Rapid Sampling Procedures

With the increasing demand to analyze more and more samples, manufacturers of autosamplers and sample introduction accessories are designing automated sampling systems to maximize sample throughput. This is being achieved in a variety of different ways by optimizing the sample delivery process to reduce the pre- and postmeasurement time. Some typical optimization procedures include the following  

There is no doubt that by optimizing these steps, a significant improvement can be made to the overall analysis time, especially in high-workload routine environmental laboratories, where high sample throughput is an absolute requirement.  

Effects of High Power Laser Radiation, Academic Press, NY, Chapters 3-4, 1972. 

Gunther and B. Hattendorf, Mineralogical Association of Canada—Short Course Series, 29, 83-91, 2001. 

SEM photo courtesy of Dr. Honglin Yuan, Northwest University, Xi an, China. 

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Identification of sources of analytical bias in method development and method validation is another very important application of reference materials in geochemical laboratories. USGS applied simplex optimization in establishing the best measurement conditions when the ICP-AES method was introduced as a substitute for AAS in the rapid rock procedure for major oxide determinations (Leary et al. 1982). The optimized measurement parameters were then validated by analyzing a number of USGS rock reference samples for which reference values had been established first by classical analyses. Similar optimization of an ICP-AES procedure for a number of trace elements was validated by the analysis of U S G S manganese nodule P-i (Montaser et al. 1984). 

Lopez-Avila et al. [59] have described a microwave assisted extraction procedure for the separation of polyaromatic hydrocarbons from sediments. Tan [71] described a rapid sample preparation technique for analysing polyaromatic hydrocarbons in sediments. Polyaromatic hydrocarbons are removed from the sediment by ultrasonic extraction and isolated by solvent partition and silica gel column chromatography. The sulphur removal step is combined into the ultrasonic extraction procedure. Identification of polyaromatic hydrocarbon is carried out by gas chromatography alone and in conjunction with mass spectrometry. Quantitative determination is achieved by addition of known amounts of standard compounds using flame ionization and multiple ion detectors. 

Wang F, Ji Z, Wang D. 1991. A rapid pretreatment procedure for determining trace organochlorine compounds in biological samples by capillary gas chromatography. Microchemical Journal 44 67-71. 

Application of any analytical method is always easier when the matrix does not contain species that interfere with determination of the analyte. However, when an interference is expected, it is necessary to isolate the component to be measured from the matrix. Therefore, the quality of the result often depends on sample preparation. This preliminary step can have a more important influence on the end result than the measurement itself or the precision of the instrument used. Sample preparation, which follows the so-called sampling procedure, can often be tedious, delicate and time-consuming. Nonetheless, it has become an active area of study that benefits from the recent progress in chemistry and robotics. Currently used instruments that allow fast and selective measurements on very small amounts of sample have encouraged the development of new, rapid sample preparation methods. 

Splitless or direct sampling procedures have been extensively studied. These methods involved trapping of the high-boiling materials in a small cooled zone followed by rapid desorption and introduction to the column. The column itself has been used at a low temperature to allow the solvent to pass while the high-boiling material was trapped on the front end. Once the solvent has passed the column is quickly heated to the desired temperature. 

Modified spectrophotometric procedures are described for the quantitative determination of cobalt and molybdenum as the 2-nitrosonaphth-l-olate and toluene-3,4-dithiolate complexes in carbon tetrachloride. The extraction, chelation and phase separation steps permitted rapid sample handling, controlled interferences more effectively and provided accurate assays. The molar absorptivities for cobalt and molybdenum were 5.1 x 104 and 2.5 xl04mol/lcm, respectively, and the detection limits for both elements were 4 ng/g. 

A sensitive and rapid chromatographic procedure using a selective analytical detection method (electrospray ionization-mass spectrometry in SIM mode) in combination with a simple and efficient sample preparation step was presented for the determination of zaleplon in human plasma. The separation of the analyte, IS, and possible endogenous compounds are accomplished on a Phenomenex Lima 5-/rm C8(2) column (250 mm x 4.6 mm i.d.) with methanol-water (75 25, v/v) as the mobile phase. To optimize the mass detection of zaleplon, several parameters such as ionization mode, fragmentor voltage, m/z ratios of ions monitored, type of organic modifier, and eluent additive in the mobile phase are discussed. Each analysis takes less than 6 min. The calibration curve of zaleplon in the range of 0.1-60.0 ng/ml in plasma is linear with a correlation coefficient of >0.9992, and the detection limit (S/N = 3) is 0.1 ng/ml. The within- and between-day variations (RSD) in the zaleplon plasma analysis are less than 2.4% (n = 15) and 4.7% (n = 15), respectively. The application of this method is demonstrated for the analysis of zeleplon plasma samples [14]. 

