Small volume sampling and

Sample collection and preparation are crucial issues for any bioanalytical application in order to address the complexity of samples originating from biological tissues and fluids. It is necessary to cope with the lack in concentration sensitivity typical for capillary separation techniques, to avoid interference from matrix components as well as to ensure analyte stability. In peptide analysis, a strong focus exists on handling small-volume samples and on selective concentration of the analyte in order to overcome limitations with respect to loadability. In addition, loss of analyte frequently occurs due to degradation by proteases and due to adsorption to surfaces, which accordingly needs to be minimized. 

Most ion-selective microelectrodes are very delicate tools, and working with them requires training and patience. Compared to conventional size electrodes, their only advantage is that they can operate in small volume samples and thus can provide very fine spatial resolution. 

Small Volume Sampling and GC/MS Analysis for PAH Concentrations in Water above Contaminated Sediments... 

Sampling artifacts. The use of in situ pumps to collect water samples for " Th analysis permits simultaneous collection (and separation) of different particle fractions as well as dissolved Th. As pumping systems have been modified to permit determination of POC on the pump filters, it became possible to compare POC determined from the pump samples with conventional POC determinations made on small volume samples (0.5 - 2 L) taken from hydrocasts. The JGOFS data from multiple studies show large discrepancies between these two sample collection methods, with pump POC values 3 to 100 times lower than bottle POC values. Possible artifacts with each approach have been identified. For example Moran et al. (1999) have suggested that DOC is adsorbed onto... 

The analysis of human plasma for acetaminophen, the active ingredient in some pain relievers, involves a unique extraction procedure. Small-volume samples (approximately 200 fiL) of heparinized plasma, which is plasma that is treated with heparin, a natural anticoagulant found in biological tissue, are first placed in centrifuge tubes and treated with 1 N HC1 to adjust the pH. Ethyl acetate is then added to extract the acetaminophen from the samples. The tubes are vortexed, and after allowed to separate, the ethyl acetate layer containing the analyte is decanted. The resulting solutions are evaporated to dryness and then reconstituted with an 18% methanol solution, which is the final sample preparation step before HPLC analysis. The procedure is a challenge because the initial sample size is so small. 

Ann McNichol is a Research Specialist at the National Ocean Sciences Accelerator Mass Spectrometry Facility at the Woods Hole Oceanographic Institution, which produces high-precision 14C measurements from small-volume samples. Dr. McNichol s research interests include the study and use of carbon, nitrogen, and oxygen isotope techniques to quantify bio-geochemical processes, the study of the fate of organic matter (both natu-... 

Using large- and small-volume samples, mixed with synthetically produced samples, excellent values were developed. Samples were analyzed for alanine, glucose, glutamine, and leucine in samples removed from an Sf-9 insect cell culture bioreactor. It was seen that purely synthetic standards led to poor predictions of actual runs. The best results were achieved from mixed — actual and synthetic — samples. 

An alternative type of cell, which consists of two parts of optically flat windows, is suitable for CD and MCD measurements of small-volume samples. One of the window affords a trough for filling in the sample. Otherwise, a well-calibrated spacer is inserted to a conventional cell for adjusting its path length. The light path length is calibrated by using the absorbance of an appropriately diluted solution of benzene or toluene. 

Sampling. Composite or continuous sampling furnishes water samples that are more representative than grab or batch samples. If possible, such samples should be used and processed immediately to avoid storage problems. However, the collection of small-volume samples may be more easily accomplished by batch sampling. 

The achievements discussed in this chapter also underline that such systems are more than just separation systems. They should rather be regarded as generally applicable fluid handling systems for small volume samples. In particular in the case of electric field controlled systems, the fluid handling requires only control of electric potentials and can be easily automated. Electrophoresis experiments on the level of single DNA molecules have already been demonstrated... 

When taking gas samples, the goal is to obtain representative samples with minimum time lag, using short, small-volume sampling lines. Whenever possible, it is preferred to draw dry and clean samples to minimize the need for filters, dryers, knockout traps, or steam tracing. 

Since the small volume vessels and minipaddles were noncompendial, additional studies were performed to confirm the appropriateness of the method parameters selected and the discriminatory ability of the method. The effect of paddle speed, paddle height and sampling zone were evaluated in an experimental design of experiment study. In addition, the discriminatory ability of the method was evaluated using purposefully perturbed or aberrant tablets, to model poorly dissolving tablets. 

PMS APSS Automated particle sampling systems are used to size and count suspended particles in liquids. These systems are ideal for applications where precise small volume sampling is needed. 

The miniaturisation of liquid chromatographic (LC) separation techniques has become increasingly important over the last ten years. The introduction of new synthetic chemistry techniques, such as combinatorial chemistry, has produced libraries of small-volume samples that require fast throughput, but also efficient and sensitive analysis. The use of miniaturised liquid chromatographic techniques offers the possibility of analysing these submicrolitre samples with high efficiency and short analysis times. 

CEC offers the ability to introduce a sample directly onto the column. This removes the need to have a high-pressure valve which can introduce unwanted dead volumes and place great demands on instrumental design. It also allows vei7 small-volume samples (5-10 pi) to be analysed multiple times, as. samples as small as. single nanolitres can be taken if required. This is very useful in the analysis of compounds where sample is very limited, such as those cleaved from single beads produced in solid-phase bead libraries [201, where only 20 pi of total sample may be available for screening and characterisation. 

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