Methanol eluent

APPLICATION METHANOL ELUENT RP-HPLC ANALYSIS FOR ESTERS OF 4-AMINOBENZENTHIOSULFINIC ACID AT PROCESS OF THEIR SYNTHESIS... 

Macaudiere et al. first reported the enantiomeric separation of racemic phosphine oxides and amides on native cyclodextrin-based CSPs under subcritical conditions [53]. The separations obtained were indicative of inclusion complexation. When the CO,-methanol eluent used in SFC was replaced with hexane-ethanol in LC, reduced selectivity was observed. The authors proposed that the smaller size of the CO, molecule made it less likely than hexane to compete with the analyte for the cyclodextrin cavity. 

Comparisons of LC and SFC have also been performed on naphthylethylcar-bamoylated-(3-cyclodextrin CSPs. These multimodal CSPs can be used in conjunction with normal phase, reversed phase, and polar organic eluents. Discrete sets of chiral compounds tend to be resolved in each of the three mobile phase modes in LC. As demonstrated by Williams et al., separations obtained in each of the different mobile phase modes in LC could be replicated with a simple CO,-methanol eluent in SFC [54]. Separation of tropicamide enantiomers on a Cyclobond I SN CSP with a modified CO, eluent is illustrated in Fig. 12-4. An aqueous-organic mobile phase was required for enantioresolution of the same compound on the Cyclobond I SN CSP in LC. In this case, SFC offered a means of simplifying method development for the derivatized cyclodextrin CSPs. Higher resolution was also achieved in SFC. 

A polyethylene-coated (PEE) silica column was used with water-methanol eluents to achieve the separation and retention of 27 pesticides.40 The retention times of 33 commercial pesticides were determined on an octadecyl (ODS)-derivatized alumina column using water-methanol eluents and compared with retention properties on an ODS-silica column packing.41 More recently, RP-HPLC was used in combination with diode array detection for the identification and quantification of 77 pesticides (acidic, basic, and neutral) in groundwater samples.42... 

Although Certify is a mixed mode sorbent with C8 and sulfonic acid moieties, the authors rationalized that the hydrophobic retention on this sorbent is more dominant and caused the nonretention of certain drugs during methanol wash. The weak WCX ion exchanger was also excluded for similar reasons. Both the mixed mode strata-X-C and the ion exchange sorbent SCX were found to be most amenable for the derivatization-based GC/MS analysis and both yielded pure extracts. However, the yields were consistently lower with strata-XC than SCX and the authors hypothesized that this was due to the inability of the 5% ammonia/methanol eluent to completely disrupt the hydrophobic and dipolar interactions between the analytes and XC. 

Ponceau 4R, E-124 and Erythrosine, E-127) using a buffered mobile phase. Separation of dyes was performed in an ODS column (150 X 3.9 mm i.d. particle size 3 pm). Components of the mobile phase were methanol (eluent A) and 0.1 M NaH2P04/Na2HP04 buffer (pH = 7). The gradient elution started with 20 per cent A and reached 100 per cent in 2 min, final hold 4 min. The flow rate was 2 ml/min and dyes were detected at 520 nm. The baseline separation of dyes in 6 min is illustrated in Fig. 3.34. Commercial samples were diluted and injected into the analytical column without any pretreatment. The amounts of dyes found in the samples are compiled in Table 3.20. It was concluded from the good validation parameters that the technique is specific, sensitive, accurate and rapid. Consequently, its application for the determination of these synthetic dyes in drinks was proposed [112],... 

Volatile buffers were reconsidered for the modified method. Triethylamine was ruled out primarily because it could not be obtained in high purity and because the secondary and primary amines contaminating it could potentially react with solutes present in the water sample. Preliminary evidence of reaction between ethidium bromide and triethylammonium bicarbonate was obtained, but the reaction product was not characterized. The components of volatile buffers that appeared acceptable on the basis of chemical purity were ammonia, acetic acid, and formic acid. A few exploratory experiments were conducted involving the elution by ammonium formate and ammonium acetate of EB or quinaldic acid exchanged onto AG MP-50 or IRA 900. These experiments showed that 1 M ammonium formate in water was a very poor eluent, but that EB could be eluted from AG MP-50 with 1 M ammonium formate in methanol. Elution was essentially complete with 6 bed volumes of the methanolic eluent, whereas neither methanol alone nor aqueous 1 M ammonium formate was able to elute this solute. This situation pointed out the necessity for a counterion to displace exchanged solutes and, additionally, indicated that the displaced solute be highly soluble in the eluting solvent. 

