Columns spectrophotometric

Indigo is considered as one of the most important dyes. Its preparations are usually analysed by HPLC with UV-Vis [46,60] or APCI MS detection. [61,62] Separation of the colouring components of indigo extracted with DMSO is usually performed with the use of a Cl 8 column. Spectrophotometric detection of blue indigotin is performed at 617 nm, red indirubin at 540 nm, and brown isoindigo at 365 and 490 nm. As mobile phases, mixtures of methanol or acetonitrile and water with the addition of TFA or formic acid are used to ensure compatibility with the requirements of the APCI source. 

Sample treated with HCI and H2O2, clean-up on anion exchange resin column Spectrophotometric (total uranium) 5 pg/L 87% at 11 pg/L Kressin 1984... 

Monitor the column spectrophotometrically at 280 nm, collect and pool void volume fractions, sterilize by filtration, and store at 4°C in lOO-pL aliquots. 

Spectrophotometric deterrnination at 550 nm is relatively insensitive and is useful for the deterrnination of vitamin B 2 in high potency products such as premixes. Thin-layer chromatography and open-column chromatography have been appHed to both the direct assay of cobalamins and to the fractionation and removal of interfering substances from sample extracts prior to microbiological or radioassay. Atomic absorption spectrophotometry of cobalt has been proposed for the deterrnination of vitamin B 2 in dry feeds. Chemical methods based on the estimation of cyanide or the presence of 5,6-dimethylben2irnida2ole in the vitamin B 2 molecule have not been widely used. 

We studied conditions for the determination of tiametoxam (TM), the active component of the fungicide Actai a (Syngenta, Switzerland) by the method of thin layer chromatography with use of the Perkin-Elmer liquid chromatograph combined with spectrophotometric detector. The 250 mm-long and 4.6 mm in diameter steel column filled with Silasorb was used. 

An alternative elution technique is to transfer the powder (e.g. for bromophenol blue) to a glass column fitted with a glass-wool plug or glass sinter, and elute the dye with ethanol containing a little ammonia. The eluted solution, made up to a fixed volume in a small graduated flask, may be used for colorimetric/ spectrophotometric analysis of the recovered dye (see Chapter 17). A calibration curve must, of course, be constructed for each of the individual compounds. 

An area worthy of study is the development of systems of increasing sample throughput beyond the single column operation. Scott has introduced a prototype multicolumn system based on the centrifugal analyzer principle (53). In this set-up a series of LC colimns is rotated on a disc, with sample delivery at the center of the disc and elution and spectrophotometric analysis on the outside. He has suggested using affinity columns for rapid serum protein analysis by this approach. Of course, other principles, such as segmented flow, could be envisioned in an automated LC system as well. Undoubtedly, we can expect to see the availability of such systems in the next few years. 

Use of 10 pm LiChrosorb RP18 column and binary eluent of methanol and aqueous 0.1 M phosphate buffer (pH 4.0) according to suitable gradient elution program in less than 20-min run time with satisfactory precision sensitivity of spectrophotometric detection optimized, achieving for all additives considered detection limits ranging from 0.1 to 3.0 mg/1, below maximum permitted levels Simultaneous separation (20 min) of 14 synthetic colors using uncoated fused silica capillary column operated at 25 kV and elution with 18% acetonitrile and 82% 0.05 M sodium deoxycholate in borate-phosphate buffer (pH 7.8), recovery of all colors better than 82%... 

The identification and quantification of potentially cytotoxic carbonyl compounds (e.g. aldehydes such as pentanal, hexanal, traw-2-octenal and 4-hydroxy-/mAW-2-nonenal, and ketones such as propan- and hexan-2-ones) also serves as a useful marker of the oxidative deterioration of PUFAs in isolated biological samples and chemical model systems. One method developed utilizes HPLC coupled with spectrophotometric detection and involves precolumn derivatization of peroxidized PUFA-derived aldehydes and alternative carbonyl compounds with 2,4-DNPH followed by separation of the resulting chromophoric 2,4-dinitrophenylhydrazones on a reversed-phase column and spectrophotometric detection at a wavelength of378 nm. This method has a relatively high level of sensitivity, and has been successfully applied to the analysis of such products in rat hepatocytes and rat liver microsomal suspensions stimulated with carbon tetrachloride or ADP-iron complexes (Poli etui., 1985). 

