CHESTER LabNet CLN provides a wide variety of analytical services, ranging from X-ray Fluorescence (XRF) analysis to Atomic Absorption and Inductively Coupled Plasma analysis to Ion Chromatography, Carbon Analyzer (OC/EC), wet chemical and gravimetric analysis. CLN is intimately familiar with air quality analysis using code of Federal Regulations and EPA Inorganic Compendium methods. As with all scientific analysis, each of these analytical techniques has its advantages and drawbacks.

Image Conventional Metals AnalysisConventional Metals Analysis

Conventional or traditional metals analysis includes Graphite Furnace Atomic Absorption (GFAA), Inductively Coupled Plasma Atomic Emission (ICP or ICAP), and Cold Vapor Atomic Absorption (CVAA). We also offer ICP-MS services for clients requiring lower detection limits.

A wide variety of sampling methods can be analyzed using these techniques, including but not limited to: all filter matrices*; US EPA 40 CFR 60 methods 12, 29, 103, and 306; NIOSH 6001, 6009, 7300; IO 3.1, 3.2, 3.3, 3.4, and 3.5; bag house dusts; waters/wastewaters; and soils/sludges. Due to the need for a digestion prior to analysis, these methods are destructive and in some cases, particularly many of the CFR methods, consume the entire sample, making reanalysis impossible.

These methods are the methods of choice when CLP data packages are desired. Detection limits for these methods are determined using SW-846 guidelines and are reported in µg/mL or µg/L. For filters the detection limit is dependent upon the amount of filter digested (cm²), the total area of the filter (cm²), and the total volume of digestate. The greater the area of filter digested, and lower the volume of digestate, the lower the detection limit is for that sample. Our standard digestion uses either the entirety of the filter (25mm, 37mm, 47mm filters) or a 66.4 cm² portion of the filter (8x10" filters) and a 40mL digestion volume. Most of the elements measured by conventional metals analysis can also be measured by XRF.

*Note: It has been the experience of CLN that carbon impregnated filters do not have high digestion efficiency, as indicated by exceedingly low spike recoveries.

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Image XRFX-ray Fluorescence (XRF)

XRF offers rapid analysis of over 35 elements (Na through Pb). XRF is an EPA approved (IO-3.3), non-destructive analytical method wherein a filter or section of filter ("punch") is loaded into the instrument, then bombarded with X-ray beams. The subsequent excitement of electrons can be measured when the electrons fall back to their valence state, releasing energy in the process. Each element has a "fingerprint" of electrical discharges which can then be measured to determine the quantity of each element being measured.

Since XRF is non-destructive, filter samples can then be used for subsequent analysis, or reanalyzed by XRF. Detection limits for XRF are dependent on the "count time" of each sample and the area of the X-ray beam, and are determined in units of µg/cm². Due to the unadulterated nature of the sample, CLP data packages cannot be generated as a true spike is not possible, and duplicates are not truly duplicates, rather replicates of the same sample. Most of the elements measured by XRF can also be measured by conventional metals analysis or Ion Chromatography.

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Image GravimetryGravimetry

Filters are purchased from commercial vendors are acceptance tested by visual inspection. Filters passing inspection are equilibrated in a temperature and humidity controlled environment, tare weighed, and either stored or shipped immediately to the client. Filters returned from the field are equilibrated in a temperature and humidity controlled environment for 24 hours prior to gross weighing.

CHESTER LabNet operates microbalances capable of measuring mass to one microgram used for smaller filters, as well as a balance that measures mass to a tenth of a milligram which is used for the larger filters. The balances are under computer control, and all weighing operations follow a strict QC program. All filters are weighed and data is recorded using a proprietary custom software program. This software automatically records analytical results. The software uses the information in the data file to calculate the net mass, as well as the difference in QA reweights. Tare and gross weights are electronically transferred to the laboratory information management system (LIMS).

CHESTER LabNet uses these gravimetric techniques for a wide variety of methods, including but not limited to NIOSH 0500, NIOSH 0600,CFR 50, Appendix B (TSP), J (PM10) and L (PM2.5) and IO 3.1.

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Image ICIon Chromatography (IC)

IC is used to determine common anions (F, Cl, Br, NO2, NO3, PO4, SO4) and common cations (Na, NH4, K) in various matrices. A wide variety of sampling methods can be analyzed using this technique, including but not limited to: all filter matrices; US EPA 40 CFR 60 methods 7, 13, 14, 26 and CTM027; NIOSH 6004, 6011, 6014, 6016, 7902, 7903; waters/wastewaters; and soils/sludges.

Due to the nature of the instrumentation, Ion Chromatography can only analyze for ions already in solution or for water-soluble ions. Some of the anions can also be determined by XRF, and some cations can be determined by both XRF and ICP.

