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A headspace solid-phase microextraction method coupled to GC-MS was successfully developed for the trace determination of formaldehyde in veterinary bacterial and human vaccines, and diphtheria-tetanus antigen. The formaldehyde was derivatized by means of the Hantzsch reaction prior to extraction and subsequent determination. Three different types of solid-phase microextraction fibers, polar, and nonpolar poly(dimethylsiloxane) and polyethylene glycol were prepared by using a sol-gel technique. The effects of different parameters such as type of fiber coating, extraction time and temperature, desorption conditions, agitation rate, and salt effect were investigated. Under the optimized conditions, the detection limit of the method was 979 ng/L using the selected ion-monitoring mode. The interday and intraday precisions of the developed method under the optimized conditions were below 13%, and the method shows linearity in the range of 1.75-800 μg/L with a correlation coefficient of 0.9963. The optimized method was applied to the determination of formaldehyde from some biological products. The results were satisfactory compared to the standard method.

Um novo método de extração em fase sólida foi desenvolvido para separar e pré-concentrar traços de tensoativos catiônicos, tais como, brometo de dodeciltrimetilamônio (DTAB), brometo de cetiltrimetilamônio (CTAB) e cloreto de cetilpiridínio (CPC). Esse método é baseado na sorção do tensoativo aniônico (AS − ), dodecilssulfato de sódio (SDS), sobre a superfície de γ-alumina, enquanto um cartucho C 18 é utilizado para a pré-concentração dos tensoativos catiônicos (CS + ). O método espectrofotométrico, utilizado para a determinação dos tensoativos catiônicos, baseia-se na competição entre o corante catiônico, azul de metileno (MB + ), e o CS + , para associação e formação do complexo SDS. O íon complexo formado (MB + ) pode ser quantitativamente substituído pelo CS + , levando a um aumento da absorvância medida em 662 nm. Foram estabelecidas ótimas condições experimentais para a separação, pré-concentração e determinação dos tensoativos catiônicos. Sob essas condições otimizadas, realizou-se a pré-concentração (2×) e os resultados mostraram que a determinação do CPC, DTAB e CTAB poderia ser realizada nas faixas de concentração de 1×10 -5 -2×10 -4 , 4×10 -5 -5×10 -4 and 5×10 -5 -5×10 -4 mol L -1 , respectivamente. Por fim, a partir de onze determinações de 10,0 mg mL -1 das soluções de CPC, DTAB e CTAB obtiveram-se RSDs de 4,3, 3,7 e 4,0%, respectivamente. O método foi validado por meio de um conjunto de diferentes amostras que continham os tensoativos catiônicos.A new solid phase extraction method has been developed to the separation and preconcentration of trace amounts of cationic surfactants i.e. dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC). This method is based on the sorption of anionic surfactant (AS -) of sodium dodecyl sulfate (SDS) on the γ-alumina surface and C 18 cartridge is used for preconcentration of cationic surfactants (CS + ). Spectrophotometric determination method used for the determination of cationic surfactants is based on the competition between the cationic dye of methylene blue (MB + ) and CS + for association complex formation with SDS. The MB + in the ion associate complex can be quantitatively substituted by CS + leading to an increase in the absorbance measured at 662 nm. Optimum experimental conditions for separation, preconcentration and determination of cationic surfactants have been reported. Under the selected optimal conditions, preconcentration factor of two-fold was achieved and the results showed that determination of CPC, DTAB and CTAB could be performed in concentration ranges of 1×10 -5 -2×10 -4 , 4×10 -5 -5×10 -4 and 5×10 -5 -5×10 -4 mol L -1 , respectively. Eleven determinations of 10.0 mg mL -1 of CPC, DTAB and CTAB solutions led to RSD's of 4.3, 3.7 and 4.0%, respectively. Method was validated using a set of different samples containing cationic surfactants.

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