CHROMATOGRAPHY 33
end of the method to ramp quicker or end sooner, resulting in an even shorter analysis than the direct translation calculates. If desired, additional optimisation for either analysis speed or system efficiency can be performed using the Pro EZGC chromatogram modeller, a software program that can be used in conjunction with the EZGC method translator for further method refinement. When moving to either a directly translated or further optimised method, make sure to confirm that your GC oven can achieve the new ramp rates. If not, Agilent users can install a GC Accelerator oven insert kit so that ramp rates can reliably be achieved and retention times remain stable.
While it may seem
counterintuitive that you can get more done with less column, faster analyses can be obtained by moving to a shorter column with a narrower inner diameter (ID) and thinner film. This is because smaller diameter columns with thinner film produce narrower peaks, which allows analysis times to be compressed without losing resolution
Te last thing to keep in mind if you
scale down to faster GC is to consider pairing a split injection technique with the narrower, thinner film column. Te much higher efficiency of scaled-down columns will produce narrower, taller peaks, which inherently provide a boost in sensitivity. Tat gain alone might allow you to still meet detection limits, even for relatively low concentration samples. Te value of the split injection is twofold. First, if there were any loading capacity concerns (e.g. a thinner film producing overloaded,
Fig. 2. Comparison of original method and modelled results based on the scaled-down column and translated method. The translated method provides the same elution order and relative peak separation, but the peaks elute in a much shorter analysis time
fronting peaks), split injection will take care of that. Second, the biggest benefit is that the very rapid transfer of sample onto the column will help keep the bands of molecules tight, and, as a result, the peaks narrow. Te slower transfer time of a splitless injection, especially into a relatively wide inlet liner (e.g. a 4mm ID), will cause band broadening, and consequently, peak widening, which might negate some of the efficiency benefits of using a scaled-down column.
Same separation, speedier solution In conclusion, equivalent chromatographic results can be obtained in much faster
analysis times for many applications by moving to a scaled-down column that has the same phase ratio and number of theoretical plates as the original column. EZGC method translation software makes it exceptionally easy to do this on any GC system, and the translated method can be even further optimised if desired. Scaling down an existing method to a faster format is a very effective way to increase lab productivity and revenue.
Scott Grossman and Christopher Rattray are with Restek.
www.restek.com
www.scientistlive.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84
