Plasma-chemical extraction technique

Procedures for chemically pretreating archaeological samples typically involve an acid-base-acid treatment 31, S2). However, we routinely eliminate both acid washes as we have shown them to be unnecessary with our plasma-chemical extraction technique. Carbonate and oxalate carbon are not extracted by the plasma only organic material was removed for radiocarbon measurements (33,34), Samples are immersed in -I M NaOH and placed in an ultrasound bath for an hour at 50 5 C. When the resulting supernatant was colored, subsequent NaOH washes were performed until the supernatant... 

Statistical analysis shows no significant systematic variation in our results with plasma-chemical extraction and those determined at other laboratories using conventional and AMS. analysis with combustion extraction. That includes the outlying TIRI wood sample that may have been influenced by plasticizers (5) and effects introduced by different pretreatments of charcoal 4 (18). Our technique appears to produce accurate and viable dates. 

No analytical technique is entirely non-destructive. However, plasma-chemical carbon extraction is more attractive than combustion methods for some types of artifacts. While some deleterious effect may in the future be observed for artifacts that have undergone plasma extraction, removing a portion of the artifact for destmctive combustion in many cases is not an option for a variety of reasons (i.e., ratio of artifact size to the amount that must be removed for analysis, information content of sample stmcture, rarity or uniqueness of object). 

McLoughlin, D.A., Olah, T.V., and Gilbert, J.D. 1997. A direct technique for the simultaneous determination of 10 drug candidates in plasma by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry interfaced to a Prospekt solid-phase extraction system. J. Pharm. Biomed. Anal. 15 1893. 

As discussed above, marijuana contains four constituents (viz,I-IV) similar in structure and chemical properties whereas the metabolites are more polar and in the case of V and VI, more acidic than I. Thus it seemed plausible that I-IV could be separated from V and VI in plasma based upon pH adjustment and solvent extraction properties. Compounds I-IV were found to be extractable at ambient pH of 7.4 using petroleum ether whereas V and VI could be extracted at pH 4.1 using 99 1, benzene isopropanol. Once the initial plasma separation was effected a chromatographic separation was feasible using normal phase conditions for I-IV and reverse phase conditions for V and VI. Each technique is detailed in the following sections. 

Various methods are available for the separation of biochemicals. These include physical methods of centrifugation and filtration, chemical methods of precipitation and extraction, and interactive techniques, such as electrophoresis and chromatography. These methods are employed to perform the steps necessary to purify biological materials from complex solutions. The isolation of a specific component (e.g. a protein) from a plasma source or a fermentation broth requires several steps ... 

Chemical analysis. Chloride ions in the extraction solution described above can be determined by different analytical techniques such as colour-based titration, poten-tiometric tritration, chloride-ion selective electrodes, etc. All of the analytical techniques have been shown to give comparable results with good accuracy, provided that frequent calibration with standard solutions is carried out. For very small amounts of liquid (as for example obtained by pore-water expression) the ICP technique (inductively coupled plasma spectroscopy) has been used successfully. However, this instrumentation is available only in specialised analytical laboratories. 

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