SPMD sampler

In the following sections we highlight only selected works that have contributed toward the further development of passive samplers for SVOCs and/or HOCs. The literature related to the development and use of passive samplers for monitoring gases or VOCs in occupational environments is large. However, these publications are discussed only briefly, because lipid-containing semipermeable membrane devices (SPMDs) are primarily designed for SVOCs. 

Table 1.1 compares key aspects and performance characteristics of selected passive samplers, including the triolein-containing SPMD. Of the eight devices examined, only a few appear to have overlapping functions. Clearly, no one device can provide the desired data for all exposure scenarios. 

Similar to the previous section, we discuss only selected works to highlight the development of SPMDs. Also, we include some discussion of several unpublished pilot smdies (Huckins, 1989) that influenced our early development of SPMDs. These pilot studies were directed solely toward sampling the aqueous phase. The flrst application of SPMDs for sampling organic vapors did not occur until several years later (Petty et al., 1993). To our knowledge, only SPMDs, PESs and SPMEs are being applied in both air and water, because the use of many passive samplers is limited to a specific medium and exposure scenario. 

Huckins, J.N. Petty, J.D. Prest, H.F. Clark, R.C. Alvarez, D.A. Orazio, C.E. Lebo, J.A. Cranor, W.L. Johnson, B.T. 2002a, A Guide for the Use of Semipermeable Membrane Devices (SPMDs) as Samplers of Waterborne Hydrophobic Organic Contaminants Publication No. 4690 American Petroleum Institute (API) Washington, DC. 

Although SPMDs are simple in design, the mechanisms governing their performance as passive samplers of HOCs can be quite complex (see Chapter 3). The underlying principle of molecular-size discrimination in the uptake and loss of chemicals by SPMDs is shown in Eigure 2.1. The sizes of the molecules shown in the illustration are scaled to the postulated 10 A diameter of the transient pores in the membrane. Temperature and the presence of plasticizers/solvent will affect the effective pore sizes. 

Some introductory comments on the conceptual basis of SPMD uptake (ku) and release (ke) rate constants and the associated sampling rates (i.e., Rs) are in order. The can be conceptualized as the volume of air or water cleared of chemical per unit sampler mass or volume per unit time (e.g., mL g d or mL mL d ) and Rs is the volume of air or water cleared per unit time (e.g., L d ). Thus, the only difference between ku and Rs is that Rs is not normalized to a unit mass or unit volume of sampler. In the context of organism exposure (see Section l.L), the SPMD is equivalent to the encounter volume times the fractional bioavailability of the chemical (which excludes dietary uptake). The release rate constant (d ) is equal to kuK J. 

Bartkow, M.E. Huckins, J.N. Muller, J.F. 2004, Field-based evaluation of semipermeable membrane devices (SPMDs) as passive air samplers of polyaromatic hydrocarbons (PAHs). Atmos. Errviron. 38 5983-5900. 

Lohman, R. Corrigan, B.P. Howsam, M. Jones, K.C. Ockenden, W.A. 2001, Further developments in the use of semipermeable membrane devices (SPMDs) as passive air samplers for persistent organic pollutants Field application in a spatial survey of PCDD/Fs and PAHs. Environ. Sci. 

Lebo, J.A. Gale, R.W. Petty, J.D. Tillitt, D.E. Huckins, J.N. Meadows, J.C. Orazio, C.E. Echols, K.R. Schroeder, D.J. Inmon, L.E. 1995, Use of the semipermeable membrane device (SPMD) as an in situ sampler of waterborne bioavailable PCDD and PCDF residues at sub-part-per-quadrillion concentrations. Environ. Sci. Technol. 29 2886-2892. 

Raw data PRC levels in non-exposed SPMDs (experimental and calculated) blank levels (fabrication, process, reagent, field) fraction processed (whole SPMD recommended ) amount of analyte per sampler... 

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