Direct fluid injection

Smith and Udseth [154] first described SFE-MS in 1983. Direct fluid injection (DFT) mass spectrometry (DFT-MS, DFI-MS/MS) utilises supercritical fluids for solvation and transfer of materials to a mass-spectrometer chemical ionisation (Cl) source. Extraction with scC02 is compatible with a variety of Cl reagents, which allow a sensitive and selective means for ionising the solute classes of interest. If the interfering effects of the sample matrix cannot be overcome by selective ionisation, techniques based on tandem mass spectrometry can be used [7]. In these cases, a cheaper and more attractive alternative is often to perform some form of chromatography between extraction and detection. In SFE-MS, on-line fractionation using pressure can be used to control SCF solubility to a limited extent. The main features of on-line SFE-MS are summarised in Table 7.20. It appears that the direct introduction into a mass spectrometer of analytes dissolved in supercritical fluids without on-line chromatography has not actively been pursued. 

Direct-fluid-injection (DFI)a Electron impact (El) Double-focusing sector (DFS)... 

Supercritical Fluid Extraction (SCFE)—Direct Fluid Injection Mass Spectrometry (DFI-MS)... 

Since SFC is in its infancy, the same is true of the hyphenated techniques that involve it. In general, it would be expected that SCF/MS should use interfaces like GC/MS since the supercritical fluid mobile phases become gases when reduced to atmospheric pressure, but the conditions are more severe because of the higher (critical) pressure. OT columns, because of their low pressure drops, are favored. The two interfaces that have been used are a direct fluid injection (DFI) and a molecular beam apparatus. DFI has been used with packed columns26 and with OT columns,27 using both chemical ionization and electron impact ionization. For a more complete discussion of both interfaces, see the chapter on SFC in the ACS Symposium Series edited by Ahuja28 the recent review on LC/MS25 also contains considerable information about SFC/MS. 

Various other types of interfaces have been used to couple SFE to high-resolution detectors. Thus, direct fluid injection (DFl) has proved suitable for sample insertion into mass spectrometric detectors [123]. Capillary Pt-lr tubing of 0.3 mm i.d. furnished with electrical and fluid circulation heating was used to connect the supercritical module to a mass detector. 

Figure 4i Schematic illustration of the Direct Fluid Injection (DFI) process. An ideal expansion through a pinhole orifice (top) and expansion through a capillary restriction (bottom).

Smith R D, Fjeldsted J C, Lee M L 1982 Direct fluid injection interface for capillary supercritical fluid chromatography/mass spectrometry. J Chromatogr 247 231-243... 

DFT Direct-flow injection/direct-fluid introduction... 

R.D. Smith and H.R. Udseth, Mass spectrometry with direct supercritical fluid injection, Anal. Chem., 55 (1983) 2266-2272. 

Hcxanc can be determined in biological fluids and tissues and breath using a variety of analytical methods. Representative methods are summarized in Table 6-1. Most methods utilize gas chromatographic (GC) techniques for determination of -hexane. The three methods used for preparation of biological fluids and tissues for analysis are solvent extraction, direct aqueous injection, and headspace extraction. Breath samples are usually collected on adsorbent traps or in sampling bags or canisters prior to analysis by GC. 

The 250 mg/mL strength is concentrated, and is not for direct IV injection dilute prior to infusion. Do not mix with sodium bicarbonate. Do not mix with other drugs prior to dilution in a suitable IV fluid. 

Severe shock IV 0.5-5 mg direct IV injection followed by 15-100 mg IV infusion in 250-500 ml fluid for conf rol of blood pressure. 

This paper presents two aspects of the research project, namely the geophysical and the minera-logical evolution of the geothermal system as a direct consequence of fluid injection. It is a geological, mineralogical, petrophysical, and geochemical study of water-rock interactions at temperatures of up to, and higher than, 200 °C... 

The Model II plants were of a greatly improved design, incorporating two basic major developments—the downflow or bottom withdrawal Fluid bed and the direct liquid injection of oil feed into the reaction zone. The downflow development permitted withdrawal of catalyst for circulation from the bottom of the bed. 

Thormann W, Minger A, Molteni S, Caslavska J, Gebauer P (1992) Determination of substituted purine in body fluids by micellar electrokinetic capillary chromatography with direct sample injection. J Chromatogr 593 275-288. 

A caveat for aU direct sample injection assays is an understanding of the analyte chemical stability in the biological fluid during the analysis period. Nonetheless, an increasingly growing body of literature is suggestive that direct injection of post-dose biological fluids for quantification purposes has become a routine and efficient procedure. 

Because they have very low viscosities (compared to oil), steam, CO2, and other gases suffer from a major problem these injected fluids never make contact with much of the reservoir and the oil it contains, but instead channel more or less directly from injection to production well, leaving the uncontacted oil unproduced. 

An effective method to increase the efficiency of a fluid drive is to plug the thief zone(s), direct fluids to areas of higher oil saturation and thus improve the ratio of oil produced to fluid injected. Emulsions have been shown to be effective permeability modification agents, but little work has been reported on their use. 

Lardeau, S., E. Lamballais, and J.-P. Bonnet. 2002. Direct numerical simulation of a jet controlled by fluid injection. J. Turbulence 3.002. 

The only variable that can be measured directly is the surface treating pressure (STP). The hydrostatic head (HH) and friction pressures (FP) must be calculated from two measured parameters, fluid injection rate and proppant concentration, and the perforation friction pressure drop (PFP) can be determined from the physical properties of the fluid. 

---