Microwave-assisted digestion procedures are used for total metal analysis in aqueous samples (EPA Method 3015) and for solid or oily samples (EPA Method 3051). These procedures allow for a rapid sample digestion with nitric acid under high pressure and temperature conditions the addition of hydrochloric acid is optional. Samples... 

The MAS does not represent a rapid throughput procedure, but because there is no sample extraction or other manipulation prior to analysis, it represents an unbiased method in which changes in tissues can be studied, and as appropriate, compared to alterations observed in biofluids. In this manner, MAS is synergistic with and complimentary to analysis of biofluids by metabonomic applications. Figure 2 shows the typical NMR-MAS spectra from the liver of a control and galactosamine-treated rat. This method readily detects glucose and glycogen, choline and related metabolites and a variety of lipids, and fatty acids. An example of the utility of NMR-MAS data in concert with biofluid analyses is described later in this review. 

It is the aim of this book to provide a concise and comprehensive treatment of this rapidly evolving field, focusing on the preparative aspect of this chemistry. In fact, the use of organocatalytic transformations in a multistep synthesis remains scare. This book wishes to promote the application of these reactions, giving solid synthetic evidence. Additionally, a collection of sample procedures of typical... 

A mobile ICP-MS has been used for on-site measurements of polluted soils [331]. A rapid digestion procedure was developed in order to reduce sample analysis time for the rapid identification of heavy metal anomalies near a mine dump where no vegetation was growing. 

According to the recommended operating procedure for the analysis of CWC-related chemicals by GC (24) using SE-54 and OV-1701 columns (25 m x 0.32 or 0.25 mm ID (internal diameter), 0.25. im film thickness), the following conditions are recommended Injector temperature 250 °C, detector temperature 280 °C, temperature program initial temperature 40 °C for 1 min, heating rate 10 °C min-1 to 280 °C for 10 min. However, the GC conditions depend on the injection techniques used, the columns, the sample types, and the analytical demands if GC is used for rapid sample screening or if maximum resolution is needed, the selected GC conditions are different. 

LC/MS is an important addition to the techniques used routinely to analyze unknown samples. It is not a substitute for other techniques but is complementary, for example, to GC/MS, GC/FTIR, and NMR. In OPCW proficiency tests, a number of laboratories use single-stage LC/MS as a rapid screening procedure for water samples and aqueous extracts of matrices such as soil, and GC/FPD or... 

Derivatization and Measurement by Different GC-ICP-MS Techniques A simple and rapid sample pretreatment procedure is based on acid leaching (5 min) of the biological material, followed by simultaneous in situ derivatization and extraction (40 min) in the presence of NaBH4 and nonane, buffered at pH 7.0, in an ultrasonic bath. The separation is done with GC, while two independent on-line detecting techniques (MIP-AES and ICP-MS) are used. This approach affords LoDs better by a factor of 2 than those offered by ICP-MS [64]. 

The enzyme-linked Immunosorbent assay (ELISA) is a rapid Immunochemical procedure which can be used for trace analysis. We have applied the procedure to paraquat and other compounds difficult to analyze by the more classical methods. The Immunoassay for paraquat shows the practicality of the method for fortified and actual residue samples, and Is being compared with a gas chromatography procedure. Our work with the ELISA Illustrates that the Immunochemical technology can be used to solve problems encountered In pesticide residue analysis. 

Kauert, G. F., Drug analysis in hair samples applications and experiences with a new rapid analytical procedure, Z. Rechtsmed., 40, 229, 1993. 

A rapid, automated procedure for single-step and simultaneous extraction of cocaine and 11 related compounds was developed by Lewis et al. [95]. Fluid and tissue specimens were extracted using an automated SPE system (Zymark Rapid-Trace) with a Bond Elute-Certify I cartridge. Samples were derivatized with pentafluoro-propionic anhydride/2,2,3,3,3-pentafluoro-l-propanol prior to GC-MS analysis. The method allowed differentiation between smoking crack and intranasal/intravenous cocaine use and was able to elucidate whether ethanol and cocaine were used simultaneously. Another way to determine cocaine in biological matrices is to measure its metabolites and/or degradation products. MEG is produced when... 

Although some efforts have been made (25-26), until now there have been no statistically sufficient, rapid and cost effective sensory quality control (QC) procedures against cork taint for either wineries or cork suppliers. At UC Davis, we have developed a Cork Sensory QC Manual (27) which evaluates the major valid sampling procedures, and exemplifies their use based on a case study at a premium winery in California. In addition, the manual provides instructions for a taste panel evaluation which is essential for wineries in order test their winemakers and cellarmasters as well as the tasting room staffs sensitivities to detect the off-odor. Once individual... 

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