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The solvent effect occurs when the sample solvent is vaporized during injection and condenses on a cool column. Where "cool" is relative to the boiling point of the injection solvent and is often ten to twenty degrees below the boiling point of said solvent. Typically, this serves to trap analytes in a narrow band producing sharp peaks. However, solvent effects can also have a negative impact. In this example we have two main solvents as listed in the following table:

Solvent	Boiling Point
Acetone	56.5°C
Acetonitrile	82°C

The GC method in use, is one using splitless injection with an injector temperature of 250°C and an initial oven temperature of 70°C. Based on the boiling points we can see that there will be solvent effects from both acetone and acetonitrile. In the following chromatograms the concentration of acetone is increased while the concentration of acetonitrile is decreased and the concentration of the analytes is held constant. In effect this creates multiple solvent effects at the head of the column, resulting in the greatest peak distortion when the ratios are around 50:50. We can see that increasing acetone concentration decreases the amount of peak distortion until sharp peaks are obtained at a concentration of 90% acetone.

Vial fill effecting reproducibility was mentioned in an Agilent document called something like "Maximizing Reproducibility in GC/MS Analysis." In this paper one of the suggestions was consistent vial fill volume with a suggested fill of 1mL. Can vial fill level have an impact on reproducibility? To find out I ran five replicates at 0.5mL, 1.0mL and 1.5mL. All samples were transferred using a Rainin EDP pipette. The method is a rapid ethanol analysis with acetonitrile as the internal standard and acetone as the solvent. The working ethanol concentration was 0.6% with a 100:1 split ratio and a injection volume of 0.1uL. A 5uL syringe was in the 7683 ALS. As you can see the 1mL fill was indeed the most reproducible.

Many texts report that an inlet temperature of 250°C is sufficient for most samples. While it may be sufficient it may not be the optimum temperature for your specific sample. The selection of the inlet parameters should yield rapid and complete vaporization, without sample back flash or degradation. Here is an example of how important inlet temperature can be.
The sample being analyzed is a PFBOA derivative dissolved in acetonitrile. The inlet liner is an SGE tapered focus liner. Pulsed splitless mode was used with a pulse pressure of 14psi for 0.5min. Purge flow was active at 0.04min with a flow of 25mL/min. As you can see the peak area increases as the inlet temperature increases up to 175°C and then starts decreasing with increasing temperature. In this particular case we are seeing sample degradation as opposed to back flash.

The 7683 is an automated liquid sampler. Agilent however, publishes information that it can be used as a kind of poor man’s headspace sampler (Matthew S. Klee and Chin Kai Meng 2000). In this mode a large volume, gas tight syringe, is used to sample the headspace of a standard auto sampler vial. The Agilent recommended sample prep is:

1. Sample in vial (less than 1/2 full), with a working concentration of 0.1% EtOH in water.
2. Add. 0.5g Na₂SO₄
3. Add internal standard
4. Cap vial tightly
5. Shake (this can be done using the barcode reader)

With these preparation steps Agilent reports and RSD of 1.82% (50uL injections from 12 different vials).
I ran this method with samples I had prepared for liquid injection with acetone as the solvent. The samples were not shaken, no Na₂SO₄ was added and screw cap vials were used. I ran the using the same parameters that I use for liquid injection but in splitless mode. The purge flow (25mL/min ) was on at injection. This was the result:
The performance is comparable with Agilent’s (n=3, different vials).

EtOH (% v/v)	%RSD
0.2	1.9
0.5	1.9
0.7	1.8
1.0	0.3

The calibration curve also looked good:
Advantages vs. liquid injection

1. Added column protection for especially dirty samples.
2. Can run samples of higher concentrations without having to dilute the sample.
3. Potentially eliminates interferences and matrix effects.

Advantages vs. standard HS injection

1. Faster, no need to heat and pressurize each vial.
2. Shorter setup.
3. No risk of exceeding column flow with diffusion pump MS systems.

Disadvantages vs. liquid injection and standard headspace injection

1. Possible oxygen column damage. There is a lot of air in the headspace. In standard headspace analysis the vial is pressurized with helium.
2. Lower limits of detection in most cases.
3. Higher RSDs.

Here are a couple examples of split pulse injections. The run conditions were: Constant flow mode at 1.0mL/min He with an inlet pressure of 6.8psi. The split was 100:1. The first example compares pulse pressure 9psi vs. 8psi:

The second example compares pulse length, 0.00min vs. 0.01min:

UPDATE: In response to Sam's email.
So what's happening here? First, the inlet pressure is higher at injection. This means that the vapor volume will be less. Second, the flow out the split vent is increasing. If this were pulsed splitless injection, lower vapor volume would mean more sample mass on the column. Pulsed split injection allows the sample vapor to exit out the split vent. With a set ratio, less sample volume means less sample mass is transferred to the column. Further, in pulsed split, the split flow increases proportional to the pulse pressure sweeping more of the sample out the split vent. In this case the solvent is n-butanol. The vapor volumes would be:

Pressure (psi)	Vapor Volume (uL)	Approximate Split Flow (mL/min)
6.8	321	100
8.0	304	118
9.0	291	132
10.0	279	147