# High Cellulose Purity by Acid Hydrolysis Pretreatment on Kenaf Outer Bast
## 3 Result and Discussion  
### Chemical Composition of Raw Kenaf Outer Bast Fiber  
The chemical compositions of the kenaf outer best fiber are shown in Table 1. As a minor component, hydrophilic by hot water extraction was a relatively higher percentage than hydrophobic extractive treatment. A similar trend was reported: goat willlow has a higher content of hydrophilic extraction, 11.4%, than hydrophobic extraction, 0.8% [25]. The hydrophobic extraction contained fatty acids and alcohols, resin acids, other diterpenoids, and sterols, where the resin acids are the most abundant group of hydrophobic analytes [26]. Compared to the hydrophobic, hydrophilic by ethanol extraction was less complex in terms of the number of different chemical classes detected [26]. Both species were primarily dominated by lignans, flavonoids, and phenolics [26]. Therefore, kenaf fiber interfacial compatibility of hydrophilic kenaf fiber with the hydrophobic resin is poor [27].  
Extractive-free kenaf fiber indicated lower lignin content than core fibers with higher cellulose and similar hemicelluloses [28]. As shown in Table 1, this fact was supported by kenaf best fiber from Malaysia which reported 9.87% of lignin content [29]. On other hand, kenaf core fiber from Korea contains 18.5% of lignin [30]. The kenaf outer best had been chosen over the core for its advantages with high cellulose content than other parts [31]. Meanwhile, other biomasses had different lignin with kenaf outer best fiber such as other annual plants (12-15.1%) [32], hardwood (17.9%) [33], and softwood (32.9%) [34]. Hence, according to the previous work and our preliminary experiment of the low lignin content of kenaf outer best fiber, bleaching was a great pretreatment as delignification prior to acid hydrolysis as the main treatment.  
Furthermore, in carbohydrate composition, kenaf outer best fiber contained 20.1% of hemicellulose and 57.2% of cellulose from 77.3% of holocellulose. In contrast, kenaf core fiber's cellulose and hemicellulose content was 46.1% and 25.4%, respectively [30]. Meanwhile, the chemical composition of kenaf best fiber from Malaysia containing 55.0%, 31.8%, 19.2%, and 10.9% was cellulose, hemicellulose, lignin, and others, respectively [35]. Therefore, kenaf's outer best makes its crops considered promising biorefinery materials to produce high-purity cellulose. Structural features and their chemical composition of it are primarily dependent on the morphological region, such as soil types, climate, and nutrition, and on the maturity stage (outer best, inner bas until core), including age [28; 35].  
NMR spectroscopy was applied to report the carbohydrate content of the kenaf outer best. The anomeric hydrogen peak integration method calculated the carbohydrate composition in \({}^{1}\)H-NMR spectra [25]. The monosaccharide composition of polysaccharides was measured based on each monosaccharide having a different anomeric chemical shift using D\({}_{2}\)O solvent. Figure 2 shows the monosaccharides peak of glucose, xylose, and other sugar from raw kenaf outer best. Besides high cellulose content, kenaf, an herbaceous plant, has a xylan as the dominant hemicellulose component, such as in hardwoods [36]. Furthermore, glucuronoxylans are the principal hemicellulose of hardwoods, with monosaccharide com  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Chemical Compositions** & **Raw Samples (\%)** \\ \hline Carbohydrates & \\ Cellulose & 57.2 \\ Hemicellulose & 20.1 \\ Xylan & 14.4 \\ Others Sugar & 5.7 \\ Lignin & 7.7 \\ Extractives & \\ Hydrophilic a  & 13.7 \\ Hydrophobic b  & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Materials’ balance of raw kenaf outer best.  
ponents are xylose, glucuronic acid, and some acetyl group [37]. This study used \({}^{1}\)H-NMR spectra to measure polysaccharides to monosaccharides with various parameters.