Capabilities of the Adsorbent Tube Injector System (ATIS)

Reporter US Volume 31.2

Introduction

The Adsorbent Tube Injector System (ATIS) was developed at Supelco by R&D Scientists, as a tool to assist in our comprehensive adsorbent research for thermal desorption tubes. The ATIS provides an efficient means of transferring calibration standards in either the gas or liquid phase onto the adsorbent packed tubes.

The ATIS employs the technique of flash vaporization to vaporize the sample in a continuous flow of inert gas; the inert gas carries the sample to the tube. The sample pathway of the ATIS is constructed of glass and stainless steel. The calibration standard is injected by a syringe through a replaceable septum in the center of the injection glassware, which is heated. After enough time has elapsed, typically less than five minutes, the tube is removed from the ATIS and analyzed using the appropriate analytical technique for that adsorbent tube.

The ATIS will accept either a 1/4” or 6 mm O.D. thermal desorption tube; a 6 mm ORBO™ sorbent tube; adsorbent tubes with male luer fittings; and gas sampling bags with a 3/16 inch stem.

Capabilities

  • Allows injection of calibration standards onto adsorbent tubes to calibrate your analytical system.
  • Permits injection of surrogates and system monitoring compounds onto an adsorbent tube before or after sampling.
  • Removes moisture from the tube prior to analysis (dry purging).

  • Vaporizes neat compounds into a gas sampling bag to create a calibration standard. By volatizing the compounds with the ATIS, this allows you to use the contents of the bag immediately without having to let it equilibrate overnight.

Expanded Capabilities with ATIS

Thermally extract solid samples and collect the volatiles onto an adsorbent tube. The temperature range is adjustable from ambient to 150 °C. Extraction glassware is available (Cat. No. 28523-U) that will accommodate solid samples up to 76 mm (3”) length and 13 mm (1/2”) in diameter.

Purge volatiles from an aqueous sample onto an adsorbent tube at ambient temperatures. A purge and trap humidifier module is available (Cat. No. 28522-U) that interfaces with the ATIS. This module can also be used to generate a dynamic humidified stream of an inert gas for spiking calibration standards. The purge and trap module includes purge and trap glassware, and a separate flow controller that allows the user to set a separate purge (wet) flow rate independently of the (dry) flow rate.

Guidelines for Using the ATIS

To accurately quantify the concentration of a sample collected with an adsorbent tube, the analytical system must first be calibrated. The ATIS simplifies this task. Below are a few starting parameters, some experimentation may be needed to optimize the conditions for your application. Allow enough time for the block heater to equilibrate to the desired temperature before injecting your standards. You will also want to make sure you have gas flowing through your adsorbent tube prior to injecting your standard, so the compounds will be carried to the tube.

Injecting Gas Phase Standards

Gas phase standards are available in compressed gas cylinders, made up in gas sampling bags, or gas sampling bulbs.

  • Set the block temperature between 60 to 75 °C.
  • Set the flow rate of the carrier gas to 50 mL/min.
  • Allow the adsorbent tube to remain attached for two to five minutes after injecting the gas mix with the carrier gas on.
  • The delivery rate of the gas syringe should be less than 10 mL/min.

Large syringe volumes of gas standards can be injected through the septum of the injection glassware, but the injection rate of the syringe plunger must be slow. The rate that you inject the gas mix will have an affect on the total flow rate passing through the adsorbent tube. For example: If you injected a 100 mL syringe volume of a gas mix into the injection glassware, and it takes 10 seconds to inject the entire 100 mL volume, the flow rate going through the adsorbent tube for those 10 seconds is 600 mL/min. That is too fast. There is a good chance that the compounds in the gas mix could break through the adsorbent and not be retained. In general, the delivery rate of the syringe should be less than 10 mL/min.

Injecting Liquid Phase Standards

Liquid standards are typically made up in a solvent such as methanol, hexane or carbon disulfide.

  • Set the block temperature 10 °C above the boiling point of the solvent. If the compounds in your liquid standard are larger than C12, set the block heater temperature to 100 °C.
  • Set the flow rate of the carrier gas to 50 mL/min.
  • Inject the liquid standard, and then allow the tube to remain attached for two to five minutes with the carrier gas flowing through the tube.

Unlike gas standards there is a limit to how much volume you can inject. If too much liquid is injected, the liquid could flashback into the plumbing of the system. Injection volumes of liquid standards should be less than 25 microliters. The injection rate for liquid standards can be quicker than that of gas standards, since the displacement of microliter volumes will have minimum impact on the flow rate going through the adsorbent tube. It is important to allow enough time for the contents of the liquid standard to be transferred to the tube before removing the adsorbent tube. For example; if the flow rate of the carrier gas is set to 50 mL/min, after two minutes the injection glassware will be purged 10 times. Ten exchanges are typically enough to completely purge all of the compounds from the injection glassware.

Summary

The ATIS is a multipurpose laboratory tool for adsorbent tubes. It provides an efficient way to spike adsorbent tubes with calibration standards, internal standards, and system monitoring compounds. The ATIS can also be used to dry purge moisture from the tubes that were exposed to high humidity. Accessories can be added that allow researchers to off-gas solid samples, purge volatiles from liquid matrices and collect the volatile compounds onto adsorbent tubes. The ATIS system will save your laboratory time in everyday sample preparation of adsorbent tubes.

Featured Products  
Description Cat. No.
ATIS System, 110V 28520-U
ATIS System, 220V 28521-U
Purge and Trap Humidifier Module 28522-U
Extraction Glassware w/Ground Joint 28524-U
Extraction Glassware w/Micro Connector 28523-U
Half-hole Septa (6 mm O.D. x 9 mm L), pk/100 20668
Ferrules, 1/4 in., PTFE, white, pk/10 29024-U

Trademarks
ORBO is a trademark of Sigma-Aldrich Co. LLC

Related Links