Use of capillary electrophoresis in the characterization of sulfonated metallophthalocyanines: a comparative evaluation of purification procedures following synthesis by the condensation method.
Capillary electrophoresis has been presented as a resourceful technique for monitoring the purity of synthetic metallophthalocyanines and evaluating comparatively purification procedures. In this study, the tetrasulfonated cobalt(II) phthalocyanine was synthesized by the condensation method and submitted to several purification procedures such as continuous Soxhlet extraction with ethanol and dioxane, percolation through a gel-filled chromatographic column, and salting-out precipitation in acid medium followed by washing with alkaline solution. The efficiency of each procedure, or combined procedures, was then evaluated by capillary electrophoresis in citrate buffer solution under constant voltage conditions and direct UV-VIS detection at 630 nm and 260 nm. The inorganic anion and cation composition of the purified fractions was also investigated by indirect UV analysis in chromate/cetyltrimethylammonium bromide (CTAB) and imidazole/hydroxyisobutyric acid (HIBA) electrolyte systems, at 254 nm and 214 nm, respectively. The electropherograms obtained at 630 nm showed a high-intensity peak surrounded by satellite peaks of small intensity with migration time of approximately 5-6 min. This profile is indicative of the formation of positional isomers under the synthesis conditions. The electropherograms obtained at 260 nm were useful to monitor contaminants, such as reaction by-products or unreacted starting materials. The salting-out precipitation of the crude product led to a good-quality product with 80% purity (elemental analysis based on nitrogen content), which is comparable to the purity of commercially available tetrasulfonated derivatives. Both UV and infrared (IR) spectra of the purified product resemble that of standards. The capillary electrophoresis ion analysis of the treated product revealed the presence of sodium carbonate as the major contaminant. The combined treatment of salting-out precipitation followed by percolation in a Sephadex column (Pharmacia, São Paulo, Brazil) was successful for the removal of carbonate ion. However, the percolation procedure seemed to cause minor demetallation of the macrocycle ring, as confirmed by the presence of free cobalt(II) in the electropherogram of the column eluted fraction.
Barbosa
C A
CA
Instituto de Química, Universidade de São Paulo, Brazil.
Constantino
V R
VR
Tavares
M F
MF
D003035:Cobalt; D019075:Electrophoresis, Capillary / Q000379:methods* / Q000706:statistics & numerical data; D005069:Evaluation Studies as Topic; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification*; D054833:Isoindoles; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification*; D013451:Sulfonic Acids
D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D013451:Sulfonic Acids; C052738:cobalt tetrasulfophthalocyanine; D003035:Cobalt; C013647:phthalocyanine