A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was develop... more A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was developed here, comparing Tween 20 and Tween 40 for the first time as the only mobile phase modifiers with a C18 column. Its application to the separation of nine hydroxycinnamic acid (HCA) derivatives (cinnamic, caffeic, ferulic, sinapic, o-, m-, p-coumaric, 3,4-dihydroxyhydrocinnamic, and chlorogenic acids) was made, due to their importance as antioxidants in a variety of natural beverages such as wine and coffee. The optimal conditions of 45 °C temperature (T), 1% surfactant in the mobile phase, and pH control with 2.5 mM sulfuric acid were determined and used to elucidate the analytical figures of merit. Although the effect of these conditions was insignificant between the two surfactants, the nine-component HCA mixture was separated faster—in about 15 min—and with less peak tailing using Tween 20 than with Tween 40. The linearity of the Van’t Hoff (lnk versus 1/T) plots was evident for Twe...
Dispersive liquid-liquid microextraction (DLLME) is a special type of microextraction in which a ... more Dispersive liquid-liquid microextraction (DLLME) is a special type of microextraction in which a mixture of two solvents (an extracting solvent and a disperser) is injected into the sample. The extraction solvent is then dispersed as fine droplets in the cloudy sample through manual or mechanical agitation. Hence, the sample is centrifuged to break the formed emulsion and the extracting solvent is manually separated. The organic solvents commonly used in DLLME are halogenated hydrocarbons that are highly toxic. These solvents are heavier than water, so they sink to the bottom of the centrifugation tube which makes the separation step difficult. By using solvents of low TPMEDA N,N′-Bis(thiophen-2-ylmethylene)ethane-1,2-diamine
Abstract The use of polychlorotrifluoroethylene (PCTFE) particles packed in 5–10 cm × 0.4 cm ID c... more Abstract The use of polychlorotrifluoroethylene (PCTFE) particles packed in 5–10 cm × 0.4 cm ID columns for the immobilization of enzymes by hydrophobic adsorption is investigated. Enzyme binding capacity of PCTFE is about 0.2 mg/gm of polymer. PCTFE-immobilized lactate dehydrogenase, alcohol dehydrogenase, and urease-glutamate dehydrogenase are demonstrated to be useful for the determinations of pyruvate, ethanol, and urea, respectively. Immobilized enzyme lifetimes are generally about 1–2 months.
The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sul... more The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sulfaguanidine (GUA), sulfamerazine (MER), sulfamethoxazole (SMX), and sulfamethizole (MET)] under different experimental conditions such as photolysis time, ...
Journal of Pharmaceutical and Biomedical Analysis, Oct 1, 2002
The diaminopyrimidine derivatives trimethoprim (TMP), pyrimethamine (PMA) and 2,4-diaminopyrimidi... more The diaminopyrimidine derivatives trimethoprim (TMP), pyrimethamine (PMA) and 2,4-diaminopyrimidine (2,4-DAP) are found to react readily and efficiently in an aqueous solution with p-benzoquinone (p-BQ) to form a colored product with an absorption optimum wavelength of about 500 nm. The optimum reaction time, pH, temperature, solvent, and [p-BQ] are determined by separate trials. These conditions are confirmed by a MultiSimplex optimization method. The molar absorptivities of the TMP, PMA, and 2,4-DAP reaction products at 500 nm are 10 830, 10 650, and 9660 l mol − 1 cm − 1 , respectively. TMP shows a linear range between 5 and 100 mg/l while PMA and 2,4-DAP exhibit linearity between 15 and 75 mg l − 1 and 5 and 30 mg l − 1 , respectively. There is some specificity to this reaction; 2-aminopyrimidine does not react. Under the optimum conditions, sulfamethoxazole (SM) reacts rather poorly with a molar absorptivity of about 110 l mol − cm − 1. Using p-BQ, TMP in a pharmaceutical sample can be determined in the presence of SM using derivative spectrophotometry. The TMP-p-BQ reaction is adaptable for flow injection analysis.
Hrc-journal of High Resolution Chromatography, May 1, 1992
Page 1. Short Communications separations are performed between 60 and 140 "C, the te... more Page 1. Short Communications separations are performed between 60 and 140 "C, the tempera-ture limitations of these connectors do not seem too restrictive. Deactivation of the quartz couplings was essential for obtaining ...
