On-line Chromatography Research Articles

A method for the highly accurate quantification of gas streams by on-line chromatography.

Quantification of the gas streams from chemical systems such as catalytic reactors are routinely performed by on-line gas chromatography. Gas chromatographs used for this purpose are typically provided with a combination of thermal conductivity (TCD) and flame ionization (FID) detectors to be able to detect and quantify both permanent gases; COx, N2, H2, etc., and hydrocarbons. However, the accuracy of the quantification is hindered by the intrinsic limitations of each type of detector. Namely, TCD has low sensitivity and FID does not detect permanent gases. Therefore, modern gas chromatographs include methanizer units to partially overcome this shortcoming by converting COx to methane. However, as far as these authors know, the literature has not presented an analytical method to characterize gas streams with high accuracy by the simultaneous use of a combination of a TCD-FID detection system provided with a methanizer. This work is an attempt to solve this problematic; it consists of the formulation of a mathematical model for the well-known external and internal standard quantification methods in gas chromatography. The analysis of the gas stream from a catalytic reactor performing the combustion of methane was used to validate the developed method. The concentration ranges of the analysed gases were: 0.8-7.7vol% of CH4, CO2, and CO, 7.7-38.5vol.% of O2, and 46.2-90.8vol.% of N2 at a total flow of 130mLmin-1. It was found that the commonly applied external standard method leads not only to inaccurate quantification but also to physically meaningless carbon balances and conclusions on the behaviour of the selected model system. In contrast, the internal standard method led to a highly accurate quantification with a physically meaningful carbon balance. Considering these findings, this contribution also draws attention to the need for a thoughtful application of chromatographic methods when studying the reactivity of gas systems.

Middle-Down Proteomic Analyses with Ion Mobility Separations of Endogenous Isomeric Proteoforms

Biological functions of many proteins are governed by post-translational modifications (PTMs). In particular, the rich PTM complement in histones controls the gene expression and chromatin structure with major health implications via a combinatoric language. Deciphering that "histone code" is the great challenge for proteomics given an astounding number of possible proteoforms, including isomers with different PTM positions. These must be disentangled on the top- or middle-down level to preserve the key PTM connectivity, which condensed-phase separations failed to achieve. We reported the capability of ion mobility spectrometry (IMS) methods to resolve such isomers for model histone tails. Here, we advance to biological samples, showing middle-down analyses of histones from mouse embryonic stem cells via online chromatography to fractionate proteoforms with distinct PTM sets, differential or field asymmetric waveform IMS (FAIMS) to resolve the isomers, and Orbitrap mass spectrometry with electron transfer dissociation to identify the resolved species.

Multi targeted cell membrane chromatography: A comprehensive method for screening the anaphylactoid components from complex samples

Anaphylactoid reactions induced by drugs are serious and can be life-threatening, and screening the anaphylactoid ingredients especially in complex samples is challenging. Here, a multi targeted cell membrane chromatography method, based on the Mas-related G protein coupled receptor X2, Fc epsilon RI and H1 receptors, online coupled with LC-MS system provides a comprehensive solution for screening the anaphylactoid components from complex samples. The validation including selectivity and suitability of this system has been evaluated, and it shows promising results. With optimized conditions, this method has been utilized to screen the anaphylactoid ingredients from Shenmai Injection. Ginsenoside Rb1, ginsenoside Rb2, ginsenoside Rc, ginsenoside Rd and 20(S)-ginsenoside Rg3 were identified as anaphylactoid components. The anaphylactoid effects of these five components were further verified by the in vitro sensitization assay, showing promising effects on some or all sensitization cells. In conclusion, the multi targeted cell membrane chromatography online coupled with LC-MS system developed throughout this study could be used to fully screen anaphylactoid components in complex samples. Moreover, it also provides new insights for drug quality control.

