{"id":43413,"date":"2020-10-27T14:30:00","date_gmt":"2020-10-27T14:30:00","guid":{"rendered":"https:\/\/discover.restek.com\/uncategorized\/faster-semivolatiles-analysis-with-a-scaled-down-method-and-gc-accelerator-kit\/"},"modified":"2026-01-03T17:45:56","modified_gmt":"2026-01-03T17:45:56","slug":"faster-semivolatiles-analysis-with-a-scaled-down-method-and-gc-accelerator-kit","status":"publish","type":"post","link":"https:\/\/discover.restek.com\/fr\/artikel\/evar2837\/faster-semivolatiles-analysis-with-a-scaled-down-method-and-gc-accelerator-kit","title":{"rendered":"Faster Semivolatiles Analysis with a Scaled-Down Method and GC Accelerator Kit"},"content":{"rendered":"\n

Analysis times for semivolatile compounds can limit sample throughput and decrease overall lab productivity. You can significantly speed up methods on your existing GC-MS by using a properly scaled-down column and appropriately adjusted instrument conditions. The challenge with this approach is that the new conditions can result in oven ramp rates that exceed the performance of standard GC ovens, especially 120 V ovens. However, by using a GC Accelerator oven insert kit, Agilent 6890 and 7890 GCs can meet aggressive scaled-down oven programs, producing the same chromatographic separations in much less time.<\/p>\n\n\n\n

In this technical article, we will walk through an example of scaling down EPA Method 8270 and using a GC Accelerator kit to reduce cycle time. Significantly faster semivolatiles analysis times were achieved, providing an opportunity for labs to increase sample throughput or process more rush samples.<\/p>\n\n\n\n

Scaling Down Your Semivolatiles Column<\/h2>\n\n\n\n

To achieve the same chromatographic results in less time, the first step is to take the traditional column for semivolatiles analysis, a 30 m long, 0.25 mm ID, 0.25 \u00b5m df arylene-type column (e.g., an Rxi-5Sil MS column) and scale it down to a more efficient format that retains the same number of theoretical plates as the original column. A 20 m long, 0.15 mm ID, 0.15 \u00b5m df Rxi-5Sil MS column (cat.# 43816<\/a>) fits these requirements. The proportionally narrower ID and thinner film will improve efficiency (i.e., give narrower peaks) and provide the same selectivity by keeping the phase ratio (\u03b2) constant. Higher efficiency results in more theoretical plates per meter of column, so by shortening the column to 20 m, a very similar total number of plates is achieved. As summarized in Table I, these changes result in the same degree of separation that is obtained on the traditional column format.<\/p>\n\n\n\n

Table I:<\/strong> Properly scaled-down columns provide the same separation in less time.<\/p>\n\n\n\n

Column Formats<\/strong><\/td><\/tr>
 <\/td>Traditional<\/strong><\/td> <\/td>Scaled-down<\/strong><\/td>Effect<\/strong><\/td><\/tr>
Part Number<\/strong><\/td>13623<\/td> <\/td>43816<\/td> <\/td><\/tr>
ID (mm)<\/strong><\/td>0.25<\/td>><\/td>0.15<\/td>Narrower ID creates greater efficiency<\/td><\/tr>
Film Thickness, df (\u00b5m)<\/strong><\/td>0.25<\/td>><\/td>0.15<\/td>Thinner film creates greater efficiency<\/td><\/tr>
Relative efficiency (plates\/m) compared to traditional format<\/strong><\/td>100%<\/td><<\/td>141%<\/td>The scaled-down column is more efficient and will produce narrower peaks<\/td><\/tr>
Phase Ratio (\u03b2)<\/strong><\/td>250<\/td>=<\/td>250<\/td>Equivalent \u03b2 will maintain the same selectivity between columns<\/td><\/tr>
Length (m)<\/strong><\/td>30<\/td>><\/td>20<\/td>Shortening the scaled-down column will create a similar total number of plates<\/em><\/td><\/tr>
Relative Total Plates compared to traditional format<\/strong><\/td>100%<\/strong><\/td>\u2248<\/strong><\/td>94%<\/strong><\/td>Very similar total number of plates means the same degree of separation in less time<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Scaling Down Method Conditions with the EZ<\/em>GC Method Translator<\/h2>\n\n\n\n

A scaled-down column requires a scaled-down method to ensure that compound elution temperatures will be the same so that equivalent separations will be achieved in a faster analysis time. Correctly translating the scaled-down column flow rates and oven temperature ramp rates can be a challenge, but this task is made simple by using Restek\u2019s EZ<\/em>GC method translato<\/a>r. This free, online tool calculates properly translated method conditions based on your original column and method in seconds. Just input your current column dimensions, flow parameters, and oven program, then define the new column format you\u2019d like to use, and the software will do the rest.<\/p>\n\n\n\n

