196:
the silica hydride. Thus positively charged analytes are attracted to the negatively charged surface and other polar analytes are likely to be retained through displacement of hydroxide or other charged species on the surface. This property distinguishes it from a pure HILIC (hydrophilic interaction chromatography) columns where separation by polar differences is obtained through partitioning into a water-rich layer on the surface, or a pure RP stationary phase on which separation by nonpolar differences in solutes is obtained with very limited secondary mechanisms operating.
187:
of water in the eluent varying. Thus a continuum of solvents can be used from 100% aqueous to pure organic. ANP retention has been demonstrated for a variety of polar compounds on the hydride based stationary phases. Recent investigations have demonstrated that silica hydride materials have a very thin water layer (about 0.5 monolayer) in comparison to HILIC phases that can have from 6–8 monolayers. In addition the substantial negative charge on the surface of hydride phases is the result of hydroxide ion adsorption from the solvent rather than silanols.
186:
Typically the mobile phases are rich with organic solvents, with amount of the nonpolar solvent in the mobile phase at least 60% or greater to reach minimal required retention. A true ANP stationary phase will be able to function in both the reversed phase and normal phase modes with only the amount
154:
mechanism, and is used for the analysis of solutes readily soluble in organic solvents. Separation is achieved based on the polarity differences among functional groups such as amines, acids, metal complexes, etc. as well as their steric properties, while in reversed-phase chromatography, a partition
195:
An interesting feature of these phases is that both polar and nonpolar compounds can be retained over some range of mobile phase composition (organic/aqueous). The retention mechanism of polar compounds has recently been shown to be the result of the formation of a hydroxide layer on the surface of
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and long-chain alkyl groups. Mobile phases for ANPC are based on organic solvents as bulk solvents (such as methanol or acetonitrile) with a small amount of water as a modifier of polarity; thus, the mobile phase is both "aqueous" (water is present) and "normal phase type" (less polar than the
110:
hydrocarbons are the preferred stationary phase; octadecyl (C18) is the most common stationary phase, but octyl (C8) and butyl (C4) are also used in some applications. The designations for the reversed phase materials refer to the length of the hydrocarbon chain.
199:
Another important feature of the hydride-based phases is that for many analyses it is usually not necessary to use a high pH mobile phase to analyze polar compounds such as bases. The aqueous component of the mobile phase usually contains from 0.1 to 0.5%
183:
stationary phase). Thus, polar solutes (such as acids and amines) are more strongly retained, with the ability to affect the retention, which decreases as the amount of water in the mobile phase increases.
98:. In reversed phase the opposite is true; the stationary phase is nonpolar and the mobile phase is polar. Typical stationary phases for normal-phase chromatography are silica or organic moieties with
316:
Pesek, J. J.; Matyska, M. T.; Prabhakaran, S. J. (2005). "Synthesis and characterization of chemically bonded stationary phases on hydride surfaces by hydrosilation of alkynes and dienes".
114:
In normal-phase chromatography, the least polar compounds elute first and the most polar compounds elute last. The mobile phase consists of a nonpolar solvent such as
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first with the more nonpolar compounds eluting later. The mobile phase is generally a mixture of water and miscible polarity-modifying organic solvent, such as
40:
150:. Retention increases as the fraction of the polar solvent (water) in the mobile phase is higher. Normal phase chromatography retains molecules via an
349:
Pesek, J. J.; Matyska, M. T.; Gangakhedkar, S.; Siddiq, R. (2006). "Synthesis and HPLC evaluation of carboxylic acid phases on a hydride surface".
134:. Retention decreases as the amount of polar solvent in the mobile phase increases. In reversed phase chromatography, the most polar compounds
171:
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C. Kulsing, Y. Nolvachai, P.J. Marriott, R.I. Boysen, M.T. Matyska, J.J. Pesek, M.T.W. Hearn, J. Phys. Chem B, 119 (2015) 3063-3069.
269:"Synthesis and characterization of chemically bonded stationary phases on hydride surfaces by hydrosilation of alkynes and dienes"
178:(-Si-OH). In a "hydride surface" the terminal groups are primarily -Si-H. The hydride surface can also be functionalized with
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75:
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Pesek, Joseph J.; Matyska, Maria T.; Boysen, Reinhard I.; Yang, Yuanzhong; Hearn, Milton T. W. (2013-01-01).
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or acetic acid, which is compatible with detector techniques that include mass spectral analysis.
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surface" which is distinguishable from the other silica support materials, used either in
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174:. Most silica materials used for chromatography have a surface composed primarily of
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226:"Aqueous normal-phase chromatography using silica-hydride-based stationary phases"
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In the aqueous normal-phase chromatography the support is based on a silica with "
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Hemström, P.; Irgum, K. (2006). "Hydrophilic interaction chromatography".
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mechanism typically occurs for the separation by non-polar differences.
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J. Soukup, P. Janas, P. Jandera, J. Chromatogr. A, 1286 (2013) 111-118
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Pesek, Joseph J.; Matyska, Maria T.; Prabhakaran, Seema J. (2005).
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122:mixed with a slightly more polar solvent such as
41:Hydrophilic interaction liquid chromatography
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106:functional groups. For reversed phase,
172:hydrophilic interaction chromatography
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86:In normal-phase chromatography, the
66:compositions and polarities between
231:TrAC Trends in Analytical Chemistry
52:Aqueous normal-phase chromatography
17:Aqueous normal phase chromatography
14:
1:
384:Journal of Separation Science
351:Journal of Separation Science
318:Journal of Separation Science
273:Journal of Separation Science
68:reversed-phase chromatography
62:technique that involves the
72:normal-phase chromatography
44:Ion exchange chromatography
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243:10.1016/j.trac.2012.09.016
94:and the mobile phase is
396:10.1002/jssc.200600199
363:10.1002/jssc.200500433
330:10.1002/jssc.200500249
285:10.1002/jssc.200500249
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279:(18): 2437–2443.
76:stationary phases
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390:(12): 1784–821.
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180:carboxylic acids
88:stationary phase
74:(NP), while the
32:Other techniques
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60:chromatographic
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435:Chromatography
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128:ethyl acetate
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164:normal phase
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144:acetonitrile
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64:mobile phase
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124:isopropanol
78:are polar.
208:References
152:adsorptive
132:chloroform
293:1615-9306
251:0165-9936
237:: 64–73.
82:Principle
70:(RP) and
429:Category
404:16970185
371:16830499
338:16405172
301:16405172
191:Features
176:silanols
140:methanol
96:nonpolar
160:hydride
120:heptane
58:) is a
37:Related
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369:
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299:
291:
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202:formic
116:hexane
170:, or
136:elute
108:alkyl
104:amino
100:cyano
92:polar
400:PMID
367:PMID
334:PMID
297:PMID
289:ISSN
247:ISSN
102:and
392:doi
359:doi
326:doi
281:doi
239:doi
148:THF
146:or
130:or
118:or
90:is
56:ANP
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259:^
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54:(
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