Sensitive determination of triazines in underground waters using stir bar sorptive extraction directly coupled to automated thermal desorption and gas chromatography-mass spectrometry.

An automated thermal desorption-gas chromatography-mass spectrometry method for the determination of triazin herbicides in aqueous solution with excellent sensitivity was developed. The method is based on the use of stir bar sorptive extraction. The main parameters such as extraction time, sample volume, the addition of salt and organic modifiers, desorption temperature, desorption flow and desorption time which affect the efficiency of the proposed methodology are fully discussed. The proposed method is sensitive and shows a good linearity within a range of 10-10000 ng L(-1) with correlation coefficients higher than 0.998. Quantitation limits are, in all cases, below the limits accepted by European legislation for human waters consumption and ranging between 11.3 ng L(-1) and 0.7 ng L(-1). The repetitivity, expressed as a relative standard deviation, has values of lower than 8% for all analytes. Using this method, determination of 10 triazines in underground water samples was successfully performed. The average concentrations obtained in the analysis of the spiked samples at two different levels of concentration correspond to mean recoveries ranging from 94.4+/-5.1% to 106.0+/-6.3% for a significance level of 0.05.