Rapid gas chromatographic determination of ethylene oxide, ethylene chlorohydrin, and ethylene glycol residues in rubber catheters

Isothermal gas chromatography with flame ionization detection was used to determine residual ethylene oxide (EtO), ethylene chlorohydrin, and ethylene glycol in soft rubber catheters that had been sterilized with EtO. Catheter samples were extracted by shaking with carbon disulfide, and the extract was analyzed on a 3% Carbowax 20M on 80-100 mesh Chromosorb 101 column, using nitrogen as the carrier gas. Ten replicate injections of a mixed standards solution gave coefficients of variation of 1.91, 1.23, and 4.74% for EtO, ethylene chlorohydrin, and ethylene glycol, respectively. A linear response was obtained with concentrations ranging from 1.0 to 7.9 micrograms EtO, 14.0 to 88.0 micrograms ethylene chlorohydrin, and 31.0 to 98.5 micrograms ethylene glycol. The proposed method detected as little as 0.5, 5.0, and 16.5 ng EtO, ethylene chlorohydrin, and ethylene glycol, respectively.     

A new rapid and accurate method for the determination of carbon in soils

The most reliable method for determining carbon in soils is the dry combustion method, the technique of which was established for the first time by JUSTUS von LIEBIG in 1831 and for nearly a century his combustion technique, essentially unmodified save for improvements in materials, constituted the standard method for determination of carbon and hydrogen. PREGL (1), in his publication on organic microanalyses in 1916, reported an excellent method in which a carbon determination could be carried out in an hour with a sample of only a few milligrams. After that, his method was improved in many respects by many investigators (2,3). Since these methods require, however, both complicated and expensive apparatus as well as trained personnel and are time-consuming, they are not considered to be suitable for practical use in soil research laboratories at all.     

Simple colorimetric method for determination of metaproterenol sulfate in pharmaceuticals

A simple colorimetric method is described for the determination of metaproterenol sulfate (orciprenaline sulfate). The method is based on measurement of a colored species formed when metaproterenol sulfate is treated with diazotized dapsone, p-nitroaniline, or benzocaine at room temperature, followed by treatment with an aqueous solution of trimethylamine in the case of benzocaine. Compounds such as starch, talc, and common excipients do not interfere in the reaction. Statistical validation showed that the method was precise and accurate. The results agree well with those obtained by other methods reported in the literature.     

Simple colorimetric method for determination of thiamine hydrochloride in pharmaceuticals

A simple colorimetric method is described for the determination of thiamine hydrochloride (vitamin B1) in dosage forms. The method is based on measurement of a yellow complex formed when thiamine HCl is treated with p-methylaminophenol sulfate (Metol) under alkaline conditions. Compounds such as vitamins A, B2, B6, B12, C, D, and E, and niacinamide, citric acid, liquid glucose, calcium pantothenate, biotin, liver extract, and folic acid do not interfere in the reaction. Extracting the complex into chloroform before quantitation enhances the stability of the reaction product and removes interference of water-soluble colored constituents in syrup samples. Statistical validation shows that the method is precise and accurate. Results agree well with those obtained by other methods in the literature.     

Simple spectrophotometric method for determination of phosphine residues in wheat

A method has been developed for determination of phosphine residues in wheat, based on the reaction of phosphine with silver nitrate in aqueous solution to form an egg-yellow chromophore with an absorption maximum at 400 nm. At this wavelength, there is a linear relationship between absorbance and concentration of phosphine in the range 10-100 ng/mL. Phosphine-fumigated wheat is soaked in a known volume of AgNO3 solution, and the absorbance of the filtrate is read against a blank at 400 nm. The method is sensitive, with lower detection and estimation limits of 0.008 and 0.01 micrograms PH3, respectively. Recovery of added phosphine from a closed system was 85-100%. Accuracy for this method has been compared with that for the gas chromatographic method.     

Purge and trap method for determination of ethylene dibromide in table-ready foods

An improved method has been developed for the determination of ethylene dibromide (EDB, 1,2-dibromoethane) in a variety of table-ready foods. Samples are mixed with water and sparged with nitrogen for 1 h with stirring in a water bath at 100 degrees C. The EDB collected on the adsorbent Tenax TA is eluted with hexane and determined by gas chromatography (GC) with electron capture (EC) and confirmed with Hall electrolytic conductivity (HECD) detection using a second GC column. The highest levels of EDB were also confirmed by full scan GC/mass spectrometry (GC/MS). Twenty-five table-ready foods from the Food and Drug Administration's Total Diet Study that were analyzed by this method exhibited levels up to 70 ppb (pecans). Recoveries from fortified samples ranged from 91 to 104%. Values from this procedure were compared to those obtained by a modified Rains and Holder codistillation method. In all 25 samples this purge and trap procedure showed equivalent or superior recoveries and detected levels of EDB.     

