Estudo de variaveis experimentais no desempenho de colunas recheadas para cromatografia liquida de alta eficiencia (CLAE)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

Interest in HPLC has increased in recent years due its high capacity for separation, as well as its sensitivity, rapidity and versatility. However, the cost of this technique is very high and all accesories, including the columns are imported. Thus, we have developed a technology for packing columns with quality as good as commercial columns. The stationary phases used in this study were inunobilized reversed phases, C-8 and C-18, because they are the most widely used in HPLC. The C-18 stationary phases were obtained commercially and C-8 were produced in our own laboratory. The success or tbe HPLC separation of a mixture into individual components is obtained as a function of 3 chromatographic parameters: plate number (N) or efficiency, retention factor (k) and selectivity factor (a). For analysis of complex samples, the efficiency has a special importance since sometimes, after the optimization of k and a, we do not obtain a good resolution. With this aim, we did a systematic study of some factors that affect N, using whenever possible, chemometrics methods to establish the best conditions of analysis. The coupling of columns was tested to increase the length and consequently to increase the chromatographic efficiency and, for this, we studied two kinds of connections: a capilary connection and head to head. Both kinds showed little dispersion either could be used for coupling columns. Coupling four similar columns provided a four times increase in the efficiency, resulting in N = 12,825 and a linear function between N and Rs was observed. The efficiency obtained with the coupling columns was sufficient to separate completly a mixture of perhalogenated compounds. We observed that for coupling columns it is better to use columns packed with larger particule sizes of stationary phase due the lower pressure of operation. The maximum length , estimated for columns packed with 5 and 3 mm particule sizes are: 750 mm and 180 mm, respectively, having, at the maximum pressure, N = 67.596 and 25.248, These are adequate to separate mixtures (k=3) and a = 1.02 and 1.03 Through Factorial Projection we observed that the length of the column is the main factor to produce an increase in the efficiency, among the possibile factors: injection volume, composition of the mobile phase and temperature of the column. Using the Sequential Modified Simplex we obtained an alternative to van Deemter plots, where we optimize the flow rate and the best temperature for analysis using a small numbers of experiments.

ASSUNTO(S)

transformações de fase (fisica estatistica) separação (tecnologia) analise cromatografica cromatografia liquida de alta eficiencia

ACESSO AO ARTIGO

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