Solids, automatic sampling

The Gilson Aspec automatic sample preparation system is a fully automated system for solid-phase extraction on disposable columns and online HPLC analysis. The Aspec system offers total automation and total control of the entire sample preparation process including clean-up and concentration. In addition, Aspec can automatically inject prepared samples into on-line HPLC systems. 

The liquid or solid sample is placed in a vial, which is sealed with a septum and heated to a predetermined temperature for a period of time. Equilibrium between the sample and vapor phase is then established and a portion of the volatiles in the gas phase (headspace) is subsequently injected onto the column. Several different methods have been used to transfer headspace volatiles into the GC, from manual withdrawal that uses a gas syringe, to sophisticated automatic sampling that involves transfer lines, and valves that lead directly onto the column. 

XRF analysis was used for the determination of ruthenium, tin, sodium and chlorine content. Solid catalysts samples were examined by automatic sequence RTG spectrometer (ARE 9400 XP). Elements loadings were evaluated by UNIQUANT analyzer. The program used a universal calibration method. 

The homogeneity problem is specific to solid samples, as liquid and gaseous samples are considered homogeneous by nature. Thus, for solid samples, an automatic sampling process is recommended to obtain reliable analytical information. To select the most adequate system to obtain a homogeneous sample it is necessary to take into account the sample complexity and the stability of the sample within a certain period of time.37 Further, it is necessary to establish first the nature of analysis that will be used in sample control, especially when the limits of detection are low. One must also be wary of the many contamination risks from reagent impurities, laboratory vessels, laboratory climate, and the operator. 

The automation of this system essentially resided in developing an automatic sample injector. The designers of the system used an automatic device for introducing solid samples into a Pye-Unicam gas chromatograph. The automatic sample introducing device designed by Coulter and Thompson [69] is illustrated in Fig. 3.6. Power supply unit 1... 

Flow techniques are particularly suitable for monitoring environmental parameters in waters. Moreover, flow methods offer unique possibilities for automatic sample pretreatment, involving inline dilution or filtration, adjustment of viscosity, ionic strength, or pH as well as removal of solid and colloidal matrix constituents via in-line dialysis separation techniques. 

To conclude, each spectrum consisted of 64 scans of 32K data points with a spectral width of 6.000 Hz and an acquisition time of 5.3 s, a recycle delay of 25 second per scan and a pulse angle of 90°. The analysis of each solid extract was performed using D2O as an internal lock. Spectra were acquired under an automation procedure (automatic shimming and automatic sample loading) requiring about 33 min per sample. 

Welin-Klinstroem et al used a null ellipsometer equipped with an automatic sample scanning device for studies of adsorption and desorption of fibrinogen and IgG at the liquid/solid interface on surface wettability gradients on silicon wafers. To follow the processes along the wettability gradient, off-null ellipsometry was used. The kinetics of adsorption and nonionic-surfactant-induced desorption varied considerably between fibrinogen and IgG. In the hydrophilic region, veiy little protein desorption was seen when a nonionic surfactant was used. 

D. Jahr, Determination of alkyl, chloro and mononiti ophenols in water by sample-acetylation and automatic on-line solid phase excaction-gas cliromatography-mass spectrometry , Chromatographia 41 49-56 (1998). 

Five synthetic and five natural colorants were identified and quantified in lyo-philized dairy products and fatty foods using an automatic method based on solid phase extraction using a stationary phase followed by RP-HPLC C,g columns for the sequential retention of colorants and diode array detection. Lyophilization of the samples coupled with the separation procedure provided clean extracts despite the complexity of the food matrices and preserved the sample for at least 2 months without changes in colorant concentrations. The detection limits achieved for the colorants were found in a wide range from 0.03 to 75 pg/g of the lyophilized sample, according to the limits established by the European Union. ... 

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