Employing Gas-liquid Chromatography Research Articles

Effect of Processing on Pesticide Residues in Some Edible Fresh Water Fishes

The present study was undertaken to ascertain the effect of processing on pesticide residues in edible fresh water fishes. The fish samples were collected from two different fish markets located in Ludhiana city. Pesticide residues were detected in five different fish species by employing Gas Liquid Chromatography. Major pesticides detected include β-HCH, γ-HCH and chlorpyriphos with levels 0.30 mg kg−1, 0.1–0.35 mg kg−1 and 0.14–0.58 mg kg−1, respectively. Catla catla, Labeo rohita and Cirrhinus mrigala were found to have higher levels of pesticide residues. These fish samples were then processed by four different processing methods viz. deep frying, steaming by pressure cooker, conventional oven baking and microwave oven baking to check the reduction in residue levels. Deep frying caused maximum reduction i.e. 40–45% as compared to other processing methods. Steaming reduced pesticide residues by 14–16%, microwave oven baking resulted in 17–20% and conventional oven baking resulted in 20–21% reduction.

Sphingolipid profiles are altered in prefrontal cortex of rats under acute hyperglycemia

Diabetes type 1 is a common autoimmune disease manifesting by insulin deficiency and hyperglycemia, which can lead to dementia-like brain dysfunctions. The factors triggering the pathological processes in hyperglycemic brain remain unknown. We reported in this study that brain areas with different susceptibility to diabetes (prefrontal cortex (PFC), hippocampus, striatum and cerebellum) revealed differential alterations in ceramide (Cer) and sphingomyelin (SM) profiles in rats with streptozotocin-induced hyperglycemia. Employing gas–liquid chromatography, we found that level of total Cer increased significantly only in the PFC of diabetic animals, which also exhibited a broad spectrum of sphingolipid (SLs) changes, such as elevations of Cer-C16:0, -C18:0, -C20:0, -C22:0, -C18:1, -C24:1 and SM-C16:0 and -C18:1. In opposite, only minor changes were noted in other examined structures. In addition, de novo synthesis pathway could play a role in generation of Cer containing monounsaturated fatty acids in PFC during hyperglycemia. In turn, simultaneous accumulation of Cers and their SM counterparts may suggest that overproduced Cers are converted to SMs to avoid excessive Cer-mediated cytotoxicity. We conclude that broad changes in SLs compositions in PFC induced by hyperglycemia may provoke membrane rearrangements in some cell populations, which can disturb cellular signaling and cause tissue damage.

Industrial hydrogenation of rice bran oil, a substitute for tallow

AbstractThe Indian soap industry's hard fat requirement was met until recent years by imported animal tallows. The search for alternate hard fats, consequent to the ban on the import of animal tallows in 1983, led to realization of the striking similarity in the fatty acid composition of mutton tallow and hydrogenated rice bran oil, except for thetrans oleic acid content. This paper traces the course of compositional changes undergone by rice bran oil during industrial hydrogenation, employing gas liquid chromatography and infra red spectroscopy.

Effect of nicotine on basal and bombesin stimulated canine plasma levels of gastrin, cholecystokinin and pancreatic polypeptide

The influence of nicotine on the basal and bombesin (BBS) stimulated plasma levels of gastrin, cholecystokinin (CCK) and pancreatic polypeptide (PP) was investigated in conscious dogs. Plasma levels of nicotine and gastrointestinal (GI) hormones were measured by employing gas liquid chromatography and specific radioimmunoassay (RIA). The basal levels of gastrin, CCK and PP were found to be in pg/ml (pmol/l) (mean±S.E.). 28±5 (13±3), 252±32 (66±8) and 347±136 (83±32) respectively and these values remained unchanged with nicotine. Significant increases in levels of gastrin, CCK and PP were, however, found with infusions of BBS alone or with BBS in combination with nicotine. Gastrin levels were higher whereas CCK and PP levels were lower with BBS alone than with BBS plus nicotine. The peak values for CCK and PP, but not gastrin, were less during second BBS infusion. These results indicate that nicotine, in presence of bombesin, has an inhibitory effect on the release of gastrin and a stimulatory effect on the release of PP and CCK.