Methanol eluent (2 X 25 mL) Measure the volume and remove 5 mL for humics analyses. Concentrate the remainder to dryness and solvent exchange to methylene chloride to a final volume of 1.0 mL spike with 20 /xg of internal standard. Analyze this fraction by capillary GC-FID for all Group I compounds with special emphasis on caffeine. 

Fig. 16 Two different gradient profiles obtained with different instruments. Gradient from methanol (eluent A) to methanol containing 100 ppm toluene. FC final conditions. (From Ref. 60. Reproduced from Vieweg with permission.)...

Takatera and Watanabe [41] used this technique for the speciation of iodide ion, I-, and five iodo amino acids (monoiodotyrosine (MIT), diiodotyrosine (DIT), 3,3,5-triiodothyromine (T3), 3,3,5 -triiodothyromine (rT3), and thyroxine (T4)) which are all found in thyroid hormones. The speciation of these compounds in clinical samples such as blood plasma and urine may assist in the identification of thyroid diseases. The RPLC-ICP-MS system was able to detect all of the I-containing compounds with no interferences. Detection limits were in the range 35-130 pg for the six compounds using a 50% methanol eluent. Detection limits were better for species eluted at a shorter retention time since the peak shapes were sharper. The detection limits calculated were an order of magnitude lower than for methods where UV absorbance detection was used. 

The criteria used to judge the performance of a low-pressure pump include compositional accuracy, ripple, flow accuracy, and pressure accuracy. Compositional accuracy is tested by following the American Society for Testing and Materials (ASTM) procedure E-19.09.07.5 In this procedure, two bottles of eluent are used, one containing 100% methanol (eluent A) and the other containing methanol with a low concentration of acetone... 

The iodide ion, I , and five iodo-amino acids, found in thyroid hormones, have been separated by using RPLC-ICP-MS [30]. A 50% methanol eluent was used and the detection limits (35-130 pg) were improved by an order of magnitude compared to that of ultraviolet (UV) absorbance detection. 

Benzodiazepines can be chromatographed with methanolic eluents containing perchloric acid (typically 0.001 M). Retention can be modified by the addition of other organic solvents (e.g. ether) or by changes to the acid concentration. 

Both acidic and basic drugs can be chromatographed on silica using aqueous methanolic eluents containing cetyltrimethylammonium bromide (S. H. Hansen,... 

The bound water may be removed by drying the sorbent under vacuum (25 mm Hg) for at least 15 min. Another approach is to add methanol or acetonitrile to the chloroform (- 20%) to allow for the dissolution of water into the eluent, which permits the infiltration of the chloroform-methanol eluent into the bonded C-18 phase. Because of retention of bound water in the C-18 sorbent, a review of the literature commonly shows that a polar solvent is mixed with a nonpolar solvent as an effective eluent in SPE. Later in such a method, the water will be removed by a drying agent such as anhydrous sodium sulfate. 

If an alcohol such as methanol can be separated by ion-exclusion chromatography using water as the eluent, why not do the reverse and separate water using a methanol eluent Stevens et al. [12] did just this. They added a small amount of sulfuric acid to the eluent and detected the chromatographic water peak by a decrease in conductivity. The main drawback with this method was a non-linear calibration curve with very poor detection sensitivity in some concentration regions. 

Fortier and Fritz [13] separated water by lEC and devised a unique equilibrium system for in-line spectrophotometric detection. This method has been refined and its capabilities expanded by continuing research by Chen and Fritz [14-17]. Water is separated chro-matographically from the other sample components on a short column packed with cation-exchange resin in the form using dry methanol as the eluent. Detection of the water peak is made possible by addition of a low concentration of cinnamaldehyde to the methanol eluent. In the presence of an acid catalyst, such as a -cation exchanger, cinnamaldehyde reacts with methanol to form the dimethylacetal. 

Lagersiroemia Speciosa L (Lythraceae) Leaves (Phillipines) When KK-Ay mice were fed with test diet of 5% of the hot water extract of leaves and 2% of the methanol eluent of the partial fraction absorbed on to HP-20 resin, reduction in blood glucose level was observed. It was suggested that Lagersiroemia speciosa L known by the name of banaba in the Phillipines have beneficial effect on the level of plasma glucose in Type II diabetes [151]. 

Croes, K. McCarthy, P.T. Flanagan, R.J. HPLC of basic drugs and quaternary anunonium compounds on microparticulate strong cation-exchange materials using methanolic or aqueous methanol eluents containing an ionic modifier. J.Chromatogr.A, 1995, 693, 289-306... 

Law, B. Gill, R. Moffat, A.C. High-performance liquid chromatography retention data for 84 basic drugs of forensic interest on a silica column using an aqueous methanol eluent. J.Chromatogr, 1984,301, 165-172... 

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