This limitation is caused by the small sample injection amount and the narrow separation window of capillary electrophoresis compared with HPLC.
The capabilities of the new CE/ESI-MS CE/ESI-MSin platformng hinh-throughperformingantitative sample analyses were demonstrated by the repeated sample injection without interrupting andongoing separation and a linear dependence of the total analyte ion abundance on the sample plug volume using a mixture of peptide standards.
In order to estimate the possible influence of the cartridge treatment on the perchlorate result, the equivalency of the analytical data obtained by direct sample injection (fundamental analytical procedure) and of the data obtained after injecting the sample after treatment (overall analytical procedure) the method of orthogonal regression described in [29] was used.
The former approach is inadequate for sample preconcentration, whereas the latter can be performed by sample injection into the capillary and subsequent EKI of strong acid (see Fig. 1c).
In our work, we focussed on perchlorate determinations that are being carried out by direct sample injection without heart-cutting techniques using standard analytical IC equipment, addressing the laboratory workflow needs, as well as the analytical and financial requirements of future users.
Limits of detection for the selected target compounds were from 0.003 to 0.01 μg/L and 0.01 to 0.5 μg/L, in MS and MS/MS mode, respectively – by direct sample injection of 100 μL.
On the other hand, a significant improvement of detection sensitivity in CE can be successfully obtained by means of sample injection techniques and careful selection of sample matrix and background electrolyte (BGE) composition [ 1– 4].
The method facilitates detection of weak binding events in a broad affinity range and could be used as a primary screening tool where ranking of binders in terms of affinity constants can be obtained by a single sample injection.
As shown in Figure 2, the relative size of the free drug fraction was affected by the flow rate used for sample injection.
The dynamic range of the quantified proteins is about 3 logs, and proteins unique to one condition or another were only observed above the LOD of the experiment, which was determined by the sample normalization prior to injection.
