Automation of the GC/MS analysis of mineral oil contaminations in water

An automation of the sample preparation and analysis of mineral oil contami nations in water was developed. The automated sample preparation was carrie d out according to ISO/DIS 9377-4 [1]. The standard is applicable to the de termination of hydrocarbons in the boiling range of n-decane (n-C10) up to n-tetracontane (n-C40) by GC. Extraction of the sample and clean-up of the extract were performed by an autosampler with a movable head which is capab le of carrying different syringes for gas and liquid handling. A GC/MS-syst em with a programmed temperature vaporizing (PTV) injector including the po ssibility of large volume injections (LVI) was employed for the analysis. T he recovery of analytes was 101.8%, the repeatability 2.9% relative standar d deviation (RSD). The linear range covered 0.3 to 40 mg/L oil but may be l arger since no higher concentrations were measured. With an FID, being the detector of choice mentioned in the standard, it should be possible to achi eve at least four orders of magnitude in the linear range. The limit of det ermination was found to be 0.3-0.4 mg/L, the limit of detection 0.1-0.2 mg/ L [2]. Measurements of spiked deionized, bidistilled water and spiked water from a lake confirmed the accuracy of the analysis. Due to automation and miniaturization of the analysis it is possible to economize time and chemic als without loss of precision and accuracy.