forensic chemistry- help (1 Viewer)

[parry]

can someone help me with the dotpoint

"perform 1st hand investigation + gather info to identify the range of solvents that may be used for chromatography and suggest mixtures that may be seperated and identified by the use of these solvents"

and

"perform 1st hand investigation to cary out electrophoresis of appropriate mixutre and identify the characteristics of the mixture which allow it to be seperated by this process

Any help would be appreciated

 

[countrydude]

man i fuking hate this topic its gona fuk my uai up bad...id help but i suk at it. good luk

 

[phenol]

my heart goes towards forensics ppl it is much harder, but you are actually learning real chemistry

i can give you some idea on the 2nd one (i dont do forensics but i have very fundamental ideas about biochemistry)

polyacrylamide gel electrophoresis

1) SDS (sodium dodecyl sulfate - a charged specie) is added to the mixture of amino acids to be separated. SDS readily binds to amino acid chains. The longer the amino acid chain, the more SDS molecules bind to it. The more SDS binds to it, the larger charge on the chain.

2) the mixture is put onto a plate with polyacrylamide gel on it

3) the plate is electrophoresced

4) the amino acid chains with longer length (hence larger charge) moves down the plate faster than the shorter chains and hence smaller charge.

The discriminating characteristic is length of the amino acid chain.

Hope this helps

 

[parry]

yeah it does thanks phenol

 

[iambored]

Originally posted by phenol
my heart goes towards forensics ppl it is much harder, but you are actually learning real chemistry

that's the only part of the course i like, it's the only interesting part

 

[Catey]

I agree forensics isn't hard and it is the only good part in the whole chemitry course....

The first experiment is about paper chromotography and you are testing the length that solvents such as ink, die, texta's and spinach will travel... it should be noted that the blue texta will tyravel the furthest because of its emmision spectra and ion arrangement

 

[Toodulu]

perform 1st hand investigation + gather info to identify the range of solvents that may be used for chromatography and suggest mixtures that may be seperated and identified by the use of these solvents
eh, i'm not sure about the emission spectra and ion arrangement thingy (help!)
but i think you should understand the principles behind chromatography (solubility etc)
erm, and there are diff. types of chromatography like, paper, GLC, HPLC,
mixtures that can be separated... you can separate the amino acids, sugar/steroids in blood, herbicides/pesticides in products, food additives...etc

perform 1st hand investigation to cary out electrophoresis of appropriate mixutre and identify the characteristics of the mixture which allow it to be seperated by this process
did you do the gel electrophoresis experiment where you injected the sample into the blue jelly thing and then when u apply the voltage they moved across the thingy? you should be able to find this in your textbook. erm, it's based on conductivity and the size of the stuff you're separating. obviously the ions would move to their respective electrodes, and the bigger the molecule the slower the migration rate.. so basically you look at which direction it's going and how far it gets. and then you can do whatever by changing the pH of the buffer etc etc.

 

[parry]

did you do the gel electrophoresis experiment where you injected the sample into the blue jelly thing and then when u apply the voltage they moved across the thingy?

our teacher only showed us the finished thing but i think i get it.

And for the first one whats the range of solvents, i think thats where im losing it

 

[Toodulu]

the solvent is just what the sample is being dissolved in.. like the thingy with all the stuff you want to separate in it. so the range of solvents is just what you can test with chromatography like the stuff i said before (blood etc). but i made some notes on it this morning erm

Paper chromatography: can separate components of dye, ink, green pigment of plants (i'm not sure if u did this, but we did a paper chromatography prac and saw these green stuff on the filter paper and they were chlorophyll compounds)
Gas chromatography: separate gas mixtures, used in combination with mass spec to analyse urine samples provided by athletes

Electrophoresis (not chromatography obviously but i'll write it anyway): separate proteins and other biological molecules, can be used to confirm identity of foods and analyse proteins to identify between particular individuals

 

[ratherbesleepin]

Okay have i missed something??

I thought the solvents were the things that you used such as water or ethanol to perform the chromotography, not the stuff your actually trying to seperate.

Am i just reading what you wrote wrong or have i got it totally wrong

 

[Toodulu]

yeeea they're both solvents.. like, with paper chromatography, you're separating according to their different solubility in the mobile and stationary

i don't really think it's that important as long as you know how everything works.

edit: no actually yea you're right, they called it 'solvent' and 'mixture'. so yea sorry, then i dont really know what the range of solvent is other than water. and what i said before would refer to the 2nd part of the dp, the 'suggest mixtures' bit