2.4. Sample preparation
Aqueous solutions of amines were prepared in the concentration range 1–50 mM by dissolving the amines in MilliQ water. Next, for diamines, 750 L of standard solution was placed in a vial and 750 L (45 wt%) of ethylene-1,2-diamine was added. Addition of
the second amine provides the shielding effect for the analyte and reduces the relative water content, protecting the GC column from negative effects of water. In the case of primary amines, addition of ethylene diamine was not possible, due to overlapping retention times. Hence, for butylamine and pentylamine, 750 L of standard solution was diluted with 750 L of methanol, in order to decrease the amounts of water injected onto the column. For analysis of diamines, dilution with ethylene diamine is favored over dilution with methanol, because of a higher analysis quality.
2.5. Sample analysis Samples of 1.0 L were injected splitless at a temperature of
200 ◦C. The oven temperature was initially kept at 90 ◦C for 3 min,followed by a temperature ramp of 40 ◦C/min up to 110 ◦C. The column was operated at a constant flow mode with a helium pressure of 43 psi (296 kPA). The detection temperature was set at 300 ◦C with an air pressure of 16 psi (110 kPA) and a hydrogen pressure of 10 psi (69 kPA). No make-up gas was used. Analyses were done by injecting samples five times. Since in the first two injections the influence of the so-called memory effect was observed, they were discarded and the last three measurements were used in calculations.
2.4. Sample preparation
Aqueous solutions of amines were prepared in the concentration range 1–50 mM by dissolving the amines in MilliQ water. Next, for diamines, 750 L of standard solution was placed in a vial and 750 L (45 wt%) of ethylene-1,2-diamine was added. Addition of
the second amine provides the shielding effect for the analyte and reduces the relative water content, protecting the GC column from negative effects of water. In the case of primary amines, addition of ethylene diamine was not possible, due to overlapping retention times. Hence, for butylamine and pentylamine, 750 L of standard solution was diluted with 750 L of methanol, in order to decrease the amounts of water injected onto the column. For analysis of diamines, dilution with ethylene diamine is favored over dilution with methanol, because of a higher analysis quality.
2.5. Sample analysis Samples of 1.0 L were injected splitless at a temperature of
200 ◦C. The oven temperature was initially kept at 90 ◦C for 3 min,followed by a temperature ramp of 40 ◦C/min up to 110 ◦C. The column was operated at a constant flow mode with a helium pressure of 43 psi (296 kPA). The detection temperature was set at 300 ◦C with an air pressure of 16 psi (110 kPA) and a hydrogen pressure of 10 psi (69 kPA). No make-up gas was used. Analyses were done by injecting samples five times. Since in the first two injections the influence of the so-called memory effect was observed, they were discarded and the last three measurements were used in calculations.
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