To set up a comparison of traditional vs. scaled-down, faster semivolatiles analysis, Figure 1 shows a chromatogram generated using EPA 8270D method conditions, split injection, and the traditional column format. In this case, the analysis time has already been shortened by a few minutes from the typical splitless injection approach by the successful adoption of a split injection.<\/p>\n\n\n

Figure 1:<\/strong>\u00a0Split analysis of semivolatiles on a traditional 30 m, 0.25 mm ID, 0.25 \u00b5m df Rxi-5Sil MS column.<\/div>
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\"Semivolatiles<\/div>

GC_EV1248<\/p>

Peaks<\/h4>\n
<\/th>Peaks<\/th><\/tr><\/thead>\n
1.<\/td>1,4-Dioxane-d8 (IS)<\/a><\/td><\/tr>\n
2.<\/td>1,4-Dioxane<\/a><\/td><\/tr>\n
3.<\/td>N-Nitrosodimethylamine<\/a><\/td><\/tr>\n
4.<\/td>Pyridine<\/a><\/td><\/tr>\n
5.<\/td>2-Fluorophenol (SS) <\/a><\/td><\/tr>\n
6.<\/td>Phenol-d6 (SS) <\/a><\/td><\/tr>\n
7.<\/td>Phenol<\/a><\/td><\/tr>\n
8.<\/td>Aniline<\/a><\/td><\/tr>\n
9.<\/td>Bis(2-chloroethyl)ether<\/a><\/td><\/tr>\n
10.<\/td>2-Chlorophenol<\/a><\/td><\/tr>\n
11.<\/td>1,3-Dichlorobenzene<\/a><\/td><\/tr>\n
12.<\/td>1,4-Dichlorobenzene-D4 (IS)<\/a><\/td><\/tr>\n
13.<\/td>1,4-Dichlorobenzene<\/a><\/td><\/tr>\n
14.<\/td>Benzyl alcohol<\/a><\/td><\/tr>\n
15.<\/td>1,2-Dichlorobenzene<\/a><\/td><\/tr>\n
16.<\/td>2-Methylphenol<\/a><\/td><\/tr>\n
17.<\/td>Bis(2-chloroisopropyl)ether<\/a><\/td><\/tr>\n
18.<\/td>4-Methylphenol<\/a><\/td><\/tr>\n
19.<\/td>3-Methylphenol<\/a><\/td><\/tr>\n
20.<\/td>N-Nitroso-di-n-propylamine<\/a><\/td><\/tr>\n
21.<\/td>Hexachloroethane<\/a><\/td><\/tr>\n
22.<\/td>Nitrobenzene-D5 (SS) <\/a><\/td><\/tr>\n
23.<\/td>Nitrobenzene<\/a><\/td><\/tr>\n
24.<\/td>Isophorone<\/a><\/td><\/tr>\n
25.<\/td>2-Nitrophenol<\/a><\/td><\/tr>\n
26.<\/td>2,4-Dimethylphenol<\/a><\/td><\/tr>\n
27.<\/td>Benzoic acid<\/a><\/td><\/tr>\n
28.<\/td>Bis(2-chloroethoxy)methane<\/a><\/td><\/tr>\n
29.<\/td>2,4-Dichlorophenol<\/a><\/td><\/tr>\n
30.<\/td>1,2,4-Trichlorobenzene<\/a><\/td><\/tr>\n
31.<\/td>Naphthalene-D8 (IS)<\/a><\/td><\/tr>\n<\/tbody><\/table>\n\n
<\/th>Peaks<\/th><\/tr><\/thead>
32.<\/td>Naphthalene<\/a><\/td><\/tr>\n
33.<\/td>4-Chloroaniline<\/a><\/td><\/tr>\n
34.<\/td>Hexachlorobutadiene<\/a><\/td><\/tr>\n
35.<\/td>4-Chloro-3-methylphenol<\/a><\/td><\/tr>\n
36.<\/td>2-Methylnaphthalene<\/a><\/td><\/tr>\n
37.<\/td>1-Methylnaphthalene<\/a><\/td><\/tr>\n
38.<\/td>Hexachlorocyclopentadiene<\/a><\/td><\/tr>\n
39.<\/td>2,4,6-Trichlorophenol<\/a><\/td><\/tr>\n
40.<\/td>2,4,5-Trichlorophenol<\/a><\/td><\/tr>\n
41.<\/td>2-Fluorobiphenyl (SS)<\/a><\/td><\/tr>\n
