Thursday, May 1, 2014

A Modified Analytical Method for the Determination of Arsine at Low ppb Levels by HG/GC/PID

The session "Innovations In IH Sampling and Analysis",  
PO131  took take place on Wednesday June 4, 2014 
from 2:00 PM to 5:00 PM
Convention Center 214C

Jennifer Maclachlan presenting at Innovations in IH Sampling and Analysis
San Antonio, TX June 4, 2014
CURRENT TOPICS: Sampling and Laboratory Analysis

TITLE: A Modified Analytical Method for the Determination of Arsine at Low ppb Levels by HG/GC/PID 3pm

The OSHA method for arsine involves the collection of arsine (PEL = 50 ppb) on a charcoal tube, desorption with nitric acid and analysis by graphite furnace/atomic absorption (GF/AA). The GF/AA is a complex and difficult technique that is often used for ppb analyses to obtain better sensitivity. We propose to replace the GF/AA method with a more sensitive method that replaces the readout method with an easier and more sensitive technique.

Since nitric acid (HNO3) is used to desorb the arsine, it is present in solution as arsenous acid (H3AsO3). The arsenous acid can be easily reduced to arsine (AsH3) using a reducing agent such as sodium borahydride. The AsH3 is collected on a solid sorbent and thermally desorbed into a GC where it is separated from other components and detected with a photoionization detector (PID). We have used this hydride generation GC/PID (HG/GC/PID) technique for the analysis of sub ppb levels of arsenic in water, seawater, soils, food and juices.

A linear calibration curve for arsenic was obtained for 5-500 ppb. The reproducibility for a set of five results provided the following data: the average value was 5.28 ppb, the standard deviation was 0.142 ppm and the coefficient of variation was excellent at 2.7%.

The HG/GC/PID method provides a very rapid and sensitive technique for the analysis of arsenic compounds at ppb levels. The precision of AsH3 for five samples at about 1/10th of the PEL. The same OSHA sampling and desorption method can be used for AsH3 and the GF/AA can be replaced with an easier to use and less costly method: HG/GC/PID.
AUTHORS/INSTITUTIONS: J.N. Driscoll, J.L. Maclachlan, PID Analyzers, LLC, Sandwich, Massachusetts, Massachusetts, UNITED STATES;

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