Impact of essential-oil-based cleaning products on indoor air quality: From liquid composition to test emission chamber

As society has become aware of health hazards related to the exposure to chemicals, major efforts have been made to address indoor air current problematic. Consequently, popularity of “green” cleaning products has upsurge. These products are formulated with essential-oils relying on their anti-bacterial properties to improve indoor air quality. Indeed, essential oils might contain a hundred of odorous molecules, mainly terpenes and terpenoids (TerVOCs) which acts as antibacterial agents. Nonetheless, do essential-oil-based products really contribute to indoor air quality improvement? This study is addressed to evaluate emissions from the use of essential-oils-based cleaning products by various scale experiments. Firstly, a correlation of liquid composition from 7 natural cleaning products with their emission potentials has been investigated. Volatile fractions are evaluated by using micro-chamber testing. A total of 28 terpenes are quantified among products in the liquid form. Nevertheless, only 22 species are detected in gas samples with a yield ranking from 9.1 % to 99.8 %. Results do not verified a direct correlation between liquid mass and emitted concentrations of terpenes. Indeed, chemical affinities between terpenes and solvent matrix in product formulation are evidenced. Then, 4 products from different cleaning purposes have been selected for emission evaluation in a test chamber of 1-m3. Product application process are correlated to real case scenario regarding applied quantity and loading factor. Emitted terpenes and carbonyl compounds are quantified by off-line and on-line chromatography measurements. Results evidenced that peak concentrations from terpenes reached up to 1.5 h after cleaning activity. Major compound emitted concentration range from 121 to 152 μg/m3, in the test chamber, for different product categories. Specific emission dynamic is evidenced for formaldehyde, in where continuous increasing concentration is revealed due to the presence of formaldehyde releasers. This study contributes to further assessment of exposure hazards related to cleaning activities.

Characterization of phenolic compound antioxidant activity in oat varieties using UHPLC–online ABTS and LC Q‐TOF

AbstractBackground and objectivesPhenolic compounds present in oats provide an opportunity for oats to increase its use in the form of functional food. In this study, eight varieties of Australian‐grown whole‐grain oat were investigated for their phenolic composition and antioxidant potential. Ultra‐high‐performance liquid chromatography–online 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid), coupled with liquid chromatography quadrupole time‐of‐flight, was used to identify and quantify individual phenolic compounds and their respective antioxidant activity.FindingsConsiderable variation in phenolic content (19.51 ± 1.20–52.49 ± 1.70 mg 100 g−1 GAE) and antioxidant activity was observed among the oat varieties. Several avenanthramides (AVNs) were detected with AVN A and AVN C being the most abundant. AVN C exhibited the highest antioxidant activity followed by caffeic acid, quercetin‐3,4′‐O‐di‐beta‐glucopyranoside derivative, and 6‐hydroxykaempferol 3,5,7,4′‐tetramethyl ether 6‐rhamnoside. Antioxidant activity in AVNs was observed to be the highest in AVN C followed by AVN B and AVN A.ConclusionsHigh levels of AVN C and the range of phenolic compounds present show promise of Australian‐grown oats as an important source of antioxidant compounds. These antioxidant compounds may contribute to consumers' health benefits.Significance and noveltyThis study contributes to the use of oats as potential functional food by characterizing its individual phenolic compounds and their antioxidant activity.

Screening the anti-allergic components in Saposhnikoviae Radix using high-expression Mas-related G protein-coupled receptor X2 cell membrane chromatography online coupled with liquid chromatography and mass spectrometry.

Saposhnikoviae Radix, the dried root of Saposhnikoviae divaricata, is commonly used in the traditional Chinese anti-allergic preparations, like Bofutsusho-san and Yupingfeng granules. A high-expression Mas-related G protein-coupled receptor X2 cell membrane chromatography coupled online with high-performance liquid chromatography combined with an ion trap time-of-flight multistage mass spectrometry system was established and used for screening and identifying the anti-allergic components in Saposhnikoviae Radix. The system was validated for excellent specificity and suitability using the appropriate standards. Two retained fractions were obtained on the cell membrane chromatography column, and three main components were identified as prim-O-glucosylcimifugin, cimifugin, and 4'-O-β-d-glucosyl-5-O-methylvisamminol. Next, the molecular docking study was conducted, which confirmed that these three components could effectively bind to MRGPRX2 through hydrogen bonds with its amino acid residues. Finally, histamine release assay was performed to investigate the bioactivities of prim-O-glucosylcimifugin, cimifugin, and 4'-O-β-d-glucosyl-5-O-methylvisamminol. Results showed that these three components could exert anti-allergic effects by inhibiting the histamine release in a dose-dependent manner (from 10 to 100 µM). In conclusion, the high-expression Mas-related G protein-coupled receptor X2 cell membrane chromatography is an effective tool for discovering the anti-allergic components in Saposhnikoviae Radix.

