Methods of chemical analysis Essay


Electrophoresis is a technique used for dividing molecules through migration on a support medium while under the influence of an electrical charge. It was foremost used as a separation technique by Tiselius in 1937.He described the separation of proteins which were placed in a buffer in a tubing and an electric field was applied. The importance of this work was recognized and earned him the Nobel Prize for Chemistry in 1947.Initially the technique was carried out on a stationary level solid stage ( slab gel technique ) .This technique was slow and cumbrous and required long analysis times and had low efficiencies ( Anastos, 2007 ) . In the 1960 ‘s the technique was greatly enhanced by transporting out the separations in narrow dullard tubings ( columns ) . Hjerten describes the separation of many different types of molecules, inorganic ions, bases, proteins and viruses in tubings merely a few millimetres thick. The technique was further refined by Jorgenson and Lukacs ( 1981 ) in the 1980 ‘s and resulted in the separations taking topographic point in narrow dullard tubings. This pioneering work led to the development of a technique known as capillary cataphoresis ( CE ) .

Capillary Electrophoresis is used in a broad assortment of analytical applications. Tavares ( 2003 ) describes it usage and versatility in countries such as clinical, forensic, cosmetological, environmental, nutritionary and pharmaceutical samples. The first usage of CE for forensic analysis was demonstrated by Weinburger and Lurie in 1991. They describe the usage of CE in the analysis of illicit drugs in man-made mixtures.

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Since so CE is widely used as a separation technique for a assortment of samples for illustration, drugs, amino acids vitamins, organic acids and inorganic ions. It has besides developed as a technique which is used widely in forensic scientific discipline research labs, countries include, analysis of drug ictuss ; gun shooting residues, explosive residues, ink analysis and toxicology,

2 Forensic Analysis Of Samples

Traditionally forensic samples were analysed utilizing instruments available in an analytical chemical science research lab. The chief instruments used were based ( and in some instances still are ) on chromatographic techniques. Gas Chromatography and High Performance Liquid Chromatography HPLC are the two major type of analytical techniques conventionally used for forensic samples. Presently in forensic scientific discipline research labs there is a preference/trend to utilize CE techniques over the traditional chromatographic technique.

Why Is This So?

There are many grounds for this conversion. Chromatographic techniques normally require pre-treatment of the sample which can be really clip consuming. Besides some compounds are thermally unstable and are non suited to GC analysis.

On the other manus the separations that can be achieved by CE are extremely efficient, have a rapid analysis clip and can be applied to impersonal and non-neutral species.

Other advantages of CE are that it requires low sample and low dissolver sums, has low bounds of sensing and is a comparatively simple, cheap technique to transport out.

3 Types Of Capillary Electrophoresis

The term CE truly describes a figure of related techniques in which separations are carried out in narrow dullard capillaries under the influence of an electric field. Other techniques include ;

Capillary Zone Electrophoresis – CZE

Micellar Electrokinetic Chromatography – MEKC

Capillary Gel Electrophoresis – CGE

It is beyond the range of this essay to depict each of these in item. It should be noted that they all operate on the rule of separation of molecules in narrow dullard capillaries with an applied electric field.

4 Applications Of CE In Forensic Science

Drug analysis

CE is widely used in the analysis of drug ictuss. All the different types of CE have been used in this type of analysis. There are legion scientific documents published in this country. In 2005 Anastos reviewed the usage of CE in forensic drug analysis for the old ages 2001-2005. This reappraisal showed how popular CE had become as a everyday method of forensic analysis. There are many surveies demoing the advantages of CE over traditional chromatographic techniques of drug analysis. Anastos ( 2005 B ) described a CE technique for the separation of caffeine, paracetamol, morphia, codeine, diacetylmorphine, and acetylcodeine. The mixture was resolved in less that 1.5 proceedingss and the consequences obtained were in understanding with a validated GC method.

Di Pietra ( 2001 ) developed a CZE technique for the analysis of pep pills and compared the consequences obtained with HPLC analysis. The decision was that the CE method provided greater peak symmetricalness and shorter tally times than the HPLC method. Luric ( 2003 ) used CZE and HPLC for the finding of opium alkaloids in opium gum and opium latex. It was found that the CZE method gave better declaration that the HPLC method, with significantly faster analysis times – 12 min V 29 min.

Aturki ( 2009 ) describes the usage of a comparatively new CE technique capillary electrochromatograohy CEC to analyze 10 different drugs of maltreatment. This new technique combines the advantages of the high velocity and efficiency of CE with the high selectivity and increased trying burden of HPLC. This survey concluded that this method offers many advantages over the traditional HPLC, these include fewer costs, minimum ingestion of dissolvers and samples and shorter analysis times.


Capillary cataphoresis is besides used to analyze different biological samples for the presence of drugs. Blood and urine samples can be successfully tested for a assortment of drugs utilizing CE. The advantages of CE over traditional methods of analysing biological samples are similar to the analysis of drug ictuss ;

– shorter tally times, little sample demands, and lower bounds of sensing.

The analysis of pep pills in blood utilizing a CZE method is described by Boatto ( 2002 ) . A sensing bound of between 10 and 30 ng/ml was recorded and a run clip of 7 proceedingss.

Alnajjar ( 2004 ) depict the analysis of piss for the presence of diacetylmorphine utilizing a CZE method.

The finding of creatinine in urine samples utilizing CZE is outlined in the research paper published by Liotta ( 2009 ) . The consequences indicate that the check described meets the rigorous demands of forensic analysis and meets the demand of a simpleness, celerity and low cost required by everyday toxicological screening..

