Quantitative analysis of styrene monomer in foods. A limited East Australian Survey

The levels of styrene monomer in foods packaged in polystyrene containers were determined by a headspace gas chromatography (g.c.) method and two reversed phase high-performance liquid chromatography (h.p.l.c.) methods. A total of 146 samples were analysed from Victoria and New South Wales which included yoghurt, cream, cheese, dessert, ice cream, egg white, onion dip and margarine. The highest level of styrene found was 0.1 mg kg^?1 in yoghurt. About 85% of all yoghurt samples were found to have values less than 0.05 mg kg^?1. The lowest values of styrene obtained were for margarine samples, of which more than 90% contained less than 0.010 mg kg^?1. The estimated limits of detection of the h.p.l.c. methods for all products except margarine were 0.005 mg kg^?1. The h.p.l.c. detection limit for margarine and the g.c. method for yoghurt were estimated to be 0.01 mg kg^?1.     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.     

Rapid assay for limonin using a new selective detecting system for limonoids

A rapid procedure is described for the direct assay of limonin which makes use of a new detecting system and a new solvent system for thin-layer chromatography (t.l.c.) of limonoids. The detecting system, which involves exposure to bromine vapour and spraying with Tollens' reagent, is more selective and sensitive than previous methods, detecting five limonoids in orange juice extracts, whereas previous t.l.c. procedures only gave one spot.     

Influence of dietary fish meal on egg fatty acid composition

Changes in the fatty acid composition of egg-yolk fat of hens fed diets with increasing fish meal content are studied by total fatty acid analysis. The fatty acid composition of the major lipid fractions in egg-yolk fat after feeding a high-level fish meal diet was determined by a combination of thin layer chromatography (t.l.c.) and gas-liquid chromatography (g.l.c.) The changes produced show a fatty acid pattern similar to those of the diets themselves. Long-chain polyunsaturated fatty acids are deposited preferentially in the phospholipids, reaching the highest concentration in cephalin and lecithin.     

Identification and quantitative analysis of sugars and non-volatile organic acids in Chinese gooseberry fruit (Actinidia chinensis Planch.).

The free sugars and non-volatile organic acids in Chinese gooseberry fruit were extracted and separated by lead salt and ion-exchange procedures. Sugars and acids were identified and quantitatively determined by gas-liquid chromatography (g.l.c.) of their trimethylsilyl (TMS) derivatives. Glucose, fructose, sucrose and trace amounts of sorbitol accounted for the total sugars. Citric, quinic and malic are the major acids, the outstanding feature being the high content of quinic acid in mature fruit. Small amounts of phosphoric, ascorbic, glucuronic, galacturonic, oxalic, succinic, fumaric, oxalacetic and p-coumaric acids are also present. Qualitative and quantitative analysis of acids prepared as lead salts agreed closely with the determination of acids isolated by the ion-exchange procedure. Identifications of sugars and acids were confirmed by paper and thin-layer chromatography. Reducing sugars, total sugars and titratable acidity were determined by AOAC methods and the results compared with those from g.l.c.     

Directed interesterification of a brazilian palm oil and analysis of the original and interesterified oil and its fractions

A commercial sample of the Brazilian palm oil from the north eastern State of Bahia after neutralisation, washing and drying was interesterified in the presence of sodium-potassium alloy (NaK) at 30°C in a nitrogen atmosphere. The catalyst was destroyed by addition of water in a carbon dioxide atmosphere and the interesterified oil was crystallised from light petroleum, yielding an olein and stearin fraction. The fatty acid and triacylglycerol composition of the neutralised oil was determined by gas chromatography (g.c.) and high-performance liquid chromatography (h.p.l.c.) respectively and was shown to be similar to that of Malaysian and African palm oil. The compositions of the interesterified Brazilian oil and its liquid and solid fractions were also determined. The physicochemical characteristics of the olein obtained by interesterification with NaK, such as iodine value (96.8) and its softening point (below ?8°C) indicated its suitability for the use as salad oil.     

Analysis and improved synthesis of parasorbic acid

An improved synthesis of parasorbic acid, 5-hydroxy-2-hexenoic acid lactone (II), provided material to develop a procedure for its analysis as a possible contaminant in sorbic acid, 2,4-hexadienoic acid (I). Column chromatography was used to separate parasorbic acid from sorbic acid; thin-layer chromatography (t.l.c.) provided a means of identification and quantitative estimation. Gas chromatography-mass spectral analysis (g.c.-m.s.) was used for positive confirmation. No parasorbic acid up to 20 parts/million, the detectable limit, was found in several commercial food grade samples of sorbic acid.     

Extraction and analysis of free amion acids from sheep digesta

A routine procedure entailing three methanol-chloroform-water extractions and an ultrafiltration step was adopted to extract the free amino acids from freeze-dried sheep digesta. Detailed estimation and idefltification of the amino acids both by thin-layer electrophoresis (t.l.e,) coupled with thin-layer chromatography (t.l.e.) and by using a Beckman IZOC analyser was undertaken, Generally, there was agreement between the two methods, the latter being preferred because several amino acids were not suficiently separated by the t.l.e. and t.l.c. methods. The t.l.e. and t.l.c. method, however, showed the presence of several unidentified ninhydrin positive compounds not detected during automatic analyser estimations. Detailed analysis of the digestive tract samples revealed that the free amino acids decreased in amount during passage through the animal. However, five amino acids had higher values in the ileum than in the duodenum.     