CO2 + n-dodecane + 1-decanol: High pressure experimental phase equilibria data and thermodynamic modelling

Ternary VLE data produced on a static analytic apparatus with dual sampling and online chromatography are presented for CO2 + n-dodecane (nC12) + 1-decanol (C10OH) at 35, 55 and 75 °C and pressures between 68 and 200 bar. Cell interior photos illustrate the value of visual observation to gauge the extent of phase separation. Co-solvency, where the ternary mixture is more soluble than the constituent binaries, occurs in the high-nC12 region. Relative solubility, a selectivity indicator, increases with C10OH content, the average of 2.25 highlights solvent efficacy, and solutes fractionation is possible across the measured nC12:C10OH ratio range. RK-ASPEN, SR-POLAR, PR-BM and PC-SAFT correlations failed at 35 °C. At 55 and 75 °C, RK-ASPEN produced the smallest percentage average absolute deviation in equilibrium pressure of 3.1%, marginally outperforming SR-POLAR and PR-BM. SR-POLAR was best-able to correlate the acute co-solvency pinch and RK-ASPEN vapour correlations were superior. Density inversions were observed.

Melamine–formaldehyde aerogel coating for in-tube solid-phase microextraction

A melamine–formaldehyde (MF) aerogel coating was prepared on basalt fibers (BFs) for in-tube solid-phase microextraction (SPME). MF aerogel-coated BFs were placed in a polyetheretherketone tube to obtain the extraction tube. To build an in-tube SPME–high performance liquid chromatography (HPLC) online system, the extraction tube was connected with HPLC equipment by replacing the sample loop of a six-port valve. The extraction tube was evaluated using eight polycyclic aromatic hydrocarbons (PAHs) as model analytes. After the optimization of important factors, an online analysis method was established. Wide linear ranges (0.03–25 μg L−1, 0.06–30 μg L−1) and low detection limits (0.01, 0.02, and 0.05 μg L−1) were observed. High sensitivity resulted from large enrichment factors ranging from 2070 to 3246. To validate the analysis method, two real water samples were detected. Most of the analytes were not detected in tap water and rainwater, and relative recoveries spiked at 2 and 5 μg L−1 were in the range of 80%–117%. The extraction repeatability on one tube and the preparation repeatability among three tubes were also tested, and their RSDs (n = 3) were in the range of 0.77%–2.04% and 0.88%–9.17%, respectively. As a result of the high surface area of the MF aerogel and π-π interactions with PAHs, the MF aerogel coating exhibits a superior extraction performance than other SPME materials, including wider linear ranges, lower LODs and higher enrichment factors.

Recent advances of online coupling of sample preparation techniques with ultra high performance liquid chromatography and supercritical fluid chromatography

Ultra high performance liquid chromatography and supercritical fluid chromatography techniques are favored because of their high efficiency and fast analysis speed. Although many sample preparation techniques have been coupled with common liquid chromatography online, the online coupling of sample preparation with the two popular chromatography techniques have gained increasing attention owing to the increasing requirements of efficiency and sensitivity. In this review, we have discussed and summarized the recent advances of the online coupling of sample preparation with ultra high performance liquid chromatography and supercritical fluid chromatography techniques. The main sample preparation techniques that have been coupled with ultra high performance liquid chromatography online are solid-phase extraction and in-tube solid-phase microextraction, while solid-phase extraction and supercritical fluid extraction are the main techniques that have been coupled with supercritical fluid chromatography online. Especially, the strategies for online coupling of sample preparation with chromatography techniques were summarized. Typical applications and growing trends of the online coupling techniques were also discussed in detail. With the increasing demands of improving the efficiency, throughput, and analytical capability toward complex samples of the analysis methods, online coupling of sample preparation with chromatography techniques will acquire further development.

Study of CO2 capture by seawater and its reinforcement

Numerous coal-fired power plants, cement plants and steel mills are concentrated in coastal areas of China, and are three major CO2 emitters. Seawater may be a potential resource to capture CO2 in coastal areas. In this study, we used seawater as a CO2 absorbent to capture CO2. An online chromatography apparatus was used to determine CO2 solubility in seawater with different temperatures, pressures and salinities. Then, the thermodynamics and kinetics were studied for the influences of temperature and salinity on CO2 capture in seawater. The experimental results show that increasing temperature and salinity were adverse to CO2 capture by seawater because of an increase in Henry's constant from a thermodynamics aspect. The kinetic results show that high temperature and low salinity can increase the CO2 absorption rate. In order to improve the CO2 absorption ability of seawater and promote CO2 fixation in carbonate precipitation, we added CaO as major components of industrial alkaline substances to enhance the seawater absorption of CO2. CO2 solubility in seawater with 0.4% CaO increased by 79.25%. It shows that the addition of CaO can enhance greatly seawater capture of CO2. The seawater and its reinforcement with CaO is a potential method to capture CO2.

