Programmed split injection

Figure D1.2.2 Sample GC chromatogram of the FAME from butter fat (Sweet Cream Butter, Wisconsin Grade AA, Roundy s, Milwaukee, Wise.) prepared using the sodium methoxide method (see Basic Protocol 2). Equipment DB-23 fused silica capillary column, 30 m x 0.32 mm i.d., 0.25 pm film thickness, FID detector. Temperature, injector 225°C detector 250°C. Column (oven) temperature program 100°C initial, hold 4 min, ramp to 198°C at 1.5°C/min, hold 10 min. Total run time was 80 min. Split injection.

Analyses of the starting material and products were carried out by GC and GC-MS analyses. For GC analyses, a Shimadzu gas chromatograph, GC-17A, was used. A 60-m-long narrow bore (0.25-mm) DB5 with 0.25-gm phase thickness supplied by J W Scientific was used. The GC parameters were as follows split injection (split ratio of 50 1), carrier gas of hydrogen at 1 cm3/min at 30°C. The heating program was as follows initial temperature of 30°C, initial time of 2 min, rate of 30-250°C at 3°C/min, final time... 

Gas Chromatographic Conditions. All analyses were performed on a Hewlett Packard 5890 GC equipped with a 5970 Mass Selective Detector or a Hewlett Packard 6890 GC equipped with a Nitrogen Phosphorous Detector (Hewlett Packard, Inc., Avondale, PA). A DB 35 (35% phenyldimethylpolysiloxane), 30 m x 0.25 mm ID X 0.25 [im column (J W Scientific, Inc., Folsom, CA) was used for all analyses. Carrier gas was helium at a linear velocity of 30 cm/sec. Samples were analyzed using split injections (split ratio = 30 1) with injector and detector (NPD) temperatures of 260°C and 250°C, respectively. Oven temperature programming was as follows initial temperature of 80°C for 1 min increase temperature at 3.5°C/min to 115°C increase at 15°C/min to 180°C increase at 60 C/min to 190°C hold at 190°C for 6 min. 

Actually, same articles show the possibility of use split injection [8] in HT-HRGC analyses of substances up to C78. However, volatile materials from the septum accumulate at the head of the column during the cooldown portion of the temperature program. When the columns are reheated to analyze the next sample, these accumulated volatiles are eluted, producing peaks, a baseline rise, or both. This difficulty can be solved using commercial septa already available for HT-HRGC, which exhibit very low bleed levels. 

Figure 4.21 GC-FID analysis of the four VPs in a wine (analytes in exploded window). Analytical conditions DBWax (PEG, 30m x 0.32mm i.d. 0.25(im coating thickness) capillary fused column (J W) split injection oven temperature program 4min at 40°C, 2.5°C/min until 185°C, isotherm for 15min, 10°C/min until 220 °C, isotherm for 10 min injector and detector temperature 250 °C carrier gas He at flow rate 1.93mL/min...

Identincation. The components in the fractionated oils mentioned above were analyzed by GC and GC/MS resulting in the identification of 12 hydrocarbon terpenes and 72 oxygenated compounds. Gas chromatographic conditions were OV-101 column, 50 m X 0.25 mm i.d., 80 C to 200 C at 2 C/min. GC/MS was conducted with a JEOL JMS-SX102AQQ (El mode, 70 eV) equipped with a JEOL MP-7010 data processor unit. The analytical conditions were almost the same as the GC conditions OV-101, 50 m X 0.25 mm i.d. temperature program, 80-200 C at 2 °C/min He, 0.64 mL/min split injection (1 50). NIST public data library of MS spectra (data number 49,496) which was supplied from JEOL LTD was used for matching of mass spectral pattern. 

CP 9002, 50 m length, 0.32 mm ID CP-SIL 5 CB column with pre-column 1 m, 0.32 mm ID, carrier gas He split injection temperature program 45-300 °C, 4°C/min FID detector. Heptane correlation ratios (ratios Cj to C5) were calculated according to the method developed by Halpern (1995). 

Deutsch, L.J. and A.L. Jeffords Simnltaneons gas chromatographic nicotine/water analysis in smoke via split injection on dnal capillary colunms 48th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 48, Paper No. 35, 1994, p. 45. 

