Indirect Atomic Absorption Determination of Cocaine via Formation and Liquid‐liquid Extraction of the Iron(III)‐cocaine Complex

Abstract

The principles of metal-alkaloid ion-pair formation and liquid-liquid extraction are applied to the development of a sensitive and convenient atomic absorption spectrophotometery (AAS) method for the indirect determination of cocaine. In an aqueous medium of 5 M hydrochloric acid, cocaine is protonated and is associated with tetrachloro ferrate (III) anion prior to its extraction into 1,2-dichloroethane. The critical experimental variables were identified and optimized. The method is simple and reproducible with a detection limit (DL) of 0.1 ng cm -3 cocaine in water, a relative standard deviation of 0.07 (n = 12), and the calibration graph was linear up to 50 ng cm -3 cocaine.

Copper thiocyanato complexes and cocaine – a case of ‘black cocaine’

“…Raman spectra and powder X‐ray diffraction (PXRD) experiments clearly show that graphite is the source of the black colour; in the red acetone extract corresponding signals of graphite are absent. Thus, the acetone‐soluble material contains Cu 2+ and Fe 3+ ions, SCN − and CocH + which strongly reminds to the above mentioned procedures for the extraction and detection of cocaine and related atropine bases using anionic thiocyanate metal complexes such as [Cr(SCN) 6 ] 3− , [Fe(NCS) 6 ] 3− , [Fe(NCS) 4 ] − , [Co(SCN) 4 ] 2− , [Ni(SCN) 4 ] 2− , but also [BiI 4 ] − (Dragendorff reagent), or [AuCl 4 ] − . The anionic complexes form tight ion‐pairs with the protonated atropine bases (or related molecules), allowing the selective liquid‐liquid extraction using organic solvents.…”

“…On the other hand it is well known that anionic transition metal complexes formed from SCN − and metal ions such as Fe 3+ , Co 2+ , Cu 2+ , Hg 2+ can form ion pairs with protonated nitrogen bases such as the alkaloids cocaine or atropine thus enabling liquid(water)‐liquid(organics) extraction methods for isolation and detection of these bases . Related liquid‐liquid extraction (LLE) was also reported for the recovery and detection of metal ions by using SCN − and suitable (large, organic) cations .…”

“…[1] On the other hand it is well known that anionic transition metal complexes formed from SCN À and metal ions such as Fe 3+ , Co 2+ , Cu 2+ , Hg 2+ can form ion pairs with protonated nitrogen bases such as the alkaloids cocaine or atropine thus enabling liquid(water)-liquid(organics) extraction methods for isolation and detection of these bases. [2][3][4][5][6][7][8][9] Related liquid-liquid extraction (LLE) was also reported for the recovery and detection of metal ions by using SCN À and suitable (large, organic) cations. [10][11][12][13][14][15] At the same time the binding of the metal cations to cocaine base in such black powder [16][17][18] might modify essential properties of cocaine such as solubility or hamper detection.…”

A novel, environmentally friendly procedure for copper extraction using dimethylindodicarbocyanine dye and subsequent graphite furnace atomic absorption spectrometric detection

“…Significantly fewer articles can be found, however, which are devoted to the utilization of LLE for the separation of analytes after complex-formation, and only a small portion of these articles deal with the application of ion associate formation with an appropriate reagent and subsequent AAS detection. We will mention and emphasize some interesting resolutions which enable, for example, speciation analysis, 3,4 determination of anions 5 or organic analytes such as cocaine 6 and surfactants. 7,8 As can be seen, the use of complex-forming reagents in combination with LLE separation and subsequent AAS detection offers new possibilities for improving atomic spectrometry.…”