SPE-HPLC

ON-LINE COUPLING OF SPE-HPLC-MS/MS FOR FAST TRACE ANALYSIS OF PESTICIDES IN DRINKING AND SURFACE... 

The chemical composition of caramel color is not yet fully understood but some compounds identified in the low weight fraction are considered caramel markers. All caramel classes contain 5-hydroxymethyl)-2-furaldehyde (5-HMF). In caramel classes in and TV, 4-methyUmidazole (4-MeI) has been detected, while 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI) was found only in class HI caramel colors. The analysis of five caramel III samples by SPE/HPLC-MS revealed concentrations between 28.3 and 46.8 iglg THI and 73.3 to 187.8 for 4-MeP (see Figure 5.2.3). 

Homero-Mendez, D., Gandul-Rojas, B., and Mmguez-Mosquera, M.L, Routine and sensitive SPE-HPLC method for quantitative determination of pheophytin a and pyropheophytin a in olive oil. Food Int., 38, 1067, 2005. 

SPE-HPLC and SPME-GC (cf. Sections 7.1 and 7.2). For meaningful results it is crucial to dispose of the correct interface between the various combined techniques. 

Table 7.17 Main features of on-line SPE-HPLC(-MS) coupling...

Development and validation of protocols for solid-phase extraction coupled to LC and LC-MS have been described [136]. Hennion [137] has reviewed online SPE-HPLC coupling followed by various detection modes. 

Mass spectrometry can be specific in certain cases, and would even allow on-line QA in the isotope dilution mode. MS of molecular ions is seldom used in speciation analysis. API-MS allows compound-specific information to be obtained. APCI-MS offers the unique possibility of having an element- and compound-specific detector. A drawback is the limited sensitivity of APCI-MS in the element-specific detection mode. This can be overcome by use of on-line sample enrichment, e.g. SPE-HPLC-MS. The capabilities of ESI-MS for metal speciation have been critically assessed [546], Use of ESI-MS in metal speciation is growing. Houk [547] has emphasised that neither ICP-MS (elemental information) nor ESI-MS (molecular information) alone are adequate for identification of unknown elemental species at trace levels in complex mixtures. Consequently, a plea was made for simultaneous use of these two types of ion source on the same liquid chromatographic effluent. 

Gon9alves J.C.S. et al., 2005. Online solid-phase extraction coupled with high-performance liquid chromatography and tandem mass spectrometry (SPE HPLC-MS-MS) for quantification of bromazepam in human plasma. Ther Drug Monit 27 601. 

Papadopouluo-Mourkidou E. et al., 2001. Use of an automated online SPE-HPLC method to monitor caffeine and selected aniline and phenol compounds in aquatic systems of Macedonia-Thrace, Greece. Frese-nius J Anal Chem 371 491. 

RP-HPLC has been employed for the determination of flavonoids and other phenolic compounds in cranberry juice. The neutral and acidic analytes were preconcentrated octadecyl silica SPE cartridges conditioned with distilled water (neutral analytes) or with 0.01 M HC1 (acidic compounds). Hydrolysis of samples was carried out in aqueous methanol solution acidified with 6 M HC1 at 35°C for 16h. Chromatographic separation was performed in an ODS column (150 X 4.6mm i.d. particle size 5/.an). Solvents A and B were water-acetic acid (97 3, v/v) and methanol, respectively. The gradient started with 0 per cent B (flow rate, 0.9 ml/min), reached 10 per cent B in lQmin (flowrate, 1.0 ml/min) and increased to 70 per cent B in 40min (flowrate, 1.0 ml/min). Analytes were detected at 280 and 360 nm. Some typical chromatograms are presented in Fig. 2.71. The concentrations of flavonoids and phenolic acids are compiled in Table 2.69. It was stated that the SPE-HPLC procedure makes possible the simultaneous determination of phenolic compounds and flavonoids, therefore, it can be employed for the measurement of these classes of analytes in other fruit juices [188],... 

In particular, the priority pollutant phenols (PPP), identified by EPA since the 1970s are widespread water pollutants that must receive the greatest attention due to their recognized toxicity. For the separation of eleven PPP, an ion-interaction reagent (HR) RP HPLC/UV method has been developed that allows limits of detection lower than 30 J,g in river waters, after LLE in dichlo-romethane and a 500-fold pre-concentration [82]. Through on-line SPE followed by both UV and electrochemical detection [83], 16 priority phenols have been determined in water samples with the LOD value for chlorophenols lower than 1 ng L [84]. LODs at ng L levels were obtained for all the PPPs in samples of river water, employing a relatively small volume of sample through an on-line SPE HPLC/MS method with an APCI source. 