Figure 5. Capillary SFC-CLND profile of hot mustard extract [0.1 gram of mustard powder extracted in 1 mL water (30%) and methanol (70%) solution]. Peaks A = allyl isolbiocyanatc, B = 2-butyl isolbiocyanatc, and C = unknown nitrogen containing compound. Chromatographic conditions pressure program from 80 atm (hold 5 min), ramp to 150 atm at 10 atm/min, then to 200 atm at 15 alm/min Cyano (20 in x 100 mm ID, 0.25 mm film thickness) column lime split injection 0.2 sec. Reprinted with permission from H. Shi,...

Carbon dioxide, P = 80 bar, program to 350 bar at 10 bar / min, T = 80°C Flow control by a fixed restrictor between the column and detector. Flame ionization detector is generally used (UV detector when organic modifiers are used). Split injection usually required. Syringe pumps commonly used (eluent flow rate 10s pl/min). 

Figure 3. SFC-MS response vs. probe tip temperature for Triton X-100. Conditions 10 m X 50 urn i.d. X 0.1 um film DB-17 column, column temperature = 90 C, probe stem temperature = 90 C, 0.1 uL of a 25 mg/ml Triton X-100 in methylene chloride solution split injected, split ratio 1 2, pressure program = 100 atm for 3 min, ramp to lAO atm in 3 min, ramp to 325 atm in 23 min, methane Cl, MS source temperature = 200 C.

Jennings has argued that splitless injection is not really without split and is a term only to be used when comparing the technique to that of split injection (31). More contemporary GCs enable the user to program a splitless injector (i.e., control of the time that a split vent remains closed). One other concept needs to be addressed before we move to the GC column in our journey through a gas chromatograph. That concept is that of sample size injected. If we are not careful, we might overload the GC column. ... 

Capillary GLC columns are excellent for the analysis of TAGs. It is essential that a precolumn (retention gap) of uncoated, silanized silica tube (1.0 m x 0.53 mm ID) be attached to the analytical column. The injection technique of choice for both EAME and TAGs should be on-column. Split injection almost always leads to quantitative errors in these analyses. Both helium and hydrogen are adequate carrier gasses. A 7-10 m bonded phase (OVl, film thickness 0.1 pm) 0.53 mm ID column is used with a temperature stability of at least 350°C, but aluminum-clad columns are avoided. A temperature program is used, starting at 100°C rising to 350°C at 10°Cmin . While the carrier gas velocity for... 

Column 12 m x 0.30 mm, coated with SE-30 methylsilicone. Uncoated tubing 40 cm X 0.2 mm i.d. Column temperature programmed from 40°C at 57min. Split injection, 1 25, injector temperature 280 °C. Carrier gas hydrogen,50 cm/s. Peaks 1 — 2,3-butanediol, 2 — n-decane, 3 — 1-octanol,... 

Figure 9.1 Separation of linear alkyl benzenes (column 25 mx 0.2 mm i.d., HPlOl, programmed from 120°C to 240 C at 3°C/min, injector/detector temperature 270 C, helium carrier, split injection, flame ionisation detector).

The purpose of this injection technique is to introduce the entire injected sample into the column and use it for trace determination. Different techniques can be used, but the most common is the solvent effect technique, which uses the same instrumentation as used for spht injection (Figure 2.4). In splitless injection, the sample is introduced into the heated liner as in split injection and brought into the gas phase. Contrary to the spht injection, the splitter outlet valve is now dosed. Hence, the total sample volume (1-2 ml of gas) is transferred to the column. When splitiess injection is carried out, the column inlet temperature is kept at a temperature that is 20-50 °C lower than the solvent Bp. Hence, when the sample arrives at the column inlet, the solvent condenses as a thick film on the column wall. This film will act as a plug of stationary phase into which the sample components will be dissolved. Following the sample transfer to the column, which will take 2 min when 2 pi is injected and the carrier gas flow rate is 1 ml min , the column oven temperature is increased. The solvent evaporates first from the column entrance and thereafter the analytes, which will subsequently be separated in the column. The sphtter valve is opened when the whole sample has been transferred to the column in order to wipe out remains of the sample before the next injection. This injection technique is used for trace determinations and can only be carried out in combination with temperature programming. 

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