Injection large volume

HOPC uses a column packed with porous materials that have a pore diameter close to a dimension of the solvated polymer to separate. A concentrated solution of the polymer is injected into the solvent-imbibed column by a high-pressure liquid pump until the polymer is detected at the column outlet. The injection is then switched to the pure solvent, and the eluent is fractionated. A schematic of an HOPC system is illustrated in Fig. 23.1. A large volume injection of a concentrated solution makes HOPC different from conventional SEC. 

The main aims in environmental analysis are sensitivity (due to the low concentration of microcontaminants to be determined), selectivity (due to the complexity of the sample) and automation of analysis (to increase the throughput in control analysis). These three aims are achieved by multidimensional chromatography sensitivity is enhanced by large-volume injection techniques combined with peak compression, selectivity is obviously enhanced if one uses two separations with different selectivi-ties instead of one, while on-line techniques reduce the number of manual operations in the analytical procedure. 

Figure 13.10 LC-LC chromatogram of a surface water sample spiked at 2 p.g 1 with ati azine, and its metabolites (registered at 220 nm). Conditions volume of sample injected, 2 ml clean-up time, 2.60 min ti ansfer time, 4.2 min The blank was subtracted. Peak identification is as follows 1, DIA 2, HA 3, DEA 4, atrazine. Reprinted from Journal of Chromatography, A 778, F. Hernandez et al, New method for the rapid detemiination of triazine herbicides and some of thek main metabolites in water by using coupled-column liquid cliromatography and large volume injection , pp. 171-181, copyright 1997, with permission from Elsevier Science.

J. V. Sancho, C. Hidalgo and P. Hernandez, Direct determination of bromacil and diuron residues in environmental water samples by coupled-column liquid cliromatog-raphy and large-volume injection , 7. Chromatogr. 761 322-326 (1997). 

C. Hidalgo, J. V. Sancho and P. Hernandez, Trace determination of triazine herbicides by means of coupled liquid cliromatography and large volume injection . Anal. Chim. Acta33 223-29(1993). 

E. A. Hogendoorn, C. Verscliraagen, U. A. Th Brinkman and van P. Zoonen Coupled column liquid chr omatography for the tr ace determination of polar pesticides in water using dhect large-volume injection method development strategy applied to methyl isothiocyanate , Awn/. Chim. Acm 268 205-215 (1992). 

K. Grob and M. Biedeimann, Vapoi ising systems foi large volume injection oi on-line ti ansfer into gas cltromatography classification, critical remarks and suggestions , 7. Chromatogr. 750 11-23 (1996). 

H. G. J. Mol, H.-G. M. Janssen, C. A. Cramers, J. J. Vreuls and U. A. Th Brinkman, Trace level analysis of micropollutants in aqueous samples using gas chr omatography with on-line sample enrichment and large volume injection , 7. Chromatogr. 703 277-307(1995). 

Chiaia AC, Banta-Green C, Field J (2008) Eliminating solid phase extraction with large-volume injection LC/MS/MS analysis of illicit and legal drags and human urine indicators in US wastewaters. Environ Sci Technol 42(23) 8841-8848... 

The advantages offered by large-volume injection (LVI) GC are described in recent... 

Direct sample injection and large-volume injection... 

Cortes, H. J., Campbell, R. M., Himes, R. P., and Pfeiffer, C. D., On-line coupled liquid chromatography and capillary supercritical fluid chromatography large-volume injection system for capillary SFC, ]. Microcol. Sep., 4, 239, 1992. 

Several sample preparation techniques are performed inside the inlet system. Large-volume injection can be carried out by a number of methods including programmed temperature vaporisation (PTV). Automated SPE may be interfaced to GC using a PTV injector for large volume injection. SPE-PTV-GC with on-column injection is suited to analysis of thermola-bile compounds. 

There are basically three methods of liquid sampling in GC direct sampling, solid-phase extraction and liquid extraction. The traditional method of treating liquid samples prior to GC injection is liquid-liquid extraction (LLE), but several alternative methods, which reduce or eliminate the use of solvents, are preferred nowadays, such as static and dynamic headspace (DHS) for volatile compounds and supercritical fluid extraction (SFE) and solid-phase extraction (SPE) for semivolatiles. The method chosen depends on concentration and nature of the substances of interest that are present in the liquid. Direct sampling is used when the substances to be assayed are major components of the liquid. The other two extraction procedures are used when the pertinent solutes are present in very low concentration. Modem automated on-line SPE-GC-MS is configured either for at-column conditions or rapid large-volume injection (RLVI). 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

Cold splitless WCOT thick film Idem Reproducible and accurate sampling Controlled evaporation No discrimination on basis of b.p. Large volume injection Low detection limits Minimisation of solvent entering column Allows polar solvents Automation Small sample size introduction (<2 xL) Thermal degradation possible (long residence times of components in liner)... 

The traditional sample volumes in CGC (0.1-3 xL) limit sample preparation possibilities. Specialised large-volume injection (LVI) techniques are designed to load more sample in the GC system (typically 150 xL) by placing a length of uncoated fused-silica tubing in front of the analytical column. This procedure also provides... 

Principles and Characteristics Although early published methods using SPE for sample preparation avoided use of GC because of the reported lack of cleanliness of the extraction device, SPE-GC is now a mature technique. Off-line SPE-GC is well documented [62,63] but less attractive, mainly in terms of analyte detectability (only an aliquot of the extract is injected into the chromatograph), precision, miniaturisation and automation, and solvent consumption. The interface of SPE with GC consists of a transfer capillary introduced into a retention gap via an on-column injector. Automated SPE may be interfaced to GC-MS using a PTV injector for large-volume injection [64]. LVI actually is the basic and critical step in any SPE-to-GC transfer of analytes. Suitable solvents for LVI-GC include pentane, hexane, methyl- and ethylacetate, and diethyl or methyl-f-butyl ether. Large-volume PTV permits injection of some 100 iL of sample extract, a 100-fold increase compared to conventional GC injection. Consequently, detection limits can be improved by a factor of 100, without... 

Particulate matter is defined in the USP as extraneous, mobile, undissolved substances, other than gas bubbles, unintentionally present in parenteral solutions. Test methods and limits for particulates are stated in the USP for large-volume injections and small-volume injections. 

The preservation efficacy aspects of parenteral products are particularly important for those products that are permitted to contain preservatives. This is not allowed for large-volume injections or for any product gaining access to the cerebrospinal fluid or for intra- or retro-ocular injection (according to the Ph Eur). Unpreserved products should be labeled to state this unequivocally. 

Blood Fluoride reactivation method Phospho-rylated BuChE (+ other proteins) GC-MS GC-HR-MS With large volume injection Phosphonofluo- ridates i.s. deuterated OP or plasma exposed to deuterated OP Easily accessible internal standards and reference compounds LOD 10 pg/ml (0.05-0.1% BuChE inhibition) Not applicable to all OP s... 

Large volume injection Miniaturization of sample preparation... 

The problems relating to increased contamination levels and/or insufficient sensitivity may be overcome by using matrix-solid phase dispersion, MS detection in selected ion monitoring (SIM) mode, and/or large volume injection. An example of combined analysis that utilizes specific detection is shown in Fig. 2.6. It entails simultaneous analyses of PAHs, PCBs, chlorobenzene, and organochlorine pesticides in soil. 

Programmed temperature vaporization (PTV) Most versatile inlet Allows large volume injection Little-no sample degradation Effective trace (to sub-ppb) analysis Expensive Requires optimization of many parameters Not well-known... 

Determination ofNitrosamines in Drinking Water by SPE and Capillary Column GC with Large Volume Injection... 

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