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Sampling and Analysis |
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Published analytical methods address several hundred possible workplace contaminants. However, these methods do not
address all chemical hazards. The following references link to resources that provide analysis information on many chemical hazards.
Analytical Methods
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Sampling and Analytical Methods. OSHA. Provides links to
information developed by OSHA including validated methods for use by the
Salt Lake Technical Center (SLTC) Laboratory.
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NIOSH Manual of Analytical Methods (NMAM). US Department of Health and
Human Services (DHHS), National Institute for Occupational Safety and
Health (NIOSH) Publication 94-113, (1994, August). Provides individual
analytical methods, listed by chemical name or method number.
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Environmental Protection Agency (EPA).
The EPA has published numerous methods relating to environmental monitoring, stack
testing, and indoor air quality. Many of these can find application in evaluating
occupational exposure. Others can be used to supplement information during specific
evaluations. The following methods were developed to monitor environmental air for volatile organic
analytes by drawing a sample onto a solid sorbent then analyzing the sample by thermal desorption/GC/MS. They provide sensitive analyses for specific compounds.
- Method TO-1. (1984, April), 110 KB PDF, 34 pages.
- Method TO-2. (1984, April), 110 KB PDF, 32 pages.
- Method TO-3. (1984, April), 80 KB PDF, 20 pages.
- Method TO-17. (1997, January), 312 KB PDF, 53 pages.
- Method TO-14A. (1997, January), 1.1 MB PDF, 97 pages. This document describes a procedure for sampling and analysis of volatile organic compounds (VOCs) in ambient air.
- Air Monitoring Database. 1.2 MB ZIP*.
Provides a computer program (PC compatible) which can
be downloaded, unzipped onto a floppy disk, and installed. This database provides references to EPA, National Institute for Occupational Safety and Health (NIOSH), and
OSHA methods that can be searched by compound or method number.
- Individual Standards Search Page.
American Society for Testing and Materials (ASTM). ASTM has developed about 100 standards which address analysis of workplace air samples.
Search specific standards of interest from this page.
Method Modification and Development
Published analytical methods address several hundred possible workplace contaminants.
However, these methods do not address all chemical hazards. Some chemicals are so
specialized that they are rarely encountered. New chemicals are constantly being
developed. Other chemicals are not stable on existing sampling media. In these instances
it becomes necessary to modify an existing method to accommodate the contaminant or a new
method must be developed.
The procedures for method modification and development vary
depending on the properties of the chemical, possible interferences, the desired sampling
medium, the desired analytical technique, sensitivity required, and similar factors.
Therefore, method modification and development should only be undertaken by an experienced
analyst or researcher. However, the following are items which should be considered and
answered by any method modification or development.
- Can the analyte be collected by and removed from the sampling media?
- What are the collection and recovery factors and are they acceptable?
- Is the detection limit sufficiently low to provide meaningful data, especially when
adjusted for collection and recovery factors?
- Will expected interferences produce false positive, false negative, or biased results?
- If possible, can the results be verified by comparison with an accepted procedure?
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NIOSH Manual of Analytical Methods (NMAM). US Department of Health
and Human Services (DHHS), National Institute for Occupational Safety
and Health (NIOSH) Publication 94-113, (1994, August). Provides
individual analytical methods, listed by chemical name or method
number.
Laboratory Selection
The selection of a laboratory is influenced by many factors. Among these are:
- Does the laboratory perform the required analysis?
- What are my requirements for quality assurance and does the laboratory quality assurance program meet these requirements?
- Does the laboratory analyze samples and report results within my required turnaround time?
- Does the analytical report contain the information I need?
- Are detection limits reported and are they sufficiently low?
- Are analytical costs acceptable?
- Does the laboratory provide the client services I desire?
- Am I confident in the results provided?
Laboratory Accreditation and Certification
Participation in accreditation and certification programs allow laboratories to compare
themselves against other laboratories and against accepted standards. Most programs
require participation in a performance evaluation testing program where samples of unknown
concentration are analyzed and reported to an independent body. Many programs require an
on-site assessment by a trained quality assessor. Successful participation in an
accreditation or certification program is an indicator that a laboratory operates under a
functioning quality assurance program. It does not guarantee that the results produced by
the laboratory are beyond question.
Laboratory (Internal)
Laboratories analyzing samples should have a documented quality assurance program. This
program should address sample receiving and storage, use and adoption of analytical
methods, control of reagents and chemicals, analyst training, analytical performance and
control limits, reporting of results, and similar topics.
Laboratory (External)
Laboratories performing industrial hygiene analyses should participate in external
performance evaluation programs, and be subject to audit by external assessors. The
appropriate accreditation and certification programs discussed above should be part of a
laboratory's quality assurance program.
When submitting samples to a laboratory, there
are several methods which can be easily used to assess the accuracy and precision of the
laboratory's results. In all cases, if a problem is detected, it would be wise to assume
that the error is in the external sample, unless other information indicates otherwise.
Once a problem has been identified, the laboratory quality assurance manager should be
contacted and the problem resolved to the satisfaction of all parties.
- Collect two samples under the same conditions. Remember, when evaluating these samples,
that the two samples are not identical. For instance, a droplet of solvent could be
splashed onto one sample but not the second giving a false reading for the first sampler.
- If the sample is a bulk material, divide it into two portions after
thoroughly
homogenizing. If the sample is not homogenized, the two portions could contain differing
amounts of analyte.
- Prepare "spiked" samples of known concentration to be submitted blind with
field samples. These must be prepared by a skilled individual. Additional spikes
should be prepared at the same time so that the spiking can be verified by a second
laboratory if questionable results are reported.
*These files are provided for
downloading only. |
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