Irth, H., De Jong, G. J., Brinkman, U. A. Th., and Frei, R. W., Determination of disulfiram and two of its metabolites in urine by reversed-phase liquid chromatography and spectrophotometric detection after post-column com-plexation, /. Chromatogr., 424, 95, 1988. 

Gagliardi et al. [72] developed a simple high performance liquid chromatographic method for the determination of miconazole and other antimycotics in cosmetic antidandruff formulations. This high performance liquid chromatographic method was carried out on a Discovery RP Amide Ci6 column and spectrophotometric detection was performed at 220 nm. The initial mobile phase was a mixture of acetonitrile and aqueous 0.001 M sodium perchlorate (pH 3) in the ratio of 15 85 (v/ v) then a linear gradient less than 46% acetonitrile in 70 min, and less than 50% in 80 min. The extraction procedure was validated by analyzing samples of shampoo... 

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

After adjusting to 2 mol 1 1 in hydrochloric acid, 500 ml of the sample is adsorbed on a column of Dowex 1-XS resin (Cl form) and elution is then effected with 2 M nitric acid. The solution is evaporated to dryness after adding 1M hydrochloric acid, and the tin is again adsorbed on the same column. Tin is eluted with 2 M nitric acid, and determined in the eluate by the spectrophotometric catechol violet method. There is no interference from 0.1 mg of aluminium, manganese, nickel, copper, zinc, arsenic, cadmium, bismuth, or uranium any titanium, zirconium, or antimony are removed by ion exchange. Filtration of the sample through a Millipore filter does not affect the results, which are in agreement with those obtained by neutron activation analysis. 

In a method for the determination of copper, nickel, and vanadium in seawater, Shijo et al. [840] formed complexes with 2-(5-bromo-2 pyridylazo)-5-(N-propyl-N-sulfopropylamino) phenol and extracted these from the seawater with a xylene solution of capriquat. Following back-extraction into aqueous sodium perchlorate, the three metals were separated on a C is column by HPLC using a spectrophotometric detector. 

Determination of Pb(II) ion by classical or reversed FIA consists of a preconcentration step either on columns packed with a chelating sorbent (PC-FIA) or on a mercury film, followed by spectrophotometric determination of the complex with 4-(2-pyridylazo)resorcinol (11, kmax 518 nm) in borate buffer solution RSD 3-6% at 0.01-1 pM. End analysis by ASV was also applied99. 

For identification, the same two tests as for aspirin itself were prescribed then (U.S.P. XII) and now (U.S.P. XIX) however, due to the pioneering work of Higuchi, Banes, Smith and Levine in the SO s,80 a test for non-aspirin salicylates was introduced using a siliceous earth column for separation from excipients and aspirin, and spectrophotometric finish at 306 nm. A limit of 0.3% is specified. 

The same column method with different eluting solvents and a spectrophotometric finish at 280 nm is used for the assay with limits of 95 to 105 percent. 

As mentioned in the historical synopsis (Section 5.1), Levine121 perfected the compendial partition column procedure in which aspirin in chloroform is first trapped in an immobile phase of sodium bicarbonate on a column of siliceous earth (celite) then eluted with a solution of acetic acid in chloroform and measured spectrophotometrically. This has been also used for separation in combination products.80 For the determination of salicylic acid in presence of aspirin by this method, see Section 5.61. Ion exchange columns filled with strongly or weakly basic anion exchange resin in the acetate or chloride cycle have also been used for separation of aspirin in combination products. 122 123/l2lf This has also been adapted for a student experiment.125 A Sepha-dex-G25 column has been used for the separation of aspirin from salicylic acid.126... 

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