Simple Transient Extension Chamber to Permit Full Mass Scans with Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry

Abstract

The design for an in-line transient extension (TEx) chamber was developed to provide a simple means of lengthening an electrothermal vaporizer (ETV) signal for the purpose of obtaining a full mass scan from a single ETV firing with inductively coupled plasma mass spectrometry (ICP-MS) detection. The TEx chamber is simply a flask (e.g., 100–500 mL) with a mated joint allowing the ETV-generated aerosol to enter the chamber in a pulse and exit the chamber exponentially diluted. Characterization of the TEx chamber was completed with the use of the following metals: Ba, Be, Ce, Co, In, Mg, Pb, Th, and Tl. A decrease in peak area of 20 ± 4% was witnessed when the TEx chamber was put in-line between the ETV and the ICP-MS for all metals tested. Comparison of the peak areas obtained with and without the addition of 10 μL of 100 ppm NaCl to the sample without the TEx chamber in-line resulted in increases from 8 to 40%, depending on the metal. Repetition of the experiment with the TEx chamber in line showed no appreciable difference in results. This outcome indicates that dilution in the TEx chamber does not influence the behavior (i.e., enhancement effect) of the carrier. Interrupting the carrier gas flow for up to 2 min after the TEx chamber was “loaded” with the aerosol caused decreases in peak area from 25 to 35%, depending on the length of time the sample was held in the chamber. This result is most likely due to settling/loss of the aerosol particles in the chamber. Addition of 10 μL of 100 ppm NaCl to the sample showed a decrease in peak area of 30-43% when the sample was held for up to 2 min in the chamber, slightly higher than when no NaCl was present. A comparison of full mass scans taken with a concentric nebulizer and the ETV with an in-line TEx chamber using identical data collection rates and times showed that the TEx chamber can be used successfully as a method for both qualitative and quantitative identification of trace elements in an unknown solution. Detection limits for the nine metals tested with the TEx chamber in line are given.