Dear Sir. Concerning your issue about the method for L-phenylacetylcarbinol(L-PAC) extraction. Biotransformation of benzaldehyde to L -phenylacetylcarbinol (L-PAC) as a key intermediate for L-ephedrine synthesis has been evaluated using immo bilized Candida utilis. During biotransformation, the benzaldehyde level and respiratory quotient signifcantly affected both L-PAC and by-product benzyl alcohol formation. By controlling the benzaldehyde level at 2 g/l, maintaining a respiratory quotient of 5—7 and pulse feeding glucose, a final concentration of 15.2 g/l L-PAC was achieved in a fed-batch process. This compares with previous published results of 10—12 g/l in batch culture and 10 g/l L-PAC in a semicontinuous process with immobilized Saccharomyces cerevisiae. In a single stage continuous process with immobilized C. utilis, the steady state L-PAC concentration was signifcantly reduced because of the sustained toxic effects of benzaldehyde. Concentrations of benzaldehyde, L-PAC and benzyl alcohol were determined by gas chromatography. Samples were prepared by extraction into dichloromethane (sample:solvent"1:5). The biotransformation sample (0.2 ml) was mixed with 1 ml dichloromethane in a microcentrifuge tube and vortexed for 2 min. A sample from the bottom organic layer was injected into a gas chromatograph with the column and its operating conditions as follows: column material, 6.4-mm glass 1 m long; packing material, Chromosorb W. Hr/SE 30WTX 10 in the mesh range of 80—100 lm; carrier gas, nitrogen (30 cm3/min); oven temperature, 115° C (isothermal); injector temperature, 180° C; detector temperature, 180° C with flame ionization detector; injection sample, 3 ll. The concentrations of benzaldehyde and benzyl alcohol were determined by comparison with standard samples (from Aldrich) and L-PAC. I think the following below links may help you in your analysis:

http://www.designer-drug.com/pte/12.162.180.114/dcd/pdf/benzaldehyde.l-pac.pdf

https://erowid.org/archive/rhodium/pdf/biotransformation.ephedrine.pdf

https://www.cheric.org/PDF/KJChE/KC18/KC18-3-0363.pdf

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Thanks a lot Professor Elgailani 

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