The most relevant advances on analytical applications of ionic liquids (IL) as binder in the construction of electrochemical sensors and biosensors based on carbon paste are presented. This new class of solvents - the IL - has received great attention in electroanalytical researches due to the excellent physical and chemical properties of these materials, such as high conductivity, low toxicity, good stability, large electrochemical window and catalytic ability. Recently, the interest in electrodes modified with IL, especially when combined with metallic nanoparticles, has increased expressively due to improve the sensitivity and others advantages discussed in this review.

Biossensores contendo lacase (Aspergillus oryzae) e líquidos iônicos derivados do cátion 1-butil-3-metilimidazol (BMI) associados com os ânions hexafluorfosfato (BMI·PF6) ou bis(trifluormetilsulfonil)imida (BMI·Tf2N) foram construídos para determinação de adrenalina. O biossensor baseado no BMI·Tf2N foi selecionado por apresentar maior resposta quando comparado ao BMI·PF6. As melhores condições para otimização foram estabelecidas por voltametria de onda quadrada (amplitude 100 mV, frequência 10 Hz e incremento 4,0 mV). O melhor desempenho foi obtido em 50:20:15:15% (m/m/m/m) de pó de grafite:lacase:Nujol:LIs em tampão acetato 0,1 mol L-1 (pH 4,0). A curva analítica foi linear na faixa de concentração 2,49 × 10-6 a 2,27 × 10-4 mol L-1 com limite de detecção de 5,34 × 10-7 mol L-1. A recuperação de adrenalina em amostras injetáveis variou de 96,3 a 101,6%. Os resultados obtidos para a adrenalina usando o biossensor proposto e o procedimento da Farmacopéia Americana estão em concordância ao nível de confiança de 95%.

Biosensors based on laccase from Aspergillus oryzae and ionic liquids derived from the 1-butyl-3-methylimidazolium cation (BMI) associated with the anions hexafluorophosphate (BMI·PF6) or bis(trifluoromethylsulfonyl)imide (BMI·Tf2N) were constructed for adrenaline determination. The biosensor based on BMI·Tf2N was selected by presenting higher response when compared with that based on BMI·PF6. The best conditions for the optimization were established by square wave voltammetry (pulse amplitude 100 mV, frequency 10 Hz and scan increment 4.0 mV). The best performance was obtained with 50:20:15:15% (m/m/m/m) as the graphite powder:laccase:Nujol:ILs composition in 0.1 mol L-1 acetate buffer solution (pH 4.0). The analytical curve was linear in the concentration range 2.49 × 10-6 to 2.27 × 10-4 mol L-1 with a detection limit of 5.34 × 10-7 mol L-1. The recovery of adrenaline in injectable samples ranged from 96.3 to 101.6%. The results obtained for the adrenaline using the proposed biosensor and the United States Pharmacopeia procedure were in agreement at the 95% confidence level.

Biosensors based on laccase immobilized on microparticles of chitosan crosslinked with tripolyphosphate (biosensor I) and glyoxal (biosensor II) obtained by spray drying for the determinations of rutin in pharmaceutical formulations were developed. Under optimized operational conditions (pH 4.0, frequency of 30 Hz, pulse amplitude of 40 mV and scan increment of 2.0 mV) two analytical curves were obtained for both biosensors showing a detection limit of 6.2x10-8 mol L-1 for biosensor (I) and 2.0x10-8 mol L-1 for biosensor (II). The recovery of rutin from pharmaceutical sample ranged from 90.7 to 105.0% and the lifetime of these biosensors were 4 months (at least 400 determinations).

Biosensors were developed by immobilization of gilo (Solanum gilo) enzymatic extract on chitosan biopolymers using three different procedures: glutaraldehyde, carbodiimide/glutaraldehyde and epichlorohydrin/glutaraldehyde. The best biosensor performance was obtained after the immobilization of peroxidase on chitosan with epichlorohydrin/glutaraldehyde. Linear analytical curves for hydroquinone concentrations from 2.5x10-4 to 4.5x10-3 mol L-1 with a detection limit of 2.0x10-6 mol L-1 and recovery of hydroquinone ranging from 95.1 to 105% were obtained. The relative standard deviation was < 1.0 % for a solution of 3.0x10-4 mol L-1 hydroquinone and 2.0x10-3 mol L-1 hydrogen peroxide in 0.1 mol L-1 phosphate buffer solution at pH 7.0 (n=8). The lifetime of this biosensor was 6 months (at least 300 determinations).

Crude extracts of several vegetables such as peach (Prunus persica), yam (Alocasia macrorhiza), manioc (Manihot utilissima), artichoke (Cynara scolymus L), sweet potato (Ipomoea batatas (L.) Lam.), turnip (Brassica campestre ssp. rapifera), horseradish (Armoracia rusticana) and zucchini (Cucurbita pepo) were investigated as the source of peroxidase (POD: EC 1.11.1.7). Among those, zucchini (Cucurbita pepo) crude extract was found to be the best one. This enzyme in the presence of hydrogen peroxide catalyses the oxidation of paracetamol to N-acetyl-p-benzoquinoneimine which the electrochemical reduction back to paracetamol was obtained at a peak potential of <FONT FACE=Symbol>¾</FONT>0.10V. A cyclic voltammetric study was performed by scanning the potential from + 0.5 to <FONT FACE=Symbol>¾</FONT> 0.5 V. The recovery of paracetamol from two samples ranged from 97.3 to 106% and a rectilinear calibration curve for paracetamol concentration from 1.2x10-4 to 2.5x10-3 mol L-1 (r=0.9965) were obtained. The detection limit was 6.9x10-5 mol L-1 and the relative standard deviation was less than 1.1% for a solution containing 2.5x10-3 mol L-1 paracetamol and 2.0x10-3 mol L-1 hydrogen peroxide (n=12). The results obtained for paracetamol in pharmaceutical products using the proposed biosensor and Pharmacopoeial procedures are in agreement at the 95% confidence level.