Recoveries Of N-alkanes Research Articles

Evaluation of N-alkanes as Faecal Markers to Estimate Diet Composition, Feed Intake, and Digestibility in European Bison (Bison bonasus)

There is a lack of knowledge on the European bison (Bison bonasus L. 1758) foraging behavior that is essential to develop an appropriate feeding strategy for each specific situation (captive or wild). Utilization of faecal markers may allow us to fill this gap, accommodating animal welfare and intensive labour issues that are major limitations of traditional techniques. This study aimed to evaluate the potential of n-alkane markers (C25 to C33) to estimate diet composition, feed intake its digestibility on three captive maleBison bonasus fed on known amounts of straw, and a beeswax labelled concentrate feed. Feeds and faecal samples were taken daily during 10 days. Prior to calculations, faecal concentrations were corrected for incomplete faecal recovery (FR). Results indicated that 4–5 days were sufficient for these markers to reach a steady concentration in bison faeces. Accurate estimates of diet composition and feed intake were obtained not differing from known values. Results suggest that faecal recovery of n-alkanes in bison are incomplete and tend to increase with carbon-chain length. Apparent dry-matter digestibility (DMDap) estimates were affected by the n-alkane (C27, C29,C31, and C33) used in the calculations. Estimates of DMDap obtained with application of FR corrections were 6.3% higher than those without correction. Results indicate that feeding a known amount of beeswax labelled supplement can be successfully used to estimate composition, feed intake, and its digestibility, requiring the application of n-alkane FR data.

An optimized accelerated solvent extraction and purification method for enhanced recovery of n-alkanes (notably short-chains) from environmental samples using the conventional dichloromethane/methanol solvent

Sedimentary lipid biomarker proxies are extensively used for paleoclimatic and paleoenvironmental research. Among all the lipid compounds, the non-polar n-alkanes (chain lengths n-C14 to n-C37) are one of the most widely used lipid fractions for such studies. However, the lack of optimized automated extraction and post-extraction sample workup procedure, using conventional polar solvent, from environmental samples, has been challenging. Conversely, extraction of the n-alkanes using non-polar solvents restricts the co-extraction of other polar lipid compounds like ketones, alcohols, acids, etc. which may be of interest to many researchers. Here we report an optimized total lipid extraction method using the conventional polar dichloromethane/methanol solvents with standardized Automated Solvent Extractor (ASE) parameters and post-extraction sample work-up protocols. The robustness of the method has been tested by extracting eight samples containing algae, leaf, and sediment/rock of varying age (spanning from recent to ∼252 Ma). The results of the extraction efficiency (yield) of the method were compared with commonly used methods, those using either non-polar n-hexane or polar dichloromethane/methanol solvents. For n-alkane extraction from algal biomass, the performance of the proposed method and the conventional polar solvent method are statistically comparable, but the new method performs better than the non-polar solvent method. Likewise, for the leaf and sediment samples, the performance of the proposed method is equivalent to the non-polar solvent method but outperforms the commonly used polar solvent method. The Terrestrial Aquatic Ratio (TAR) and long-chain hydrocarbon/short-chain hydrocarbon (LHC/SHC) ratios calculated from the algae and sediment samples also show that our recommended extraction approach can be confidently used in calculating n-alkane ratio proxies, which critically depend on the extraction efficiency of the short-chain n-alkanes. Taken together, the new method will be highly useful for studying the n-alkanes from a wide spectrum of natural sample matrices and provide reliable data for paleoclimatic inference.

N-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore

Habitat management for herbivores often depends on an understanding of the food habits of animals. Plant cuticular waxes containing nearly indigestible complex mixture of n-alkanes and long-chain alcohols (LCOHs) have recently shown promise for diet analyses, but the accuracy of the technique depends strongly on the efficiency of recovery of the markers in feces. Fecal recovery of n-alkanes and LCOHs from 10 browse stems or leaves and two ensiled grass hays fed to moose (Alces alces (Linnaeus, 1758)) during in vivo digestion trials was investigated. n-Alkanes and LCOHs were extracted using a single-step accelerated solvent extraction technique and the recovery of these cuticular components was calculated from the feces of the animals. n-Alkane recoveries from feces averaged 0.82, ranging from a low of 0.58 (haylage) to a high of 0.95 (browse stems). LCOH recoveries averaged 0.92 across all forages, ranging from 0.80 (haylage) to a high of 1.13 (browse stems). n-Alkane and LCOH fecal recovery increased with increasing chain length, similar to findings in other studies. Although fecal recovery of n-alkanes and LCOHs were variable, we conclude that they are inversely related to forage digestibility, are consistent within forage classes, and are therefore predictable markers for use in assessing herbivore diets.

