Acetonitrile water eluent systems

An advanced HPLC system has been developed to separate cisltrans isomers of tocotrienols using a chiral permethylated P-cyclodextrin column and an acetonitrile/ water eluent mixture (Drotleff and Temes, 1999). 

Several studies have been published on the use of special stationary phases (using packed GC columns) or special types of deactivated retention gaps [11,12]. Among these, a series of papers by Goosens et al. [13-15] on the use of a carbo-wax-deactivated retention gap to transfer acetonitrile-water eluents from the LC to the GC part of the system, merit attention. When using an on-column interface and a solvent vapor exit (SVE), up to 200 Xl of aqueous-organic eluent could be introduced, provided that the water content of the eluent did not exceed that of the azeotropic mixture (16 vol%). Otherwise, water will be left in the retention gap after evaporation of the azeotropic mixture and will mar the analysis. In order... 

Figure 12.10 Microcolumn SEC-LC analysis of an acrylonitrile-butadiene-styrene (ABS) teipolymer sample (a) SEC ti ace (b) EC ti ace. SEC conditions fused-silica column (30 cm X 250 mm i.d.) packed with PL-GEL (50 A pore size, 5 mm particle diameter) eluent, THE at a flow rate of 2.0 mL/min injection size, 200 nL UV detection at 254 nm x represents the polymer additive fraction (6 p-L) tr ansferred to EC system. EC conditions NovaPak CIS Column (15 cm X 4.6 mm i.d.) eluent, acetonitrile-water (60 40) to (95 5) in 15 min gradient flow rate of 1.5 mL/min detection at 214 nm. Peaks identification is follows 1, styrene-acrylonitrile 2, styrene 3, benzylbutyl phthalate 4, nonylphenol isomers 5, Vanox 2246 6, Topanol 7, unknown 8, Tinuvin 328 9, Irganox 1076 10, unknown. Reprinted with permission from Ref. (14).

Quantitative HPLC analysis was carried out on a Spectraphysics 8720 chromatography system, a rapid scan detector by Barspec on a Zorbax ODS column with acetonitrile water 75/25 as the eluent. 

In addition to water, virtually any organic polar modifier may be used to control solute retention in liquid-solid chromatography. Alcohols, alkyl2aiines, acetonitrile, tetrahydrofuran and ethyl acetate in volumes of less than one percent can be incorporated into nonpolar mobile phases to control adsorbent activity. In general, column efficiency declines for alcohol-moderated eluents cogqpared to water-moderated eluent systems. Many of the problems discussed above for water-moderated eluents are true for organic-moderated eluents as well. 

Using the Tomtec Quadra 96 workstation, 0.1 mL of the ethyl acetate layer was transferred to a 96-well collection plate containing 0.4 mL of acetonitrile in each sample well. The solution was mixed 10 times by aspiration and dispersion on the Tomtec. The plate was then covered with a sealing mat and stored at 2 to 8°C until LC/MS/MS analysis. The HILIC-MS/MS system consisted of a Shimadzu 10ADVP HPLC system and Perkin Elmer Sciex API 3000 and 4000 tandem mass spectrometers operating in the positive ESI mode. The analytical column was Betasil silica (5 fim, 50 x 3 mm) and a mobile phase of acetonitrile water formic acid with a linear gradient elution from 95 5 0.1 to 73.5 26.5 0.1 was used for 2 min. The flow rate was 1.0 mL/min for the API 3000 and 1.5 mL/min for the API 4000 without any eluent split. The injection volume was 10 jjL and a run time of 2.75 min was employed. 

The nitrobenzene oxidation mixture was analyzed using the HPLC method. 0.2 mL of the stock solution was pipetted into a 25 mL volumetric flask and acetonitril-water (1 2 vA ) was added to it. About 20 gL of the sample solution was next injected into the HPLC system (Shimatzu) equipped with a Hypersil bond C,g coluitm (particle size 5 gL, 25 x 4.6 mm i.d.) to quantitatively determine the vanillin component while another component was determined qualitatively. Acetonitril-water (1 8) containing 1% acetic acid was used as an eluent with a flow rate of 2 tuL/min. The eluent was then monitored with an UV (ultraviolet) detector at 280 ran [6]. 

Miwa et al. (26) have demonstrated that both short- and long-chain fatty acids can also be converted into their 2-nitrophenylhydrazides and separated bv RP-HPLC with acetonitrile-water as the eluent. They have described a method for the direct derivatization without an extraction step and the simultaneous microanalysis of 14 kinds of C 0 0-C22 6 fatty acid hydrazides in a reverse-phase HPLC system (27). 