42.<\/td>2-Chloronaphthalene<\/a><\/td><\/tr>\n
43.<\/td>2-Nitroaniline<\/a><\/td><\/tr>\n
44.<\/td>1,4-Dinitrobenzene<\/a><\/td><\/tr>\n
45.<\/td>Dimethyl phthalate<\/a><\/td><\/tr>\n
46.<\/td>1,3-Dinitrobenzene<\/a><\/td><\/tr>\n
47.<\/td>2,6-Dinitrotoluene<\/a><\/td><\/tr>\n
48.<\/td>1,2-Dinitrobenzene<\/a><\/td><\/tr>\n
49.<\/td>Acenaphthylene<\/a><\/td><\/tr>\n
50.<\/td>3-Nitroaniline<\/a><\/td><\/tr>\n
51.<\/td>Acenaphthene-d10 (IS)<\/a><\/td><\/tr>\n
52.<\/td>Acenaphthene<\/a><\/td><\/tr>\n
53.<\/td>2,4-Dinitrophenol<\/a><\/td><\/tr>\n
54.<\/td>4-Nitrophenol<\/a><\/td><\/tr>\n
55.<\/td>2,4-Dinitrotoluene<\/a><\/td><\/tr>\n
56.<\/td>Dibenzofuran<\/a><\/td><\/tr>\n
57.<\/td>2,3,5,6-Tetrachlorophenol<\/a><\/td><\/tr>\n
58.<\/td>2,3,4,6-Tetrachlorophenol<\/a><\/td><\/tr>\n
59.<\/td>Diethyl phthalate<\/a><\/td><\/tr>\n
60.<\/td>4-Chlorophenyl phenyl ether<\/a><\/td><\/tr>\n
61.<\/td>Fluorene<\/a><\/td><\/tr>\n
62.<\/td>4-Nitroaniline<\/a><\/td><\/tr>\n<\/tbody><\/table>\n\n
<\/th>Peaks<\/th><\/tr><\/thead>
63.<\/td>4,6-Dinitro-2-methylphenol<\/a><\/td><\/tr>\n
64.<\/td>N-nitrosodiphenylamine<\/a><\/td><\/tr>\n
65.<\/td>1,2-Diphenylhydrazine<\/a><\/td><\/tr>\n
66.<\/td>2,4,6-Tribromophenol (SS) <\/a><\/td><\/tr>\n
67.<\/td>4-Bromophenyl phenyl ether<\/a><\/td><\/tr>\n
68.<\/td>Hexachlorobenzene<\/a><\/td><\/tr>\n
69.<\/td>Pentachlorophenol<\/a><\/td><\/tr>\n
70.<\/td>Phenanthrene-D10 (IS)<\/a><\/td><\/tr>\n
71.<\/td>Phenanthrene<\/a><\/td><\/tr>\n
72.<\/td>Anthracene<\/a><\/td><\/tr>\n
73.<\/td>Carbazole<\/a><\/td><\/tr>\n
74.<\/td>di-n-Butyl phthalate<\/a><\/td><\/tr>\n
75.<\/td>Fluoranthene<\/a><\/td><\/tr>\n
76.<\/td>Benzidine<\/a><\/td><\/tr>\n
77.<\/td>Pyrene-D10 (SS)<\/a><\/td><\/tr>\n
78.<\/td>Pyrene<\/a><\/td><\/tr>\n
79.<\/td>p-Terphenyl-d14 (SS)<\/a><\/td><\/tr>\n
80.<\/td>3,3′-Dimethylbenzidine<\/a><\/td><\/tr>\n
81.<\/td>Butyl benzyl phthalate<\/a><\/td><\/tr>\n
82.<\/td>Bis(2-ethylhexyl)adipate<\/a><\/td><\/tr>\n
83.<\/td>3,3′-Dichlorobenzidine<\/a><\/td><\/tr>\n
84.<\/td>Benz[a]anthracene<\/a><\/td><\/tr>\n
85.<\/td>Chrysene-D12 (IS)<\/a><\/td><\/tr>\n
86.<\/td>Bis(2-ethylhexyl)phthalate<\/a><\/td><\/tr>\n
87.<\/td>Chrysene<\/a><\/td><\/tr>\n
88.<\/td>Di-n-octyl phthalate<\/a><\/td><\/tr>\n
89.<\/td>Benzo[b]fluoranthene<\/a><\/td><\/tr>\n
90.<\/td>Benzo[k]fluoranthene<\/a><\/td><\/tr>\n
91.<\/td>Benzo[a]pyrene<\/a><\/td><\/tr>\n
92.<\/td>Perylene-D12 (IS)<\/a><\/td><\/tr>\n
93.<\/td>Indeno[1,2,3-cd]pyrene<\/a><\/td><\/tr>\n
94.<\/td>Dibenz[a,h]anthracene<\/a><\/td><\/tr>\n
95.<\/td>Benzo[ghi]perylene<\/a><\/td><\/tr>\n<\/tbody><\/table><\/div>