Multiple-metal exposure, diet, and oxidative stress in Uruguayan school children

Oxidative stress (OS) is an important consequence of exposure to toxic metals but it is unclear to what extent low-level metal exposures contribute to OS in children. We examined the cross-sectional association between urinary concentrations of arsenic (As), cadmium (Cd), and lead (Pb) and urinary markers of OS: F2–8α isoprostane and 8-hydroxy-2-deoxy-guanosine (8-OHdG). We also tested effect modification by dietary intakes. Of the 211 children aged 6–8 years living in Montevideo who were eligible for the study because they had at least one OS marker measured via ELISA, 143 were included in a complete-case analysis. Urinary metals were measured with inductively coupled plasma mass spectrometry (ICP-MS: Pb, Cd) and high-performance liquid chromatography online with hydride generation ICP-MS (As-metabolites); concentrations were log2-transformed. All urinary markers were adjusted for specific gravity of urine. Two 24-h dietary recalls were conducted to estimate children's dietary intakes, including total fruit and vegetable consumption and vitamin C, zinc and fiber intake. Ordinary least square (OLS) and weighted quantile sum (WQS) regressions were used to estimate the association between metals and each OS marker as outcome. Metal exposure was generally low: median urinary As, Cd, Pb 9.6 μg/L, 0.06 μg/L and 1.9 μg/L, respectively. Median 8-isoprostane concentration was 1.1 and 8-OHdG 39.6 ng/mL. Log2-transformed urinary As concentrations were positively associated with 8-OHdG concentrations (10.90 [3.82, 17.97]) in covariate-adjusted OLS models which also took account of exposure to Cd and Pb. In WQS, a mixture index was also associated with higher 8-OHdG (8.71 [1.12, 16.3] for each 25% increase in index value), mostly driven by As exposure. There was little evidence of effect modification by dietary antioxidants. In sum, even at low-level, As exposure is associated with detectable oxidative damage to the DNA.

Novel Dual Two‐Dimensional Liquid Chromatography Online Coupled to Ultraviolet Detector, Fluorescence Detector, Ion‐Trap Mass Spectrometer for Short Peptide Amino Acid Sequence Determination with Bottom‐Up Strategy

A novel dual two‐dimensional (2D) high‐performance liquid chromatography (LC) setup coupled online to an ultraviolet (UV) detector, fluorescence (FL) detector, and ion‐trap mass spectrometer (MS) has been developed for determining the amino acid sequence of short peptides using a novel bottom‐up strategy. Short peptides were electrothermally hydrolyzed to shorter peptides and amino acid enantiomers. The first 2D LC‐UV and FL system was used to separate and identify the produced parent and daughter short peptides and amino acid isomers and enantiomers in the hydrolysate; the second 2D LC‐MS was used to identify the presence of cysteine and obtain the molecular mass signals and N‐terminal peptide fragment ion signals for parent and daughter short peptides. The identified amino acid enantiomers are used to form any possible short peptides by permutation and combination in an order from dipeptide to a tripeptide, to a tetrapeptide, and to even higher short peptides. The correct short peptides are confirmed by comparing the molecular weights of the constituent amino acid enantiomers and the molecular weights of identified short peptides together, with the characteristic N‐terminal peptide fragment ion signals. The amino acid sequence of the dipeptide ester aspartame and the tripeptide glutathione was successfully determined by this method.

