Hydrophobic Inorganic Contaminants (POPs) Flashcards by Nancy He

A pollutant is considered to have toxicity if: (2)

evidence of adverse health effects (humans/animal/environment)

or indication of potential damage

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How are POPs different from other PBTs?

POPs are also LONG RANGE TRANSPORT: able to travel far from pollution source and accumulate

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What are the criteria for persistence in water and soil?

water: half life > 2 months
soil: half life > 6 months

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The bioaccumulative properties of a chemical can be measured in: (3)

Bio Concentration Factor (BCF)
Bio Accumulative Factor (BAF)
log Kow (hydrophobicity; partition coefficient)

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The defining characteristics of POPs: (4)

Persistent
Bioaccumulative
Toxic
Long Range Transport

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POPs stands for:

Persistent Organic Pollutants

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The higher the Kow, the more ____ the substance is.

hydrophobic

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At what levels of BCF/BAF or Kow is the substance considered bioaccumulative?

BCF/BAF higher than 5000

log Kow >5

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Kow is used instead of BCF or BAF when _____

data is unavailable

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What is Kow and how is it determined?

Octanol-Water partition coefficient (measure of HYDROPHOBICITY)

add compound into 2 phase media (octanol and water)
allow to partition (move in/out freely of each phase until reach equilibrium)
measure conc of compound in each phase

Kow = (conc in octanol)/(conc in water)

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How are POPs dispersed through the environment? (2)

Oceanic transport

Global Distillation effect (evaporation + deposition) - known as “grasshopping”

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Where do hydrophobic bioaccumulative compounds accumulate in organisms?

fatty tissue

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The concentration of pollutants can be millions of times higher than the environment in top predators due to what effect?

biomagnification

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Why are mountains/lakes/polar regions particularly at risk from pollution by POPs?

global distillation effect; evaporate in warmer climates and condense down and deposit in cool regions of Earth

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Define and differentiate BAF and BCF:

BCF: only consider 1 route of exposure (water):
(conc organism)/(conc in water)
rate of uptake vs rate of elimination from body (accumulation)

BAF: consider multiple exposure routes (water, air, food) - result of both accumulation + magnification:
(conc organism)/(conc in surrounding medium)

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The 3 annexes of the stockholm convention:

Annex A: ELIMINATION: phase out use of chemicals
Annex B: RESTRICTION: Limit use of irreplaceable chemicals (DDT)
Annex C: UNINTENTIONAL PRODUCTION: properly dispose waste, eliminate pollutant byproducts

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What POPs can be produced both intentionally and as a chemical byproduct?

PCBs (polychlorinated biphenyls)

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What are 2 notable POPs produced unintentionally?

Dioxins
PCBs
(also: dibenzofurans, polychlorinated naphthalenes, pentachlorobenzene)

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What program was implemented by the UN to reduce/regulate POPs?

Stockholm convention

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Give the general formula for PCBs:

C(12)H(10-n)Cl(n)

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Describe the structure of PCBs and PCDDs:

flat, planar chlorinated hydrocarbons

multi-ringed structures

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What do PCDD and PCDF stand for, and in what industries are these produced?

PCDD: polychlorinated dibenzo-p-dioxins
PCDF: polychlorinated dibenzofurans
Produced as byproducts in pulp/paper, chem industry, heat/power generation, metal industry, waste incineration

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What compound is found in treated wood, and could lead to dioxin production?

PCPs (polychlorophenyls): incomplete combustion, generates dioxins and fumes (leads to contamination/toxicity)

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True/False: since the Stockholm convention, changes in the industry have led to PCB levels in organisms and the environment to drop significantly

False: levels are still high due to persistant nature of chemical. Can take many decades to have a significant reduction

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Does organic or conventional meat have a higher level of POPs? Why?

Organic: more exposure routes (conventional farm animals are limited from outside environment, controlled diet)

What were PCBs once widely used in?

electric transformers (good dielectric fluid)

What is a congener?

variation of the chemical; amount/position of chlorination or bromination

How many congeners exist for PCBs?

209

True/False: cooking decreases PCB levels in meat due to thermal destruction of compound.

