Home>API standards>API Publ 4690-2002 pdf free download

API Publ 4690-2002 pdf free download

API Publ 4690-2002 pdf free download.A Guide for the Use of Semipermeable Membrane Devices (SPMDs) as Samplers of Waterborne Hydrophobic Organic Contaminats.
SAMPLING AND ANALYSIS Unlike most sampling methods, SPMDs are applicable to nearly all environmental conditions, selectively sample residues from the dissolved phase, operate in situ, and passively extract hydrophobic organic contaminants from relatively large volumes of water (typically > 10 L for a ≥ 1 0 d exposure to a standard SPMD [see “SPECIFICATIONS OF THE STANDARD SPMD”, page 4-3]). Also, hydrophobic contaminants are generally sampled without affecting the fractional distribution of residues in components of the sampled environment (excludes sediment-soil and some ground water), and fewer analyses (compared to grab samples) are required to assess the chronic exposure of aquatic organisms to contaminants. One of the major advantages of SPMDs over biomonitoring organisms is that a standard design can be used regardless of water quality or environmental conditions. Samplers of uniform and reproducible material are required to delineate differences in sources (e.g., comparison of sample fingerprints or instrumental response profiles using pattern recognition programs) of complex chemical mixtures such as PAHs. In Section 4 we provide key specifications of the commercial or “standard” SPMD. Clearly, a standardized design is a prerequisite for global comparability of SPMD data. Analytical interferences must be minimized in SPMDs to enable detection of trace/ultra- trace levels of hydrophobic contaminants. Because SPMDs sample organic vapors as well as dissolved residues, a clean room is required for the assembly of SPMD components. In addition, careful attention must be paid to adequate precleaning of SPMD materials. Storage and transport conditions must also be designed to minimize air exposure prior to the deployment and after the retrieval of SPMDs.
The exact level of QC required is determined during the development of the experimental design phase of a project and is dependent on project goals. In Section 4, we describe the various types of QC samples that may be used in a project using SPMDs. These include SPMD-fabrication blanks, SPMD-process blanks, reagent blanks, field-blank SPMDs, PRC samples, SPMD spikes, and procedural spikes. The QC samples listed above are designed to provide information on sample integrity and background interferences associated with the entire sampling and analytical process. In general, QC samples represent 20 to 50% of a sample set. Using the materials and procedures described in this document, the precision or coefficient of variation (C.V.) of replicate SPMD analyses is about the same or less than properly executed standard analytical methods (i.e., the C.V.s are typically ≤ 25 %). Other environmental sampling methods have QC samples similar to those listed for SPMDs. However, PRC samples are unique to the SPMD approach but are only used in projects that require estimation of ambient contaminant concentrations. As suggested earlier, PRC samples are designed to improve the accuracy of SPMD-derived water concentration estimates. PRCs should not be confused with analytical internal standards or surrogates, which are used to determine procedural recovery of analytes. Processing, enrichment, and fractionation of analyte residues generally include the following steps: 1) removal of exterior surficial periphyton (organism that live attached to underwater surfaces) and debris, 2) organic solvent dialysis, 3) gel permeation chromatography (GPC), and 4) class-specific fractionation using Florisil  , silica gel and/or alumina adsorption chromatography. These procedures are similar to those used for the analysis of fish tissues and sediments minus the sample drying and grinding steps.
Because many toxic organic chemicals are in environmental waters at trace or ultra-trace levels, direct use of biomarker/immunoassay tests and acute bioassays may fail to show adverse effects or detect evidence of their presence. Unfortunately, this does not rule out the possibility of chronic toxic effects, especially when hydrophobic organic contaminants are highly bioconcentrated. SPMDs have been shown to enrich trace/ultra-trace residues that are known to bioconcentrate, thus they are often used as a convenient sample preconcentration method for the bioassays. SPMDs offer several advantages over other preconcentration methods.

Related PowerPoint Templates

Template Categories
Popular Tags