Sample Handling Devices

The most common method of introducing liquid samples into a gas chromatographic inlet is by means of a microsyringe. Typically, this consists of a calibrated glass barrel 

Syringe handling techniques for injection of liquid samples 

Filled needle Sample is taken up into the syringe needle without entering the barrel. Injection is made by placing the syringe needle into the injection zone. No mechanical movement of the plunger is involved and the sample leaves the needle by evaporation. 

Cold needle Sample is drawn into the syringe barrel so that an empty syringe needle is inserted into the injection zone. Immediately the sample is injected by depressing the plunger. Sample remaining in the syringe needle leaves by evaporation. 

Hot needle Injection follows the general procedure described for the cold needle method except that prior to depressing the plunger the needle is allowed to heat up in the injector for 3-5 seconds. 

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Products/technologies The high-throughput sample-handling devices for drug discovery applications provide a means of transferring vast numbers of samples in parallel from the macro world of microtiter plates to the micro world of chips. 

Figure 3.12. Schematic diagram of the sample handling device for solid-phase microextraction. (From ref. [139] Wiley-VCH).

Mass spectrometry is unique among many modern analytical methods in that sample molecules are physically and irretrievably introduced into the instrument. The sample handling devices must be transport devices that accommodate a wide dynamic range of sample quantities, efficiently transporting aU sample molecules from the outside world into the ionization source of the mass spectrometer. Given the diversity of sample types, there is a concurrent diversity of sample introduction systems. 

Sample Handling System. Venous or capillary blood, urine, and cerebrospinal fluid are specimens routinely used in medical diagnostic testing. Of these biological fluids, the use of venous blood is by far the most prevalent. Collection devices such as syringes and partial vacuum test tubes, eg, Vacutainer, are used to draw ten milliliters or less of venous blood. At collection time, the test tubes are carefully labeled for later identification. 

Modem HPLC is adequately provided with complete data handling devices. Thousands of samples routinely analysed in Quality Assurance Laboratories in Pharmaceutical Industries/Bulk Drug Industries etc. are duly processed and the data stored in the computerised data-handling devices. Each stored data may be retrieved from the memory of the computerised device with the flick of a finger, as and when needed, in the form of print-out. 

Figure 63 Schematic of a nanoscale capillary ESI interface. This specialized LC/MS interface, operating at flow rates from 20-500 nL/min and using 50 to 100 pm ID columns, typically provides low femtomole sensitivity. Fully automated sample handling and prearation procedures (i.e., desalting and preconcentration) combined with specialized devices for high separation and variable nL gradient flow rates provide unique capabilities for high-throughput analysis of proteins. (Courtesy of New Objective, Inc., Woburn, Ma., USA.)...

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