ELSD

Mengerink et al. [243] describe for the analysis of ether carboxylic acids and mixtures thereof with ethoxylated alcohols an HPLC method with the use of a evaporative light-scattering detector (ELSD). 

Progress has been made in developing electrochemical methods for detection of amino acids without derivatization.74 75 Evaporative light scattering (ELSD) is also a promising detection method.76 Flow-injection analysis... 

As mentioned previously, this detector has been claimed to be universal, i.e., it has been reported that the response of the ELSD is not a function of the nature of the solute. Although this is not, strictly speaking, true, the detector is almost universal. The detector functions by nebulizing column effluent into droplets, which are evaporated in a heated gas stream. A droplet of evaporate, containing some solvent, remains. Light of a wavelength considerably smaller than the evaporate particles, which are 5 to 15 pm in size,161... 

The limit of detection for this instrument is about 10 pg/ ml for polystyrene in 2-butanone,163 which is close to two orders of magnitude higher than that of the deflection-type DRI. Moreover, the response of the ELSD is linear over only two decades in concentration.163 The ELSD is a useful backup detector when the DRI or UV detectors are not appropriate, e.g., when the UV absorbance or RI change is a function of copolymer composition as well as concentration or in gradient elution systems where changes in solvent composition cause drift in baselines of the UV and DRI detectors. Compounds about as volatile as the solvent are poorly detected by ELSD. 

Many of the promising features noticed by Freitag and John [96], Nielson [90] and Jassie et al. [454] have further been developed by Marcato and Vianello [210,461], who have described a unique total concept for in-polyolefin additive analysis based on MAE-HPLC-ELSD/UV. In this procedure Montell has aimed at setting up a total solution scheme for different... 

OSM extracts were analysed by HPLC-UV/ELSD each compound present in the sample solution was identified by comparing its retention time with that of... 

ELSD Evaporative light scattering detector Raleigh scattering of atomised eluent... 

ELSD Quasi-universal No dependence on eluent conditions Droplet size control Moderate sensitivity (low ng) Compound-dependent and non-linear detector response [31,51-53]... 

The most important area for packed column use involves modified mobile phases (MPs). Consequently, pSFC needs detection systems in which the MP modifier and possible additive(s) do not interfere, and in which detection of low or non-UV-absorbing molecules is possible in combination with pressure/modifier gradients. The disadvantage of adding even small amounts of modifier is that FID can no longer be used as a detector. In the presence of polar modifiers in pSFC the detection systems are restricted basically to spectroscopic detection, namely UVD, LSD, MSD (using PB and TSP interfaces as in LC). ELSD can substitute FID and covers the quasi-universal detection mode, while NPD and ECD cover the specific detection mode in pSFC on a routine basis. As ELSD detects non-UV absorbing molecules dual detection with UV is an attractive option. 

No FID with most modifiers (ELSD as a poor substitute)... 

Some typical areas for SFC comprise waxes, surfactants and dyes. Marked advantages of SFC over GC in the analysis of surfactants (e.g. ethoxylates) have been reported [246]. It is arguably the best chromatographic method for the separation of nonionic surfactants, as reviewed by Cserhati and Forgacs [306]. pSFC-UV-ELSD has been used for separation of oligomers of the nonionic surfactant Triton X-100 [249]. 

SFC has played an important role in the extraction and isolation of fatty acids [355,356]. Underivatised fatty acids and methyl esters of fatty acids are surprisingly easy to elute using a bonded phase or a silica based packed column and pure C02, probably due to the long hydrocarbon tails on the molecules [357]. On the other hand, most aromatic and polysubstituted acids will not elute. Triglycerides with saturated fatty acids can be analysed faster with pSCF-ELSD than with GC-FID and do not require sample preparation [358]. Using... 

Specifications for modem detectors in HPLC are given by Hanai [538] and comprise spectroscopic detectors (UV, F, FUR, Raman, RID, ICP, AAS, AES), electrochemical detectors (polarography, coulometry, (pulsed) amperometry, conductivity), mass spectromet-ric and other devices (FID, ECD, ELSD, ESR, NMR). None of these detectors meets all the requirement criteria of Table 4.40. The four most commonly used HPLC detectors are UV (80%), electrochemical, fluorescence and refractive index detectors. As these detectors are several orders of magnitude less sensitive than their GC counterparts, sensor contamination is not so severe, and... 

UV/VIS, F RI ECD, ELCD ELSD, MS UV-grade non UV-absorbing solvents No mobile phase gradients Conducting mobile phase Volatile solvents and volatile buffers... 

RPLC-ELSD has been used for analysis of polyolefin additives [678], Improvements in sensitivity by use of narrow-bore columns were reported. MAE-RPLC-ELSD/UV (273 nm) has been proposed as a universal one-step and/or two-step procedure for the analysis of additives in polyolefins (Section 3.4.5.1), with the reference mixture of standard additives for... 

Aromatic amines formed from the reduction of azo colorants in toy products were analysed by means of HPLC-PDA [703], Drews et al. [704] have applied HPLC/ELSD and UV/VIS detection for quantifying SFE and ASE extracts of butyl stearate finish on various commercial yarns. From the calibrated ELSD response the total extract (finish and polyester trimer) is obtained and from the UV/VIS response the trimer only. Representative SFE-ELSD/UV finish analysis data compare satisfactorily to their corresponding SFE gravimetric weight recovery results. GC, HPLC and SEC are also used for characterisation of low-MW compounds (e.g. curing agents, plasticisers, by-products of curing reactions) in epoxy resin adhesives. 

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