Journal of Chromatography B: Biomedical Sciences and Applications, Nov 1, 1980
A direct assay for creatine kinase (CK) activity was developed based on the separation and quanti... more A direct assay for creatine kinase (CK) activity was developed based on the separation and quantitation of adenosine triphosphate (ATP) by high-performance liquid chromatography. The total incubation time is 13 min and the elution time for ATP is 16 min. Using lyophilized CK as the sample, a sensitivity in the range of 8 U/l (units/liter) was obtained. The method presented also has clinical significance in that CK levels in serum can easily be determined with minimal sample preparation. Using serum samples from a healthy patient and a heart attack victim, activities of 26.6 U/l and 609.0 U/l, respectively, were obtained. Because of the direct measurement of ATP, this method eliminates the coupled reactions encountered in the common spectrophotometric and colorimetric methods of analysis resulting in a simpler and inexpensive assay.
and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coate... more and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coated with Tween 20, Analytica Chimica Acta,
Industrial & Engineering Chemistry Product Research and Development, Jun 1, 1983
Page 1. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 303-307 303 Reactivity of Kel-F Polymers with O... more Page 1. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 303-307 303 Reactivity of Kel-F Polymers with Organolithium and Organomagnesium Compounds Neil D. Danlelson,' Rlchard 1. Taylor, Jeffrey A. Huth, Rlchard W. Slerglej, James 0. Galloway, and Joseph B. Paperman ...
Picolyl Kel-F (PIKF) Is prepared by reacting Kel-F 6061 (100 % poly(chiorotrlfluoroethyiene)) and... more Picolyl Kel-F (PIKF) Is prepared by reacting Kel-F 6061 (100 % poly(chiorotrlfluoroethyiene)) and 4-plcolyillthium In THF under helium. Elemental analysis and I R data show that the primary reaction occurring Is substitution of the chlorine In the polymer for plcoiine. The anlon exchange capaclty was determined to be 22 pequlv/g. The effects of ionlc strength and pH on solute retention are studied to Indicate the presence of Ion exchange processes. Selectlvlty data also Indicate that the retention mechanism is reverse phase In nature. Appilcatlons of picolyi Kel-F for the separation of simple drug mixtures, nltrophenols, and carboxylic acids are possible.
Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to re... more Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to react with Fe 3+ in the presence of an acetic acid-sulfuric acid mixture to form a colored product having a useful absorption band at 592 nm. Troleandomycin forms only a weakly colored product upon reaction. The molar absorptivity is about 29001mol-~ cm-' for erythromycin and the detection limit is 5 lag ml-~. This colorimetric method permits the analysis of fermentation broths containing either erythromycin or tylosin without a separation step.
An ultramicro cylindrical internal reflectance (CIRCLE) cell with an internal volume of 1.75 pl, ... more An ultramicro cylindrical internal reflectance (CIRCLE) cell with an internal volume of 1.75 pl, which is used with an IR-PLAN infrared microscope, is described. The path length and reflectance parameters of the cell have been determined and compared to those of the micro CIRCLE cell. The path length of the cell is 3.43 x 10e4 cm, which is approximately 44% shorter than that of the micro cell. The cell's utility is tested by means of a previously described flow injection analysis system to measure succinylcholine in aqueous solution. The detection limit for the ultramicro CIRCLE cell is approximately 3 ppt, which is an order of magnitude higher than that of the micro CIRCLE cell. o 1~ Academic PRS. I~C.
n-Butylllthlum will react easily with Kel-F (poly(chlorotrlfluoroethylene) or PCTFE) to form n-bu... more n-Butylllthlum will react easily with Kel-F (poly(chlorotrlfluoroethylene) or PCTFE) to form n-butyl-Kel-F and LICI. Kel-F 6300, a copolymer of PCTFE and 3 % vinylidene fluoride, was 85% derlvatlzed causing the surface area to lncrease to 14 m2/g. Although n-butyl-Kel-F 6300 showed promise as a column packing material for llquld chromatograpy (LC), column lifetime due to Insufficient rigidity of the polymer was short. Kel-F 6061 (PCTFE) upon reaction with n-butyllithlum was only derlvatlzed to an extent of 25 % with a surface area Increase from 1.6 to 3.6 m*/g. However, a variety of substituted aromatic compounds could be separated on a 25 cm X 4.6 mm 1.d. column packed with n-butyl-Kel-F 6061 and the column lifetime was excellent. Both n-butyl-Kel-F polymers were markedly better LC column packlngs than underlvatlzed Kel-F for small molecules.
