Mass limits of detection

IS(TD) Internal standardisation (calibration) mLOD Mass limit of detection... 

One of the advantages of CE, which is also a disadvantage, is the very small volume needed for analysis. Typical injection volumes are 1-10 nL. This ability to inject small volumes has been shown to be useful in the analysis of single cells and microdialysis samples. Although the concentration-based detection limits of LCEC and CEEC are similar, detection limits based on actual mass analyzed are much lower for CEEC. Typical mass limits of detection for an electroactive compound are in the attomole range. 

The limit of detection (LOD) of a system can be defined in two ways the concentration limit of detection (CLOD) and the mass limit of detection (MLOD). The CLOD of a typical peptide is about 1 jLg/mL using absorbance detection at 200 nm. If 10 nL are injected, this translates to an MLOD of 10 pg at three times the baseline noise. The MLOD illustrates the measuring capability of the instrument. The more important parameter is the CLOD, which relates to the sample itself. The CLOD for HPCE is relatively poor, whereas the MLOD is quite good, especially when compared to HPLC. In HPLC, the injection size can be 1000 times greater compared to HPCE. 

NECEEM-based quantitative affinity analysis is simple, fast, and accurate. The limit of detection is defined by the sensitivity of the detection system used. Eor best systems utilizing laser-induced fluorescence detection, the mass limit of detection can be as low as 1000 molecules and the concentration limit of detection can reach picomolar. 

The same group followed up on this initial design by adding the capability for on-column sample enrichment into the sheathless interface." A small solid-phase extraction cartridge, made of RP material, was attached to the CE capillary near the point of injection. Optimization of the proper capillary diameters showed that they could achieve a mass limit of detection of 500 amol for CE-MS/MS analysis of a standard peptide using a 20-p.m i.d. capillary. This design brings to reality a true zero dead-volume sheathless CE— MS interface with the ability to preconcentrate the sample within the same capillary. 

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