This manual contains both PART A and PART B programs. All the programs are copies of executed ones. NOTE: Please read every note given in the pdf.
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Civil Technology Lab manual. QCET Sahiwal.
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Experiment 5: Thin-Layer Chromatography of Ink Objective To To understand and experience ink analysis using Thin-layer chromatography technique
Introduction Thin-layer chromatography (TLC) is one of the simplest techniques in separation chemistry. It is inexpensive simple to perform and one of the most common chromatographic methods in the forensic la!oratory. This method"s stationary phase is a thin layer of gel adsor!ent coated onto plastic#metal !acking called a TLC plate. $s the liquid mo!ile phase is dra%n into the gel it is carried !y capillary action up to%ard the top of the plate. $long the %ay the samples are separated into their constituent chemicals.
ateria!" &encil
*+ ethanol # pyridine
'etric ruler
,thyl acetate
&recoated silica chromatography plate
istilled %ater
everal !all-point pens sampled on %hite paper
/ *01 2/,3IC C4,'IT/5 C4,'IT/5
Capillary tu!e eveloping cham!er
#rocedure To prepare the mo!ile phase6 7sing a 8*mL graduated cylinder add6 9.*mL ethyl acetate :.*mL *+ ethanol and :.;mL distilled %ater to a 1;;mL scre% cap reagent storage !ottle. $ do any of the exemplars resem!le it either in color of ink or hand%riting? 'ake note of your preliminary o!servations. @. Clip a ;.*cm square from the text of each document and transfer each to a %ell of the spot plate. *. $dd t%o drops *+ ,t24 # pyridine to each %ell and gently s%irl spot plate to agitate. 5ou should o!serve the solvent turning !lue or purple indicating that the ink is dissolving into the liquid. A. 'ark a pencil line 1cm from the !ottom of a short edge of the TLC plate. 9. 7se a clean capillary tu!e for each sample to spot along the =rst pencil line. 0. Be sure to note the location of each sample in your note!ook. . Carefully and quickly position the TLC plate in the cham!er and cover. 1;.Check the progress of the solvent front every 8-: minutes. 11.2nce the solvent front reach a!out of the TLC plate length remove the plate from the cham!er and mark the solvent front %ith your pencil. 18.$llo% it to dry completely. 1:.ra% a diagram of the plate including each !and#spot. 5ou might %ant to photograph the plate to include in your report. 1@.'ark the center of each !and. 1*.Calculate the /f value for each !and !y dividing the distance travelled !y the !and !y the distance travelled !y the solvent. 1A.,ach ink should yield a unique pro=le !y comparing the num!er the num!er of !ands and their corresponding / f values. 19.Compare your TLC results !et%een questioned document and exemplars.
$ue"tion" 1. $part from TLC %hat other methods can !e used to diDerentiate ink? 8. 4o% does ink analysis helps in forensic investigation? :. Ehat are the advantages and disadvantages of using TLC in ink analysis?
Experiment %: #aint Chip &na!y"i"
Objective To morphologically and spectroscopic diDerentiate paint chips layers from diDerent cars
#rocedure #art & 1. 'ount the paint chip samples on the plasticine side%ays. 8. Fie% the layers of the paint chip using stereomicroscope. :. 3ote the %ideness or thinness of each layer colour and the overall num!er of layers for each paint chip sample. @. ra% each of the paint chip samples provided.
#art ' 1. &aint chips are mounted on TI/ microscope for mapping. 8. $T/ mapping measurements %ere performed using a 8; x $T/-o!Gective in com!ination %ith a motoriHed sample stage. :. 'easurement positions and sampling areas %ere set speci=cally for each layer. @. $n acquisition time of 1@ sec at a spectral resolution of @cm -1 %as used. *. uring the infrared measurement the sample is !rought into contact %ith the tip of the ermanium (e) crystal (1;;Jm in diameter) of the $T/o!Gective on all prede=ned sampling positions.
A. The eDective =eld of vie% at all sampling positions is adGusted automatically !y a motoriHed aperture. The example of paint chips analyHed using $T/ TI/ mapping is sho%n in =gure 1!.
(igure )b 2vervie% image $ sho%s measurement positions %ith individual aperture siHe. B sho%s corresponding spectra of A layers.
$ue"tion" 1. Ehat is the advantage of using mapping in TI/ spectroscopy? 8. Ehat does each layer in the paint chips represent? :. Ehat are other techniques for analysis of paint chip in forensic investigation? @. Ehat are the choices of analysis that you %ill you do if the paint is in the form of smear?
Experiment *: +eria! ,umber e"toration
Objective To demonstrate the o!literation done on chasis#engine num!er and restore the original num!er
#rocedure 1. ,ach student takes a piece of steel plate. 8. $ set of A com!inations of num!ers and alpha!ets %ere stamped onto the steel plate using the metal stamp. :. These set of num!ers and alpha!ets are then o!literated using sand papers. @. $ ne% set of A com!inations of num!ers and alpha!ets are then stamped onto the same steel plate. *. Eipe the plate %ith acetone using the cotton !ud. A. Take a photograph of the plate !efore the etching process. 9. 'oisten cotton tip applicators (s%a!s) %ith the ry"s reagent solution and apply to the o!literated area. 0. $fter a fe% seconds %ipe oD the solution and inspect for visi!le num!ers. /epeat as necessary. This process may take several hours. . $lternate !et%een s%a!s saturated %ith the ry"s /eagent and the 8*+ 3itric $cid solution. 1;.To speed up the process the examiner may %ish to use an electrochemical process. The positive (K) terminal of a standard lantern !attery or other source is connected to the o!literated item and the negative terminal (-) is connected to the cotton s%a!. 11.If any characters !ecome visi!le note these characters.
$ue"tion" 1. Ehat are other reagents and their respective suita!le surface for etching process? 8. ,xplain the principle of serial num!er restoration. :. Ehat are the forensic cases that require etching to !e done in such cases?