ISO 28540-2011 pdf download.Water quality一Determination of 16 polycyclic aromatic hydrocarbons (PAH) in water一Method using gas chromatography with mass spectrometric detection (GC-MS).
The PAH (see Table 1) present in the aqueous sample are extracted from the water sample by liquid-liquid extraction with hexane. An internal standard mixture is added to the sample prior to extraction. The extract is concentrated by evaporation, and the residue taken up in a solvent appropriate for clean-up or GC analysis.
NOTE 1 Other volatile solvents can be used as well if it is proven that there is equal or better recovery (recovery mass fraction between 70 % and 110 %).
The liquid-liquid extraction method shall not be used with samples containing more than 150 mg/I of suspended matter.
WARNING — The use of this International Standard may involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
NOTE 2 For samples that contain more than 150 mg/I suspended matter the procedure described in ISO 17858:2007161, 4.1, 4.2 and 4.3, can be used.
If necessary, extracts of surface water samples can be cleaned by column chromatography prior to analysis. Prior to injection, injection standards are added to each extract, and an aliquot of the extract is injected into the gas chromatograph.
PAH are separated on a suitable fused silica capillary column, coated with a film of cross-linked non-polar polysiloxane or slightly polar modified polysiloxane with an efficient separation. The column shall be suitable for separating benzo[a]pyrene and benzo(ejpyrene. Identification and quantification is performed by means of mass spectrometry using electron impact ionization (El).
5 Interferences
5.1 Interferences with sampling, extraction, and concentration
Use sampling containers of materials that do not affect the analyte content during the contact time (preferably of stainless steel or glass). Avoid plastics and other organic materials during sampling, sample storage or extraction. Care should be taken when using surfactants for cleaning sample containers, because they may lead to the formation of emulsions during liquid-liquid extraction
If automatic samplers are used, avoid the use of silicone or rubber material for the tubes. If these materials are present, ensure that the contact time is minimized. Rinse the sampling line with the water to be sampled before taking the test sample. Use ISO 5667-1 and ISO 5667-3 for guidance.
Keep the test samples away from direct sunlight and prolonged exposure to light. Store the samples in amber containers. Clear glass botiles are suitable as well, but then the samples shall be kept in a dark place.
During storage of the test samples, losses of PAH may occur due to adsorption on to the walls of the containers. The extent of the losses may depend on the storage time.
5.2 Interferences with GC-MS
Substances that co-elute with the target PAH may interfere with the determination. These interferences may lead to incompletely resolved signals and may, depending on their magnitude, affect accuracy and precision of the analytical results. Non-symmetrical peaks and peaks broader than the corresponding peaks of the reference substance suggest interferences.
Chromatographic separation between dibenzo[a.h]anthracene and indeno(1 ,2,3-cdJpyrene is most critical. Due to their molecular mass differences, quantification can be made by mass selective detection. When incomplete resolution is encountered, peak integration shall be checked and, when necessary, the baseline corrected. Sufficient resolution (e.g. not less than R = 0,8) between the peaks of benzo(bjfluoranthene and berizo(k]fluoranthene as well as of benzo[ajpyrene and benzo[ejpyrene is to be set as quality criterion for the capillary column. Benzo[/Jfluorantt,ene cannot be separated from benzo[kjfluoranthene and benzofbjfluoranthene. It is possible that triphenylene is not completely separated from benzo[aJanthracene and chrysene. If this is the case, state this fact in the test report.
NOTE Benzo[]f1uocanthene. benzo[e]pyrene, and triphenylene are not part of the 16 target arialytes.
6 Reagents
WARNING — The use of this International Standard may involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.ISO 28540 pdf download.