determination of toxicants in foods 2

8/8/2019 Determination of Toxicants in Foods 2

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DETERMINATION OF

TOXICANTS IN

FOODS


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Foods and drink can cause people to be ill becausethey are contaminated with harmful micro-organisms and/or their toxins (poisons) - this isoften called food poisoningfood poisoning.

To detect : food samples

Two major processes:

To detect the presence of a toxicant in foods To qualitate and quantitate the toxicants


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Food safety : An important step in the initial phase is

assessment to estimate the levels of the toxicant towhich the population is exposed.

Method: a) dietary survey

b) market basket analysis

chemical analysis in food toxicology involve separating

a toxicant from other chemicals and then determiningthe amount


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sampling

To obtain a portion for the estimation orobservation of attributes of the particular lot; thesample must be representative of the lot.


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Qualitative and quantitative

Require both an assay for detecting the poison and amethod for separating it from the rest of the chemicals inthe foods

Separation methods:

Gas chromatography (GC)

High performance liquid chromatography (HPLC)

Column & thin layer chromatography (CC,TLC)

Distillation

extraction


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chromatography GC

HPLC CC,TLC


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a way of separating out a mixture of chemicals, which are in

gas or liquid form, by letting them creep slowly past anothersubstance, which is typically a liquid or solid

involve the interaction of a mixture between a stationary anda mobile phase

The key thing to remember is that chromatography isa surface effect.


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Different types of chromatographic techniques.


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Gas chromatography

used in organic chemistry for separating and analyzing compounds thatcan be vaporized without decomposition.

include testing the purity of a particular substance, or separating thedifferent components of a mixture

moving phase (or mobile phase) is a carrier gas, usually an inert gas such

as helium or an un reactive gas such as nitrogen.

stationary phase is a microscopic layer of liquid or polymer on an inertsolid support, inside a piece of glass or metal tubing called a column.


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High performance liquid chromatography

utilizes a column that holds chromatographic packing material(stationary phase), a pump that moves the mobile phase(s)through the column and a detector that shows the retention timesof the molecules.

Retention time varies depending on the interactions between thestationary phase, the molecules being analyzed and the solvent(s)used.

one of the most powerful tools in analytical chemistry. It has the abilityto separate, identify, and quantitate the compounds that are present inany sample that can be dissolved in a liquid.


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Column chromatography

to purify individual chemical compounds from mixtures ofcompounds.

used for preparative applications on scales from micrograms uptokilograms, and for cleaning the analyte of the matrix

interferences, for use with more sophisticated techniques


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Biological Determination of

Toxicants

Genetic toxicity

Acute toxicity

Bioassay

Metabolism

Subchronic toxicity Teratogenesis

Chronic toxicity


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GENETIC TOXICITY

Definition:

refers to the ability of substances or physical agents todamage the DNA and/or chromosomes of cells. Such

damage can lead to mutations that increase thelikelihood of certain diseases, such as cancer and birth

defects.

determined using a wide range of test speciesincluding whole animals and plants (e.g., rodents,

insects, and corn), microorganisms, and mammaliancells.


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The most common gene mutation tests involve:


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Acute toxicity

Definition:

the toxicity produced by pharmaceutical when it is

administered in one or more doses during a periodnot exceeding 24 hours.

Acute toxicity tests are generally the first tests

conducted.They provide data on the relative toxicitylikely to arise from a single or brief exposure.

Standardized tests are available for oral, dermal,

and inhalation exposures.


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Purpose to identify the dose of the

pharmaceutical which causesmajor adverse effects, to helpset doses for further preclinical

studies and to predict theeffects of overdose in humans.


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Basic parameters of these tests

are:


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Bioassay

Definition:

the use of a living organism to test for the presenceof a compound or to determine the amount of thecompound that is present in a sample.

a procedure for the determination of theconcentration of a particular constituent of amixture.

a measurement of the effects of a substance on

living organisms.


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Types of Bioassays

[1]Quantal Assays [ Direct endpoint ] Elicits an All or None response in different animals

Eg.

Digitalis induced cardiac arrest in guinea pigs

hypoglycemic convulsions in mice.

Digitalis induced head drop in rabbits

Calculation of LD50 in mice or rats

[2]Graded Response Assays [mostly on tissues]

Graded responses to varying doses

Unknown dose response measured on same tissue


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Examples of Biological Assay:

LimulusTest

a sensitive method for detection of bacterial

endotoxins and endotoxin.

