Ion-pair HPLC

Chlorphenylid, Flucofuron and Sulcofuron Waters (Tentative Methods based on methylation and GC-ECD, ion-pair HPLC and hydrolysis of Sulcofuron to 4-chloro-3-trifluoromethylaniline by GC-ECD), 1993... 

A method developed to analyze alkylbenzenesulfonates by reverse phase ion pair HPLC with UV detection has also been applied to the determination of alcohol ether sulfates [286]. 

We have developed reverse-phase ion-pairing HPLC separations of substituted EDTA metal chelates of several transition metals (including Cd, Zn, Fb, and Hg) and several lanthanides (La, Ce, Eu, Dy, Er, Yb, Lu). Detection levels of these chelates are currently being assessed. A sensitive metal ion analysis employing an inherently fluorescent EDTA seems feasible. 

Ion pair HPLC Formation of ion pairs witii cetylpyridinium Diode array, 430 nm Drinks, milks. ... 

High-performance liquid chromatography (HPLC) with a micellar mobile phase or with a selective pre-column or reaction detection system has also been used to determine alkylenebis(dithiocarbamaes). ° Zineb and mancozeb residues in feed were determined by ion-pair HPLC with ultraviolet (UV) detection at 272 nm. These compounds were converted to water-soluble sodium salts with ethylenediaminetetra-acetic acid (EDTA) and sodium hydroxide. The extracts were ion-pair methylated with tetrabuthylammonium hydrogensulfate (ion-pair reagent) in a chloroform-hexane solvent mixture at pH 6.5-8.S. The use of an electrochemical detector has also been reported. ... 

Folonari, C. V. and Garlasco, R., Ion-paired HPLC characterization of cathodic electrodeposition paint polymers, /. Chromatogr. Sci., 19, 639, 1981. 

Part 24 Determination of maleic acid and maleic anhydride in food simulants Ion pair HPLC of maleic acid with cetyl trimethyl ammonium chloride and UV detection (245 nm) with citraconic acid as internal standard... 

A method has been reported [481] for the determination of flavins in seawater. The method is based on solid-phase extraction. With ion-pair HPLC using fluorescence detection, concentrations in the picomolar range can be measured. 

Since the order of increasing CL intensity for alkyl amines reacted with Ru(bpy)32+ is tertiary amines > secondary amines > primary amines, pharmaceutical compounds bearing a tertiary amine function (e.g., antihistamine drugs [99], anticholinergic drugs [100], erythromycin [101], and its derivatives [102]) have been sensitively determined after HPLC separation (Table 3). The method was applied to the detection of d- and L-tryptophan (Trp) after separation by a ligand-exchange HPLC [103], The detection limits for d- and L-Trp were both 0.2 pmol per injection. Oxalate in urine and blood plasma samples has also been determined by a reversed-phase ion-pair HPLC (Fig. 18) [104], Direct addition of... 

Crystal structures are available for many (N)4Co-amino acid complexes (Table I). Many of the diastereomers (AS, AS) in the bis-en series have been resolved using classic crystallization (usually via bromocamphor sulfonate, arsenyl-, or antimonyl-tartrate salts) or ion exchange methods (Table II). Reversed-phase ion-pair HPLC, using aryl phosphate or aryl/alkyl sulfonate ion pairing reagents in MeOH/ H20 eluent, has allowed diastereomer separations to be carried out on analytical amounts (28) (Table II). 

One of the most important advantages of HPLC over spectrophoto-metric methods lies in its specificity and selectivity due to its separation capability. Through chromatographic separations, the analytes of interest can be detected and quantified without interference from the typical matrix that includes excipients, antioxidants, preservatives, and dissolution media. Ion-pair HPLC was used to monitor the dissolution of pentamidine from EVA sustained-release film where polymeric matrices could create significant bias if a spectrophotometric method were used. Due to their strong UV absorbance, the antioxidants and preservatives (e.g., BHA, BHT, ascorbic acid and propyl gallate) are often the major... 

The fact that the EP wants to replace old TEC methods with more selective, efficient, and sensitive separation methods provides the chance for the introduction of more CE methods. The continuous development of analytical methods is reflected in the national and international pharmacopoeias. This might be demonstrated for atropine sulfate. Whereas the Deutsches Arzneibuch, 7th Edition (DAB 7) only limits the tropic acid by extraction and titration with NaOH and phenolphthalein indication, the 4th edition of the EP looked for foreign alkaloids and decomposition products by means of TEC with a potassium iodobismuthate for detection. By intensity comparison of the obtained spots, it was possible to limit these impurities to 0.5%. The EP 5 utilizes an ion-pair HPLC method that is able to limit most of the impurities to less than 0.2%. To make the method more robust, an HPLC method using a polar embedded was applied, which might be the next step for the EP. However, recently the same authors have reported on a MEEKC method being as robust and precise as the latter HPLC method (see Eigure 6) but far more sensitive and, therefore, a future perspective for the EP. 

