Sample handling liquid samples

The diversity of equipment with which manufacturers have flooded the market is exemplified by Zymark Corporation. In the last few years, this firm has launched six different types of workstations for handling liquid samples, namely ... 

Poor reproducibility can result if the sample is not homogenous. If possible, stir or shake the container prior to sampling. Use similar techniques to those described for handling liquid samples. 

Porro, T. J. Pattacini, S. C. Sample Handling for Mid-Infrared Spectroscopy, Part 1 Solid and Liquid Sampling, Spectroscopy 1993, 8(7), 40-47. 

Figure 3.4. Simple diagram for the sample handling and hght collection system used for a typical nanosecond TR experiment for a flowing liquid stream of sample. See text for more details.

Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction with a sorbent interface). All of these techniques use a nonporous membrane, involving partitioning of the analytes [499]. SLM is a sample handling technique which can be used for selective extraction of a particular class of compounds from complex (aqueous) matrices [500]. Membrane extraction with a sorbent interface (MESI) is suitable for VOC analysis (e.g. in a MESI- xGC-TCD configuration) [501,502]. 

Instrumental cell isolation and sample handling in liquid culture. 

BioEPR samples are generally (frozen) aqueous solutions since water is the only solvent compatible with terrestrial life. The high-frequency dielectric constant of ice is circa 30 times less than that of water. As a consequence liquid-phase EPR is experimentally rather different from frozen-solution EPR. We start with a discussion of sample handling for low-temperature experiments. 

The DEP ends with a filament wire onto which a drop of sample is deposited. After evaporation to dryness, the probe is introduced into the source of the mass spectrometer and is rapidly heated to a temperature that can reach 1000°C. This probe is ideal for the study of high molecular weight or polymeric components. It is mostly dedicated to the analysis of samples in the liquid state. Although a small solid fragment of matter may be placed on the filament, this critical operation may lead to the loss of the sample, especially if it is particularly small. To avoid such a difficult handling, the sample may be ground and homogenised in a mini-mortar and then made into suspension with a few drops of appropriate solvent (Scalarone et al., 2003). 

Lucky you. You have a solid instead of a liquid. This presents one problem. What are you going to dissolve the solid in Once it s a solution, you handle it just like a liquid sample. Unfortunately, if the solvent has protons and you know there ll be much more solvent than sample, you ll get a major proton signal from your solvent. Not a good thing, especially if the signals from your solvent and sample overlap. 

The popularity of this extraction method ebbs and flows as the years go by. SFE is typically used to extract nonpolar to moderately polar analytes from solid samples, especially in the environmental, food safety, and polymer sciences. The sample is placed in a special vessel and a supercritical gas such as CO2 is passed through the sample. The extracted analyte is then collected in solvent or on a sorbent. The advantages of this technique include better diffusivity and low viscosity of supercritical fluids, which allow more selective extractions. One recent application of SFE is the extraction of pesticide residues from honey [27]. In this research, liquid-liquid extraction with hexane/acetone was termed the conventional method. Honey was lyophilized and then mixed with acetone and acetonitrile in the SFE cell. Parameters such as temperature, pressure, and extraction time were optimized. The researchers found that SFE resulted in better precision (less than 6% RSD), less solvent consumption, less sample handling, and a faster extraction than the liquid-liquid method [27]. 

The micropipette tip containing solid phases is a relatively new sample preparation technique that permits handling of microliter to submicroliter amounts of liquid samples, using the techniques of SPE, dialysis, and enzyme digestion. Various phases (reversed-phase, affinity, size-exclusion, etc.) are packed, embedded, or coated on the walls of pipette, permitting liquid samples to be transferred without undue pressure drop or plugging (Fig. 2.5). 

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