“…Carbon dioxide has been the dominant mobile phase of choice for SFC, mostly because of its relatively mild critical parameters, low cost, chemical inertness and detector compatibility (2). However, CO, has limited usefulness as a mobile phase because of its nonpolarity (3).…”
Section: Introductionmentioning
confidence: 99%
“…Comparison of cliromatogram wing (A) pure CO, and (B) 0.3 %formic acid in CO, for the following solutes: ( I ) pentanoic acid,(2) phenethyl alcohol, (3) 2'-acetonaphthone and (4) oleic acid. Chromatographic conditions: initial density of 0.075 g mL" for 8 min, 0.1 g mL-' min-' ramp to 0.8 g d-'; 75°C oven temperature; Comparison of chromatogrums using (A) pure CO, and (B) 0.3 % fom'c acid in CO, f o r the following solutes:(I) pentanoic acid, (2) phenethyl alcohol, (3) m-bromobenzoic acid, (4)p-nitrophenylacetic acid and (5) o-benzoylbenzoic ucid.…”
Abstract. A small percentage (0.3 % w/w) of formic acid was added to supercritical carbon dioxide to increase mobile phase polarity and improve separation of polar solutes on three different commercially available capillary columns. Formic acid reduced retention and altered selectivity for several polar compounds. Thermodynamic studies revealed that the enthalpy of solvation was as much as 27 kcal mol-' more negative when formic acid was added due to increased solute-solvent interactions. Entropy measurements show that formic acid modified mobile phase is more ordered than a pure carbon dioxide mobile phase, apparently as a result of modifier clustering around polar solutes. Van't Hoff plots for some very polar solutes showed a region of retrograde behavior at low temperatures and pressures, indicating an increase in modifier clustering. Comparisons between pure and modified mobile phases were also made by examining practical separations obtained with each, revealing differences in retention, selectivity and peak shape.
“…Carbon dioxide has been the dominant mobile phase of choice for SFC, mostly because of its relatively mild critical parameters, low cost, chemical inertness and detector compatibility (2). However, CO, has limited usefulness as a mobile phase because of its nonpolarity (3).…”
Section: Introductionmentioning
confidence: 99%
“…Comparison of cliromatogram wing (A) pure CO, and (B) 0.3 %formic acid in CO, for the following solutes: ( I ) pentanoic acid,(2) phenethyl alcohol, (3) 2'-acetonaphthone and (4) oleic acid. Chromatographic conditions: initial density of 0.075 g mL" for 8 min, 0.1 g mL-' min-' ramp to 0.8 g d-'; 75°C oven temperature; Comparison of chromatogrums using (A) pure CO, and (B) 0.3 % fom'c acid in CO, f o r the following solutes:(I) pentanoic acid, (2) phenethyl alcohol, (3) m-bromobenzoic acid, (4)p-nitrophenylacetic acid and (5) o-benzoylbenzoic ucid.…”
Abstract. A small percentage (0.3 % w/w) of formic acid was added to supercritical carbon dioxide to increase mobile phase polarity and improve separation of polar solutes on three different commercially available capillary columns. Formic acid reduced retention and altered selectivity for several polar compounds. Thermodynamic studies revealed that the enthalpy of solvation was as much as 27 kcal mol-' more negative when formic acid was added due to increased solute-solvent interactions. Entropy measurements show that formic acid modified mobile phase is more ordered than a pure carbon dioxide mobile phase, apparently as a result of modifier clustering around polar solutes. Van't Hoff plots for some very polar solutes showed a region of retrograde behavior at low temperatures and pressures, indicating an increase in modifier clustering. Comparisons between pure and modified mobile phases were also made by examining practical separations obtained with each, revealing differences in retention, selectivity and peak shape.
“…A higher background is obtained with nitrous oxide than with carbon dioxide (Schaefer, 1972;Baas toe and Lundanes, 1991). The use of SF 6 requires a gold-plated collector to avoid corrosion by HF (Schwartz and Brownlee, 1986;Fields and Grolimund, 1989). …”
“…9 The literature is somewhat contradictory regarding this effect, but the formation of insoluble carbamates seems to be the main reason for this behavior. [10][11][12] Sulfur hexafluoride (SF 6 ), in contrast, only elutes monofunctional amines, 13 and laughing gas (N 2 O), despite its higher polarity, was also only described for the elution of monofunctional amines by capillary SFC. 14,15 As no further mobile phases for the separation of amines by capillary SFC are reported in the literature, this paper first describes the development of a capillary SFC method for the elution of highly polar multifunctional amines, which is then applied for the characterization of phenolic-based Mannich bases by SFC with UV detection and SFC-UV coupled to MS.…”
mentioning
confidence: 99%
“…Carbon dioxide (CO 2 )as the most common mobile phase in capillary SFCelutes only amines with relatively low basicity . The literature is somewhat contradictory regarding this effect, but the formation of insoluble carbamates seems to be the main reason for this behavior. − Sulfur hexafluoride (SF 6 ), in contrast, only elutes monofunctional amines, and laughing gas (N 2 O), despite its higher polarity, was also only described for the elution of monofunctional amines by capillary SFC. , 1 Scheme for the preparation of the mobile phase (for details, see text). 2 SFC/MS interface. The eluent is passed through the UV detector into the restrictor.…”
The analysis of phenolic Mannich bases [Formula: see text] which are used as hardeners and accelerators for epoxy resins [Formula: see text] by capillary supercritical fluid chromatography (SFC) with dimethyl ether modified ethane as the mobile phase is described. The elution properties of several different mobile phases with respect to amines are shown. SFC with UV detection is coupled via a custom-built interface to a mass spectrometer with atmospheric pressure chemical ionization. Two technically important Mannich bases prepared by different production processes are characterized and compared with respect to their byproducts. The role of dimethyl ether during the ionization process and the fragmentation of phenolic Mannich bases is discussed.
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