Field analytical methods
This presentation is the property of its rightful owner.
Sponsored Links
1 / 17

Field Analytical Methods PowerPoint PPT Presentation


  • 95 Views
  • Uploaded on
  • Presentation posted in: General

Field Analytical Methods. Considerations for Field Analytical Methods. Which parameters are anticipated to occur at the site? What media will be analyzed? What concentrations are expected? Is there matrix interference? (High concentrations of one constituent can mask other constituents.)

Download Presentation

Field Analytical Methods

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Field analytical methods

Field Analytical Methods


Considerations for field analytical methods

Considerations for Field Analytical Methods

Which parameters are anticipated to occur at the site?

  • What media will be analyzed?

  • What concentrations are expected?

  • Is there matrix interference? (High concentrations of one constituent can mask other constituents.)

  • Will my methods work under these conditions? (i.e. Color of sample may prevent colorimetric methods from working.)

  • Cost? How does the field analytical method compare to a laboratory or remote laboratory analysis?


Additional considerations

Additional Considerations

  • in situ – the measurement is taken in place without a sample being collected.

    • no error associated with sample collection

    • possible error from environment

  • ex situ – measurement taken in a sample that has been collected.

    • sampling error and bias


Field analytical methods

pH

pH= –log H+

  • Can be measured using pH meter and probe, or using a field test kit. The probe and meter is easy to use and accurate if calibrated.

  • The pH meter needs to be calibrated. Most models automatically adjust for temperature, but some may require additional calibration.


Conductivity

Conductivity

  • Conductivity is a measure of the ability of water to pass an electrical current. It is affected by the presence inorganic cations and anions. Conductivity is affected by temperature. Increase in temperature increases conductivity. Conductivity is generally reported at 25° C.

  • Conductivity is mainly affected by the geology of the area, although discharges could increase conductivity.

  • Conductivity is measured in microsiemens per centimeter.


Dissolved oxygen

Dissolved Oxygen

DO concentrations are influenced by water temperature, atmospheric pressure, the rate of photosynthesis, the degree of light penetration (turbidity), the degree of turbulence or wave action, and the amount of oxygen used by the respiration and decay of organic matter.

  • Can be measured using titration or using a meter and probe. The meter and probe is easy and quick to use. Since DO does depend on atmospheric pressure, a barometer or altimeter may be required in addition to your meter.


Alkalinity

Alkalinity

  • Alkalinity is the quantitative capacity of a water or water solution to neutralize an acid. It is expressed in terms of its calcium carbonate equivalent.

  • Alkalinity is measured by titration. A 0.02N solution of NH2SO4 is titrated into the sample until the pH is equal to 4.5. A colorimetric indicator or a pH meter and probe may be used. A stronger solution may be used if the alkalinity is very high.


Colorimetric

Colorimetric

  • Reagent test kits are self-contained.

  • Highly potable

  • Inexpensive

  • Often no sample preparation required.

  • Available for a wide range of analytes

  • Limited training needed.


What does it mean

What Does it Mean?

  • Qualitative – is the constituent present?

    • Based on color change.

  • Quantitative – how much of the constituent is present?

  • Based on color intensity.

    • Compared to color chart or photograph.

    • Subject to bias regarding color interpretation.

    • Accuracy may be questionable – maybe semi-quantitative data.


Immunoassay

Immunoassay

A measure of immune system response to an analyte.

Uses antigen in an enzyme conjugate.

  • Enzyme immunoassay.

  • Radioimmunoassay.

  • Fluorescent immunoassay.

  • Enzyme-Linked Immunoabsorbant Assay (ELISA)


Immunoassay1

Immunoassay

  • Widely used in food and health-care industry.

  • In the environmental industry, provide semi-quantitative and quantitative data for a wide range of organic and inorganic compounds in soil and water.

  • Commonly used for gasoline, diesel, jet fuel, BTEX, PAH, PCP, pesticides and herbicides, explosives and propellants, PCBs, etc.

  • Used to measure lighter aromatic petroleum fractions, which cause immune system responses. (Not used for heavy petroleum or degraded petroleum).


Application to environmental sciences

Application to Environmental Sciences

  • ELISA is most commonly used.

  • Can be optimized for speed, sensitivity, and selectivity.

  • Long shelf life.

  • Does not require the use of radioactive materials.


Advantages

Advantages:

  • Speed of analysis.

  • Portability

  • Ease of Use

  • Relatively low cost per sample.

  • Methods available for a wide range of contaminants.

  • EPA SW846 methods for PCP, 2,4D, PCBs, Dioxen, TPH, PAHs, Toxaphane, Chlorodane, DDT, RDX, TCE, Triazine as atrazine, Mercury.

  • Low detection limits (ppb for water, ppm for soils)


Disadvantages

Disadvantages:

  • You must correctly identify the analyte or family of analytes of interest at the site because the kits are contaminant specific.

  • Similar compounds may cause “cross-reactivity”.

  • Many sample reagents highly sensitive to direct sunlight and temperature.

  • Sample reagents expire.


X ray fluorescence xrf

X-Ray Fluorescence (XRF)

  • Used where trace metal concentration is concerned.

  • Radioisotope source and detector.

  • Miniature X-ray tube source.

  • Can be used in situ or ex situ.

  • In situ – rapid screening of soils in place. Count times are low so detection limits are higher.

  • Ex situ – sample is analyzed. Count times are longer so detection limits are lower.


Gas chromatograph gc

Gas Chromatograph (GC)

  • Widely used for the analysis of organic compounds in air, soil gas, soil, and water samples.

  • Can be combined with Mass Spectrometer for definitive identification of complex compounds.


Questions

QUESTIONS?


  • Login