Detection limits for IC methods are determined using SW-846 guidelines and are reported in µg/mL. For filters the detection limit is dependent upon the amount of filter extracted (cm²), the total area of the filter (cm²), and the total volume of extraction. Our standard extraction uses either the entirety of the filter (25mm, 37mm, 47mm filters) or a 16.6 cm² portion of the filter (85mm, 102mm, 110mm, 8x10" filters) and a 10mL extraction volume. For methods using sorbent tubes (NIOSH methods), the extraction procedure listed in the method is followed.

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Image Source (Stack) TestingSource (Stack) Testing

Source testing is the sampling of gasses directly from their source, usually a smoke stack or bag house, and is also referred to as Stack Testing. It is usually performed using US EPA 40 CFR 60 methods, although many state agencies have their own methods which are usually very similar to the federal methods (i.e. CARB, ODEQ etc). These methods use analytical techniques including ICP, GFAA, CVAA, IC and many wet chemical methods. See our list of methods for specific method numbers.

 



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Image IC-PCRIon Chromatography Post Column Reaction (IC-PCR)

Chromium is a natural constituent of the earth's crust and is present in several oxidation states. Trivalent chromium (Cr+3) is naturally occurring, while hexavalent chromium is anthropogenic from a number of commercial industrial sources. Hexavalent chromium readily penetrates biological membranes and has been identified as an industrial toxic and carcinogenic.

At CHESTER LabNet Cr+6 is analyzed by ion chromatography using a system comprised of a guard column, analytical column, a post-column reaction/derivatization module and a UV-Vis detector. After separation through the column, Cr+6 forms a complex with the diphenylcarbohydrazide (DPC), which is detected at 530 nm. This method yields an extremely low detection limit that should meet even the most rigorous requirements. Both ambient air and source samples can be analyzed by this method.

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Image OC/ECOrganic Carbon/Elemental Carbon (OC/EC)

OC/EC analysis is a highly specialized thermo-optical method which analyzes for the presence of organic carbon and/or elemental carbon on quartz filters. Typically, total carbon discharges are not monitored as a singular species; rather the specific carbon compound of interest is monitored. The EPA, however, has constructed a nationwide source profile library which characterizes the possible sources of carbon emissions based on the percentage of organic carbon vs. elemental carbon. For large scale source identification work, OC/EC provides a relatively inexpensive starting point. CLN's instrument uses the laser transmittance configuration and the temperature program specified in NIOSH method 5040. This is the carbon analysis protocol of choice for the U.S. EPA PM2.5 speciation project. Briefly, particulates are collected on quartz fiber filters (note that other matrices cannot withstand the heat of the instrument). A filter section is heated in steps from ambient to 800 °C. Carbon species are volatilized off the filter, oxidized to carbon dioxide, reduced to methane, and quantitated with a flame ionization detector. Laser transmittance is used to correct for pyrolized organic carbon. The split between organic (low temperature) and elemental (high temperature) carbon is operationally defined. Detection limit is 0.2 µg carbon/cm².

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Image Wet ChemicalWet Chemical

Wet Chemical methods are used for a variety of sampling techniques, primarily US EPA 40 CFR 60 methods 6, 8, 11, 13b and 20. Many of the preparatory steps for other methods involve wet chemical techniques as well (i.e. method 202). Due to the complexity of each method and the wide variation in wet chemical techniques, it is not possible to describe this group of methods in any detail here. Types of wet chemical techniques includes: distillations (M13b); titrations (M6, 8, 11); Ion Selective Electrodes (M13b); biphase extractions (M5, 201, 202); and a plethora of preparatory steps.




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Image MiscellaneousMiscellaneous

CLN prides itself in our ability to work closely with clients to ensure the best data for that client's needs. Although we have listed the most common methods, techniques, reporting formats etc on our web page, we are by no means limited to them. If you have a project related to air quality which may not fall neatly into the methods or techniques we have listed on our site, please contact us. Our experience in the industry can be as big a resource to you as our instruments.

 



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Image Detection limitsDetection limits

Detection limits are determined following EPA guidelines where possible. Detection limits, while remaining consistent at the instrument level, will vary depending on the matrix of the sample, and/or the size of the filter analyzed. For XRF, detection limits vary considerably between Quartz/Glass fiber filter matrices and Teflon matrices. For other instrumental analysis, the matrix does not play a significant role in the overall detection limit, however, digestion/extraction efficiencies may be very significant, as is total sample volume in the case of source samples.

For a listing of commonly requested detection limits, click here.

Each page has a table of the instrument detection limits based on the sample matrix. For further questions please contact us.

Please note that to view this detection limit table, you must have Adobe Acrobat Reader installed on your computer (click here download now).

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