MTBE extraction

The MTBE extraction method was further improved for extraction of lipids from brain samples with mechanical homogenization utilizing ceramic beads to enhance high throughput and automation [40]. Another development based on this method is to utilize an intermediate fraction as well as the aqueous phase for total analysis of lipids and metabolites [41]. 

It seems that the extraction recoveries of many lipid classes examined by the MTBE method are comparable to those using chloroform. The 1-h incubation period may be shortened by using low-power sonication [42] or a microwave oven [43]. One drawback of the MTBE extraction method is that the organic phase contains quite a large amount of aqueous component. This may prolong the evaporation of 

---

Ionic pair extraction 2 x MTBA-HSO4/MTBE extraction centrifugation. Eiltered by 0.1 pm nylon... 

A 100-mL sample aliquot adjusted to pH 11.5 sample extracted with methyl tert-butyl ether (MTBE) chloroacetic acid partitions into aqueous phase basic and neutral compounds in MTBE phase discarded the aqueous phase now adjusted to pH 0.5 and extracted again with MTBE the MTBE extract dried and concentrated chloroacetic acid in the MTBE extract esterified with diazomethane the methyl ester determined by capillary GC on an ECD (U.S. EPA Method 552, 1990). 

The MTBE extract is concentrated down to 2 mL either at room temperature under a stream of dry N2 or on a water bath at 35°C. 

HILIC (Ch. 1.4.5) was promoted for apphcation in bioanalytical LC-MS by Naidong et al. [66-67, 131-132]. In initial studies [131], 5-8-fold and 20-fold gain in sensitivity was achieved in HlLlC for basic and acidic compounds, respectively, compared to reversed-phase LC. The use of HlLlC in the analysis of LOR and DCL was discussed in Ch. 11.4.5 [66]. Different from RPLC, an organic solvent is a weak solvent in HlLlC. This opens the possibility to direct injection of organic extracts from LLE, as demonstrated with MTBE extracts after 96-well plate LLE of LOR and DCL [67]. The potential of HlLlC in bioanalysis with LC-MS was reviewed by Naidong [132]. 

Sample preparation Homogenize liver at 20 mg/mL in 50 mM pH 7.4 TWs-HCl buffer. 200 (xL Plasma or 250 p.L liver homogenate + 250 ng IS -i- pH 7.3 ammonium phosphate buffer -I- MTBE, extract. Remove the organic layer and add it to 250 xL 50 mM phosphoric acid, extract. Remove the aqueous layer and add it to 100 pL MeCN, inject an aliquot. 

Transfer into aqueous phase, TOPO/MtBE extraction, PFBBr deriv. 

Clean-up with hexane, 0.5% TOPO in MtBE extraction at pH2, PEBBr deriv. 

Furrer et al. have tested different solvents to recover PHA and tested the influence on the toxicity of the polymer. The results showed significant differences in endotoxicity of PHA due to the use of different solvents. Ethyl acetate, acetone, tetrahydrofuran (THF), 2-propanol and t-hutyl methyl ether (MTBE) extracts showed a much lower endotoxin content than the extracts with methylene chloride (CH2CI2) and hexane. ... 

Figure 6.52 HPLC assay of meptazinol. Column 125 x 5 (i.d.) mm Spherisorb S5P phenyl-modified silica. Eluent methanolic ammonium perchlorate (/Ommol L , apparent pH 6.7) Flow-rate 2.0mL min Detection V25 grade GCE (+/.0V vs Ag/AgCl) Injection 700 mL MTBE extract of (a) Standard solution containing meptazinol (5 mg L j in equine plasma, (b) Meptazinol-free human plasma, (c) Pla.sma sample from volunteer who had ingested meptazinol (meptazinol concentration 7 mg L ) The initial concentration of the internal standard (imipramine) was 50 mg L in each case Peaks 7 = meptazinol, 2 = imipramine.

---