CO2 + 3,7-dimethyl-1-octanol + 1-decanol: High pressure experimental phase equilibria data and thermodynamic modelling

New VLE data are presented for CO2 + 3,7-dimethyl-1-octanol (37DM1O) + 1-decanol (C10OH) at 35, 55 and 75 °C and pressures between 68 and 237 bar. Phase compositions were analysed using a static analytic apparatus with dual sampling and online chromatography. The mixture displays virtually no enhanced solubility, liquid curves remain convex throughout, and coexisting detached two-phase regions were not detected. CO2 can fractionate all measured 37DM1O:C10OH ratios though with limited efficacy, as highlighted by relative solubilities ranging from 1.1 to 1.5. RK-ASPEN, SR-POLAR, PR-BM and PC-SAFT correlations failed at 35 °C, the optimum fractionation temperature. At 55 and 75 °C, RK-ASPEN and SR-POLAR produced the smallest percentage average absolute deviations in equilibrium pressure of 4.0%, and RK-ASPEN was marginally superior at correlating vapour and liquid phase curves. At 35 °C and 187.5 bar, the 25:75 37DM1O:C10OH mixture passed through a density inversion and interesting images thereof are presented.

Metaproteomic analysis of the relationship between microbial community phylogeny, function and metabolic activity during biohydrogen-methane coproduction under short-term hydrothermal pretreatment from food waste

Short-term hydrothermal pretreatment (SHP) is an attractive method for food waste anaerobic digestion, which facilitates the solubilisation of recalcitrant particles. This study employed metaproteomic method to evaluate the relationships among microbial community phylogeny, function, and metabolic activity during two-stage anaerobic digestion under SHP (SHPT) from food waste. The presence of 651 bacterial proteins and 477 archaeal protein has been detected by liquid chromatography online linked to mass spectrometry, revealing a high metabolic heterogeneity during SHPT. The different stages of SHPT highlighted important roles for the bacterial proteins from Gammaproteobacteria, Bacilli, and Clostridia and the archaeal proteins from Methanosarcinales. The identified proteins related to biohydrogen production come from pyruvic acid decarboxylase and formic acid decomposition pathway in carbohydrate metabolism and methanogenesis from acetate, CO2 and a methylotrophic pathway during energy metabolism. This could provide functional evidence of the metabolic activities and biogas production during SHPT.

N- and O-Glycomics from Minor Amounts of Formalin-Fixed, Paraffin-Embedded Tissue Samples.

The availability of well-defined samples in sufficient numbers represents a major bottleneck for any biomarker related research. The utilization of preserved, archived and clinically well-described samples therefore holds a great potential to bridge this gap. This chapter describes a universal workflow for the comprehensive characterization of N- and O-glycans released from whole formalin-fixed, paraffin-embedded tissue sections, including an option for further partitioning using laser microdissection of specific tissue areas/cell populations. Glycoproteins are extracted and subsequently immobilized onto a PVDF membrane prior enzymatic release of N-glycans. Following N-glycan retrieval O-glycans are released using reductive β-elimination from the same sample spot, significantly reducing the required amount of starting material. Released and reduced glycan structures are characterized using porous graphitized carbon liquid chromatography online coupled to an electrospray ionization-ion trap mass spectrometer. This technique provides information on the relative abundances of individual glycans along with detailed structural information, including isomer differentiation and functional epitope characterization of N- and O-glycans obtained from minimal amounts of tissue down to a few thousand cells.

Screening anti-allergic components of Astragali Radix using LAD2 cell membrane chromatography coupled online with UHPLC-ESI-MS/MS method.

Huangqi (Astragali Radix), a traditional Chinese herb, is widely used in clinical therapy in China. In addition, an anti-allergic effect of constituents in Huangqi has been reported in the scientific literature. In the present study, cell membrane chromatography coupled online with UHPLC-ESI-MS/MS method was developed to screen, analyze and identify the anti-allergic components of Huangqi. The Laboratory of Allergic Disease 2 (LAD2) cell was used to establish cell membrane chromatography, which was combined with UHPLC-ESI-MS/MS. The coupled system was then used to screen anti-allergic components from Huangqi. Effects of active components were verified by histamine release assay. A component retained on the LAD2 cell membrane chromatography was identified as formononetin. Bioactivity of formononetin was investigated by histamine release assay in LAD2 cells, and it was found that formononetin could inhibit histamine release in a dose-dependent manner from 1 to 100 μm. The LAD2 cell membrane chromatography online with UHPLC-ESI-MS/MS method is an effective technique for screening the anti-allergic components of Huangqi.

