Solid phase extraction drug analysis

Shinozuka T, Terada M, Tanaka E (2006) Solid-phase extraction and analysis of 20 antidepressant drugs in human plasma by LC/MS with SSI method. Forensic Sci Int 162 108-112... 

Description of Method. Fluoxetine, whose structure is shown in Figure 12.31a, is another name for the antidepressant drug Prozac. The determination of fluoxetine and its metabolite norfluoxetine. Figure 12.31 b, in serum is an important part of monitoring its therapeutic use. The analysis is complicated by the complex matrix of serum samples. A solid-phase extraction followed by an HPLC analysis using a fluorescence detector provides the necessary selectivity and detection limits. 

Kasprzyk-Hordern B, Dinsdale RM, Guwy AJ (2008) Multiresidue methods for the analysis of pharmaceuticals, personal care products and illicit drugs in surface water and wastewater by solid-phase extraction and ultra performance liquid chromatography-electrospray tandem mass spectrometry. Anal Bioanal Chem 391(4) 1293-1308... 

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

The study concluded that Once wash steps are optimized, samples prepared by solid phase extraction are cleaner than those prepared by protein precipitation. Samples prepared by extraction with a Multi-SPE plate resulted in lower LOQs than samples prepared by solvent precipitation. Drug recoveries were acceptable (>80%) for both the SPE and the solvent precipitation methods. Well-to-well reproducibility of samples was slightly better with extraction with a Multi-SPE plate. Evaporation and reconstitution, while more time-consuming, yield better chromatographic performance, allow analysis of lower concentration samples, and require optimization for good analyte recovery. 

Zang X. et al., 2005. A novel online solid-phase extraction approach integrated with a monolithic column and tandem mass spectrometry for direct plasma analysis of multiple drugs and metabolites. Rapid Commun Mass Spectrom 19 3259. 

Huang Z-P, Chen X-H, Wijsbeek J, Franke J-P, de Zeeuw RA. 1996. An enzymic digestion and solid-phase extraction procedure for the screening for acidic, neutral, and basic drugs in liver using gas chromatography for analysis. J Anal Toxicol 20 248. 

When using PFT with a neutral selector, it is quite difficult to avoid any entrance of the chiral selector into the ionization source, particularly at a high pH, where EOF is important. The use of BGE at low pH and/or coated capillary to minimize EOF is therefore mandatory. However, the coaxial sheath gas, which generally assists the ionization process, leads to an aspirating phenomenon of the chiral selector in the MS direction. Javerfalk et al. were the first to apply PFT with a neutral methyl-/i-CD for the separation of racemic bupivacaine and ropivacaine with a polyacrylamide-coated capillary and an acidic pH buffer (pH 3). Cherkaoui et al. employed another neutral CD (HP-/1-CD) with a PVA-coated capillary for the analysis of amphetamines and their derivatives. To prevent a detrimental aspiration effect, analyses were carried out without nebulization pressure. Numerous other studies presented excellent results such as the enantioselective separation of adrenoreceptor antagonist drugs using tandem mass spectrometry (MS/MS) the separation of clenbuterol enantiomers after solid-phase extraction (SPE) of plasma samples or the use of CD dual system for the simultaneous chiral determination of amphetamine, methamphetamine, dimethamphetamine, and p-hydroxymethamphetamine in urine. 

Diethylstilbestrol is particularly difficult to quantitate below 1.0 ppb in bovine tissues, especially in liver, which is among the last tissues to contain diethystilbestrol after cattle are withdrawn from receiving tire drug (101, 102). Interferences from tissue matrix constitute a major problem that might be due to nonspecific interference of lipids and fatty compounds (103, 104). In addition, problems with false-positive results often appear in urine analysis unless a chromatographic step such as a solid-phase extraction cleanup (105, 106) is introduced. Simple sample preparation procedures such as those based on solvent extraction and liquid-liquid partitioning do not usually give satisfactory results (107, 108). 

