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food toxicants and analysis > Chromatography and Vet Drugs > Flashcards

Chromatography and Vet Drugs Flashcards

1
Q

Why can’t we inject food samples directly into a detector? (2)

A
  1. analyte is in very LOW concentrations

2. matrix interference

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2
Q

What is a common sample preparation step for many toxin analyses? What is its purpose?

A

chromatography: to SEPARATE the analyte from the matrix

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3
Q

Describe the basic function of chromatography:

A

separates components of a sample, distributing them between its MOBILE PHASE or STATIONARY PHASE

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4
Q

chromatography is a ____ separation method.

A

physical

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5
Q

What is GC? What analytes is it used for? (6)

A

gas chromatography:
used for organic compounds:
pesticides, POPs, PAHs, process induced contaminants, plasticizers, vet drugs + hormones

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6
Q

What type of chromatography is used for inorganic substances?

A

Ionic chromatography: used for ions: sulfites, nitrates, cyanide

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7
Q

What type of chromatography is mostly used for vet drugs? What else is it used for?

A

LC (liquid chromatography)

also for pesticides, POPs, process induced, plasticizers, vet drugs + hormones, mycotoxins

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8
Q

What is used to seperate detergents?

A

ionic chromatography

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9
Q

What is Tr?

A

retention time: time from sample injection to max elution peak (for compound of interest)

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10
Q

What are the 4 mechanisms involved in chromatography? What is the basis for each?

A
  1. adsorption - affinity
  2. sieving - size
  3. ion exchange - charge
  4. partitioning - hydrophobicity/solubility
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11
Q

The (greater/less) the affinity, the longer the retention time.

A

greater

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12
Q

The (larger/smaller) the particle size, the longer the retention time in size exclusion chromatography.

A

smaller

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13
Q

Describe the basic parts of of GC system.

A
  1. long COLUMN Inside column oven (coiled) is stationary phase
  2. CARRIER GAS is supplied, through FLOW CONTROLLER (mobile phase)
  3. sample injected -> carried by gas through column
  4. travel to DETECTOR -> generate SIGNAL
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14
Q

What are some common GC detectors? (6)

A 
Flame ionization (FID)
Nitrogen-Phosphorus (NPD)
electron capture (ECD)
MS
tandem MS (MS/MS)
Hi-res MS (HRMS)
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15
Q

What GC detector can be used for all organics?

A

FID

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16
Q

what effect does increasing temperature have on GC?

A

increase volatility of compounds -> faster process

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17
Q

What can be done do separate compounds based on volatility in GC?

A

temperature gradient: start high, then lower (volatiles eluted out first)

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18
Q

FID is ___ but not ____. why?

A

sensitive; selective (lack specificity)

based on burning; many compounds in food are C containing.

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19
Q

NPD is good for:

Why? What might be a problem?

A 
carbamates (pesticides)
contain N (reacts w/ N)
problem: compounds in food also can have N or P (interference)
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20
Q

Which of the GC detectors are accepted for REGULATORY PURPOSES?

A

MS, MS/MS, HRMS

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21
Q

What is the basis of the ECD in GC and what is it good for? Why might this be problematic?

A

react w/ electronegative atoms (Cl, Br): good for OCPs, PCBs

food can also have electroneg atoms (interference)

22
Q

What detector is used for dioxins?

A

HRMS

23
Q

POPs should be analyzed with:

A

MS or MS/MS

24
Q

PAHs should be analyzed with:

A

MS

25
Q

how does LC system differ from GC? (4)

A
  1. mobile phase is LIQUID SOLVENT
  2. delivered through PUMP
  3. stationary phase is HPLC column - SOLID PHASE
  4. use different DETECTORS
26
Q

why is a pump necessary for LC?

A

require PRESSURE to push liquid through solid phase (HPLC column)

27
Q

What are the detector types for LC? (6)

A 
UV-Vis Spectrophotometer
diode-array (DAD)
fluorescence (FLUO)
conductivity (COND)
MS/MS
HRMS
28
Q

Pesticides are used with what types of LC Detectors? (4)

A

UV-vis, DAD, MS/MS, HRMS

29
Q

What is the basis of UV-vis detectors and DAD?

A

UV vis: based on ABSORPTION (measure @ 1 wavelength)

DAD: also absorption, but many wavelengths

30
Q

What LC detector is used for aflatoxins, and what is its basis of detection?

A

FLUO: detect fluorescence (absorbing and emitting light @ diff wavelength)

31
Q

COND is used for:

A

ions (cyanide)

32
Q

the data generated by GC or LC is called a:

A

chromatogram

33
Q

How are compounds identified through GC or LC? (2)

A
  1. retention time (or relative retention time, comparing to standard)
  2. criteria specific to detector (fluorescence, max absorbnce, exact mass, etc)
    * need to match BOTH CRITERIA
34
Q

True/False: we can identify a compound based on its retention time only

A

False; compounds may have same retention time, need to also observe detector criteria (exact mass, etc)

35
Q

What should be done to increase accuracy of the detector?

A

proper sample preparation; remove interferences, concentrate analyte

36
Q

The size of the peak on a chromatogram depends on:

A
  1. concentration

2. sensitivity to analyte (some produce bigger signals)

37
Q

How can a chromatogram peak be used to quantify the analyte?

A

integrate area under curve

compare to standard

38
Q

the 2 types of vet drugs:

A
  1. growth promoters - increase growth

2. antibiotics - treat/prevent disease

39
Q

What is the major antibiotic type? What are some others used?

A

TETRACYCLINES

macrolides, penicillin, lincosamides, aminoglycosides, sulfas

40
Q

What are the “not medically important” vet drugs?

A

growth promoters: ionophores & NIR

41
Q

most drugs are administered by:

what other methods are possible?

A

feed

water, injection, intramammary, oral/topical

42
Q

What are the concerns related to vet drug use?

A

RESIDUES in food!

  1. acute effects (allergy, toxicity)
  2. long term effects (damage reproductive health, carcinogen, mutagen)
  3. impact on gut microflora: kill ‘good’ gut microbes; INCREASING BACTERIAL RESISTANCE!
43
Q

True/False: there is a higher incidence on non-compliant vet drug residue levels in imported animal products

A

False; not for all animal products (sometimes domestic is higher)

44
Q

What carcinogenic compound was used in aquaculture? why? is it still used today?

A

MALACHITE GREEN
antifungal/anti-protozoa properties; cheap and effective
PROHIBITED; but still found in some imported seafood

45
Q

analysis of vet drugs follows a similar procedure as:

What are some key differences?

A

POPs

but: more POLAR (use polar solvents)

46
Q

Describe the basic procedure for analysis of vet drugs:

A
  1. preparation: homogenize and dry (oven or freeze-dry)
  2. extraction: SPE or solvent (LPE) - ethanol, acetone
  3. clean-up: column separation (or SPE)
  4. concentration: rotary or N2 evap
  5. analysis (LC-UV, LC-FLUO, LC-MS/MS, GC-MS, GC-MS/MS)
47
Q

what procedure can accomplish both extraction and clean-up?

A

SPE (solid phase extraction)

48
Q

what are the analysis machine methods used for vet drugs? (5)

A 
LC-UV
LC-FLUO
LC-MS/MS
GC-MS
GC-MS/MS
49
Q

the standard/official methods for vet drug analysis are:

A

HPLC-MS/MS

HPLC-HRMS

50
Q

vet drug residues are usually found in what foods, and in what concentration range?

A

animal origin foods (meat, fish, eggs, milk)

ppb-ppm

51
Q

What is the preferred separation method for vet drugs analysis?

A

LC

food toxicants and analysis (11 decks)

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