The global crisis resulting from adulterated heparin in late 2007 and early 2008 revived the impo... more The global crisis resulting from adulterated heparin in late 2007 and early 2008 revived the importance of analytical techniques for the purity analysis of heparin products. The utilization of ion chromatography techniques for the separation, detection, and structural determination of heparin and structurally related glycoaminoglycans, including their corresponding oligosaccharides, has become increasingly important. This review summarizes the primary HPLC approaches, particularly strong anion exchange, weak ion exchange, and reversed-phase ion-pair, used for heparin purity analysis as well as structural characterization. Strong anion exchange HPLC has been studied most extensively and currently offers the best separation of crude heparin and heparin-like compounds. Weak anion exchange HPLC has been shown to provide shorter analysis times with lower salt concentrations in the mobile phase but is not as widely developed for the separation of all glycoaminoglycans of interest. Reversed-phase ion-pair HPLC offers fast and effective separations of oligosaccharides derived from glycoaminoglycans that can be coupled to mass spectrometry for structural analysis. However, this method generally does not provide sufficient retention of intact glycoaminoglycans.
A triply charged eluent has been characterlzed for anion-exchange chromatography with lndlrect ph... more A triply charged eluent has been characterlzed for anion-exchange chromatography with lndlrect photometric detectlon. Sodium naphthalenetrlsulfonate has shown particular promise for the separation and detectlon of NO2-, Br-, NO9-, SO:-, I-, and SCN-. The analysis of a mixture contalning these anions can be performed In less than 18 min with detection limits of 0.4-1 ng for ail anions. The determination of the strongly retained sulfur oxides such as dithlonite, tetrathlonate, and other poiythionates can be easily accomplished with this highly charged eluent in a short time with high sensitivity. The chromatographlc performance of thls eluent requires no pH adjustment of the mobile phase. I n addition, chromatograms obtalned with thls eluent were free from any system peaks.
Journal of Liquid Chromatography & Related Technologies, 2007
Alkylammonium formate (AAF) ionic liquids, RNH3 [HCO2 ], R=C2H5, C3H7, or C4H9, are prepared in h... more Alkylammonium formate (AAF) ionic liquids, RNH3 [HCO2 ], R=C2H5, C3H7, or C4H9, are prepared in high yield and purity by slowly reacting an alkylamine and formic acid in an ice bath under N2. UV spectra of undiluted ethylammonium formate (EAF), n‐propylammonium formate (PAF), n‐butylammonium formate (BAF) show no appreciable background absorbance down to about 250 nm, 270 nm, and 295 nm, respectively. Physical
Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have... more Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have been used as mobile phase "solvents" for liquid chromatography (LC), we have shown that methylammonium formate (MAF), in part because of its lower viscosity, can be an effective replacement for methanol (MeOH) in reversed-phase LC. Plots of log retention factor versus the fraction of MeOH and MAF in the mobile phase indicate quite comparable solvent strength slope values of 2.50 and 2.05, respectively. Using a polar endcapped C18 column, furazolidone and nitrofurantoin using 20% MAF-80% water could be separated in 22 min but no baseline separation was possible using MeOH as the modifier, even down to 10%. Suppression of silanol peak broadening effects by MAF is important permitting a baseline separation of pyridoxine, thiamine, and nicotinamide using 5% MAF-95% water at 0.7 mL/min. Using 5% MeOH-95% water, severe peak broadening for thiamine is evident. The compatibility of MAF as a mobile phase modifer for LC with mass spectrometry detection of water soluble vitamins is also shown.
The structural stability of cytochrome c has been studied in alkylammonium formate (AAF) ionic li... more The structural stability of cytochrome c has been studied in alkylammonium formate (AAF) ionic liquids such as methylammonium formate (MAF) and ethylammonium formate (EAF) by fluorescence and circular dichroism (CD) spectroscopy. At room temperature, the native structure of cytochrome c is maintained in relatively high ionic liquid concentrations (50%-70% AAF/ water or AAF/phosphate buffer pH 7.0) in contrast to denaturation of cytochrome c in similar solutions of methanol or acetonitrile, with water or buffer co-solvents. Fluorescence and CD spectra indicate the conformation of cytochrome c is maintained in 20% AAF-80% water from 30-50 °C. No such temperature stability is found in 80% AAF-20% water. About one third of the enzyme activity of cytochrome c in 80% AAF-20% water can be maintained as compared to phosphate buffer and this is greater than the activities measured in corresponding methanol and acetonitrile aqueous solutions. This biophysical study shows that AAFs have potential application as organic solvent replacements at moderate temperature in the mobile phase for the separation of proteins in their native form by reversed phase liquid chromatography.