Comparative study techniques for TPH and PAH extraction from clayey and sandy soils for chromatography analyses

The objective of this study was to compare three extraction procedures: soxhlet (SOX), microwaves (MARS) and accelerate extraction with solvent (ASE) regarding the extraction efficiency of different fractions of total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAH) from sandy and clayey soil with aged contamination analyzed by gas chromatography. Besides the extraction efficiency, water, solvent and time consumption were considered. Regarding clayey soil, for the extraction of different fractions of total petroleum hydrocarbons (TPH), ASE resulted in better recovery of n-alkanes and hydrocarbons resolved fraction (HRF). SOX and MARS performed better for the heaviest fraction (non-resolved complex mixture-NRCM). Regarding sandy soil, ASE performed better during extraction of all TPH fractions. In the case of polycyclic aromatic hydrocarbons (PAH), extraction with ASE showed the best result in both clayey and sandy soils. When other variables were taken into account (water, solvent and time consumption), MARS is the most economical method, particularly when TPH is the group of interest and n-alkanes is relatively less important in the analysis. Therefore, in aged contaminations, soil texture and the petroleum fraction of interest in the first place and availability of resources such as water, solvent and time in the second place must be considered before deciding what is the most appropriate extraction method.

Using plant wax markers to estimate diet composition and intakes of mixed forages in sheep by feeding a known amount of alkane-labelled supplement

The feeding of known amounts of supplements to grazing animals can be accomplished relatively easily. If the supplement and the other diet components have distinctive profiles of cuticular wax n-alkanes, then the supplement intake and the alkane profiles of the supplement, other dietary components and faeces can be used to estimate the proportions and hence intakes of several forages by the grazing animal. However, this method requires knowledge of recoveries of n-alkanes in faeces. Twenty four wethers were fed one of four diets comprising equal combinations of 1, 2, 3 or 4 forages. Forages used were subterranean clover, phalaris, annual ryegrass and wheat straw. Forages were chopped using a chaff cutter and fed with solvent-extracted cottonseed meal (CSM) labelled with beeswax and synthetic C28 alkane to provide a characteristic alkane profile. Faecal grab samples were taken from sheep from 14 to 23 days after administration of an intra-ruminal controlled-release device (CRD) containing 1 g of each of C32 and C36 alkane. Total faeces were collected from half the sheep on each treatment in order to measure alkane recoveries in individual sheep. Faecal concentrations of the n-alkanes C25 to C31 and C33 were corrected for recovery using the individual sheep value, the treatment mean or the grand mean for all four treatments. Dietary compositions were then estimated from corrected faecal concentrations of n-alkanes using a least-squares procedure and, together with the known supplement intakes, were used to estimate the intakes of all other diet components. Estimates from this ‘labelled supplement’ method were compared with the amounts fed or those estimated using the alkanes derived from the CRD. The labelled supplement method accurately and precisely estimated dietary component proportions and intake for all treatments when measured recoveries for individual sheep were used. Precision declined when recovery was based on estimated recoveries for treatment means or the grand mean. Estimates of intake based on dietary C33 and the measured release rates of C32 or C36 alkanes from the CRD did not differ from measured intakes. Estimates based on the C32 : C31 alkane pair over-estimated intake. Estimates of whole-diet digestibility based on the various ways of estimating intake were all very close to the digestibilities calculated from directly-measured intakes and faecal outputs. It is concluded that the feeding of a known amount of supplement can be successfully used to estimate dietary proportions and hence intakes of diet components, in mixed diets with up to five ingredients, but this approach requires estimates of faecal alkane recovery.

