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food toxicants and analysis > Hydrophobic Inorganic Contaminants (POPs) > Flashcards

Hydrophobic Inorganic Contaminants (POPs) Flashcards

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1
Q

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

A

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

or indication of potential damage

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2
Q

How are POPs different from other PBTs?

A

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

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3
Q

What are the criteria for persistence in water and soil?

A

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

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4
Q

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

A

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

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5
Q

The defining characteristics of POPs: (4)

A

Persistent
Bioaccumulative
Toxic
Long Range Transport

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6
Q

POPs stands for:

A

Persistent Organic Pollutants

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7
Q

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

A

hydrophobic

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8
Q

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

A

BCF/BAF higher than 5000

log Kow >5

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9
Q

Kow is used instead of BCF or BAF when _____

A

data is unavailable

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10
Q

What is Kow and how is it determined?

A

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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11
Q

How are POPs dispersed through the environment? (2)

A

Oceanic transport

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

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12
Q

Where do hydrophobic bioaccumulative compounds accumulate in organisms?

A

fatty tissue

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13
Q

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

A

biomagnification

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14
Q

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

A

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

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15
Q

Define and differentiate BAF and BCF:

A

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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16
Q

The 3 annexes of the stockholm convention:

A

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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17
Q

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

A

PCBs (polychlorinated biphenyls)

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18
Q

What are 2 notable POPs produced unintentionally?

A

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

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19
Q

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

A

Stockholm convention

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20
Q

Give the general formula for PCBs:

A

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

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21
Q

Describe the structure of PCBs and PCDDs:

A

flat, planar chlorinated hydrocarbons

multi-ringed structures

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22
Q

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

A

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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23
Q

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

A

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

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24
Q

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

A

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

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25
Q

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

A

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

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26
Q

What were PCBs once widely used in?

A

electric transformers (good dielectric fluid)

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27
Q

What is a congener?

A

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

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28
Q

How many congeners exist for PCBs?

A

209

29
Q

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

A

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

30
Q

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

A

endocrine disruptor; chronic exposure (long term effects)

31
Q

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

A

hydrophobic; fatty tissue

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

32
Q

Endocrine disrupting chemicals are classified as _____ toxins.

A

non-threshold (no safe level)

33
Q

What hormone does PBDEs interfere with?

A

thyroxine

34
Q

True/False: PBDEs are no longer used

A

False

35
Q

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

A

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

36
Q

Both PBDEs and DDT have what effect on human health?

A

endocrine disruptor

37
Q

What health hazard do dioxins pose?

A

carcinogen

38
Q

What does PFOS affect? (3)

A

GI tract, liver, thyroxine effects

39
Q

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

A
  • hydrophobic nature
  • semi-volatile organic compounds
  • Cl or Br
  • mass spectra (fingerprint)
40
Q

How could cooking increase or decrease concentration of POPs?

A

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

41
Q

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

A

gas chromatography

42
Q

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

A

nonpolar organic solvents

exception: PFOS (use slightly more polar solvent)

43
Q

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

A 
preparation
extraction
clean up
concentrate
analysis
44
Q

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

A

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

45
Q

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

A

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

46
Q

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

A

1-10%

47
Q

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

A

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)

48
Q

Why is a cleanup step necessary?

A

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

49
Q

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

A

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

50
Q

The reading obtained from a chromatography analysis is a:

A

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

51
Q

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

A

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

52
Q

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

A

Digestion of lipids/interferences (cleanup step)

Not applicable for POPs that may be degraded

53
Q

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

A

dioxins

PCBs

54
Q

How is the cleanup step done? (3)

A

removal of lipids/interferences

Use ACID or SORBENTS or GEL COLUMN

55
Q

What type of cleanup column is based on particle size?

A

GPC (gel permeation)

56
Q

What are some properties that columns can separate based on?

A

hydrophobicity/hydrophilicity
affinity
charge
size

57
Q

Describe how sorbents work.

A

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

58
Q

What are two methods of concentration of the sample?

A

Rotavap

N evaporator

59
Q

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

A
  • reduce volume for analysis

- INCREASE concentration to produce good signal

60
Q

What are some GC instruments used in POPs analysis?

A

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

61
Q

In what concentration range are POPs usually present?

A

ng/g

62
Q

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

A

SAMPLE PREPARATION

63
Q

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

A

HRGC-HRMS

64
Q

Why might HRGC-ECD not be reliable?

A

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

65
Q

how does tandem MS differ from normal MS?

A

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)

66
Q

mass to charge ratio is represented by:

A

m/z

67
Q

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

A

retention time

68
Q

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

A

isotopes: different forms have different weights

food toxicants and analysis (11 decks)

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