The analysis of diacetylmorphine metabolites in human piss is described by Jong. ( 2009 ) utilizing the MEKC method. The separation was achieved in less than 10 proceedingss and the consequences were confirmed utilizing liquid chromatography/mass spectroscopy.

A simple rapid low cost MEKC method of analysing anabolic steroids in piss is presented by Zhang ( 2009 ) . This method was validated by GC-MS. This new technique is less expensive and a much quicker analytical technique that GC-MS for this type of analysis.

Aturki ( 2009 ) besides demonstrated the advantages of CE over traditional chromatographic methods of drug analysis in biological samples. The consequences obtained for the coincident analysis of 10 illicit drugs in human urine demonstrate several advantages, these include fewer costs, minimum ingestion of dissolvers and samples and shorter analysis times.

CE has besides been used for the analysis of human hair samples for the presence of drugs. Tavares ( 2003 ) analysed hair samples for the presence of opiates and metabolites. A recent survey by Zhang ( 2009 online ) illustrates how CE can be used in the finding of Co in a individual human hair sample. Traditional spectroscopic techniques are used for hair analysis. They are seldom used in the analysis of individual hair samples due to their deficient insensitiveness and big sample demands. The CE method described overcomes these restrictions. As a consequence the finding of hint elements in hair samples can take to utile forensic information. This includes life location, the working environment of the individual, and possibly their dietetic wonts which could contract the hunt for the suspect ( s ) .

Gun Shot Residues

Gun shooting residues are produced when a piece is discharged and can be deposited onto a surface after discharge. These residues are typically divided into organic and inorganic constituents. The methods of analysis of both differ, the organic residue have traditionally been analysed utilizing chromatographic techniques, GC-MS, LC-MS and HPLC. The inorganic constituents are analysed utilizing non chromatographic techniques ( SEM-EDX ) .

These tradition techniques tend to be slow and require expensive equipment. The demand for fast, inexpensive options has seen Capillary Electrophoresis being used to analyze both the organic and inorganic constituents of gun shooting residues. Morales ( 2004 ) developed a capillary cataphoresis method to analyse at the same time 11 organic and 10 inorganic constituents of gunshot residues. This technique is suited as a cheaper and perchance more specific method comparing to traditional techniques. The consequences obtained were compared with electrothermal atomic soaking up spectrometry, an established technique for gunshot residue analysis. Good understanding between both techniques for lead was found. MacCrehan ( 1998 ) depict how the MEKC technique can be applied to the analysis of gunshot residues from tape lifts and swabs. A figure of other surveies ( Northrop 2001, MacCrehan 2003, and Cascio 2004 ) all describe the suitableness of utilizing MEKC in the word picture of organic gunpowder constituents.


Since the mid 1990 ‘s CE is routinely used technique for the analysis of the organic and inorganic constituents of explosive. The grounds for its rapid rise in popularity are similar to its advantages in the old mentioned forensic samples. This rapid rise can be seen in the reappraisal of the usage of CE in explosive analysis published by McCord and Bender ( 1998 ) .

Tagliaro ( 2001 ) describes a CE method for nitrite and nitrate finding to be used as a showing tool for look intoing the residues of piece discharge. The usage of CE allowed the rapid finding of nitrite and nitrate, which are major inorganic constituents of gunshot residues. The method is simpler, cheaper, and faster than the modern attacks ( AA, ICP-MS, and SEM ) to gunshot residue analysis

A farther development of Capillary Electrophoresis, CE micro chip, has led to the possibility of a portable analytical instrument for field analysis of explosive residues. Two surveies ( Lu, 2002, Vladislav 2000 ) have demonstrated the viability of utilizing this micro chip engineering to analyze explosive residues and have shown the advantages it offers over traditional more cumbrous research lab based techniques.

Inks analysis

The word picture of inks is of import in forensic scientific discipline because it can let the forensic scientist find the genuineness of a questioned papers. Traditionally inks were analysed by chromatographic techniques, ab initio paper and later thin bed chromatography.

HPLC has replaced these as the separation technique most normally for the analysis of inks. GC tends to hold limited usage in ink analysis as most constituents are non-volatile.

CE has gained popularity in the analysis of inks due to its advantages over HPLC. These include, little samples required ( nanolitres ) , this can a large advantage over HPLC as the harm to the papers in inquiry will be minimized.

The first study of the usage of CE for ink analysis was documented in 1991 by Fanalli. Different black ruddy and H2O soluble fiber tipped pen inks were quantitatively distinguished utilizing CE.

A survey by Tsutsumi ( 1996 ) compared the usage of HPLC and CE for the favoritism between ruddy and bluish pen inks. CE was found to be more suited for analysing inks that contain ionic dyestuffs. Fakhari ( 2006 ) examined the usage of CE for the separation of ink samples from 6 fibre tip and 2 ball point blue or black pens and showed that a alone migration clip for the chief dye constituent in seven of the eight pens could be obtained.

A figure of surveies report the usage of MEKC to the analysis of inks from different pens ( Vogt 1999 and Mania 2002 ) . Both surveies indicate that the rapid analysis clip and the little sample demand show the advantage of this technique over traditional chromatographic techniques.

5 Decision

Capillary cataphoresis is widely used in forensic research labs for the routing analysis of a assortment of samples typically found at a offense scene. It offers many advantages over chromatographic techniques for the analysis of these samples. These advantaged include, quicker analysis clip, the demand of less ample and dissolvers, lower bounds of sensing and less expensive equipment. These advantages will guarantee that analysis of forensic samples utilizing CE techniques will go on to turn and develop in the coming old ages.

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