Analytical Toxicology
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (24 张)
What are the steps in undertaking an analytical toxicology investigation?
Pre analytical Analytical Post analytical
What happens during the pre analytical step?
Obtain details of suspected poisoning episode Obtain the patients medical and occupational history Decide the priorities for an analysis
What happens during the analytical step?
Perform the agreed analysis
What happens during the post analytical step?
Interpret the results
Questions asked when conducting analytical toxicology?
Which sample should be collected/is relevant? How should it be interpreted? Which analytical technique should be chosen? Qualitative and quantitative analysis - screening tests or target analysis? Disposition of xenobiotics in the body - look for parent compound or metabolite?
What is phase 1 metabolism?
Functionalisation - chemical modification of the original xenobiotic molecule by oxidation, reduction or hydrolysis (may activate the compound)
What is phase 2 metabolism?
Conjugation - conjugation reactions, in which a second, hydrophilic molecule such as glucuronic acid is added to the molecule (toxic effects will be lower change structure of molecule)
What is phase 3 metabolism?
The products of phase 2 biotransformations may be father metabolised in what is sometimes termed phase 3 reactions
What is the point of metabolism?
Makes the molecule more polar so easier to be excreted by urine, half life is shorter
What is metabolism catalysed by?
Enzymes
Examples of phase 1 metabolism?
Oxidation, reduction, hydrolysis, hydration, dehalogenation
Examples of phase 2 metabolism?
Sulphation, glucuronidation, glutathione conjugation, acetylation, amino acid conjugation, methylation
What is the organic solvent water partition coefficient P?
P - ratio of the concentration of unionised compound X in organic solvent ( eg octane, chloroform) to the concentration of compound X in water
What is P a measure of?
The hydrophobicity and hydrophilicity of chemicals - higher partition to organic solvent higher value of P and higher hydrophobicity for unionised compounds only, most drugs and toxins will be charged at particular conditions
What is the organic solvent water partition coefficient D?
D - ratio of the sum of the concentrations of all forms (ionised and unionised) of the compound X in organic solvent (eg octanol, chloroform) in each of the two phases - higher partition organic solvent higher D value higher hydrophobicity
What is logD dependent on?
pH dependent, hence one must specific the pH at which the logD was measured log P = log D at any pH for unionisable compounds
What is logKoW?
Octanol water partition coefficient - value changes on pH for charged molecules focus on particular pH, if in non charged state, probability of partitioning into organic state higher
Absorption values for high P values?
High absorption happens for higher P values - more hydrophobic compounds easily transported and distribution round the body
Characteristics of lipophilic xenobiotic substance?
Rapidly absorbed Rapidly and widely distributed in body tissues Extensively metabolised before it is excreted
What is the acid dissociation constant Ka?
Equilibrium constant for the following reaction of a weak acid HA, the smaller the value of pKa the stronger the acid
What is pKa?
pKa is defined as the pH where chemical exists as 50% ionised and 50% unionised
When are acids most highly ionised?
Acids are most highly ionised at high pH (pH > pKa)
When are bases most highly ionised?
Bases are most highly ionised at low pH (pH < pKa)
What information do dissociation constants give on the fate of chemicals?
Living organisms (sorption, distribution, metabolism and excretion) Environment (sorption, distribution, bioaccumulation)