Unsaponifiable matter of crude and processed coconut oil.

Coconut oil samples were taken prior to and during processing. Hydrocarbons, alcohols and sterols were separated from unsaponifiable matter (UNS) by column chromatography (c.c.) on Florisil and characterised by gas-liquid chromatography (g.l.c.) Hydrocarbons ranged from the C-17 to C-32 straight chain homologs and squalene. Small amounts of iso- and/or anteiso and branched chain hydrocarbons were found. Straight chain, iso- and/or anteiso-aliphatic alcohols, and four triterpenoid alcohols were identified. The UNS contained cycloartenol, α- and β-amyrin and 24-methylenecyloartenol. Campesterol, stigmasterol and β-sitosterol were found, with the latter comprising as much as 69.0% of the total sterol fraction. Some minor changes were noted in relative distribution of certain components at various stages in oil processing.     

The gas-liquid chromatographic analysis of the lysine content of feedstuffs

A method for the analysis of the lysine content of feedstuffs employing acid hydrolysis followed by enzymic decarboxylation of lysine and subsequent gas-liquid chromatographic (g.l.c.) analysis of the cadaverine produced, is described. The method is relatively rapid and a comparison of the results from a wide range of feedstuffs analysed by g.l.c. and by conventional ion-exchange chromatography gave confidence in the method.     

Separation of fructose,glucose and sucrose in fruit by high performance liquid chromatography using UV detection at 190 nm

Fructose, glucose and sucrose were separated by high performance liquid chromatography (h.p.l.c.) on a 5 μm amine column and detected by absorbance at 190 nm. The procedure quantified these sugars in orange juice and in carambola fruit, but preliminary ion exchange column chromatography was necessary before satisfactory h.p.l.c. results could be obtained. The method is sensitive to 1.2 μg of fructose or 9 μg of glucose or sucrose.     

Presence of quercetin-3-O-glucuronoside in Spanish table wines

Quercetin-3-O-glucuronoside has been identified in several Spanish table wines by thin-layer (t.l.c.) and high-performance liquid (h.p.l.c.) chromatographic methods. This is thought to be the first report of its occurrence in wine.     

Volatile components of cooked tubers of the water yam (Dioscorea alata)

Volatile constituents were isolated from yams, during cooking, by concurrent steam distillation-solvent extraction. The essence which resulted was analysed by linked gasliquid chromatography-mass spectrometry (g.l.c.-m.s.) employing capillary columns and by gas-liquid chromatography coupled with sensory evaluation of the column effluent (nasal appraisal). In addition to hydrogen sulphide and a number of high-boiling fatty acids, 29 compounds, comprising seven hydrocarbons, eight alcohols, eight aldehydes, four ketones, a furan and a disulphide, were identified for the first time in yam. A further five components were tentatively identified by g.l.c.-m.s. and by thinlayer chromatography of derivatives. 4-Phenylbutan-2-one was the major constituent of the acid-free essence.     

Ethyl acetate and fusel oil determination in distilled spirits by gas-liquid chromatography and confirmation by mass spectrometry

A gas-liquid chromatography (g.l.c.) method was developed for the determination of ethyl acetate, n-propyl, isobutyl, primary active amyl and isoamyl alcohol using Carbowax 400 as a liquid phase. These compounds were determined with a single injection at isothermal conditions with a minimum of bleed from the substrate. The procedure described, has certain points of advantage over the Official A.O.A.C. method because of improved column efficiency and resolution as shown in the separation of primary active amyl and isoamyl alcohols. Mass spectrometry was used to identify the individual compounds and to show its feasibility in such types of analysis.     

Selective extraction and quantitative analysis of non-starch and starch lipids from wheat flour.

Wheat flour non-starch lipids (lipids not bound to starch) were quantitatively extracted with water-saturated n-butanol (WSB), benzene-ethanol-water (10:10:1, by vol.) or ethanol-diethyl ether-water (2:2:1, by vol.) in 10min at 20 °C. Starch lipids (lipids bound to starch) were subsequently extracted with WSB at 90–100 °C. Carotenoid pigments were quantitatively extracted with the non-starch lipids. There was no significant hydrolysis of esterified fatty acids and no detectable autoxidation of unsaturated acids in the hot solvent extracts. Non-starch and starch lipids from a high grade spring wheat flour and three grades of winter wheat flour were separated by thin-layer chromatography and quantified as fatty acid methyl esters (FAME) by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (or its methyl ester) as internal standard. Total flour and starch lipids after acid hydrolysis were also converted to FAME for quantitation by g.l.c. Non-starch lipids consisted of 59–63% non-polar (neutral) lipids, 22–27% polar glycolipids and 13–16% phospholipids. Steryl esters, triglycerides, and all the diacyl galactosylglycerides and phosphoglycerides were present only in non-starch lipids. Starch lipids consisted of 6–9% non-polar (neutral) lipids (mostly free fatty acids), 3–5 % polar glycolipids and 86–91 % phospholipids (mostly lysophosphatidyl choline). Starch lipids were almost exclusively monoacyl lipids. Factors are given for converting weight of FAME into weight of original lipid for all individual lipid classes in wheat which contain O-acyl groups. Factors for total lipids are: total starch lipids = FAME × 1.70, total non-starch lipids = FAME × 1.20, and total flour (non-starch + starch) lipids = FAME × 1.32. Similar factors could be used to convert weight of lipids obtained by conventional acid hydrolysis methods into weight of unhydrolysed lipids. Phospholipid contents are given by: total starch phospholipids = P × 16.51, total non-starch phospholipids = P × 23.90, total flour phospholipids = P × 17.91.     

