Table of Contents

Guide for Packing Position of Silica Wool

Hint

Packing position and the amount of silica wool shown here are general guidelines. The optimal values may be different depending on analytical conditions and samples.

Normally, pack approximately 8 to 10 mg of wool for split analysis, or approximately 2 to 4 mg of wool for splitless analysis.
When analyzing samples with high latent heat of vaporization (e.g. aqueous solution), it may be good to increase the amount of packed silica wool. On the other hand, when analyzing highly adsorptive samples, it may be good to decrease the amount of packing.
For splitless injection or wide bore direct injection, it may be good not to pack silica wool. (To prevent absorption and decomposition)
When packing silica wool in tapered inserts, the reproducibility generally becomes better if wool is packed near the needle end of the syringe. However, when analyzing high matrix samples or highly adsorptive samples, the reproducibility and the recovery rate may be increased by packing wool at the bottom of the taper.
When analyzing samples with high-boiling compounds, the recovery rate may be increased by bringing down packed silica about 10 to 20 mm lower.
It is recommended to use inactivated inserts and silica wool to prevent absorption and decomposition in the injection inlet.
For split analysis, reproducibility may improve by smoothing the top surface of silica wool.

(Refer to Glass insert for capillary )

Guide for wool packing position for glass insert for capillary (SPL or WBI)¶

Injection method	Syringe Type	Packed position
When using AOC	Syringe for AOC
Manual Injection	Syringe with a needle length of 43 mm (for AOC)
Manual Injection	Syringe with a needle length of 51 mm

Note

Manual injection
Normally, pack silica wool at the position shown in the above figure. However, when using the syringe passing through a septum, place it 6.5 mm higher per septum.
For example, when using a "syringe with 43 mm needle" passing through a septum, pack wool at the position 20.5 mm from the top end, not 27 mm.

Guide for wool packing position for glass insert for PTV¶

Note

In PTV analysis, the best position of silica wool is significantly different depending on the target compound.
Consider the best position using the following descriptions as a reference. When the amount of injection is standard (1 to 2 µL), pack 1 to 2 mg of silica wool.
To analyze thermally unstable samples by cold injection, set silica wool near the needle end of the syringe.
In cold injection, the influence of the amount or the position of silica wool on the analysis is less compared to hot injection.
When analyzing samples with a wide boiling point range or high-boiling compounds, it is likely that recovery rate is better when silica wool is packed at 35 to 50 mm from the top end.
It is recommended to use inactivated silica wool to prevent absorption and decomposition in the injection inlet.

Injection method	Syringe Type	The position of the nearest silica wool from the needle end
When using AOC	Syringe for AOC	22 mm
Manual Injection	Syringe with a needle length of 43 mm (for AOC)	27 mm
Manual Injection	Syringe with a needle length of 51 mm	35 mm