Determination of low levels of chlorine in adipose tissue by means of the oxygen-flask combustion technique and gas-liquid chromatography

The oxygen-flask technique has been adapted to the determination of low levels of chlorine by employing gas-liquid chromatography. Following combustion and dissolution, chloride in aqueous solution was converted into phenylmercury(II) chloride by treatment at low pH with phenylmercury(II) nitrate. The phenylmercury(II) chloride was extracted quantitatively into toluene and determined by gas-liquid chromatography with an electron-capture detector. The method has been applied successfully to the analysis of rat and mouse adipose tissue, the chloride concentrations of which ranged from 10 to 2800 mg kg–1.

Formation of hydroxyl radicals from the paraquat radical cation, demonstrated by a highly specific gas chromatographic technique. The role of superoxide radical anion, hydrogen peroxide, and glutathione reductase

Yeast glutathione reductase catalyzes an NADPH-dependent reduction of the herbicide paraquat invitro. The single-electron reduced paraquat radical reacts with O 2 to generate the superoxide radical, ▪. Hydroxyl radicals ( ▪) can also be detected in this assay system by their reaction with phenol to form diphenols, as assayed quantitatively by a highly specific and sensitive method employing gas-liquid chromatography. Formation of hydroxyl radicals can be virtually completely suppressed by catalase and partially suppressed by superoxide dismutase. The role of hydroxyl radicals and superoxide in paraquat toxicity in vivo is discussed.

Time course of changes in porcine myocardial phospholipid levels during ischemia. A reassessment of the lysolipid hypothesis.

This study was performed to determine the early and delayed metabolic effects of myocardial ischemia on the major membrane phospholipids and to reassess the potential role of lysophospholipids in the genesis of malignant dysrhythmias induced by ischemia. Samples taken from in situ hearts before ant at various intervals up to 40 minutes after abrupt ligation of LAD were extracted by the classical Folch technique with modifications to avoid artifactual lysophospholipid production and losses. Following thin layer chromatography of lipid extracts, phospholipid fractions were quantified by phosphorus estimation and lysophospholipids by a more sensitive method employing gas liquid chromatography. The total phospholipid content with the exception of lysophospholipids remained essentially constant throughout the early phases of acute ischemia, but fell by 6 and 14% after 8 and 24 ours, respectively. At 8 minutes, lysophospholipid levels n ischemic myocardium were significantly increased by 60% compared to pre-occlusion controls in the ischemic zone and by 25% in post-occlusion controls. They changed little thereafter. The molecular species of lysophospholipids remained unchanged throughout the period of ischemia studied. The mole fraction of other phospholipids as well as their fatty acyl and aldehyde profiles also were unchanged. Despite significant elevations in lysophospholipids levels, their absolute quantities were very small (0.6% of total phospholipid P) and 15-fold smaller than that reported in vitro to simulate electrophysiological manifestation of ischemia. However, such small amounts in vivo, if produced in the microenvironment of certain membrane-bound enzymes along with acidosis, hypoxia, and fatty acids, could be potentially deleterious to cell functions.

Comparison of different methods of quantitative analysis employing gas-liquid chromatography, illustrated by the determination of water in organic solvents

The methods used in quantitative analysis employing gas-liquid chromatography are critically examined, and a division into three major categories is suggested. The various methods have been applied to the determination of water in organic solvents. It was found that for a moisture content of 0.1–5 wt.-% the external standard method is preferable to the internal standard method, and the method of standard additions is the least satisfactory. The “volume effect” and the “solute effect” were examined for various water-standard-solvent systems, and the errors were evaluated.

A test for heterozygocity of 21-hydroxylase deficiency

The urinary excretion of steroids was studied in 8 parents of children with congenital adrenal hyperplasia due to 21-hydroxylase deficiency of the simple virilizing and of the salt-losing type. Eight parents of normal children served as controls. 24-hour urines before and after the injection of 40 IU of ACTH were fractionated using gas liquid chromatography on glass capillary columns. Before stimulation no excretion of pregnanetriolone was detected in heterozygous and in normal parents. Following ACTH only heterozygotes showed an excretion of pregnanetriolone in the urine. This averaged 289 mug per 24 h. Employing gas liquid chromatography on glass capillary columns heterozygous carriers of congenital adrenal hyperplasia due to 21-hydroxylase deficiency may reliably be detected by their increased urinary excretion of pregnanetriolone following ACTH.

