Injection of sample

Mouse Bioassay. The mouse is the traditional animal of choice for detecting biological activity due to STX and TTX. Mice receive an intraperitoneal injection of sample and are observed for symptoms of intoxication, i.e., dypsnea, convulsions, and death. This method is effective for detecting biological activity of STX and TTX in numerous samples. For the standard STX assay, one mouse unit is defined as that quantity of STX injected i.p. in 1 ml solution that will... 

Table 4.15 fists the many possibilities for solid sampling for GC analysis. In general, sample preparation should be considered in close conjunction with injection. Robotic sample processors have been introduced for automatic preparation, solvent extraction and injection of samples for GC and GC-MS analyses. Usually, facilities are included for solvent, reagent, and standard additions and for derivatisation of samples. 

Gas chromatographic analysis starts with introduction of the sample on the column, with or without sample preparation steps. The choice of inlet system will be dictated primarily by the characteristics of the sample after any preparation steps outside the inlet. Clearly, sample preparation has a profound influence on the choice of injection technique. For example, analysts may skip the solvent evaporation step after extraction by eliminating solvent in the inlet with splitless transfer into the column. Sample introduction techniques are essentially of two types conventional and programmed temperature sample introduction. Vogt et al. [89] first described the latter in 1979. Injection of samples, which... 

Fig. 3.161. (A) Zone electrophoresis patterns of FITC-labelled transferrin samples by fluorescence detection. The unbound dye (providing a main peak and several minor ones) was not removed from the samples. Experimental conditions background electrolyte, 100 mM borate buffer, pH 8.3 voltage, 20 kV capillary 59 cm (effective length 41 cm) X 75 pm i.d. injection of samples 100 mbar x s 20°C detection with fluorescence detector (240 - 400 nm, broadband excitation filter and a 495 nm cut-off emmision filter). The reaction was left to continue for 20 h, and the reaction mixtures contained 13 pm (1 mg/ml) Tf and (a) 0.01 mM FITC, (b) 0.1 mM FITC, and 1 mM FITC. (B) Zone electrophoresis patterns of an FITC-labelled transferrin sample by simultaneous fluorescence (upper trace, left axis) and UV detection (lower trace, right axis). The unbound dye shows several peaks with both detections. Experimental conditions background electrolyte, 100 mM borate buffer, pH 8.3 voltage, 20 kV capillary 59 cm (effective length fluorescence 41 cm, UV 50.5 cm) X 75 pm i.d. injection of samples 100 mbar X s 20°C detection with fluorescence detector (240 - 400 nm, broadband excitation filter and a 495 nm cut off emmision filter). The reaction was left to continue for 20 h, and the reaction mixtures contained 6.5 pm (0.5 mg/ml) Tf and 0.1 mM FITC. Reprinted with permission from T. Konecsni et al. [199].

Conditions columns, Asahipak GS320 (vinyl alcohol copolymer gel), 50 cm x 7.6 mm i.d. eluent, 0.1 M sodium phosphate containing 0.3 M sodium chloride pH 7.0 flow rate, 1 ml min-1 detection, UV 250 nm direct injection of sample. Peaks l, protein, 2, orotidine 3, creatinine, and 4, uric acid. 

For semivolatile constituents of petrolenm, the gas chromatograph is generally eqnipped with either a packed or a capillary colnmn. Either neat or dilnted organic liqnids can be analyzed via direct injection, and componnds are separated dnring movement down the column. The flame ionization detector nses a hydrogen-fneled flame to ionize compounds that reach the detector. For PAHs a method is available (EPA 8100) in which injection of sample extracts directly onto the colnmn is the preferred method for sample introdnction for this packed-colnmn method. 

Many appHcations of chromatography have been automated to some degree attention has focused primarily on the automatic injection of samples or on data processing and reporting. However, the separation power of the column can be usefully exploited as a pretreatment process. 

Filtration injection of sample directly dilution and injection elution from reverse-phase HPLC column with methanol/water... 

Figure 13.12 Performance of the chip with the sharp inlet interface. Typical electro-pherograms of repetitive injections of sample mixtures containing (a) 20 ppm TNB, (b) TNT, and (c) DNT. (Reproduced by permission of the Royal Society of Chemistry [44].)...

