Wood lignin samples preparation

Universal Calibration. The aspen wood lignin samples chosen for this study were prepared by organosolv, steam explosion, dilute acid hydrolysis, and ball-milling procedures. 

Lignin Samples. Ball-milled (BM) aspen lignin was prepared following the procedure of Lundquist et al. (21). The yield of purified milled wood lignin obtained was usually about 10% w/w that of ethanol/benzene-extracted aspen wood. 

Alkaline-extracted/steam-exploded (AESE) aspen lignin samples were prepared from steam exploded wood samples (55 s residence time at 240°C) obtained from Iotech Corp. Exploded wood pulp was treated with a series of carbon tetrachloride and alkaline extractions (12). 

Alkaline-extracted/acid hydrolysis (AH/NaOH) lignin samples were prepared by subjecting aspen wood flour to a one hour cook at 120°C in 0.05N sulfuric acid (22), followed by mixing the clarified supernatant with 1% w/w NaOH at 25°C with a Waring blender. The insoluble lignins were precipitated by addition of acid and water washes (32% yield). 

Harbour JR, Hopper MA, Marchessault RH, Dobbin CJ, Anczurowski E (1985) Photoacoustic spectroscopy of cellulose, paper and wood J Pulp Pap Sci 11 J42-J47 Hauser M, Oelichmann J (1988) A critical comparison of solid sample preparation techniques in infrared spectroscopy Microchim Acta (Wien), Spec Issue, I 39-43 Hergert HL (1971) Infared spectra In Sarkanen KV, Ludwig CH (eds) Lignins Occurrence, formation, structure and reactions Wiley-Interscience, New York, 267-293 Hirschfeld T (1987) In McClure GL (ed) Computerized quantitative infrared analysis ASTM, Philadelphia, 169-179... 

Transient infrared spectroscopy (TIRS) is a mid-infrared technique [82] that has been developed to obtain spectra of moving solids and viscous liquids. TIRS spectra are obtained from the generation of a thin, short-lived temperature differential that is introduced by means of either a hot or cold jet of gas. When a hot jet is used, an emission spectrum is obtained from the thin, heated surface layer. This technique is known as transient infrared emission spectroscopy (TIRES). When a cold jet is used, the blackbody-like thermal emission from the bulk of the sample is selectively absorbed as it passes through the thin, cooled surface layer. The result is a transmission spectrum convoluted with the observed thermal spectroscopy. This method is known as transient infrared transmission spectroscopy (TIRTS). TIRS is ideally suited for online analysis because it is a single-ended technique that requires no sample preparation. This technique has been applied to the lignin analysis of wood chips [83]. 

Another sample of enzymatic lignin freshly prepared from Hurricane-pulverized wood was suspended in 0.1 M EDTA and stored at 4°C for one week. This treatment also enhanced the adsorption of nitrosamine (Figure 2). It therefore appears that ion exchange of heavy metals, notably iron, by complex formation with EDTA enhances the adsorption of nitrosamine on enzymatic lignin. Systematic control of the heavy metal ions in enzymatically prepared lignins is a necessary feature of future studies. 

However, there are some methods for extraction of cellulose from plants. Han and Rowell s (1996) method describes a procedure for extraction of holocellulose, hemicelluloses, cellulose and lignin [18]. The method consists of four principle steps (1) preparation of sample (grinding of the wood), (2) removal of extractives, (3) preparation of holocellulose (removal of lignin), (4) preparation of a-cellulose (removal of hemicellulose). Several other procedures for a-cellulose extraction from wood samples have already been described during the last decades. Older methods used benzene-methanol instead of toluene-ethanol as organic solvent for the second step. Toluene-ethanol works as well as benzene-methanol mixture, and reduces health risks associated with the use of benzene and methanol. 

Subsequently the wood material was subjected to a bleach pretreatment with sodium chlorite (NaQ02) to remove lignins, resins, waxes. In case of very small samples or poorly preserved fragments the temperature and the time of each step was individually match. In the next stages of samples preparation to dating the combustion in vacuum to obtain carbon dioxide from organic material and reduction were used. Finally, graphite with iron was pressed to form a cathode ready for AMS measurement. 

Srinivasa Rao Y, Shukla RN, Maheshwari S, Kulkarni AY, Jivendra Y (1983) Determination of permanganate and kappa number of pulp with high ash content. IPPTA 20(3) 55-56 Stewart CM, Foster OH, Cohen WE, Leslie RT, Watson AJ (1951) The selection and preparation of a reporducible wood sample for chemical studies. Appita 5 267- 311 Swan B (1965) Isolation of acid-soluble lignin from the Klason lignin determination. Sven Papperstidn 68 791-795... 

Methanol formation generally levels off after two days reaction in the case of wood samples (Fig. 7.2.IB). For lignin preparations, the maximum formation of methanol is usually reached within 36h (Adler et al. 1958). 

Aminolysis is a laborious procedure, e.g., for wood samples, a 6-7-h reaction period may be required for the aminolysis step alone. The accuracy of this method is critically dependent upon both a quantitative acetylation of phenolic hydroxyl groups and a selective deacetylation of phenolic acetyl groups. Although these requirements may not represent a serious concern in the analysis of soluble or reagent-accessible lignin preparations, they could present a problem in the case of lignocellulosic materials. 

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