Analytical Instrumentation Experimental Conditions


Table 1 lists the full experimental conditions developed for this analysis.


Gas


Chromatograph Oven


Injector Detector


Backflush Device Precolumn


Analytical Column


Midpoint Restrictor


Carrier Gas


Carrier Gas Pressure


Programming Injection Sample Preparation PerkinElmer Clarus® 680


100°C isothermal for 4 minutes. 0.5-min equilibration time


Split/Splitless or Programmable Split/Splitless. 100mL/min Split at 200°C


Flame Ionization at 200°C Air 450mL/min, Hydrogen 45mL/min Range x1, Attenuation x8


S-Swafer in S6 configuration 30m x 0.25mm x 0.25µm Elite-1 50m x 0.25mm x 0.4µm TCEP


Fused silica, 60cm x 0.100mm Hydrogen


Inlet: 30psig for 1.62 minutes, then 5psig by timed event until end of run Midpoint: 20psig for 1.61 minutes then 25psig by timed event until end of run


0.3µL by Autosampler in fast mode. 4 solvent washes following injection.


1mL 2-butanol (I.S.) added to 25-mL volumetric flask and gasoline sample added to bring total volume to 25mL.


Table 1: Full experimental conditions Analytical Performance


Good response linearity is an important requirement for this method as it will greatly simply the calibration process. Figure 4 shows the plots obtained from running D-3606 calibration standard mixtures on this system. Excellent linearity is evident.


A good method should demonstrate excellent quantitative


precision. To check this on this system, a gasoline sample was run 100 times and the standard deviations were calculated for the quantitative results. These data are shown in Table 2. For each analyte, the quantitative repeatability requirements of D- 3606 are easily met.


Component


Benzene Toluene


Mean


0.723 5.713


Concentration (% v/v) Std Dev


0.003 0.092


D 3606-07 Requirement


0.032 0.191


Table 2: Quantitative precision obtained from 100 injections of a single gasoline sample


Chromatographic peak retention time precision is a good indicator of a robust method. Table 3 shows the relative standard deviations obtained for the three components from the 100 gasoline sample runs. For such short chromatography, these results are excellent.


Retention Time


Component Benzene


2-Butanol (I.S) Toluene


Mean (min) 3.478 3.563


3.887


RSD (%) 0.020 0.021


0.019


Table 3: Retention time precision obtained from 100 injections of a single gasoline sample.


Another important requirement for this method is to demonstrate that there is no interference between successive analyses. This is particularly important in cases where a concentrated sample is followed by a low level sample. Figure 5 shows chromatography of a concentrated standard mixture immediately followed by chromatography of a solvent blank.


The carry-over value of 0.013% from an injection of toluene at a 20% v/v concentration represents a potential interference of 0.0026% v/v in the determined concentration which is far below the 0.5% v/v minimum calibration level.


Figure 4: System calibration plots


11


Figure 3: Analytical column chromatography of a gasoline sample with added internal standard.


Figure 5: Chromatography of a concentrated sample followed by injection of blank solvent to test for system carry-over.


Annual Buyers’ Guide 2011


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  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108