H.p.l.c. Determination of trace levels of succinic acid in orange juice from Freeze-damaged and undamaged fruit

Succinic acid was determined by high-performance liquid chromatography (h.p.l.c.) in juice from oranges subjected to freeze damage on the tree and by storage at below freezing temperatures. Succinic acid levels did not change in fruit subjected to freezing temperatures while on the tree or in storage. In order to measure succinic acid at these low levels (5–180 mg litre^?1 juice) an earlier h.p.l.c. procedure was modified.     

The composition of acyl lipids and tocopherols in wheat germ oils from various sources

The compositions of acyl lipids, fatty acids and tocopherols were determined for a series of laboratory-extracted and commercial wheat germ oils and a comparison made of the total carotenoid contents. High-performance liquid chromatography (h.p.l.c.) with fluorescence detection was used to determine tocopherols and tocotrienols without the need for pretreatment of the oils. The laboratory-extracted oils were similar in composition except for the content of free fatty acids and the β-tocotrienol derived from bran in the unpurified mill germ; carotenoid content was lower in oil from rancid or cooked germ. The commercial oils contained very low concentrations of carotenoids and polar lipids and three samples had unusual tocopherol compositions very different from those of the laboratory-extracted oils. One of these samples contained no detectable amount of linolenic acid which is usually present in cereal oils. It is concluded that the quality and composition of commercial wheat germ oil is very variable and that methods of assessing quality and detecting adulteration are essential. H.p.l.c. with fluorescence detection is well-suited to the analysis of tocopherols, tocotrienols and α-tocopherol acetate in wheat germ oil.     

The assay of the coccidiostat clopidol in animal feeds by high-pressure liquid chromatography

A simple method for the assay of the coccidiostat clopidol by high performance liquid chromatography (h.p.l.c.) is described. After extraction the solution is neutralised and filtered and injected on the h.p.l.c.-column. It is quantified by u.v.-detection. The method has been tested on commercial feed samples. The agreement with a standard reference method is good. The precision of the proposed method has a standard deviation of 2%. The recovery of added clopidol is 101% with a standard deviation of 2.4%. No interferences to the method have been found.     

Gas chromatographic determination of indole glucosinolates—a re-examination

The use of gas-liquid chromatography (g.l.c.) as a technique for the analysis of glucosinolates, including indole glucosinolates, in low-glucosinolate rapeseed meal and seed was assessed. Variation contributed by various steps of g.l.c. methodology was studied, and following modifications to the method analytical results were compared with those estimated from thiocyanate ion (SCN) release following treatment of samples with myrosinase enzyme. The volume of water required to effectively elute glucosinolates from a DEAE Sephadex column was shown to cause variability in analytical results. The effect was dependent upon the internal standard used and was most pronounced for indole glucosinolates. Heat treatment (95°C) required in the procedure for the inactivation of myrosinase enzyme was shown to result in substantial decomposition of indole glucosinolates. In this regard a standard procedure involving 15 min dry heat treatment followed by 3 min wet heat treatment is recommended. With these modifications the g.l.c. methodology was shown to be adequate as a routine procedure for the analysis of glucosinolates in low-glucosinolate rapeseed meal and seed.     

A Routine method for identification and quantitative determination by gas—liquid chromatography of galacturonic acid in pectic substances

A semi-micro method is described for the determination by gas-liquid chromatography (g.l.c.) of galacturonic acid in pectic substances which has been solubilised in aqueous ammonium oxalate. Galacturonic acid, liberated by hydrolysis with polyanhydrogalacturonase [poly-(1,4-α-D-galacturonide) glycanohydrolase; EC 3.2.1.15] and then converted to the L-galactono-1,4-lactone via potassium borohydride reduction and lactonisation using methanolic hydrogen chloride. The derived lactone was analysed by g.l.c. as the trimethylsilyl derivative, and was easily distinguished from the glucuronic acid reduction product, L-gulono-1,4-lactone. The method was applied to the analysis of pectic materials in leaflets, petioles, and stem of three tropical legumes, and also to the polygalacturonic content of commercial pectin preparations. The possibility of simultaneous determination of starch extracted with pectin is also discussed.