The qualitative and quantitative analyses of monosaccharide, glycine and ARP were performed on a Waters HPLC-system equipped with a Nucleosil 5-NH2 (aminopropylsilica) HPLC-column using acetonitrile/phosphate-buffer (pH-3 75/25 (v/v)) as eluent. An external standard method was used to determine the mono- saccharide-, glycine-, and the ARP-intermediate concefttrations (reference compounds were available). 

A chromatographic system consisting of the binary eluent (e.g., acetonitrile-water) with liophilic salt added in low concentration (not more than lOOmM), along with basic analyte, is considered here. Adsorption behavior of acetonitrile in the column has been discussed in Section 2.12, and we assume that low concentrations of liophilic salt additives and injection of small amount of the analyte does not noticeably disturb its adsorption equilibrium. 

In a binary eluent system (acetonitrile-water), an adsorbed organic phase with finite thickness and composition different from the bulk mobile phase is preferentially accumulated near the surface of the bonded phase. The organic layer accumulated near the bonded ligands could behave as a liquid stationary phase in reversed-phase HPLC, and it contributes to the overall analyte retention process. 

HPLC Analytical RP-HPLC was performed using a Phenomenex Jupiter Cig (250 X 4.6 mm, 5 pm, 300 A) reverse phase column and a Waters system composed of No. 600 pump, No. 600 controller, and No. 490 programmable multiwavelength detector (Nihon Waters, Tokyo, Japan). Eluent A was 0.1% TFA in water and eluent B was 0.1% TFA in acetonitrile-water (80 20, v/v). A linear gradient of eluents (0-90% B in 45 min) with a 1 mL/min flow rate was used as the mobile phase. Three different wavelengths were applied for the detection of peaks (k = 214, 254, and 280 nm). 

In the analysis of inorganic anions using acetonitrile-water (3-1-7) containing citric acid and hexadecyltrimethylammonium hydroxide as eluent. Wheals reported that bromide, cyanide, dithionite, ferrocyanide, iodide, metabisulfite, nitrite, perborate, peroxide, sulfide, thiocyanate and thiosulfate respond at a GCE (-1-0.75 V vs Ag/AgCl). Dou and Krull have further shown that post-column irradiation (low pressure Hg arc discharge lamp) can facilitate the EC detection of chromate, dichromate and perchlorate and give improved sensitivity for thiocyanate. Despite this work, however, the application of EC detection to the analysis of these ions in biological systems has not been reported as yet. 

Sample extraction and HTpSPE followed the procedure presented in Section 10.3.1.1 for fruit and vegetables. For pL-FlA-TOFMS analysis, acetonitrile/water (1/1, v/v) was applied including 0.05% formic acid at a capillary flow rate of 2 j,L/min. The eluent included 5% mass calibration solution to perform the mass axis calibration of the system. High-resolution mass spectra were recorded in the full-scan mode, and the quantitation of pesticides was done using the signal-to-noise ratios of the exact mass signals, normalized to TDCPP, when pure solvent standards were applied for comparison [27]. 

New selectors for the separation of enantiomers based on LEC were synthesized (Pig. 5 (b-d)). Iminocarboxylic acid (Fig. 5 (b)) was used for the enantiomeric separation of S,5-diniethyI-3-thiazoI-ine-4-acetic acid with the eluent system acetonitrile-methanol-water (3 5 5, v/v/v)(l66), whereas... 

Remelli et al. (168) described a selector based on histidine. With this chiral selector L-hr-n-decylhistidine (Fig. 5(c)) the simultaneous enantiomeric separation of D,L-tiyptophan and D,L-phe-nylalanine was successfully performed on hydrophobic layers with MeOH-acetonitrile-THF-water (7.3 5.9 33.9 52.9, v/v/v/v) as eluent. Sinibaldi et al. (165) resolved D,L-dansyl amino acids on reversed phase TLC plates pretreated with a copper -complex of poly-L-phenylalanine amide (Fig. 5 (d)). The polymeric ligand was synthesized by the reaction of optically active amide with ethylene glycol diglycyl ether. The method makes use of a sophisticated liquid chroinatogr q)h for obtaining the desired polymer fraction which is subsequently used for the LEC, and this might limit the application of the separation procedure. However, a simple method is performed by Bhushan et al. (169). Here L-proline was used as a chiral selector on normal phase silica gel (169) and amino acids were resolved with the eluent systems n-butanol-acetonitrile-water (6 2 3, vWv), chloroform-meth-anol-propionic acid (15 6 4, v/v/v) and acetonitrile-methanol-water (2 2 1, v/v/v). 

Eluent To achieve short analysis times, ternary mixtures of water-miscible alcohol, water, and acetonitrile proved useful. Most racemate separations could be accomplished using one of two eluent systems ... 

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