Determination of a mannose-containing trisaccharide in the urine of patients and heterozygotes of mannosidosis

A method employing gas-liquid chromatography and combined gas-liquid chromatography mass spectrometry was developed for the quantitative determination of α-D-mannopyranoside-(1 → 3)-β-D-mannopyranoside-(1 → 4)-2-acetamido-2-deoxy-D-glucose in urines. The concentration of this trisaccharide varied between 123 and 469 mg per litre of urine in the patients with mannosidosis but was not detected in twenty normals and two heterozygotes.

Metabolism of Sulfur Amino Acids by Rumen Microorganisms

The production of methanethiol and ethanethiol from L-methionine, s-methyl-l-cysteine, ethionine, and s-ethyl-l-cysteine during in vitro fermentation by rumen microorganisms was determined by employing gas-liquid chromatography to analyze the head-space gas produced by the fermentations. Each substrate with rumen fluid was incubated at 39C in serum bottles equipped to permit syringe sampling of the head-space gas evolved. All substrates were used at a concentration of 1.67 mg/ml rumen fluid. It was found that methanethiol was formed during the in vitro fermentation of s-methyl-l-cysteine and of methionine and that ethanethiol was produced from s-ethyl-l-cysteine and from ethionine. When dimethyl thetin chloride was used as substrate, dimethyl sulfide was formed. s-ethyl-l-cysteine inhibited production of methanethiol from s-methyl-l-cysteine in the early stages of fermentation, but inhibition was largely overcome as fermentation proceeded. Some indication of utilization of methanethiol was obtained and appeared to be related to diet. This is in accord with the production of methanethiol by the reaction: methionine →s-methyl-l-cysteine → methanethiol. However, it is possible that both methionine and s-methyl-l-cysteine were directly dethiomethylated.

Lipi composition of the developing larval fat body of Phormia regina.

The lipid composition of the larval fat body of Phormia regina was analysed at different periods during third-instar development. Lipid represented 21·8 per cent of the fat-body dry weight in the early third instar, whereas in the mature larva it constituted 52·5 per cent. Fractionation of the lipid into triglyceride, partial glycerides (includes free fatty acids), and phospholipid was accomplished using column and thin-layer chromatography. Triglyceride was found as the predominant lipid class accounting for almost 90 per cent of the total lipid of the prepupal fat body. Fatty-acid analysis of the three lipid fractions, employing gas-liquid chromatography, revealed the presence of three major (palmitoleic, oleic, and palmitic) and three minor (myristic, stearic, and myristoleic) fatty acids. The major fatty acids constituted 81·6 to 96·8 per cent of the total fatty acids and in general palmitoleic acid predominated. Phospholipid exhibited a greater percentage of palmitoleic and oleic acids than did triglyceride with the exception of the prepupal fat body. The change in the pattern of distribution of fatty acids in the prepupa resulted from a decline in the percentage of palmitoleic and oleic acids of phospholipid with a corresponding increase in the percentage of palmitic acid. The distribution of fatty acids in triglyceride did not change appreciably during development.

Plasma progesterone concentrations during pregnancy and lactation in the rat.

Summary. Plasma progesterone concentrations in rats were determined by a method employing gas-liquid chromatography with electron capture detection. Progesterone concentration was found to decrease before parturition and to increase again during lactation. A maximal post-partum concentration of this hormone was found during the 4th day of lactation. Removal of the litter or the placenta at delivery resulted in a decrease in the progesterone concentration at this time. Injection of large doses of prolactin in hypophysectomized female rats was associated with an increase in plasma progesterone concentration.

Progesterone in the blood. A quantitative method employing gas liquid chromatography.

A new method for the measurement of progesterone in the blood has been described in detail. After addition of NaOH to 5 ml plasma, the progesterone was extracted with acetone and then ether. The extract was purified by chromatography through a miniature celite column using trimethylpentane as the mobile phase and 90% methanol as the stationary phase. This step removed a large quantity of pigmented material and cholesterol. Further purification was achieved by thin layer chromatography in the system chloroform/acetone 9:1. After transfer to a simple dry sample application device, the progesterone was separated and the quantity was measured by means of gas liquid chromatography using a 6 ft XE 60 column. The method has been used to assay samples of plasma from patients at all stages of pregnancy and parturition. Its accuracy and reproducibility have been assessed by multiple measurements of 0.1 Mg progesterone added to male pooled plasma. The mean recovery at this level was 78.6%, SD±11.7%, coeflicient of v...