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
PRESENTATION TYPE: Podium
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
ABSTRACT BODY

Objective: 
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.

Methods: 
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.

Results
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%.


Conclusions: 
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 (FIRST NAME INITIAL LAST NAME): J. N. Driscoll1, J. L. Maclachlan
AUTHORS/INSTITUTIONS: J.N. Driscoll, J.L. Maclachlan, PID Analyzers, LLC, Sandwich, Massachusetts, Massachusetts, UNITED STATES;

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