A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was develop... more A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was developed here, comparing Tween 20 and Tween 40 for the first time as the only mobile phase modifiers with a C18 column. Its application to the separation of nine hydroxycinnamic acid (HCA) derivatives (cinnamic, caffeic, ferulic, sinapic, o-, m-, p-coumaric, 3,4-dihydroxyhydrocinnamic, and chlorogenic acids) was made, due to their importance as antioxidants in a variety of natural beverages such as wine and coffee. The optimal conditions of 45 °C temperature (T), 1% surfactant in the mobile phase, and pH control with 2.5 mM sulfuric acid were determined and used to elucidate the analytical figures of merit. Although the effect of these conditions was insignificant between the two surfactants, the nine-component HCA mixture was separated faster—in about 15 min—and with less peak tailing using Tween 20 than with Tween 40. The linearity of the Van’t Hoff (lnk versus 1/T) plots was evident for Twe...
Dispersive liquid-liquid microextraction (DLLME) is a special type of microextraction in which a ... more Dispersive liquid-liquid microextraction (DLLME) is a special type of microextraction in which a mixture of two solvents (an extracting solvent and a disperser) is injected into the sample. The extraction solvent is then dispersed as fine droplets in the cloudy sample through manual or mechanical agitation. Hence, the sample is centrifuged to break the formed emulsion and the extracting solvent is manually separated. The organic solvents commonly used in DLLME are halogenated hydrocarbons that are highly toxic. These solvents are heavier than water, so they sink to the bottom of the centrifugation tube which makes the separation step difficult. By using solvents of low TPMEDA N,N′-Bis(thiophen-2-ylmethylene)ethane-1,2-diamine
Abstract The use of polychlorotrifluoroethylene (PCTFE) particles packed in 5–10 cm × 0.4 cm ID c... more Abstract The use of polychlorotrifluoroethylene (PCTFE) particles packed in 5–10 cm × 0.4 cm ID columns for the immobilization of enzymes by hydrophobic adsorption is investigated. Enzyme binding capacity of PCTFE is about 0.2 mg/gm of polymer. PCTFE-immobilized lactate dehydrogenase, alcohol dehydrogenase, and urease-glutamate dehydrogenase are demonstrated to be useful for the determinations of pyruvate, ethanol, and urea, respectively. Immobilized enzyme lifetimes are generally about 1–2 months.
The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sul... more The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sulfaguanidine (GUA), sulfamerazine (MER), sulfamethoxazole (SMX), and sulfamethizole (MET)] under different experimental conditions such as photolysis time, ...
Journal of Pharmaceutical and Biomedical Analysis, Oct 1, 2002
The diaminopyrimidine derivatives trimethoprim (TMP), pyrimethamine (PMA) and 2,4-diaminopyrimidi... more The diaminopyrimidine derivatives trimethoprim (TMP), pyrimethamine (PMA) and 2,4-diaminopyrimidine (2,4-DAP) are found to react readily and efficiently in an aqueous solution with p-benzoquinone (p-BQ) to form a colored product with an absorption optimum wavelength of about 500 nm. The optimum reaction time, pH, temperature, solvent, and [p-BQ] are determined by separate trials. These conditions are confirmed by a MultiSimplex optimization method. The molar absorptivities of the TMP, PMA, and 2,4-DAP reaction products at 500 nm are 10 830, 10 650, and 9660 l mol − 1 cm − 1 , respectively. TMP shows a linear range between 5 and 100 mg/l while PMA and 2,4-DAP exhibit linearity between 15 and 75 mg l − 1 and 5 and 30 mg l − 1 , respectively. There is some specificity to this reaction; 2-aminopyrimidine does not react. Under the optimum conditions, sulfamethoxazole (SM) reacts rather poorly with a molar absorptivity of about 110 l mol − cm − 1. Using p-BQ, TMP in a pharmaceutical sample can be determined in the presence of SM using derivative spectrophotometry. The TMP-p-BQ reaction is adaptable for flow injection analysis.
Hrc-journal of High Resolution Chromatography, May 1, 1992
Page 1. Short Communications separations are performed between 60 and 140 "C, the te... more Page 1. Short Communications separations are performed between 60 and 140 "C, the tempera-ture limitations of these connectors do not seem too restrictive. Deactivation of the quartz couplings was essential for obtaining ...
