Elution extraction cartridge

Repaglinide stock solution in MeOH then diluted with water Sample SPE continued with LLE Sample added with 250 ml water and 500 ml 0.1 ammonium acetate, then loaded on 1 ml Chem Elut extraction cartridge. LLE performed with 4 ml dicholorometane, dried, and reconstituted with 200 [A of mobile phase... 

The use of extraction cartridges in the separation of azines, discussed in the last Section, is an example of on-column concentration using off-line column switching. A chromatogram can be cut off-line by collecting the zones of interest at the detector outlet followed by reinjection of the collected fraction onto a secondary column. The mobile phases used with the two columns should be compatible, eg they should be miscible and the mobile phase used with the first column should not have too high an eluting power in the second column. If the mobile phases are incompatible it may be possible to evaporate the primary mobile phase and redissolve the sample in a suitable solvent. 

Emara [53] developed a rapid, simple, accurate and reproducible method for the quantitative determination of niclosamide ethanolamine salt (NES), the most widely used molluscicide against snail vectors of schistosomiasis, in both distilled and natural canal waters. The biocide was extracted completely from water samples by passing through Sep-Pak Ci8 cartridge and eluting the cartridge with methanol. The eluate was then analyzed directly for NES by UV Vis spectrophotometry at 330 nm [53]. 

Direct elution of analyte from extraction cartridge into LC system... 

Other techniques to improve throughput are instrumentation based and may involve multiple HPLC systems. The simplest method involves the automated use of solid phase extraction cartridges for sample cleanup followed by direct injection into the mass spectrometer [114], Coupling of multiple HPLC systems to one mass spectrometer allows one column to equilibrate and separate while another column to flow into the mass spectrometer. Multiple HPLC systems may be configured such that the mass spectrometer is only exposed to each serial HPLC eluent as the analyte of interest is eluted [115,116]. Although multiple H P LC-based methods may increase throughput, they also typically decrease sensitivity and may confound data workup and interpretation. 

For tissue analysis, the sample is extracted with ethyl acetate in the presence of sodium chloride and piperonyl butoxide. After centrifugation, the supernatant is evaporated to dryness, and the residue is dissolved with dichloromethane/ hexane (1 1) to be applied onto a Bond-Elut silica cartridge. Following successive cartridge washing with petroleum ether and ethyl acetate/hexane (4 6), chloramphenicol is eluted with ethyl acetate/hexane (7 3) and the eluate is evaporated to dryness. The residue is dissolved in 0.05 M Tris/hydrochloric acid buffer pH 10.4, extracted with diethyl ether, and the extract is evaporated to dryness. Tlie... 

To obtain clear solutions, the extracts are either filtered or centrifuged and the residues reextracted with the same solvents (108). Another possibility is to transfer the chlorophylls from the acetone phase into an ether phase by adding sodium chloride (114) or sodium sulfate (93). More recently acetone extracts were purified and fractionated with C18 solid-phase extraction cartridges, and dephytylated pigments were eluted with 70% acetone and phytylated pigments with 90% acetone (115). Often a concentrating of the pigment solution with a rota-evaporator under vacuum is necessary before analysis. Chlorophyll extracts should be analyzed as soon as possible, but if they have to be stored they must be kept in the cold and dark (107). 

Silica gel Vortex cream with hexane-ethyl acetate (1 1). Add to extraction cartridge and wash with hexane-acetone (8 2). Dry sorbent, elute with methanol. 

The Zymark and Gilson ASPEC workstations process solid-phase extraction samples sequentially without the intervention of a human analyst. These workstations are programmed to activate extraction cartridges with solvent to prepare them to receive a specimen. After the sample application, cartridges are washed to remove impurities. The analytes of interest are then eluted into collection tubes or injected onto a liquid chromatograph for sequential analysis. 

DEC and the internal standard (Istd), 1-diethylcar-bamyl-4-ethyl piperazine HC1 (E-DEC), were extracted from human plasma - that has been alkalised with carbonate buffer - after loading onto a conditioned Cl8 solid phase extraction cartridge, rinsed with water and eluted with methanol. After evaporation under a stream of nitrogen and reconstitution in methanol, 3 il. were injected into the GC system and detected using a flame ionization detector (FID). The retention time for DEC was 5.5 min and for the internal standard (E-DEC) it was 7.28 min. 

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