Eluents buffered

Change eluent, buffer components Wash column with water then methanol Wash and fix injector and pump Dilute cone, buffer and counter-ion Select appropriate wavelength Wash flow cell with water and methanol... 

Eluent buffers A 0.067 M sodium citrate, 0.33 mM thymol, pH 3.0, except pH 5.0 for furosine analysis B 0.25 M sodium nifrafe, 0.024 M boric acid, pH 10.2 (pH adjusted with NaOH and HNO3). 

Two separate analyses of a sample, utilizing two eluent buffer systems of different ionic strength, are required for the complete characterization of a sample because As(lll), if present in the sample, will interfere with the resolution and determination of DMA. The two eluent buffers which are used are Eluent 1 - 0.0024 M NaHC03/0.0019 M Na2C03/0.001 M NapB Oj and Eluent 2 - 0.005 M... 

Particle size (pm) Eluent buffer ve/vt enantiomer l-> (+) Selectivity factor... 

As mentioned previously, the analysis of amphetamines and other basic drugs was one of the first forensic applications of HPLC. Many analyses of basic drugs are still performed by the same method of ion-exchange chromatography on unmodified silica columns with an eluent buffered to about pH 9. Dissolution of the silica in the analytical column is prevented by using a pre-saturation column which is packed with a 40 pm particle size silica. This type of column is situated in the eluent line between the pump and the injection valve and should always be used when performing analyses with aqueous eluents on silica-based columns. By using these columns the lifetime of the analytical column can be extended considerably. 

Gentle and flexible because it uses a wide range of eluents/buffers/detectors. 

A similar example in which 5-fluorouracil has been included demonstrates the wide appUcability of reversed phase systems coupled with aqueous phosphate buffers for the separation of nucleoside bases (Miller et al., 1982). This study also includes a useful comparison of nine different analytical reversed phase columns in combination with different isocratic conditions and clearly demonstrates subtle differences between them. The study concluded that the best stationary phase to maximise the resolution of the test compounds was Spheri-sorb ODS-2 in combination with ammonium phosphate (pH 3.5) as eluent buffer (Fig. 11.1.3). 

FIGURE 47.7 Layout of the microfluidic chip including running buffer reservoir (1), eluent buffer reservoir (2), sample reservoir (3), sample waste reservoir (4), washing reservoirs (5,6) and waste reservoir (7) and electropherograms of human serum albumin detected above (a) and below the affinity monolith column with immobilized Pisum sativum agglutinin (b). (Reprinted with permission from Mao, X., et al.. Anal. Chem., 76, 6941, 2004. Copyright 2004 American Chemical Society.)... 

Optimum capacity factors were obtained on columns of intermediate capacity (27 and 46 p,moFg). Retention times decreased with an increase in eluent buffer concentration, typically by half with a doubling of buffer concentration. " ... 

Compound Eluent buffer pH Acetonitrile. buffer Potential (V) (vs Ag/AgCl) Extraction LLoQ (pg L- ) Reference... 

Isocratic separations are performed with an eluent at a constant concentration of eluent buffer or salt solution. Isocratic elution is desirable because it is simpler, but it is sometimes necessary or desirable to perform separations using eluent... 

The quahty of the eluent solvent is critical to achieve a low background signal. The amount of residue after evaporation must be less than 1 mg L . Solvents must be filtered through compatible sub-micron filters (0.4 or 0.2 pm). Ttlso, if possible, samples must also be filtered with special filters before injection. Obviously, the salt or buffer in the eluent is also important because this can produce a background signal. The ideal eluent solvent for this detector contains no salts or buffers. Another possibility is to remove the eluent buffer with a suppressor device before detection. Of course this may Hmit the types of chromatography... 

Figure 5.28 Separation of a hydrolysate standard on a totally sulfonated cation exchanger. Column LCA K06 temperature program 68-80 °C from 0-1 min, 80 °C from 1 -6 min, 80-66 °C from 6-9 min, 66 °C from 9-22 min, 66-74 °C from 22-47 min, 74 °C from 47-63 min, 74-64 °C from 63-68 min, and 64 °C until 76 min eluent buffer A-4/Na, A-5/...

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