A fully automated on-line SPE-HPLC-MS-MS method was developed and validated for the direct analysis of 14 antidepressants and their metabolites in plasma by de Castro et al. [75]. After direct injection of 50pL of plasma without prior sample pre-treatment, gradient RP separation was completed in 14 min, with a sample throughput of 3h. LOQs were estimated to be at 10 ng/ mL. Analytes proved to be stable during sample process with the exception of clomipramine and norclomipramine. 

E Brandsteterova, P Kubalec, P Simko, L Machackova. SPE-HPLC determination of trimethoprim in tissue samples. Pharmazie 51 984-986, 1996. 

The SAMOS is based on SPE-HPLC-DAD. In one study, which applied SAMOS in analyzing samples from six European rivers, nearly all cases found one or more pesticide in concentrations over 1 ytig/L in many cases the pesticides were OCPs or OPPs (53). 

Galceran et al. (199) developed an SPE-HPLC method for the determination in beef extract of five mutagenic amines, namely Trp-P-1 (3-amino-1,4-dimethyl-5//-pyrido[4,3-fc]indole),... 

Body fluids, such as serum, contain several different carotenoids in low amounts. The crucial point in the isolation and analysis of these samples is the enrichment factor. Serum samples can be directly analysed with hyphenated extraction-sample enrichment-separation systems, such as on-line SPE-HPLC employing tailored stationary phases [29]. By using special restricted access materials (RAMs) for sample enrichment, the carotenoids are retarded on the pre-column while the protein binding is broken and the macromolecules are eluted. The preparation of artifacts is hindered, as the whole analysis steps take place under conditions of light- and oxygen-exclusion. The scheme of on-line SPE-HPLC is presented in Figure 5.2.2. 

Figure 5.2.2 Scheme for the isolation and separation of geometrical carotenoid isomers from serum samples employing on-line solid phase extraction (SPE)-HPLC coupling... 

Koal, T., A. Asperger, J. Efer, and W. Engewald (2003). Simultaneous determination of a wide spectrum of pesticides in water by means of fast on-line SPE-HPLC-MS-MS - a novel approach. Chromatogr. Suppl., 57 S93-S101. 

CME Capillary microextraction Fused silica capillary of up to 40 cm coated internally with the stationary phase analyte elution by solvent Suited for on-line SPE-HPLC, for example, with MTMS/ PEO-coated capillary... 

On-line SPE is the most elegant, but at the same time the most difficult enrichment technique to implement. On-line SPE-GC requires a dedicated interface that allows the introduction of the large solvent volume needed for the elution of the SPE cartridge. For on-line SPE-HPLC, which can be performed with simple valve-switching systems as well as with dedicated instrumentation (Figure 13.10), a number of restrictions have to be taken into consideration. 

FIGURE 13.10 Generic setup for (a) on-line SPE-HPLC implemented with a simple valve-switching system (G. Maio, R. Morello, F. Arnold, and K.-S. Boos, Analysis of Antimycotic Drugs in Biofluids by On-Line SPE-LC Application note LPN 1859-01 06/06 Diones Corporation, Sunnyvale, CA 94088-3603 Figure 2, p. 1, 2006. With permission.) and for (b) on-line SPE-GC implemented with a large volume injector with a solvent venting option. 

Selected data published by Patsias and Papadopoulou-Mourkidou [114] illustrate sorption s dependence on sample volume (Figure 2.36). Their research pursues development of an automated online SPE-HPLC methodology for analysis of substituted anilines and phenols. Recovery (%) was measured for numerous compounds on various polymeric sorbents, but the only data presented here are those in which a styrene-divinylbenzene polymeric sorbent was used for analysis of aniline, phenol, 4-nitroaniline, and 4-nitrophenol. Aqueous sample volumes of 5, 10, 25, 50, 75, 100, 125, and 150 mL were acidified to pH 3 before SPE. 

Fig. 1 Using a T-piece between HPLC and MS, a syringe pump can be utilized to infuse a constant flow of analytes at therapeutic concentrations whilst drug spiked whole blood samples are delivered via SPE-HPLC. Ion traces of the analytes (here everolimus at 6 ng/ml) are recorded. In this particular case, no ion yield attenuation due to the spiked drug can be observed, although strong effects can be seen in the solvent front elution zone shortly prior to the analyte elution time window...

ASPEC XL Gilson Medical Electronics, Box 27, Middletown, WI SPE, HPLC injection PC or front panel/basic Serial or batch Standard SPE columns... 

SPME is also an excellent tool for extracting compounds amenable to GC, which provides an alternative to well-established sample preparation methods for polar compounds based on on-line SPE-HPLC. 

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