Conditions<\/h4>
Column<\/th>Rxi-5Sil MS, 30 m, 0.25 mm ID, 0.25 \u00b5m (cat.# 13623<\/a>)<\/td><\/tr>
Standard\/Sample<\/th><\/td><\/tr>
<\/td>8270 MegaMix (cat.# 31850<\/a>)<\/td><\/tr>
<\/td>8270 Benzidines mix (cat.# 31852<\/a>)<\/td><\/tr>
<\/td>Benzoic acid (cat.# 31879<\/a>)<\/td><\/tr>
<\/td>1,4-Dioxane (cat.# 31853<\/a>)<\/td><\/tr>
<\/td>Revised B\/N surrogate mix (cat.# 31888<\/a>)<\/td><\/tr>
<\/td>Acid surrogate mix (4\/89 SOW) (cat.# 31063<\/a>)<\/td><\/tr>
<\/td>Revised SV internal standard mix (cat.# 31886<\/a>)<\/td><\/tr>\n
Diluent:<\/th>Methylene chloride<\/td><\/tr>
Conc.:<\/th>40 \u00b5g\/mL (IS\/SS 20 \u00b5g\/mL)<\/td><\/tr>
Injection<\/th><\/td><\/tr>
Inj. Vol.:<\/th>1 \u00b5L split (split ratio 10:1)<\/td><\/tr>
Liner:<\/th>Premium 4 mm Precision liner w\/wool (cat.# 23305<\/a>)<\/td><\/tr>
Inj. Temp.:<\/th>270 \u00b0C<\/td><\/tr>
Split Vent Flow Rate:<\/th>12 mL\/min.<\/td><\/tr>
Oven<\/td><\/tr>
Oven Temp.:<\/th>70 °C (hold 1 min) to 285 °C at 28 °C\/min to 305 °C at 3 °C\/min to 320 °C at 30 °C\/min (hold 1 min)<\/td><\/tr>
Carrier Gas<\/th>He, constant flow<\/td><\/tr>
Flow Rate:<\/th>1.2 mL\/min<\/td><\/tr><\/table>
Detector<\/th>MS<\/td><\/tr>
Mode:<\/th>Scan<\/td><\/tr>
Transfer Line Temp.:<\/th>280 \u00b0C<\/td><\/tr>
Analyzer Type:<\/th>Quadrupole <\/td><\/tr>
Source Temp.:<\/th>270 \u00b0C<\/td><\/tr>
Quad Temp.:<\/th>150 \u00b0C<\/td><\/tr>
Electron Energy:<\/th>70 eV<\/td><\/tr>
Solvent Delay Time:<\/th>1.3 min<\/td><\/tr>
Tune Type:<\/th>DFTPP <\/td><\/tr>
Ionization Mode:<\/th>EI <\/td><\/tr>
Scan Range:<\/th>35-550 amu<\/td><\/tr>
Scan Rate:<\/th>5.36 scans\/sec<\/td><\/tr>
Instrument<\/th>Agilent 7890A GC & 5975C MSD<\/td><\/tr><\/table><\/div><\/div><\/div>
<\/path><\/g><\/path><\/g><\/svg>Download PDF<\/a><\/div><\/div><\/div>\n<\/div><\/div><\/div>\n\n\n

Figure 2 shows how the split injection semivolatiles analysis illustrated in Figure 1 can be easily translated to the scaled-down column format using the EZ<\/em>GC method translator. Split injection is particularly important with the scaled-down analysis to avoid overloading the column and to transfer a sample band narrow enough to be compatible with the very narrow peaks that the more efficient, scaled-down column produces. Because the narrower peaks are also taller, there is the additional benefit of enough sensitivity to still meet the low detection limits commonly required for semivolatiles analysis. In the scaled-down example shown later in this article, the split ratio was successfully increased from 10:1 to 20:1.<\/p>\n\n\n\n

Note that in the examples presented here, the final oven ramp rates and final hold times may differ from the method translator output in Figure 2. The final oven ramp rate shown in the original method of the EZ<\/em>GC method translator example was lowered to 20 \u00b0C\/min (compared to 30 \u00b0C\/min Figure 1) in order to represent a rate that is attainable by analysts using Agilent 6890 and 7890 120 V GC ovens. Because the last compound elutes before the final oven ramp, these differences do not affect the chromatographic comparison. Final hold times also do not affect the chromatographic separations and are generally defined in analytical methods.<\/p>\n\n\n

Figure 2:<\/strong>\u00a0Use the\u00a0EZ<\/em>GC method translator to move from a traditional column format to a scaled-down column for faster semivolatiles analysis: (a) Fields to input original method conditions; (b) field to input new column dimensions; (c) calculated scaled method conditions, with ramp rates that pose a problem for certain GCs but that can be resolved with the GC Accelerator kit; (d) calculated analysis time changes.<\/div>
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