Tech Notes
| Technical Brief Evaluation of disposable syringes for the collection of soil gas Background Disposable plastic syringes are commonly used to collect soil gas for on-site analysis. While these syringes are inexpensive and convenient, the syringes have not been fully validated for VOC recovery. To evaluate the significance of VOC adsorption during sample storage in the plastic syringe, a multi-component VOC standard was prepared and stored in a plastic syringe from 5 minutes to 30 minutes to model typical field holding times. After the hold-time duration, the contents of the syringe were analyzed by EPA Method TO-15 to determine recovery. Two concentrations were tested, and the VOC test standard was prepared at approximately 70% RH to simulate a typical soil gas matrix. The syringes tested were Norm-Ject®, Air-Tite 60 ml capacity manufactured by Henke Sass and Wolf. These syringes are composed of a polypropylene barrel and a polyethylene plunger. Because they do not contain contaminates often associated with disposables, they are often used for VOC analysis. To request a copy of the complete study, please click here. Results Recoveries for several VOCs are graphed in Figures 1 and 2. The VOCs are represented on the x-axis and ordered left to right in terms of decreasing vapor pressure. Figure 1. 50 ppbv VOC recovery from disposable syringes  Figure 2. 1000 ppbv VOC recovery from disposable syringes  Discussion Polyethylene/polypropylene disposable syringes should be used for soil gas collection with extreme caution. If soil gas measurements are being used for vapor intrusion investigations, disposable syringes may not provide the level of quality required for health risk assessments. To request a copy of the complete study, please click here. |