Sample Handling Liquids

The main vessels used for measuring out liquids in environmental analyses can be sub-divided into those used for quantitative work and those used for qualitative work. For the former, we frequently use volumetric flasks, burettes, pipettes and syringes, and for the latter, beakers, conical flasks, measuring cylinders, test tubes and Pasteur pipettes. 

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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Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction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 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]. 

There are different modes of handling liquid, solid and gaseous samples in a GC which will be discussed briefly here ... 

Neilen MWF, Frei RW, Brinkman UAT (1989) In Frei RW, Zeich K (eds) Selective sample handling and detection in high-performance liquid chromatography. Elsevier, Amsterdam, 39 A, p 5... 

R.W. Frei and K. Zech (eds.), Selective Sample Handling and Detection in High-Performance Liquid Chromatography , Elsevier, Amsterdam, 1988. 

Many analyses of organic compounds in liquid samples require selective cleanup and concentration. Direct on-line coupling of sample preparation to the analytical instrumentation minimizes sample handling and thereby the risk for contamination or loss of analyte. Also, on-line coupling makes... 

Flow injection analysis is based on the injection of a liquid sample into a continuously flowing liquid carrier stream, where it is usually made to react to give reaction products that may be detected. FIA offers the possibility in an on-line manifold of sample handling including separation, preconcentration, masking and color reaction, and even microwave dissolution, all of which can be readily automated. The most common advantages of FIA include reduced manpower cost of laboratory operations, increased sample throughput, improved precision of results, reduced sample volumes, and the elimination of many interferences. Fully automated flow injection analysers are based on spectrophotometric detection but are readily adapted as sample preparation units for atomic spectrometric techniques. Flow injection as a sample introduction technique has been discussed previously, whereas here its full potential is briefly surveyed. In addition to a few books on FIA [168,169], several critical reviews of FIA methods for FAAS, GF AAS, and ICP-AES methods have been published [170,171]. 

One of the most important factors in the selection of the sample handling technique is to attempt to analyze the sample, as it exists, without any form of chemical or physical modification. For gases and certain liquids, simple transmission cells, often with a flow-through configuration meet these requirements. 

T.J. Porro, S.C. Pattacini, Sample handling for mid-infrared spectroscopy. Part I solid and liquid sampling. Spectroscopy, 8(7), 40 7 (1993). 

Figure 12.2 SGX-CAT data acquisition station. The CCD detector and cryogenic sample handling robot appear in the foreground. The pump to deliver the liquid nitrogen that removes ice from the sample is located at the rear right.

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