Using molasses as an alternative to controlled release devices for administering n-alkane markers to cattle

AbstractAn experiment was conducted to determine if molasses could be successfully used to administer dotriacontane (C32) and hexatriacontane (C36) n-alkane markers to steers and to compare this method with a commercially available intra-ruminal controlled release device (CRD). The experiment was conducted over two similar periods (runs) using 24 Brahman crossbred steers in each run to study the effect of marker delivery methods and tropical grass hay diets in a randomized complete block design with three replicates. All steers were housed individually in partially covered pens, received one of two buffel-grass hays (B20: 20-week regrowth; 0·72 g nitrogen (N) per 100 g and B8: 8-week regrowth; 1·11 g N per 100 g) and one of four marker delivery treatments (control: no marker; 200 mg/day of C32 and C36 n-alkanes from a CRD or offered three times (Ms ✕ 3) or five times (Ms ✕ 5) a day in molasses). Voluntary intake (VI) and dry matter digestibility (DMD) for diets differed (P < 0·001) with B8 greater than B20. There was no difference among marker treatments for VI but the control treatment had greater, unexplained and possibly spurious, DMD than the Ms ✕ 3 marker treatment. Although the recovery of n-alkanes was variable (0·84 to 1·05) adjacent odd- and even-chain n-alkanes were similar with no differences (P > 0·05) due to marker treatment or diet. The CRD supplied a consistent marker dose between 6 and 18 days after insertion. Deviation from the 24-h mean faecal concentration seldom varied more than 0·03 for the individual markers and 0·05 for C31/C32 and C33/C32 ratios for all treatments. Over all the n-alkanes studied, the between-day variation was less than the within-day variation. For instance, the average of subsamples taken at 06:00 h and 18:00 h was within proportionately 0·05 of the 10-day mean concentration for 0·38 and 0·25 of records for C32 and C36 markers, respectively. It was concluded that molasses containing C32 and C36 n-alkane markers and given either three or five times daily was as accurate as the commercial CRD in administering n-alkane markers to steers and provides a method of delivering n-alkanes over an extended period in grazing studies.

Estimating the voluntary intake and digestibility of buffel-grass and lucerne hays offered to Brahman-cross cattle using n-alkanes

AbstractThe n-alkane method was developed in temperate areas as a tool to estimate voluntary intake (VI) at pasture. The present study aimed to investigate the performance of n-alkanes as markers for estimating VI of steers (mean live weight 213 kg) offered a range of tropical grass hays and lucerne. Tropical and temperate forages have different n-alkane profiles and little is known about the issues which affect the accuracy of the method under tropical conditions. In two pen experiments (no. = 20 and no. = 24) n-alkanes were dosed using intraruminal controlled-release devices. Actual mean voluntary dry matter intakes for the diets ranged from 3·12 to 4·60 kg/day and actual mean dry-matter digestibility varied between 439 and 620 g/kg. n-Alkane profiles (C30 to C36) of the diets and the faeces for each animal were determined using gas chromatography. The recovery of each n-alkane was determined for each animal. Recoveries of n-alkanes were highly variable and generally varied between diets and between experiments. When adjacent n-alkanes were used to estimate VI (ratio method), agreement with actual VI was often poor. Despite this, where the recoveries of n-alkane pairs were similar, group mean VI were accurately estimated. From these data, it is concluded that estimation of VI in cattle offered tropical grass hays or lucerne hay, requires measured recoveries of both dosed and natural plant n-alkanes. The dosed and natural n-alkane pairs having the most similar recoveries should be used in the ratio method to estimate VI.

High-throughput reactor for simulating the flame photometric detector

Quenching of luminescing species by co-eluting hydrocarbons has been widely reported in the flame photometric detector (FPD). This paper describes a novel method of investigating the chemical behavior of both analyte and quencher molecules in the FPD. The method is designed to reproduce the FPD’s behaviour on a large scale by using a custom-built reactor. The high-throughput reactor’s multi-capillary burner, situated inside a glass housing, is well suited to approximate the low-temperature, fuel-rich conditions of the conventional FPD, and also allows the study of various other flame phenomena. Wide regions of gas composition can be accessed by both diffusion- and premixed-type flames, and products can be easily sampled. Effluent collection demonstrates that 2 to 82% of various organic compounds may survive passage through the diffusion flame and be recovered intact. The recovery of several (unchanged) model hydrocarbons was found to decrease with increasing carbon number. Hetero-atoms such as sulfur, nitrogen, or oxygen greatly decrease the recovery of molecules relative to their pure hydrocarbon analogues. Compared to a diffusion flame, the recoveries of n-alkanes from a premixed flame are much lower and largely independent of carbon number or volatility.

