Membrane devices for sample

Membrane Devices for Sample Preparation 13.1.3.1 Flat-Sheet Devices... 

Huckins, J.N. Petty, J.D. Orazio, C.E. Zajicek, J.L. Gibson, V.L. Clark, R.C. Echols, K.R. 1994, Semipermeable Membrane Device (SPMD) Sampling Rates for Trace Organic Contaminants in Air and Water. Abstract of the 15 th Annual meeting of Society of Ertvironmental Toxicology and Chemistry Denver, CO. Abstract MBOl. 

Smith and co-workers designed a microfabricated dialysis device for sample cleanup before ESI MS. A microdialysis membrane sandwiched between two chips having micromachined serpentine channels provided efficient desalting for both DNA and protein samples before subsequent ESI ion trap MS. In a continuation study, they used a fabricated dual microdialysis membrane for removing both high- and low-molecular-weight species that... 

Pervaporation can be used in microfluidic devices for sample concentration. Microchannels 500 nm high, 4 mm long, and 2 to 30 pm thick have been fabricated with polyimide using thin film deposition [263]. Pervaporation occurs through the polyimide polymer membrane (Fig. 7.18). In this study, water was... 

An interesting variation of the membrane inlet is to use it as a sampling device for sampling dissolved organic gases in water by flowing a carrier gas through a capillary of poly(dimethylsiloxane) immersed in the water sample. 

The most widely employed techniques for the extraction of water samples for triazine compounds include liquid-liquid extraction (LLE), solid-phase extraction (SPE), and liquid-solid extraction (LSE). Although most reports involving SPE are off-line procedures, there is increasing interest and subsequently increasing numbers of reports regarding on-line SPE, the goal of which is to improve overall productivity and safety. To a lesser extent, solid-phase microextraction (SPME), supercritical fluid extraction (SEE), semi-permeable membrane device (SPMD), and molecularly imprinted polymer (MIP) techniques have been reported. 

Due to the predicted and previously detected low concentrations of pesticides in environmental samples (usually around the nanogram per liter level), a preconcentration step of the water samples is necessary prior to measurement. In this way, a preconcentration factor of several orders of magnitude (200-1,000-fold) is mandatory to reach the low detection limits necessary for the identification of pesticides, especially in complex wastewater samples. Also, the use of surrogate standards (e.g., triphenyl phosphate) added before the extraction step is a common practice in order to account for possible errors during the extraction process and for quantitative purposes. The commonly used extraction methods for polar compounds from water matrices involve isolation using liquid-liquid extraction (LLE) and solid-phase extraction (SPE), which are commented on below. Other methods such as semipermeable membrane devices (SPMD) are also mentioned. 

Based on earlier work (Lieb and Stein, 1969 Chiou, 1985 Sddergren, 1987 Zabik, 1988) Huckins etal. (1989,1990a, 1993) flrstdeveloped and tested two types of lipid-containing semipermeable membrane devices (SPMDs) for in situ passive sampling of bioavailable dissolved aqueous-phase HOCs. The lipid-containing... 

Gustavson, K.E. and Haikin, J.M. 2000 Comparison of sampling techniques and evaluation of semipermeable membrane devices (SPMDs) for monitoring polynuclear aromatic hydrocarbons (PAHs) in groundwater. Environ Sci. Technol. 34 4445 451. 

Prest, H.F. Jacobson, L.A. Wilson, M. 1997, Passive water sampling for polynuclear aromatic hydrocarbons using Upid-containing semipermeable membrane devices (SPMDs) Application to contaminant residence times. Chemosphere 35 3047-3063. 

The authors have been intimately involved in eondueting research to address many aspects of environmental contaminants for about three decades. Historically, samples of environmental matrices, particularly water and air have been collected at narrow windows of time (i.e., minutes or several hours) which are not representative of the exposure experienced by organisms. Consequently, we initiated the development of what would ultimately be the semipermeable membrane device (SPMD). The SPMD has subsequently proven to be an effective passive sampler for a wide range of hydrophobic contaminants in multiple media. To date, there are more than 180 peer reviewed publications in the open scientific literature, where SPMDs are used for a variety of applications. Some of these publications are critical of the use of passive samplers for certain applications. However, constructive criticism has greatly aided in defining information gaps and limitations of the passive sampling approach. 

Someday we will have small portable devices that sample and analyze during exposure to the workplace atmosphere. Devices small enough to be worn comfortably by an active person, devices that will give warnings in real-time when danger of hazardous exposure occurs. These devices may be in the form of integrated circuits with sensors covered with permi-selective membranes, the combination of which will lead to both sensitive and selective measurements. Ten years from now current methods and devices may be, for the most part, but a memory. 

A straightforward way to collect solutes from the interstitial fluid (ISF) space would be to have a semipermeable, hollow fiber, membrane-based device as originally described by Bito et al.1 Two semipermeable membrane-based devices that have been used to collect different types of analytes from various mammalian tissues include microdialysis sampling probes (catheters) and ultrafiltration probes. The heart of each of these devices is the semipermeable polymeric membrane shown in Figure 6.1. The membranes allow for collection of analytes from the ISF that are below the membrane molecular weight cutoff (MWCO). Each of these devices provides a sample that has a significantly reduced amount of protein when compared to either blood or tissue... 

Both microdialysis and ultrafiltration collection obtain analytes from a sample in the reverse direction regardless of how a normal hemodialysis membrane is used. In hemodialysis, the blood is passed through the inner fiber lumen and filtrate is then collected on the outside of the hollow fiber. When these fibers are used as microdialysis or ultrafiltration devices for collection of samples, the outside of the fiber is interfaced with the sample and the analyte is collected into the inner fiber lumen of the hollow fiber. This is important particularly for the asymmetric membranes that have their large porous support layer on the outside facing the tissue sample. 

Brumbaugh, W.G., J.D. Petty, J.N. Huckins, and S.E. Manahan. 2002. Stabilized liquid membrane device (SLMD) for the passive, integrative sampling of labile metals in water. Water Air Soil Pollut. 133 109-119. 

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