Welchrom™ C18E (endcapped C18) is very hydrophobic and the most popular SPE sorbent in Welchrom™ SPE products because of its extreme retentive nature for non-polar compounds. C18 is generally regarded as having the broadest spectrum of retention among bonded silica sorbents, since it
retains most organic analytes from aqueous matrices. When analyzing small to intermediate molecules, Welchrom ™ C18E can be used for desalting aqueous matrices prior to ion exchange, as salts pass through the sorbent unretained.
Because of its strong binding ability, it has less selectivity for non-polar organic compounds, so it is often used for separation of compounds with big difference in structure and polarity.

• Similar polarity to C8
• Additional polar secondary π-π interactions enhanced retention of aromatic compounds
• Different selectivity compared with the C18 and C8 phases when both aromatic and non-aromatic compounds are being extracted

Welchrom™ Phenyl is commonly used to extract nonpolar compounds. Its polarity is similar to C8, but because of unique aromatic π-π polar interaction, conjugated compounds have strong retention. WelchromTM Phenyl has the best selectivity for a mixture of aromatic compounds and non-aromatic compounds.

• Unbonded acid washed high purity silica, ideal for normalphase SPE and other modified flash techniques
• Considered the most polar normal-phase sorbent available
• Highly polar sorbent to retain polar compounds from nonpolar matrices
• Separating compounds with very similar structure

WelchromTM Silica is generally regarded as the most polar SPE sorbent available. Its retention is mainly due to hydrogen bonds. WelchromTM Silica is particularly effective at separating compounds with a very similar structure. It also exhibits a character of weak acids; at the mid pH conditions, silica surface silanols can be ionized.

Welchrom™ CN is a cyano bonded polar phase, and can be used in either normal phase or reversed phase mode for polar and non-polar compounds. In the normal phase mode, it is the least to retain polar adsorbent; in reversed phase mode, it is also the least to retain non-polar adsorbent. It can be used as a non-polar sorbent for extraction of both polar and non-polar molecules from aqueous samples, and for extraction of polar molecules from relatively non-polar solvents. It is ideal for applications in which extremely non-polar compounds would be irreversibly retained on high carbon load sorbents such as C8 and C18.

• Normal phase or anion exchange sorbent
• Weaker anion exchange than SAX
• Amenable to separating structural isomers
• Allows the rapid release of very strong anions such as sulfonic acids that may be retained irreversibly on SAX (a quarternary amine sorbent that is always positively charged)

Welchrom™ NH2 is anaminopropyl bonded sorbent for polar compounds. This dual purpose sorbent can act either as a polar phase or weak anion exchanger. When using nonpolar solvent such as n-hexane as eluting solvent, it can be used for compounds containing-OH,-NH or-SH group by hydrogen bonding. Because of its pKa value of 9.8, in an aqueous environment with pH 7.8 or less, it can function as a weak anion exchanger. Similar to Diol and Silica sorbents, Welchrom™ NH2 is excellent for the separation of structural isomers.

WelchomTM PSA is an ethylene diamine-N-propyl bonded sorbent, and is similar to WelchromTM NH2. In reversed phase condition, its polarity is between C18 and silica. It has excellent selectivity for a broad range of polar and mediumpolar compounds. It is also can be used as a weak anion exchange cartridge. WelchomTM PSA has two amino groups (pKa values of 10.1 and 10.9), providing a higher ion exchange capacity. WelchomTM PSA can effectively remove fatty acids in the pesticide residues in food (including oleic acid, palmitic acid, linoleic acid, etc.), organic acids, some polar pigments, sugars, and other matrices. It can also be used as a metal ion chelating agent by two amino groups.

• Polymerically bonded, 2,3-Dihydroxypropoxypropyl (7% C)
• Provides polar and non-polar modes
• Strong hydrogen bonding with analytes
• Resembles WelchromTM Silica in its capabilities

Welchrom™ Diol is a silica-based polar SPE adsorbent bonded with two hydroxyl groups for polar compounds. Depending on the cartridge preparation and sample matrix, this polar bonded sorbent can exhibit both polar and weak nonpolar interactions, It is more frequently used to extract polar molecules from relatively non-polar solvents using hydrogen bonding interactions. With appropriate cartridge conditioning, it can be used as a non-polar sorbent to extract relatively nonpolar molecules from aqueous samples. It could differentiate among isomers and other structurally similar compounds. It is a better choice than WelchromTM Silica when used as an absorbent to extract polar compounds in a polar solvent.

WelchromTM SCX is a strong cation exchanger with a very low pKa. It is used to extract positively charged basic compounds. The presence of the benzene ring in the functional group increases the potential for non-polar interactions. This nonpolar characteristic becomes particularly important when conducting ion-exchange from aqueous systems.

WelchromTM SAX is a silica-based strong anion exchange SPE adsorbent, usually used for extraction of negatively charged substances from water or aqueous solution, especially for the extraction of weak acids such as carboxylic acids, which may not retain effectively on weak anion exchange sorbents.

• A moderate polarity sorbent and weak cation exchanger(pKa 4.8)
• Cation exchange with no need for extreme basic conditions
• Wider selectivity range provides more eluent options
• Polar or non-polar depending on matrix or solvent
• Typically used when dealing with very strong cationic(high pKa) compounds that may be irreversibly retained on strong cation exchangers