Sample preparation reducing time

Industrial analytical laboratories search for methodologies that allow high quality analysis with enhanced sensitivity, short overall analysis times through significant reductions in sample preparation, reduced cost per analysis through fewer man-hours per sample, reduced solvent usage and disposal costs, and minimisation of errors due to analyte loss and contamination during evaporation. The experience and criticism of analysts influence the economical aspects of analysis methods very substantially. 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

Automation is one issue of paramount importance, as the biggest problem with sample preparation is time. The benefits of automation, apart from the obvious economic one, include the reduced manual operations and laboratory materials required, the increased sample throughput... 

The LC/MS separation and detection shown in this method illustrate the multiresidue capabilities of LC/MS. The combination of the LC separation for six sulfonylurea herbicides within 25 minutes and the selectivity and structure confirmation of the mass selective detector offer the basis for efficient residue analysis. LC/MS residue methodology can be a cost effective alternative to conventional residue methodology. The mass selectivity will simplify the extraction procedure and minimize sample clean up. A simplified sample preparation saves time and reduces analyte loss during sample preparation which will maximizes recovery. 

To summarise, microwave sample preparation reduces blank contribution from environmental exposure, reagent use and losses from evaporation, and in addition, reduces sample preparation times. It also offers a more reproducible method for duplicating metals determination, both within a laboratory and between laboratories (Lamble Hill 1998). But, in the case of contaminated soil sample digestions, due to surface effects of PTFE, a microwave-cleaning step is highly recommended between each bath of samples in order to avoid any memory effects (carry over contamination) from previous digested samples. 

Another development in HPLC analysis is the interfacing of on-line sample clean-up technologies at the front end of the HPLC analytical column. Using a switching valve, complex samples can be injected directly onto a sample preparation column, the stationary phase of which is designed to bind the analyte(s) of interest to the exclusion of the rest of the matrix, which runs to waste. Then the valve is switched and the mobile phase flows through the sample preparation column where it picks up the analyte(s) and carries them onto the analytical column and through to the detector in the normal way. This automation of sample preparation saves time and effort and reduces errors. There are many applications of HPLC assays in conjunction with on-line sample clean-up methods in the literature ... 

There has also been a move from slow manual sample preparation techniques to faster automated techniques. Automated sample preparation can be carried out on-line (with sample preparation connected directly to the analysis system) or off-line (sample preparation is automated, but the sample has to be manually transferred to the analysis system). Automated sample preparation offers the potential of performing sample clean-up, concentration, and analyte separation in a closed system. This reduces the sample preparation time, and the whole sample becomes available for analysis, leading to improved limits of detection. It also removes some of the human element from a procedure, thereby improving precision and reproducibility. Eurther-more, automated sample preparation reduces cost by using... 

Certain raw materials, such as free fatty acids, are too polar to analyse directly by GC or LC. Traditionally they are converted into methyl esters to improve their volatility for GC. This sample preparation was time-consuming, and sample was quite often lost, thereby reducing the accuracy of quantitative measurements. Capillary SFC can handle these polar fatty acids without derivatization [38]. Figure 9.10 shows an SFC chromatogram of Cs-C g... 

MLC. Sample preparation/measurement time was also reduced from 45 min to <5 min [13],... 

Recently, SPE cartridges and disks have been widely and successfully used in preconcentration processes [1-3]. They reduce solvent usage, disposal costs, and extraction time for sample preparation and obtain large enrichment factors. 

Thus, it is shown, that use of ultrasonic at the stage of sample preparation or different type soils allows considerably to reduce time of extracts obtaining for determination of soil forms of heavy metals and realization of full decomposing for an estimation of the gross contents. 

SFE of fruits and vegetables and meat products has been reported, but the sample preparation techniques necessary to obtain reproducible results are extremely time consuming. Solid absorbents such as Hydromatrix, Extrelut " anhydrous magnesium sulfate or absorbent polymers are required to control the level of water in the sample for the extraction of the nonpolar pesticides. Without the addition of Hydromatrix, nonpolar pesticides cannot penetrate the water barrier between the sample particles and the supercritical CO2. The sample is normally frozen and the addition of dry-ice may be required to reduce losses due to degradation and/or evaporation. Thorough reviews of the advantages and limitations of SFE in pesticide residues... 

Integrates the sample preparation step (to reduce analysis time and costs)... 

Direct injections using RAM or TFC have simplified sample preparation and increased throughput. Matrix ion suppression was greatly reduced or eliminated in several cases compared with traditional off-line sample cleanup procedures such as PPT, SPE, and LLE. Method development time was minimized with generic methods15 that suit most applications. Detailed applications can be found in a recent review.8... 

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