| CPC B01J 20/287 (2013.01) [B01J 20/285 (2013.01); B01J 20/3282 (2013.01); G01N 30/6065 (2013.01); G01N 30/6078 (2013.01); G01N 2030/025 (2013.01)] | 18 Claims | 

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               9. A method of peak focusing in a gas chromatography device, comprising: 
            introducing two or more target analytes into an inlet of a chromatographic column comprising a stationary phase deposited inside the chromatographic column and having a positive thickness gradient, wherein the stationary phase extends from the inlet to an outlet and has a first thickness at the inlet of the chromatographic column and a second thickness at the outlet of the chromatographic column, wherein the second thickness is at least about 10% greater than the first thickness; 
                separating two or more target analytes in the chromatographic column; and 
                eluting the two or more target analytes from the outlet of the chromatographic column. 
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