Simple and rapid spectrophotometric method for determination of adrenaline and isoprenaline

A simple, rapid, and specific method for determination of adrenaline bitartrate and isoprenaline sulfate was developed. The method is based on the oxidation reaction in aqueous solution of either adrenaline bitartrate or isoprenaline sulfate in the presence of silver oxide to give a red aminochrome measurable at 490 nm. The color is stable for 2 h. Beer's law is valid within a concentration range of 5-80 micrograms/mL for each drug. All variables were studied to optimize the reaction conditions. The method is specific for catecholamine drugs having a secondary amine in the side chain. Other catecholamines such as orciprenaline and noradrenaline do not interfere, and no interference was observed in the presence of common pharmaceutical adjuvants. Interference due to sodium metabisulfite and sodium chloride was circumvented. The validity of the method was tested by analyzing adrenaline injections and isoprenaline tablets. Good recoveries were obtained for these preparations. The results were comparable to those obtained by official procedures. The proposed method is also recommended as a stability indicating assay for oxidative degradation of both drugs.     

Simple saponification method for the quantitative determination of carotenoids in green vegetables

A simple, reliable, and gentle saponification method for the quantitative determination of carotenoids in green vegetables was developed. The method involves an extraction procedure with acetone and the selective removal of the chlorophylls and esterified fatty acids from the organic phase using a strongly basic resin (Ambersep 900 OH). Extracts from common green vegetables (beans, broccoli, green bell pepper, chive, lettuce, parsley, peas, and spinach) were analyzed by high-performance liquid chromatography (HPLC) for their content of major carotenoids before and after action of Ambersep 900 OH. The mean recovery percentages for most carotenoids [(all-E)-violaxanthin, (all-E)-lutein epoxide, (all-E)-lutein, neolutein A, and (all-E)-beta-carotene] after saponification of the vegetable extracts with Ambersep 900 OH were close to 100% (99-104%), while the mean recovery percentages of (9'Z)-neoxanthin increased to 119% and that of (all-E)-neoxanthin and neolutein B decreased to 90% and 72%, respectively.     

Improved codistillation method for determination of carbon tetrachloride, ethylene dichloride, and ethylene dibromide in grain and grain-based products

A method is described for the determination of the common fumigants carbon tetrachloride (CCl4), ethylene dichloride (EDC), and ethylene dibromide (EDB) in grain and grain-based products. A properly prepared sample is mixed with water and hexane, an internal standard mixture of 1,2-dichloropropane (DCP) and 1,2-dibromopropane (DBP) is added, and the fumigants are codistilled with the hexane into an appropriate receiver. After the hexane solution is dried over sodium sulfate, the quantities of fumigants present are quantitated on a gas chromatograph (GC) equipped with an electron capture detector (ECD). For the matrices investigated, the relative standard deviation of the method was 6.0, 9.7, and 23.1% for CCl4, EDC, and EDB, respectively. Recoveries of added fumigants were 107, 95, and 101%, respectively. Comparison with an acetone-water soak extraction method gave a correlation of 0.967 between methods for EDB with odds of a difference between methods of 35%.     

Simple colorimetric method for determination of terbutaline sulfate from pharmaceutical preparations

A simple colorimetric method is described for the determination of terbutaline sulfate. The method is based on measurement of a colored species formed when terbutaline sulfate is treated with diazotized dapsone and p-nitroaniline at room temperature. Compounds such as starch, talc, and common excipients do not interfere in the reaction. Statistical validation showed that the method was highly precise and accurate. The results agree well with those obtained by other methods reported in the literature.     

Simple, rapid method for determination of total extractable fat in canned pet foods

The rapid column method described, unlike AOAC method 7.056, determines both neutral ("crude") and total fat in canned pet foods, and uses nonflammable solvent mixtures and simple laboratory equipment. Neutral fat values are obtained by eluting the column with dichloromethane, whereas total fat values are determined by using dichloromethane-methanol (9 + 1). For 7 samples analyzed in triplicate, fat ranged from 2.9 to 10.8%. Neutral fat values by the dry column method were significantly lower (P less than 0.05) than were those by 7.056 (6.29 vs 6.49), although these differences were practically unimportant. Total fat determinations by the dry column method and by 7.056 yielded overall means of 7.40 and 6.49%, respectively. The 0.91% mean difference is significant (P less than 0.01) and represents a more complete extraction of polar lipids by the proposed method.     

