... 

Engelhart, W.G. (1997) Microwave hydrolysis of proteins and peptides for amino acid analysis, in Microwave-Enhanced Chemistry (eds H.M. Kingston... 

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