In contrast to liquid-liquid partitioning cleanup, which is particularly suitable for individual drugs or groups of drugs with similar chemical properties, solid-phase extraction is more appropriate for multiresidue analysis. On that account, solid-phase extraction in combination with liquid-liquid partitioning has become the method of choice in many laboratories for the purification of residues of sedatives and -blockers that may occur in biological matrices. Purification is usually accomplished on reversed-phase solid-phase extraction columns. Optimum retention of seven sedatives and carazolol on a reversed-phase solid-phase extraction column was reported when 10% sodium chloride solution was added to the acetonitrile hssue extract prior to its solid-phase extrachon cleanup (523, 524). A silica-based diol solid-phase extraction column was further suggested for efficient isolation of sedative and -blocker residues from food extracts (526). 

Mallet, C. R., Mazzeo, J. R., and Neue, U. (2001). Evaluation of several solid phase extraction liquid chromatography/tandem mass spectrometry on-line configurations for high-throughput analysis of acidic and basic drugs in rat plasma. Rapid Commun. Mass Spectrom. 15 1075-1083. 

Figure 11.5 Chromatograms of plasma samples obtained with fully automated on-line SPE-LC (a) drug-free human plasma (b) human plasma spiked with omeprazole (100 ng/ml) and phenacetin (internal standard 1000 ng/ml). Reprinted from Journal of Pharmaceutical and Biomedical Analysis, 21, G. Garcia-Encina et al., Validation of an automated liquid chromatographic method for omeprazole in human plasma using on-line solid-phase extraction, pp. 371-382, copyright 1999, with permission from Elsevier Science.

Electropherograms of a urine sample (8 ml) spiked with non-steroidal anti-inflammatory drugs (10 (Jig/ml each) after direct CE analysis (b) and at-line SPE-CE (c). Peak identification is as follows I, ibuprofen N, naproxen K, ketoprofen F, flurbiprofen. Reprinted from Journal of Chromatography, B 719, J. R. Veraart et al., At-line solid-phase extraction for capillary electrophoresis application to negatively charged solutes, pp. 199-208, copyright 1998, with permission from Elsevier Science. 

Relative standard deviation of repeat HPLC analysis of a drug metabolite standard was between 2 and 5%. Preliminary measurements of several serum samples via solid-phase extraction cleanup followed by HPLC analyses showed that the analyte concentration was between 5 and 15 mg/L and the standard deviation was 2.5 mg/L. The extraction step clearly increased the random error of the overall process. Calculate the number of samples required so that the sample mean would be within +1.2 mg/L of the population mean at the 95% confidence level. 

De Boeck G, Samyn N (2005) Quantitative analysis of multiple illicit drugs in preserved oral fluid by solid-phase extraction and liquid chromatography-tandem mass spectrometry. Forensic Sci Int 150(2-3) 227-238. doi S0379-0738(05)00131-3 [pii] 10.1016/j. 

The analysis of compounds of pharmaceutical relevance is one of the most promising application areas for CEC—MS, because it offers high sensitivity, high selectivity and structural information [38,98,99,105], Paterson et al. [105] utilized CEC—ESI-MS for the analysis of potential drug candidates down to the 1 ng/ml level in solid-phase extracts of plasma samples. Relative standard deviations of retention time and peak area of 0.4-1.7% and 2.6-10.7%, respectively, were achieved, which proves, that the method is also applicable to quantitative analysis. The analysis of a pair of... 

T. Hirai, Usability of a normal solid-phase extraction as the sample clean-up procedure for urinary drug analysis by high-performance liquid chromatography, CCAB 97 Mini Review, http //neo.pharm.hiroshima-u.ac.jp/ccab/lst/mini review/mr002 /hirai.html (August 1, 2002). 

As early as 1997, Taylor et al. [57] demonstrated the gradient separation of corticosteroids in extracts of equine urine and plasma (Figure 10). The sample were purified using solid-phase extraction and automated dialysis, respectively. A reproducibility study revealed that peak broadening occurred only after the analysis of 200 urine extracts. Later, Stead et al. observed that on-line sample concentration could be easily achieved, as longer injection times had minimal influence on peak shape [58]. They demonstrated that the CEC separation of steroids in plasma was superior to HPLC. Several other groups also reported successful CEC separations of drugs and major metabolites in extracts of urine and plasma [59-62],... 

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