Endpoint Determination

an establishment of the level of a quantifiable

effect indicative of a biologic process.Theevaluation is frequently to detect the degree of

toxic or therapeutic effect.


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Metabolism

First, Santorio in 1614 in his book Ars de statica medicina(vital force which later known as metabolism)

Metabolic studies can be conducted after mutagenicity

test. Objective:

To gain understanding of the:

Absorption,

Biotransformation,

Disposition (storage),

Elimination characteristics of an ingested substance after singleand repeated doses.


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Metabolism

Knowledge of the metabolism and

pharmacokinetics of a substance is essential

for establishing the relevance of results fromanimal testing to projecting likely hazards in

humans.


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Subchronic toxicity

Objective

Determine the possible cumulative effects on

tissue or metabolic system To evaluate the safety of food components.

Determine if test substance toxic or not.

Performed for several months duration.


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Subchronic toxicity

Procedure :

Inspection of physical appearance and behavior

Body weight Food consumption

Characteristics of excreta

Blood, urine, hepatic, body temperature renal and

more.


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Teratogenesis

Birth defects are known to occur in 3-5% of all newborns.

They are the leading cause of infant mortality in the United States,accounting for more than 20% of all infant deaths.

7% to 10% of all children will require extensive medical care to diagnose ortreat a birth defect.

And although significant progress has been made in identifying the etiology

of some birth defects, approximately 65% have no known or identifiablecause.

It was previously believed that the mammalian embryo developed in the

impervious uterus of the mother, protected from all extrinsic factors. However, after the thalidomide disaster of the 1960s, it became apparent

and more accepted that the developing embryo could be highly vulnerableto certain environmental agents that have negligible or non-toxic effects toadult individuals.


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What is teratogenesis ?

Teratology is the study of abnormalities of

physiological development. It is often

thought of as the study of birth defects, but itis much broader than that, taking in other

developmental stages, such as puberty; and

other life forms, such as plants


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Wilson's 6

principles

These principles of teratology were put forthby Jim Wilson in 1959 and in his monograph

Environment and Birth Defects.Theseprinciples guide the study and understanding

of teratogenic agents and their effects ondeveloping organisms:


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Teratogenic agents

A wide range of different chemicals and environmental factors aresuspected or are known to be teratogenic in humans and in animals.A selected few include:

Drugs andmedications: tobacco, caffeine, drinking alcohol

(ethanol), isotretinoin (13-cis

-retinoic acid, Roaccutane).

Environmental chemicals: polychlorinated biphenyls (PCBs),polychlorinated dibenzodioxins a.k.a dioxin, polychlorinateddibenzofurans (PCDFs), organic mercury, ethidium bromide.

Ionizing radiation: background radiation, diagnostic x-rays,

radiation therapy. Infections: cytomegalovirus, herpes virus, parvovirus B19, rubella

virus (German measles), syphilis, toxoplasmosis, Venezuelanequine encephalitis virus.

Metabolic imbalance: alcoholism, endemic cretinism, diabetes,

folic acid deficiency, iodine deficiency, hyperthermia.


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Chronic toxicity

chronic toxicity: the adverse effects occurring after the administration

of a test sample for a major part of the lifespan (usually 6-12 months).

Chronic toxicity represents cumulative damage to specific organsystems and takes many months or years to become a recognizableclinical disease.

With repeated exposures or long-term continual exposure, the damagefrom these subclinical exposures slowly builds-up (cumulative damage)until the damage exceeds the threshold for chronic toxicity. Ultimately,the damage becomes so severe that the organ can no longer function

normally and a variety of chronic toxic effects may result.

Examples of chronic toxic affects are:

cirrhosis in alcoholics who have ingested ethanol for several years

chronic kidney disease in workmen with several years exposure tolead

chronic bronchitis in long-term cigarette smokers

pulmonary fibrosis in coal miners (black lung disease)


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Objective:

To assess toxicity resulting from long-term, relatively low

-level

exposure, which would not be evident in subchronic testing.

Test designed so that each treated and control group will includesufficient numbers of animals of both sexes of the chosen species

and strain to have an adequate number of survivors. The chronic toxicity test provides the final piece of biological

information on whether to accept or reject a substance suggestedfor food use.

If no carcinogenic effects are found, this information will be used in

the overall risk assessment of a substance

determination of toxicants in foods 2

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