Martelli, A., Arlorio, M. and Tourn, M.L. (1993). Determination of amines and precursor amino acids in gorgonzola cheese by ion pair HPLC without derivation, Li Rivista di Scienza delValimentazione, 3, 261. 

Breitholtz, A. et al.. Plasma ochratoxin A levels in three Swedish populations surveyed using an ion-pair HPLC technique, Food Addit. Contam., 8, 183, 1991. Gastello, M.M., Sumner, S.S. and Bullerman, L.B., Stability of fumonisins in thermally processed com products, J. Food Prot., 61, 1030, 1998. 

Analysis of the drug and metabolites in biological samples by ion-pair HPLC 207... 

C. Raba. and K. Fischer, Ion-Pair HPLC Determination of Sugars, Amino Sugars, and Uronic Acids, Anal- Chem. 2001,... 

Reverse-phase and ion-exchange HPLC have been used for the determination of intermediates and subsidiaries of synthetic dyes. However, reverse-phase ion-pair HPLC has been found particularly useful for the separation and detection of these compounds (195). 

Ion-pair HPLC (194,195) was used to separate amaranth from its subsidiary dye l-(4-sulfo-l-naphthylazo)-2-naphthol-6-sulfonic acid disodium salt (fast red E) and from its intermediates 1-naphthylamine 4-sulfonic acid (naphthionic acid) and 2-naphthol-3,6-disulfonic acid disodium salt (R-salt). Ion-pair HPLC was also used for the determination of total free and bound nonsul-fonated aromatic amines in amaranth after diazotization and coupling with R-salt (198). 

Sunset yellow was separated from its subsidiary dye l-p-sulfophenylazo-2-naphthol-3,6-disulfonic acid trisodium salt (195) and from its intermediates sulfanilic acid and Schaeffer s salt (194) by means of ion-pair HPLC. Ion-pair chromatography has also been used to determine free and bound nonsulfonated aromatic amines in sunset yellow after reduction with dithionite, diazotization with sodium nitrite, and coupling with R-salt (202). 

The application of ion-pair HPLC in the analysis of food colors is summarized on Table 8. As indicated, TBA has been the most widely used ion pair. It can be observed that using gradient mobile phase elution, a larger number of synthetic dyes can be separated. However, the mobile phase programming should include a return to the initial condition as well as reequilibration of the column by maintaining the initial composition for a period of time. This procedure provides reproducible result (222). 

Table 8 Ion-Pair HPLC Methods for the Simultaneous Determination of Synthetic Food Colors... 

Roughly 10 years ago, an ion-pair HPLC was introduced for the determination of sulfites in foods (32). The method combined the chemical approach of the Monier-Williams technique for liberating the sulfite from the matrix with ion chromatography. The ion chromatographic procedure... 

CR Warner, DH Daniels, MC Fitzgerald, FL Joe Jr, GW Diachenko. Determination of free and reversibly bound sulphite in foods by reverse-phase, ion pairing HPLC. Food Addit Contam 7 515-581, 1990. 

Cad, His, Phe, Ion-pair HPLC with post- Novapak C-18 as stationary 0.30-0.65 mg/L Beer, hops, malt, HC104 extraction. 38... 

His Tyr Ion-pair HPLC of PA derivatives and fluorimetric detection at 425 nm (Aex = 338 nm). Nova-Pak C-l 8 stationary phase. Mobile phase MeOH, hydrogen-phosphate, heptanesul-fonic acid, pH = 3.0. 1-5 mg/L in cheese Dairy products, infant formulae, yogurt, cheese found in cheese 25-223 mg/L Homogenization with MeOH at T = 60°C, cooling, MeOH addition, filtration. 159... 

Aniline, 1-NA, 2-NA, 2-ABP, 4-ABP Ion-pair HPLC with spectro-photometric detection at 426, 512, and 625 nm. Supelco LC-18 column. Mobile phase MeOH, TBA-I in gradient elution. 

NA, 2-NA Ion-pair HPLC and spectro-photometric detection at 522 nm. Supelco LC-18 as stationary phase. Mobile phase MeOH and TBA phosphate. 

The quantitative analysis of Chincona bark by the classical methods of titrimetry, gravimetry, and polarimetry has been performed for many years in order to ascertain its commercial value. These compounds have been analyzed by GC, GC-MS, TLC, and mainly HPLC (353-361) with UV or electrochemical detection. Ion-pair HPLC was also used with UV or fluorescence detection by Jeuring et al. (357). Photoreactions of Qn in aqueous citric acid solution have been studied by Laurie et al. (358). After isolation of the components by HPLC and TLC, different spectroscopic techniques (MS, NMR, IR) were used to identify the photoproducts. 

---