tailieunhanh - HPLC A Praactical User'S Guide Part 10

Tham khảo tài liệu 'hplc a praactical user's guide part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | AUTOMATED METHODS DEVELOPMENT 175 Figure Random walk optimization. resolution sum is calculated. This process continues with the lowest value of each new triad being discarded reflection around the axis joining the best two points and a new injection made at the new set of conditions. This technique will hunt and search until a point 10 is found that meets the search criteria. The search can be stopped at this point but there is a danger that only a local best value has been found. If the overall best condition is desired this final point can also be discarded a new point selected at random and the random walk can be continued. If the computer continues to return to the previous best point then it probably represents the true best value within the limits. Obviously a limiting maximum number of injections should be set to keep the computer from wandering around forever. Although flow rate and solvent composition are the most commonly optimized variables there is no reason why temperature and other mobile phase modifiers could not be used. Variables such as mobile phase pH buffer concentration ion pairing reagents a chelator s concentration or organic modifiers could all be optimized using resolution sums. If the computer can control the variable UV detector s wavelength wavelength and detector sensitivity settings could both be included as independent variables to be searched and optimized. To create a method you would need a computer-controlled gradient HPLC system with an autoinjector or autosampler capable of making repeated 176 AUTOMATION injections from a large supply of the target solution an HPLC column and a detector. Data acquisition and processing can be done in an integrator and sent to the computer or can be handled using an A D card and software running in the control computer. The system would be set up with sufficient mobile phase for an overnight run limits set and the system allowed to run unattended overnight. When you come in the next day the