Lichrospher elution

Fig. 2.3.6. Overlay of reversed-phase chromatograms of four commercial mixtures of alkylphenols and alkyl phenolethoxylates f-OP, OP[EO]8/9) 4-NP, and NP[EOJio. Column 125 X 4 mm2 Lichrospher RP-18 (5 pm), isocratic elution 1.0 mL min-1, mobile-phase 8 2... 

Following the method developed by Pfeiffer to detect nine BAs, wine was applied to a Bond-Elut SCX SPE column and the eluted portion was derivatized with PA. The reaction mixture was analyzed on a LiChrospher 100-RP-18-5 column with gradient elution (MeOH-phos-phate buffer) and fluorimetric detection at 440 nm the DL was about 50 /zg/L (133). 

The enantiomers of pantoprazole were separated using HPLC at 40°C on Chiralcel OJ-R columns with 25% acetonitrile and 50 mM NaC104 (3 1 v/v) as the mobile phase [11]. Elution was performed at a flow rate of 0.5 mL/min, and detection was at 286 nm. Lichroprep PR-2 was used as a pre-column, and Lichrospher 100 RP-18 was used as a guard column. 

Zhou et al. developed an HPLC method for the determination of dipyridamole, aspirin, and salicylic acid [67]. The HPLC system consisted of a Lichrospher 5-Cig (4.6 mm x 150 mm) column and a UV detector operated at 227 nm. The mobile phase (eluted at a flow rate of 1 mL/min) was composed of disodium hydrogen phosphate solution(methanol (50 50, pH adjusted to 3 by addition of phosphoric acid). The mean recovery of dipyridamole and aspirin was 100.9-104.1% and 97.01-97.89, respectively. 

Ketoprofen enantiomers/plasma HPLC UV Column Chlral-HSA (100 x 4 mm, 5 pm) Mobile phase 0.01 M phosphate buffer 2-propanol (94 6 v/v) with 5 mM octanoic acid, pH 5.5 (isocratic elution) Detection 2 = 260 nm On-line SPE/column LiChrospher Ci8 ADS LOQ 16 ng/mL [47]... 

Fig. 2 Separation of 25 flavonoid standards (1—eriocitrin 2— neoeriocitrin 3—robinetin 4—narirutin 5—naringin 6— rutin 7— hesperidin 8—neohesperidin 9—isorhoifolin 10— rhoifolin 11—diosmin 12—neodiosmin 13—neoponcirin 14—quercetin 15— poncirin 16—luteolin 17—kaempferol 18—apigenin 19—isorhamnetin 20—diosmetin 21— rhamnetin 22—isosakuranetin 23— sinensetin 24—acacetin 25—tangeretin) using Cig Lichrospher 100, 250 x 4.0 mm, 5 pm, Merck gradient elution with 0.01 M phosphoric acid-methanol with flow rate of 0.6 mL/min at 40°C and detection at 285 nm. (From Ref. [8].)...

Figure 1.7 HPLC chromatogram of organic acids analysis of Prosecco grape must sample. 1. tartaric acid, 2. malic acid, 3. citric acid, 4. shikimic acid. Analytical conditions Lichrospher 100 RP-18 (250 x4mm, 5p,m) column (Merck, Darmstadt, Germany) at room temperature, detection at wavelength 210 nm, sample volume injected 20/xL solvent H3P04 5 x 10 3 M with isocratic elution at flow rate 0.6 mL/min...

As an example, Fig. 4.30 shows the separation of three pharmaceutical intermediates on LiChrospher RP-18 with a mobile phase composition of acetonitrile-water (80 20). Intermediate 1 elutes at 2.28 min while intermediates 3 and 2 co-elute at 3.16 min. Obviously, the separation problem is not solved and, thus, the mobile phase composition must be adjusted in subsequent batch runs with higher water fractions. 

Figure 9.9 Separation of co-bromoundecanoic acid [reproduced by permission ofMarcel Dekker, Inc.,from R. Schwarzenbach, J. Liq. Chromatogr.,2,205(1979)]. Conditions sample, raw material from esterification column, 25cm x 3 mm i.d. stationary phase, LiChrospher SI 100, Bpm mobile phase, 1 ml min hexane-diethyl ether (2 3) UV detector. (A) Untreated silica bromoundecanoic acid is eluted with extreme tailing and cannot be quantitatively determined. (B) Silica treated with citrate buffer (pH 2.8) bromoundecanoic acid appears as a distinct peak and the other components remain unaffected.

N acetic acid (1 1) flow rate 0.9 mL/min detection UV absorption at 263 nm]. A detection limit of 125 ng/injection for palytoxin was obtained by Mereish et al. [103] by use of a Bio-Sil 5 ODS column (Table 29.4) while Lau et al. [99] carried out the HPLC analysis of Caribbean palytoxin using a Novapak C18 reversed-phase column (75 mm x 3.9 mm), a gradient elution with 80% acetonitrile water (4 1) and detection at 230 nm. Reversed-phase HPLC was also applied for the analysis of Caribbean palytoxin [column Lichrospher 300 RP-8 mobile phase 0.1% TFA and 80% acetonitrile linear gradient detection UV absorption at 230 nm] with a lower tracing quantity of 10 [tg [21]. Other HPLC methods for palytoxin detection using different combinations of columns and solvent mixtures have also been reported [14,26]. 

Fig. 2. Reverse phase HPLC fractionation of a tryptic digest of Ado-P..-[ H]P1 modified PRK. Sample (1.9 nmol)was loaded onto a LiChrospher RP-18 column and eluted with a 0-70% gradient of CH CN in 0.1% trifluoroacetic acid. The top panel shows 215 nm absorbance, with the inset depicting a 20-fold scale expansion to indicate (arrow) the UV peak corresponding to the radiolabeled peptide. The bottom panel shows the H profile measured using 10% of the column effluent.

Small porous silica particles in the 10 pm size range, such as LiChrospher (Merck), provide columns with much higher efficiency than CPG or Spherosil. The elution volumes of carboxymethylcellulose (CMC), po1y(methacrylic acid) (PMA), and heparin - a sulfonated mucopolysaccharide - were examined as a function of sample concentration and ionic strength on high-resolution (30,000 plates m"l) LiChrospher columns (50). Ve for heparin was found to increase smoothly with I, approaching a constant value at 0.7 < I < 1. In 0.5 M NaAc Ve increased linearly with sample mass. Chromatograms for CMC and PMA in 0.5 M NaAc were also reported essentially without discussion. 

The ionic-strength dependence of the elution of CMC was studied by Barth and Regnier (51) on glycerylpropylsilyl derivatized LiChrospher. No explicit attempt was made to separate polyion expansion effects from polyion-substrate interaction. However, one could note that the salt-dependence of the intrinsic viscosity essentially vanished at I > 0.1, whereas Ksec continued to decrease in the range 0.1 < I < 0.5. This rather qualitative observation suggests that polyion-substrate repulsion persists even for derivatized silica. 

The newly developed HPLC analytical condition for cephalosporins LiChrospher 100 RP 18(e) (5 Jim, 4 X 250 mm) elution, 5 mM 1-heptanesulfonic acid sodium salt, 5 mM 18-Crown-6, 100 mM citric acid monohydrate, and 3.9 mM tiisodium citrate with 16% methanol and 0.5% tetrahy-drofuran column temperature. 40 C flow rate. I ml/min detection, UV at 254 nm. 

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