Fig.6.1.5a-c Connections and positions of the three high-pressure valves used for columnswitching HPLC of oxidized pterins. Position a 0-2 min, injection of sample with precolumn and analytical column in series. Position b 2-12 min, gradient elution of fast-moving compounds from the precolumn into the detector. Position c 12-32 min, elution of slower-moving compounds from the analytical column into the detector, with simultaneous cleaning of precolumn... 

Despite their distinct advantages, on-line SPE and column-switching proce-dures do not always represent ideal separation techniques. In many cases, only a small number of samples can be analyzed before contamination of the precolumn by proteins occurs. Alternative techniques that prevent the adsorption of macromolecules onto column packings and allow direct injection of sample extracts are those based on use of specific LC columns. Shielded hydrophobic phase (27), small pore reversed-phase (28), and internal surface reversed-phase (29, 30) columns can be used to elute proteins in the excluded volumes, allowing small... 

Use the same instrumental conditions to analyze the samples from part A. The samples will contain a mixture of fatty acid methyl esters, so several recorder peaks will be obtained. Do not inject a second sample until you are sure all the fatty acids have been eluted from the first sample. Determine the retention time for each standard FAME and for each FAME in the unknown samples. Retention time is the time interval between injection of sample and maximum response of the recorder. 

A typical composite chromatogram of three runs on the ozokerite from Russia is shown in Figure 1. Time in minutes from injection of sample is given at the bottom of the figure, and the temperature of the oven in which the columns are heated is given at the top. A partial chro-... 

For direct injections of sample extracts Equation 6 or 10, Appendix 22... 

Iron-containing compounds in biological and clinical samples have been studied by separating them on chromatographic columns that were coupled to inductively coupled plasma mass spectrometers. Four iron-containing proteins, namely ferritin, haemoglobin, myoglobin and cytochrome-c were separated on a gel permeation column (Takatera and Watanabe, 1991). The absolute detection limits were 0.01-1 mg for the four proteins when 10 ml injections of samples were analysed. In other research, excess iron accumulations in human and animal... 

A 96-well SPE system for the simultaneous extraction of drugs and metabolites in biological matrices developed by Wu and coworkers (Simpson et al, 1998) is shown in Figure 6.39. In this approach, smaller elution volumes (75-200 FL) are used to improve SPE performance. This volume reduction allowed for the direct injection of samples without any evaporation and reconstitution. The collection plate that contains the elution fraction is loaded to an autosampler that is compatible with 96-well plates, thereby, eliminating the transfer to injection vials. This quantitative process improvement led to an improved analytical performance, considerable savings in time, and reduced cost. 

The focusing bi-laminating micro mixer was realized in the framework of the development of a flow injection analysis (FIA) system [114,115]. The mixer is placed downstream of the two-fold injection of sample and reagent streams into the carrier. Thereafter, the mixed stream enters a reaction chamber and finally passes a detector. An easy integration is required, as the mixing element is part of an integrated system which has the minimization of size as one issue. 

The sample injection system allows the injection of sample volumes from 1 to 500 pL. To prevent depressurization of the system, samples are injected through special six-way valves to which a sample loop has been attached. The sample is injected directly into the loop by means of a microliter syringe (filling position) while the eluent flows to the column. The eluent flow is then directed via the sample loop to the column when the valve is switched to the injection position. 

The advantage to MHE is that sample matrix effects (which are mainly an issue only with solid samples) are eliminated since the entire amount of analyte is examined. This examination is done by performing consecutive analyses on the same sample vial. With the removal of each sample aliquot from the vial, the partition coefficient K will remain constant however, the total amount of analyte remaining in the sample will decline as each analysis is performed and more of the analyte is driven up into the vial headspace for removal and analysis. Chromatograms of each injection of sample show... 

Capillary electrophoresis can be a powerful tool for separation and quantification of ionic substances found in soil samples. Separation speed and direct injection of samples to the capillary without labor-intensive sample preparation are the major advantages of the method for a range of samples (Cengiz and Sakul 2001). 

A device can be implemented to the instrument in order to rejuvenate or recycle the capillary column after multiple injections of samples. The recycling or cleanup procedure of the column would ensure good performance, as well as prolonging the life of the capillary column. 

Hage, D.S., Thomas, D.H., Chowdhuri, A.R., and Clarke, W. 1999. Development of a theoretical model for chromatographic-based competitive binding immunoassays with simultaneous injection of sample and label. Anal Chem 71 (15) 2965—2975. 

Determination of trace elements or anions. (i) Direct injection of sample into carrier stream of... 

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