Journal of Chromatography B: Biomedical Sciences and Applications, Nov 1, 1980
A direct assay for creatine kinase (CK) activity was developed based on the separation and quanti... more A direct assay for creatine kinase (CK) activity was developed based on the separation and quantitation of adenosine triphosphate (ATP) by high-performance liquid chromatography. The total incubation time is 13 min and the elution time for ATP is 16 min. Using lyophilized CK as the sample, a sensitivity in the range of 8 U/l (units/liter) was obtained. The method presented also has clinical significance in that CK levels in serum can easily be determined with minimal sample preparation. Using serum samples from a healthy patient and a heart attack victim, activities of 26.6 U/l and 609.0 U/l, respectively, were obtained. Because of the direct measurement of ATP, this method eliminates the coupled reactions encountered in the common spectrophotometric and colorimetric methods of analysis resulting in a simpler and inexpensive assay.
and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coate... more and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coated with Tween 20, Analytica Chimica Acta,
Industrial & Engineering Chemistry Product Research and Development, Jun 1, 1983
Page 1. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 303-307 303 Reactivity of Kel-F Polymers with O... more Page 1. Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 303-307 303 Reactivity of Kel-F Polymers with Organolithium and Organomagnesium Compounds Neil D. Danlelson,' Rlchard 1. Taylor, Jeffrey A. Huth, Rlchard W. Slerglej, James 0. Galloway, and Joseph B. Paperman ...
Picolyl Kel-F (PIKF) Is prepared by reacting Kel-F 6061 (100 % poly(chiorotrlfluoroethyiene)) and... more Picolyl Kel-F (PIKF) Is prepared by reacting Kel-F 6061 (100 % poly(chiorotrlfluoroethyiene)) and 4-plcolyillthium In THF under helium. Elemental analysis and I R data show that the primary reaction occurring Is substitution of the chlorine In the polymer for plcoiine. The anlon exchange capaclty was determined to be 22 pequlv/g. The effects of ionlc strength and pH on solute retention are studied to Indicate the presence of Ion exchange processes. Selectlvlty data also Indicate that the retention mechanism is reverse phase In nature. Appilcatlons of picolyi Kel-F for the separation of simple drug mixtures, nltrophenols, and carboxylic acids are possible.
Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to re... more Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to react with Fe 3+ in the presence of an acetic acid-sulfuric acid mixture to form a colored product having a useful absorption band at 592 nm. Troleandomycin forms only a weakly colored product upon reaction. The molar absorptivity is about 29001mol-~ cm-' for erythromycin and the detection limit is 5 lag ml-~. This colorimetric method permits the analysis of fermentation broths containing either erythromycin or tylosin without a separation step.
An ultramicro cylindrical internal reflectance (CIRCLE) cell with an internal volume of 1.75 pl, ... more An ultramicro cylindrical internal reflectance (CIRCLE) cell with an internal volume of 1.75 pl, which is used with an IR-PLAN infrared microscope, is described. The path length and reflectance parameters of the cell have been determined and compared to those of the micro CIRCLE cell. The path length of the cell is 3.43 x 10e4 cm, which is approximately 44% shorter than that of the micro cell. The cell's utility is tested by means of a previously described flow injection analysis system to measure succinylcholine in aqueous solution. The detection limit for the ultramicro CIRCLE cell is approximately 3 ppt, which is an order of magnitude higher than that of the micro CIRCLE cell. o 1~ Academic PRS. I~C.
n-Butylllthlum will react easily with Kel-F (poly(chlorotrlfluoroethylene) or PCTFE) to form n-bu... more n-Butylllthlum will react easily with Kel-F (poly(chlorotrlfluoroethylene) or PCTFE) to form n-butyl-Kel-F and LICI. Kel-F 6300, a copolymer of PCTFE and 3 % vinylidene fluoride, was 85% derlvatlzed causing the surface area to lncrease to 14 m2/g. Although n-butyl-Kel-F 6300 showed promise as a column packing material for llquld chromatograpy (LC), column lifetime due to Insufficient rigidity of the polymer was short. Kel-F 6061 (PCTFE) upon reaction with n-butyllithlum was only derlvatlzed to an extent of 25 % with a surface area Increase from 1.6 to 3.6 m*/g. However, a variety of substituted aromatic compounds could be separated on a 25 cm X 4.6 mm 1.d. column packed with n-butyl-Kel-F 6061 and the column lifetime was excellent. Both n-butyl-Kel-F polymers were markedly better LC column packlngs than underlvatlzed Kel-F for small molecules.