Simple method of genomic DNA extraction from Rhizobia in dried nodules of Phaseolus vulgaris for strain differentiation by PCR-based DNA fingerprinting

Repetitive DNA peR fingerprinting of bacterial genomic DNA is a useful tool for typing and differentiation of rhizobial strains. The method was reported to be suitable for strain differentiation of Rhizobia present in individual root nodules of some leguminous plants without the need for isolation and cultivation of the strains, in which rhizobial genomic DNA was extracted directly from each fresh or frozen nodule. We developed a new protocol of rhizobial genomic DNA extraction/purification from dried nodules of Phaseolus vulgaris for generating repetitive DNA peR fingerprints of Rhizobia present in the nodules. The simplified protocol consists of only three major steps, heat extraction of genomic DNA from rhizobial cells prepared from dried nodules, ethanol precipitation of the DNA and Sephadex G-50 column purification of the DNA, and generated fingerprints with good quality for differentiation of Rhizobia strains. The protocol will be useful to examine the nodule occupancy of inoculated rhizobial strains in field experiments.     

Simple combustion-vapor trapping technique for determination of mercury in fish

A simple combustion train was constructed for analyzing mercury in fish samples. A nitric acid trap was used to capture the mercury vapors which were released later by adding a tin salt. The method is rapid, accurate, and reproducible and permits one person to analyze 40 samples daily. Sample matrix had no apparent effect on the recovery of mercury. Mean recoveries from fish samples spiked with 0.3 and 1.0 microgram mercuric chloride/g ranged from 97 to 105% with an average recovery of 101.5% and a standard deviation of 2.74%.     

Comparison of methodology for determination of ethylene dibromide in grains and grain-based foods

Three commonly used methods for determination of ethylene dibromide (EDB) in grains and grain products have been compared. EDB residues were extracted by soaking in hexane, triple co-distillation with hexane from an aqueous sample solution, and soaking in acetone-water (5 + 1). Each method was used for triplicate analyses of 12 samples containing incurred residues of EDB ranging from about 10 to 1000 ppb and representing whole grains (wheat and oats) and intermediate grain-based products such as corn meal and flour. The 4-day hexane soaking method extracted the least EDB. In some cases, this was half of the amount determined by the other methods. Levels from soaking in acetone-water were equal to, or up to 25% greater than, those from distillation. Although soaking for 2 days is required for whole grains in the method, a period of only 16 h was found acceptable for ground products. Results were obtained faster with the distillation method, but more analyst time per sample was required. A single distillation recovered about 80% (40-60% from wheat) of total EDB extracted by triple distillation. Foaming was reduced by the addition of concentrated H2SO4 to the aqueous hexane-sample mixture, plus stirring during distillation, thereby allowing complete recovery of the hexane.     

Simple method for derivatization of monoglycerides and diglycerides

A method has been developed for derivatization of monoglycerides and diglycerides to their propyl esters by using propionic anhydride in the presence of pyridine. The derivatives are volatile and thus can be separated and identified by gas chromatography (GC). Completion of the reaction is monitored by thin-layer chromatography. Monoglyceride propyl esters were positively identified by gas chromatography and by gas chromatography/mass spectrometry. No side products were observed in the derivatization reaction which requires 35 min at 75 degrees C. GC analysis of the mono- and diglyceride propyl esters can be completed in approximately 30 min.     

Simple analytical method for organophosphorus pesticide determination in unpolished rice, using removal of fats by zinc acetate

A rapid and simple method is developed for the determination of organophosphorus pesticides in unpolished rice. The new method incorporated acetonitrile-water (1 + 1) extraction, removal of fats by zinc acetate, and further cleanup on an activated charcoal chromatographic column. The higher fatty acids in the extract react rapidly with zinc acetate to form insoluble zinc carboxylates, which precipitate. Additional interferences were cleaned up on an activated charcoal chromatographic column, and organophosphorus pesticides adsorbed on the activated charcoal were eluted with acetone-hexane. Dimethoate is not retained on the activated charcoal and must be extracted with dichloromethane from the first acetonitrile-water eluate. Pesticides are measured by flame photometric gas chromatography. Recoveries from 50 g unpolished rice samples fortified with 5-50 micrograms diazinon, 6-30 micrograms parathion, 8-40 micrograms fenitrothion and IBP, 10-50 micrograms dimethoate and fenthoate, 20-100 micrograms malathion, or 40-200 micrograms EPN ranged from 75.7 to 95.8%.     

食用肠衣的精确测量装置及方法

食用肠衣质量轻,经济价值高,具有弹性、油腻和光滑等特性,精确测量其长度比较困难。通过研究市场的需求,设计了一种肠衣传送测量机构,由传送带牵引肠衣移动,步进电动机控制传送带的速度。采用高精度圆形编码器记录测长轮数据,可编程序控制器调控步进电动机的运行速度,触摸屏输入控制参数和显示测量数据等技术,解决了肠衣精确测量问题。系统的测量速度可达0.84m/s,测量效率是人工测量的2倍,系统自动化程度高,工作可靠,生产环境卫生。实践证明,肠衣测量系统可满足生产工艺的要求,肠衣测量误差≤0.4%,提高了测量精度。