Acetonitrile, as mobile phase

Fio. 37. Van t Hoff plots for various compounds. Eluites (1) cinnamyl aldehyde, (2) es-tragole, (3) cinnamyl alcohol, (4) cinnamyl acetate. (5) methyleugenol, and (6) s role. The data were obtained on pyrocarbon, 400 x 2.17 mm i.d., with acetonitrile as mobile phase. Reprinted with permission from Colin ei al. (142). 

Ostermeyer (87) described the rapid and sensitive determination of acesulfame, saccharin, aspartame, SA, and BA in fishery products. Aspartame is determined directly in the aqueous extract of samples. For the other additives, cleanup of the extract is performed by anion-exchange chromatography. Ostermeyer used a Nucleosil 100-5 C lg (Macherey-Nagel) (250 X 4 mm, 5 /xm ) column and 0.02 mol/L KH2P04 acetonitrile as mobile phase and 219 nm detection using a diode array detector. Recoveries of spiked samples at concentrations of 50-400 mg sweetener/kg and 50-4000 mg preservative/kg were in the range 84-102% for all analyzed substances (87). The HPLC conditions for the determination of OAs are summarized in Table 5. 

Gottschlich et al. [26] described the separation of tetramethyl rhodamine isothiocyanate (TRITC)-labeled tryptic peptides of (3-casein. The field strength was 220 V/cm in the NCEC channel with lOmM sodium borate with 30% (v/v) acetonitrile as mobile phase. Throckmorton et al. [27] described the separation of papain inhibitor, proctolin, opioid peptide (a-casein fragment 90-95), Ile-angiotensin III and angiotensin III on a porous polymer monolith... 

Table 4.14 Chromatographic parameters corresponding to case study 2, obtained using acetonitrile as mobile phase.

The chromatographic evaluation was done using acetonitrile as mobile phase. The polymers were prepared at 60°C, using isopropanol as diluent and at the pressures given in the table. 

The polymers were evaluated using either acetonitrile/acetic acid/ water 92.5/5/2.5 (v/v/v) or acetonitrile as mobile phase. 10 nmol of solute were injected in 10 /rl of the mobile phase. 

Matantseva and co-workers87,101,103 separated the major opium alkaloids on a pellicular sulfonic acid cation-exchange stationary phase, using a pH 4.5 phosphate buffer containing 30% acetonitrile as mobile phase. 

HPLC separation of potential impurities of HMM has been studied. A Waters HPLC system was used with a 5 pm ultrasphere Cig column with mixtures of water and acetonitrile as mobile phase... 

HPLC conditions 200 X 4 mm ID analytical column with Nucleosil 5 SA, acetonitrile as mobile phase, fluorimetric detection. 

A typical example of FDNB derivatization is the determination of amikacin in human serum [28,29], In a pre-column derivatization method, the aminoglycoside was extracted from serum by using a cation exchange column [29]. The eluate was treated with FDNB in dimethyl sulphoxide (DMSO) at pH 10. The derivative was then separated on an RP-Cjg column with water/ acetonitrile as mobile phase and monitored at 365 nm. The recovery of amikacin was only 72%, and kanamycin was used as an internal standard. The sensitivity was 1 mg 1 and 200 1 of serum was needed. 

Reversed-phase LC with water-methanol or water-acetonitrile as mobile phases is suitable for the resolution of vitamin D2 and D3 and the 25-hydroxy-metabolites, but exhibits inferior selectivity for the dihydroxylated metaboHtes. When it is to be applied to biosamples a normal-phase LC prefractionation is mostly required for selectivity reasons. 

For instance, Ribas-Agustf et al. used a 100 mm, 1.8 pm HSS T3 column and mix-tnre of methanol-water-formic acid as mobile phase for the determination of phenolic acids and flavonols in lettnce, achieving a separation of 11 compounds in 30 min [94]. Ortega et al. used the same column in combination with acidified water with 0.2% acetic acid, and acetonitrile as mobile phase for the determination of 28 compounds (including phenolic acids, flavanols, and flavonones) in 20 min [103]. These parameters as well as other important factors of the chromatographic separation have been indicated in Table 16.6. 

Fig. 1.4. Reversed-phase separation of fatty acid methyl esters, including CLA. A Nucleosil C g column (250 x 10 jim i.d. 5 mm particles) was used with acetonitrile as mobile phase, and ultraviolet detection at 234 nm. Methyl esters (20 mg) in acetone were injected, with acetonitrile as mobile phase and a flow rate of 4 mL/min. The fraction corresponding to the C g dienes may also contain some 14 0, 16 1, and certain polyunsaturated fatty acids. (Chromatogram kindly supplied by J.-L. Sebedio and P. Juaneda.)...

More efficient separations are obtained with the above-mentioned tetradecyl-substituted materials based on 18-crown-6. Ion-exchange interactions are dominating the separation mechanism in this case [46]. By using two of those stationary phases in series, 14 different inorganic and organic anions can be separated utilizing potassium hydroxide and acetonitrile as mobile phase (Fig. 3-59). The use of two stationary phases in series is necessary to ensure adequate capacity for the sufficient separation of all analytes. In comparison with conventional anion exchangers, crown ether phases exhibit less selectivity for divalent anions ... 

A micromembrane suppressor for ion-exclusion chromatography has been introduced under the trade name AMMS-ICE. Its structure corresponds to the systems developed for anion and cation exchange chromatography (see Sections 3.6.3 and 4.3.3). However, in its mode of operation, it corresponds to the AFS-2 hollow fiber suppressor. An AMMS-ICE micromembrane suppressor also contains membranes that are compatible with water-miscible organic solvents. Therefore, it is used for the analysis of long-chain fatty acids, which are separated on a non polar stationary phase in a weakly acidic medium with methanol or acetonitrile as mobile phase components. In this case, a dilute potassium hydroxide solution is used as the regenerant. With respect to the ion-exchange... 

FIGURE 2.10 Preparative reversed-phase high-performance liquid chromatography (RP-HPLC) separation of fatty acid methyl esters (FAME) (5-10 mg) from cheese on a Nucleosil C18 column (250 mm X 10 mm i.d.) with acetonitrile as mobile phase at a flow rate of 4 mL/min. Detection of FAME was by refractometry and the fraction containing conjugated linoleic acid (CLA) (also containing 14 0, 16 1, and 18 2) was monitored by ultraviolet (UV) detection at 234 nm. (Reproduced from Lavillonniere, F., Martin, J.C., Bougnoux, P., and Sebedio, J.-L., J. Am. Oil Chem. Soc., 75, 343-352, 1998.)... 

Chemical purities were determined by HPLC on a Hewlett-Packard liquid chromatograph HP1090 series II using a LichroCART 125-4 Superspher 60-RP Select B column (Merck) and UV-detection at 254 nm wavelength. Separations were achieved with a linear gradient of Ig H3PO4 85% in 100 mL water and Ig H3PO4 85 % in 100 mL acetonitrile as mobile phase at a 1.2 mL/min. flow. 

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