The global crisis resulting from adulterated heparin in late 2007 and early 2008 revived the impo... more The global crisis resulting from adulterated heparin in late 2007 and early 2008 revived the importance of analytical techniques for the purity analysis of heparin products. The utilization of ion chromatography techniques for the separation, detection, and structural determination of heparin and structurally related glycoaminoglycans, including their corresponding oligosaccharides, has become increasingly important. This review summarizes the primary HPLC approaches, particularly strong anion exchange, weak ion exchange, and reversed-phase ion-pair, used for heparin purity analysis as well as structural characterization. Strong anion exchange HPLC has been studied most extensively and currently offers the best separation of crude heparin and heparin-like compounds. Weak anion exchange HPLC has been shown to provide shorter analysis times with lower salt concentrations in the mobile phase but is not as widely developed for the separation of all glycoaminoglycans of interest. Reversed-phase ion-pair HPLC offers fast and effective separations of oligosaccharides derived from glycoaminoglycans that can be coupled to mass spectrometry for structural analysis. However, this method generally does not provide sufficient retention of intact glycoaminoglycans.
A triply charged eluent has been characterlzed for anion-exchange chromatography with lndlrect ph... more A triply charged eluent has been characterlzed for anion-exchange chromatography with lndlrect photometric detectlon. Sodium naphthalenetrlsulfonate has shown particular promise for the separation and detectlon of NO2-, Br-, NO9-, SO:-, I-, and SCN-. The analysis of a mixture contalning these anions can be performed In less than 18 min with detection limits of 0.4-1 ng for ail anions. The determination of the strongly retained sulfur oxides such as dithlonite, tetrathlonate, and other poiythionates can be easily accomplished with this highly charged eluent in a short time with high sensitivity. The chromatographlc performance of thls eluent requires no pH adjustment of the mobile phase. I n addition, chromatograms obtalned with thls eluent were free from any system peaks.
Journal of Liquid Chromatography & Related Technologies, 2007
Alkylammonium formate (AAF) ionic liquids, RNH3 [HCO2 ], R=C2H5, C3H7, or C4H9, are prepared in h... more Alkylammonium formate (AAF) ionic liquids, RNH3 [HCO2 ], R=C2H5, C3H7, or C4H9, are prepared in high yield and purity by slowly reacting an alkylamine and formic acid in an ice bath under N2. UV spectra of undiluted ethylammonium formate (EAF), n‐propylammonium formate (PAF), n‐butylammonium formate (BAF) show no appreciable background absorbance down to about 250 nm, 270 nm, and 295 nm, respectively. Physical
Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have... more Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have been used as mobile phase "solvents" for liquid chromatography (LC), we have shown that methylammonium formate (MAF), in part because of its lower viscosity, can be an effective replacement for methanol (MeOH) in reversed-phase LC. Plots of log retention factor versus the fraction of MeOH and MAF in the mobile phase indicate quite comparable solvent strength slope values of 2.50 and 2.05, respectively. Using a polar endcapped C18 column, furazolidone and nitrofurantoin using 20% MAF-80% water could be separated in 22 min but no baseline separation was possible using MeOH as the modifier, even down to 10%. Suppression of silanol peak broadening effects by MAF is important permitting a baseline separation of pyridoxine, thiamine, and nicotinamide using 5% MAF-95% water at 0.7 mL/min. Using 5% MeOH-95% water, severe peak broadening for thiamine is evident. The compatibility of MAF as a mobile phase modifer for LC with mass spectrometry detection of water soluble vitamins is also shown.
The structural stability of cytochrome c has been studied in alkylammonium formate (AAF) ionic li... more The structural stability of cytochrome c has been studied in alkylammonium formate (AAF) ionic liquids such as methylammonium formate (MAF) and ethylammonium formate (EAF) by fluorescence and circular dichroism (CD) spectroscopy. At room temperature, the native structure of cytochrome c is maintained in relatively high ionic liquid concentrations (50%-70% AAF/ water or AAF/phosphate buffer pH 7.0) in contrast to denaturation of cytochrome c in similar solutions of methanol or acetonitrile, with water or buffer co-solvents. Fluorescence and CD spectra indicate the conformation of cytochrome c is maintained in 20% AAF-80% water from 30-50 °C. No such temperature stability is found in 80% AAF-20% water. About one third of the enzyme activity of cytochrome c in 80% AAF-20% water can be maintained as compared to phosphate buffer and this is greater than the activities measured in corresponding methanol and acetonitrile aqueous solutions. This biophysical study shows that AAFs have potential application as organic solvent replacements at moderate temperature in the mobile phase for the separation of proteins in their native form by reversed phase liquid chromatography.
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