Characterization of the bio-oil obtained by fast pyrolysis of sewage sludge in a conical spouted bed reactor

Sewage sludge fast pyrolysis bio-oil, produced in a conical spouted bed reactor (CSBR) in the 450–600°C range, has been characterized. On the one hand, the effect of temperature on bio-oil composition has been analyzed by means of online chromatography and, furthermore, the ultimate analysis and the higher heating value of each liquid have been determined. On the other hand, the bio-oil collected at 500°C, at which the liquid yield is maximized (77wt.% on dry ash free), has been characterized in detail by determining its density, viscosity, water content and pH. The major organic compounds in the bio-oil were oxygenated and nitrogenated ones (phenols, ketones, alcohols, amides and nitriles among others). It is noteworthy that the bio-oil obtained in this work contains a lower amount of O than those derived from lignocellulosic materials; therefore, the concentrations of C and H in this bio-oil, as well as the lower heating value (LHV), are higher. In addition, the simulated distillation reveals that >70% of the sewage sludge pyrolysis oil corresponds to the gasoil range. The fuel properties of sewage sludge bio-oil evidence that it has the potential to substitute conventional fuels; however, some properties need to be improved, i.e., the heating value should be increased and the nitrogen content reduced by subjecting this bio-oil to further treatments.

Performance evaluation of a novel CO2 absorbent: Dimethyl carbonate

Vapor–liquid equilibrium (VLE) data for the binary carbon dioxide (CO2)+dimethyl carbonate (DMC) systems at 283.15, 293.15, 303.15 and 308.15K up to 4.67MPa are reported from pseudo on-line chromatography with liquid phase sampling experiments. These novel experimental results are discussed and compared with available literature data. The measured VLE data for the CO2-DMC system are then modeled using the Prausnitz–Shair activity coefficient method, molecular connectivity index and the Peng–Robinson (PR) equation of state. To comprehensively evaluate DMC's ability to capture CO2, a continuous absorption and desorption experimental apparatus was designed. A range of operating conditions that can influence the CO2-DMC absorption and desorption processes are investigated, including liquid–gas ratio, absorption temperature, desorption temperature and N2 flow. Finally, this paper compares established CO2 capture absorbents with DMC using AspenPlus2006 process modeling and finds that DMC is a potential absorbent and has prospects for future applications.

Arsenic compounds occurring in ruderal plant communities growing in arsenic contaminated soils

Wild growing phytocenosis from three different areas near former gold or silver mines—Kutná Hora, Roudný and Nalžovské Hory (Czech Republic) were investigated for total arsenic and arsenic species concentrations. The most abundant plant families that occurred were Fabaceae, Lamiaceae, Asteraceae, Poaceae and Plantaginaceae. Several plant species such as Achillea millefolium L. (Asteraceae), Anthoxanthum odoratum L. (Poaceae), Plantago lanceolata L. (Plantaginaceae) are widespread and could be found in all of the investigated areas. Total As concentrations in aboveground biomass of plants growing on those three sites were determined by an inductively coupled plasma mass spectrometry (ICPMS) and ranged from 0.02*mgAskg−1 (Stellaria spp.) to 39.30±6.32mgAskg−1 (Daucus carota L.). The concentrations seem to be dependent on both plant species and physico-chemical soil properties. For the arsenic speciation a high performance liquid chromatography (HPLC) online connected with the ICPMS was used. Results have shown that arsenite and arsenate are the prevalent arsenic compounds. Methylarsonic acid (MA), dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TETRA), and trimethylarsine oxide (TMAO) were identified as minor species. Arsenobetaine was found at significant concentrations in Carex praecox Schreb. (28% of the extractable As amount) and P. lanceolata L. (1.2% of the extractable As amount).

Argentation high performance liquid chromatography on-line coupled to gas chromatography for the analysis of monounsaturated polyolefin oligomers in packaging materials and foods

Multidimensional chromatography based on two-dimensional high performance liquid chromatography on-line coupled to gas chromatography (on-line HPLC–HPLC–GC) enables the separate analysis of saturated, monounsaturated and aromatic hydrocarbons in packaging materials like polyolefins or paperboard and their migrates into foods. Since normal-phase HPLC on silica gel did not preseparate saturated from monounsaturated hydrocarbons, a separation step on a normal-phase HPLC column treated in the laboratory with an optimized amount of silver nitrate was added. The preparation of this HPLC column and the instrumental set-up are described, followed by examples showing the potential of the method. In a preliminary investigation of 11 polyolefin granulates for food contact up to 40% monounsaturated hydrocarbons among the oligomers C16–35 were determined.