Validation of the n-alkane technique for measuring herbage intake in sows

N-alkanes are components of plant cuticular wax which have been successfully used as markers for the estimation of grass intake and digestibility in grazing ruminants (Dove and Mayes, 1991). Natural n-alkanes are predominately odd chain, and a known dose of an artificial even chain n-alkane (normally c32 or c36) is used to enable intake to be measured. Dietary n-alkanes may behave differently in the gastro-intestinal tract of ruminants and non-ruminants (Mayes et al, 1995). Therefore, in order to utilise this methodology in studies of outdoor pigs, this experiment was carried out to validate the faecal recovery of n-alkanes in this species. Since n-alkanes are soluble in lipid, which is often incorporated at high inclusion levels in pig diets, the experiment was also designed to determine whether n-alkane recovery is influenced by dietary lipid content.

Improved determination of n-alkanes by forming of urea inclusion compounds.

This report describes the trace analytical method of n-alkanes, based on the inclusion ability of urea, from a mixture of iso-alkanes, cycloalkanes, poly aromatic hydrocarbons and organic sulfur compounds. n-Alkane-urea inclusion complexes were formed by adding ethanol 2 ml of saturated with urea to 0.5 ml of a mixed solution of acetone and n-hexane (3 : 2) containing the above described compounds. The inclusion compounds formed in the hydrophobic medium were precipitated by adding ice-cold ethyl ether and then cooling for 5-10 min in an ice-bath. The precipitates were separated with centrifuge (3000 rpm, 6 min) at 5°C from organic reaction medium. The precipitates were dissolved in 30 ml of 4% Na2SO4 and extracted with n-hexane (total volume, 20 ml), and also the supernatant by the addition of 30 ml of 4% Na2SO4 was treated with n-hexane (20 ml). n-Alkanes were measured in the former n-hexane solution while iso-alkanes and/or others in the latter by each gas chromato-graphic analysis. The recoveries of n-alkanes of C12 and C14 were 67% and 80%, respectively, being recoverd in the past reports with yield of under 40%. The yields of n-alkanes of C15-C28, 2, 2, 4, 4, 6, 8, 8-heptamethylnonane, heptylbenzene, pristane, dibenzothiophene and 3, 4-benzpyrene were 91% on the average, 77%, 79%, 80%, 83% and 84%, respectively. This analytical method was applied to the solvent extracts of a bait of cultured fish and the sea bottom sediment.

The use of long-chain n-alkanes for estimating intake and digestibility of herbage in cattle

Studies with sheep suggest that accurate estimates of herbage intake can be obtained by using the herbage alkane tritriacontane (C33) and dosed dotriacontane (C32) as markers, since the faecal recoveries of both alkanes have been shown to be very similar. To validate the technique for herbage intake estimation in grazing cattle there is a need to compare in cattle, the faecal recoveries of both herbage and dosed n-alkanes. It has been observed in sheep that the faecal recoveries of n-alkanes increase as their chain lengths increase, suggesting that the recovery of hexatriacontane (C36), an alkane absent from herbage but available commercially at low cost, should be complete. C36 may therefore have potential as a dosed marker for estimation of faecal output. Thus it may .30 be possible to obtain estimates of both herbage intake and diet digestibility in the same individual grazing animal using n-alkanes as markers. The purpose of the experiment described here was to determine the faecal recoveries in cattle of odd-chain n-alkanes from fresh herbage and of C32 and C36 dosed n-alkanes.

N-Alkane adduct formation with urea in diesel fuel distillate dewaxing

This article reports on a study of the influence of the alcohol concentration and urea content of the solution and the temperature and time of adduct formation on the composition and completeness of recovery of n-alkanes from diesel fuel cuts. The study was carried out with solutions of n-alkanes in a 193-326/sup 0/C diesel fuel cut from Baku crudes containing 19.8% aromatic hydrocarbons. Dewaxing was performed in a cylindrical metal reactor with a blade stirrer. The quantities of n-alkanes remaining in the dewaxed fuel was determined by an adduct formation method. The adduct obtained in the basic dewaxing experiment was decomposed, and the composition of the paraffins that were recovered was determined chromatographically. It is determined that for maximum recovery of n-alkanes from diesel fuels containing 20% by weight of adduct-forming hydrocarbons, a 40% urea solution should be used.