False: levels decrease, but it is due to fat and PCBs leaking out and lost from meat (not destroyed)

What are the toxicity concerns of PBDEs? Is the concern more acute or chronic?

endocrine disruptor; chronic exposure (long term effects)

Most POPs are (hydrophobic/hydrophilic) and accumulate in _____. What is the exception?

hydrophobic; fatty tissue exception: PFOS (perfluorooctanesulfonic acid) - partition to PLASMA/LIVER PROTEINS (not lipid)

Endocrine disrupting chemicals are classified as _____ toxins.

non-threshold (no safe level)

What hormone does PBDEs interfere with?

thyroxine

True/False: PBDEs are no longer used

False

What is a POP with similar structure to dioxins and PCBs, used as a flame retardant for polyurethane? How does it differ in structure?

PBDEs (polybrominated diphenyl ethers) brominated instead of chlorinated also has 209 congeners

Both PBDEs and DDT have what effect on human health?

endocrine disruptor

What health hazard do dioxins pose?

carcinogen

What does PFOS affect? (3)

GI tract, liver, thyroxine effects

What properties of POPs are considered for their analysis? (4)

- hydrophobic nature - semi-volatile organic compounds - Cl or Br - mass spectra (fingerprint)

How could cooking increase or decrease concentration of POPs?

increase: reusing oil -> concentration effect decrease: fat loss (pan fry, grill) (POPs migrate with fat)

A low boiling point for POPs allows for what type of analysis?

gas chromatography

The hydrophobic nature of POPs makes them easy to extract using ____, with what exception?

nonpolar organic solvents | exception: PFOS (use slightly more polar solvent)

List the steps for the general approach for POPs analysis: (5)

``` preparation extraction clean up concentrate analysis ```

What is mass spectra, and what is it used for?

"fingerprint" of organic molecule, specific pattern that allows for identification/quantification

Why is the presence of Cl or Br significant for analysis of POPs?

electronegative atoms: Can use ECD (electron capture detector) as a detector

A lipid mass fraction of ____ remaining in the sample will hinder the analysis of POPs traces.

1-10%

What are the extraction methods for liquid samples? (3)

liquid-liquid extraction (partition with liquid solvent) solid phase extraction (pass through column) solid phase microextraction (silica thread inserted; molecules extracted onto surface according to affinity)

Why is a cleanup step necessary?

other hydrophobic substances (lipids) are CO-EXTRACTED with the analyte, and will cause interference if not removed

Why might microwave assisted solvent extraction or pressurized liquid extraction be more efficient?

with elevated temperature or pressure the solvent can enter the matrix more easily

The reading obtained from a chromatography analysis is a:

chromatogram, showing peaks of elution (retention times) for each compound

What are the extraction methods for solid samples? (3)

soxhlet (reflux nonpolar solvent, condense down onto sample to extract) microwave assisted solvent extraction (aid extraction with microwaves) pressurized liquid extraction (elevated pressure)

When might acid be used in POPs analysis, and when is it not applicable?

Digestion of lipids/interferences (cleanup step) | Not applicable for POPs that may be degraded

What POPs analyses can use sulfuric acid as a cleanup agent?

dioxins | PCBs

How is the cleanup step done? (3)

removal of lipids/interferences | Use ACID or SORBENTS or GEL COLUMN

What type of cleanup column is based on particle size?

GPC (gel permeation)

What are some properties that columns can separate based on?

hydrophobicity/hydrophilicity affinity charge size

Describe how sorbents work.

silica column with affinity either for interferences or analyte sample passed through - depending on affinity, compounds are retained for different times (eluted out at different times) -> separation

What are two methods of concentration of the sample?

Rotavap | N evaporator

What are the reasons for concentration of the sample? (2)

- reduce volume for analysis | - INCREASE concentration to produce good signal

What are some GC instruments used in POPs analysis?

HRGC-ECD HRGC-MS HRGC-MS/MS HRGC-HRMS

In what concentration range are POPs usually present?

ng/g

The results of an analysis depend largely on:_____ (The most tedious step)

SAMPLE PREPARATION

What is the only approved method for dioxin analysis in Canada?

HRGC-HRMS

Why might HRGC-ECD not be reliable?

electronegative atoms present as contamination -> interference with results (method is good for CLEAN extracts)

how does tandem MS differ from normal MS?

Two MS systems: particle fragmented -> charged -> pass through mass filter (filter for specific mass/charge ratio) fragmented further -> pass through 2nd system (more specific than regular MS; eliminate possibility of another compound with same charge/mass ratio interfering)

mass to charge ratio is represented by:

m/z

The ___ ____ on a chromatogram is used to identify the compound.

retention time

Why doesn't a MS reading only display one peak for a compound?

isotopes: different forms have different weights