Aminopropyl columns

Elution of non-ionic surfactants of varying chain lengths from an aminopropyl column with a hexane/ chloroform/methanol gradient and ELSD detection. 

NSAR, NPRO, NHPRO, and several IV-ni-troso dipeptides in cured meats 1. Extraction with ethyl acetate from aqueous suspension containing H3P04 and ammonium sulfamate 2. Cleanup on Bond-Elut Aminopropyl column None 250 X 4.5 mm Micro-bondapak CN n-Hexane ethanol acetic acid (87 12 1) TEA 55-80 49, 50... 

Chromatographic System (See Chromatography, Appendix HA.) Use a high-performance liquid chromatograph equipped with a 4.6- x 250-mm aminopropyl column (5 jxm Spherisorb NH2, or equivalent) and a refractive index detector and operated at a flow rate of about 1.3 mL/min. 

L. D. Olsen and R. J. Hurtubise, Mobile phase effects on aromatic hydroxyl compounds with an aminopropyl column and interpretation by the Snyder model, /. Chromatogr. 479 (1989), 5-16. 

However, Hamilton and Comai described a procedure which allows good recovery and separation of the neutral lipids from FFA on a silica SPE matrix [5]. Separation of the different phospholipids can be also achieved on an aminopropyl column. These polar compounds are tightly bound to the matrix, so they are retained while eluting neutral lipids and FFAs. Then, the different phospholipids can be washed from the column by changing the pH and the ionic strength of the solvent. Stepwise elution of phospholipids was obtained (PC, PE, PS, and PI) by increasing, progressively, the polarity of the solvent and its pH [7]. 

If the sample contains very polar constituents, it is advisaUe to remove them through sample preparation techniques like solid-phase extraction. Samples dissolved in water should not be injected directly onto a normal-phase column. When an aminopropyl column is used, additional precautions are necessary, which were outlined above when we discussed this stationary ffiase. 

Solid-phase extraction (SPE) offers an alternative way for enrichment of chlorinated fatty acids. Akesson-Nilsson presented an aminopropyl-based SPE technique for enrichment of chlorinated FAMEs in a cell-culture medium and for previously silver nitrate and urea treated eel lipids. In this application, a 500-mg aminopropyl column was connected to a vacuum manifold and conditioned with 2 ml of hexane. After transesterified lipid samples in 0.2 ml of hexane were loaded, the column was first eluted with 6 ml of hexane and then with 4 ml of a solvent mixmre made of hexane-diethyl ether-dichloromethane (89 1 10). In this way, the majority of non-chlorinated FAMEs were removed in the first elution and chlorinated FAMEs enriched in the later elution. 

The retention behavior of four tocopherols (a, / , y, and S) and 5,7-dimethyltocol was studied in detail using 0.5-2% levels of ethanol, IPA, n-propyl alcohol, 1-butanol and t-butyl alcohol in hexane (A = 298 nm, ex 345 nm, em) on an aminopropyl column [338]. Significant selectivity differoices were noted, with the butyl alcohols giving the best results. 

Tan et al. [615] successfully resolved the group VI (Cr(VI), W(VI), and Mo(VI)) metal-decacarbonyl (diphenylphosphinyl)alkane (ethyl to hexyl) bridge complexes on a mixed mode cyanopropyl/aminopropyl column (A = 254nm). A 97/3 hexane/chloroform mobile phase was used. Plots of Id versus alkyl bridge length were shown with the kf values varying fi-om 4 to 12. Individual k values were tabulated for all compound combinations. 

The Ni(II) and VO(II) complexes of etioporphyrins and deoxophylloerythroetio-porphyrins from fuel and crude oils were studied on an aminopropyl column (A = 400 run, ex 620 nm, em) using a 25-min 45/55/0—20/30/50 toluene/ hexane/dichloromethane gradient [617]. A chromatogram of four neat metal-porphyrin standards and four crude oil extracts are shown. Due to the very large number of possible homologs of the porphyrins, a manifold of peaks was obtained. These distributions were distinctly different for each crude oil sample. Tentative identification, as related to the retention of the neat standards, is given. 

Metabolites of 7,9- and 7,10-dimethylbenz[c]acridine (e.g., 7-[hydroxymethyl]-9-mediylbenz[c]acridine, 7,9-ditnethylbenz[c]acridine-5,6-oxide) were separated in 80 min using a silica column (A = 270 nm) and 95/5 petroleum ether/ethanol or 90/10 petroleum ether/ethyl acetate, respectively. At least 23 metabolites were positively identified [621], The retention behavior of benz[c]acridines and 11 methyl, dimethyl, and trimethyl analogs were studied on silica and aminopropyl columns [622]. Individual solute retention times were tabulated. For the silica column a 95/5 hexane/ethanol mobile phase was used and retention times ranged fiom 2.5 to 33 min. Incomplete resolution of three isomers resulted. Hexane and the aminopropyl column produced retention times of 8-26 min with at least partial resolution obtained for all isomers. 

Heavy petroleum was characterized with respect to its aromatic (e.g., benzoie, I-methylnaphthylene), and nonaromatic (e.g., tetradecane) content These results were comparable to the lengthier ASTM D2549-91 meOiod. Two 300 x 4.1mm 35°C aminopropyl columns (Rl detector) and a 95/5 hexane/IPA mobile phase generated complete elution in <15 min [627]. 

Ethoxylated alkylphenols are used widely as detergents, emulsifiers, and surface-active agents. Oligomers of up to 10 ethylene oxide units were separated on a silica column (A = 270nm) using a 15-min 90/5/5 70/15/15 heptane/chloroform/ methanol gradient [642]. A gradient to 10% (50/50 chloroform/methanol)/90% (70/10//0 heptane/chloroform/methanol) reduced the analysis time with minimal loss of resolution. This study also presented the effects of mobile phase composition (80/10/10 to 90/5/5 heptane/chloroform/methanol) on an aminopropyl column for... 

Ethoxylated alcohols with the alkyl chain length of 12 and the number of ethoxylate chains varying from 2 to 20 were extracted from influent and effluent wastewaters and were well resolved as their phenylisocyanate derivatives on an aminopropyl column (2 = 240nm). A 30-min 100/065/35 (35/15 hexane/ ethylene dichloride)/( 185/65 acetonitrile/IPA) with 800 pL acetone/L added gradient was used. Detection limits down to lOOppb were reported [225]. 

Although this paper is ostensibly to differentiate packing materials, it also provides excellent information regarding the separation of tocopherols (a, P, y, and S) and tocotrienols (a, p, y, and d). Excellent separation of all compounds was achieved in 20 min on a silica colunm (A = 294 nm, ex 326 nm, em) using a 96/4 hexane/1,2-dioxane mobile phase [666]. A diol column was also effective when a 94/4 hexane/methyl /-butyl ether mobile phase was used. Aminopropyl columns were less effective overall. 

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