The determination of optical brighteners in laundry detergents by reverse phase and ion pair high performance liquid chromatography

Eleven optical brighteners have been qualitatively and quantitatively determined using C₁₈, C₈, or C₂ reverse phase high performance liquid chromatography (HPLC) columns. Comparable results also were obtained using radially compressed reverse phase HPLC cartridges. Mobile phases consist of acetonitrile and methanol in water with 0.05 M phosphate buffer. Quaternary ammonium salts also are added to the mobile phase for ion pair formation. Ultraviolet (UV) detection at 340 nm gives more than adequate sensitivity for brighteners formulated between 0.05 and 2.0%. Sample preparation is simple and all components can be eluted within 15 min. Powdered and liquid detergents, fabric softeners, and bleach boosters have been routinely analyzed and results closely agree with those obtained using thin layer chromatography and densitometry.     

The analysis of phospholipids in soy lecithin by HPLC

A high performance liquid chromatography (HPLC) method is described for the HPLC analysis of major phospholipids in soy lecithin. The method entails dissolving soy lecithin in chloroform prior to analysis. The HPLC determination uses a normal phase column and a mobile phase of acetonitrilemethanol-H₃PO₄ with detection at 205 nm. The data presented illustrates that the method is rapid, accurate and precise for the determination of phospholipid in soy lecithin.     

The Measurement Of Very Low Level Bromate Ion

The potential to form BrO₃ ^? as a byproduct during ozone treatment of raw water containing bromide ion is a major concern for utilities planning to use ozone. The proposed BrO₃ ^? Maximum Contaminant Level (MCL) of 10 μg/L in the USA has been established largely by using ion chromatography. A spectrophotometric method based on the oxidation of chlorpromazine in the presence of BrO₃ ^? has been developed. The method detection limit (MDL) in reagent water is 0.8 μg/L BrO₃ ^? The procedure has an operating range of 1 to 40 μg/L BrO₃. The precision of the method is calculated to be better than 2.5% with an accuracy within ± 1 μg/L BrO₃ ^?. Details of the method are presented along with data gathered by ion chromatography using borate and carbonate eluants; chlorpromazine post column studies; and low level capillary electrophoresis studies.     

Ultrafast preparation of branched poly(methyl Acrylate) through single electron transfer living radical polymerization at room temperature

Ultrafast preparation of branched poly(methyl acrylate) (BPMA) with high‐molecular weight through single electron transfer living radical polymerization (SET‐LRP) of inimer at 25°C has been attempted, atom transfer radical polymerization (ATRP) at 60°C was also carried out for comparison. Gas chromatography, proton nuclear magnetic resonance, and triple detection size exclusion chromatography were used to analyze these polymerizations. As expected, SET‐LRP system showed much faster polymerization rate than ATRP system, the calculated apparent propagation rate constants (k_p^app) are 3.69 × 10^?2 min^?1 and 6.23 × 10^?3 min^?1 for SET‐LRP and ATRP system, respectively. BPMA with high‐molecular weight (M_w._MALLS = 86,400 g mol^?1) compared with that in ATRP (M_w.MALLS = 61,400 g mol^?1) has been prepared. POLYM. ENG. SCI., 54:1579–1584, 2014. © 2013 Society of Plastics Engineers     

Analysis of polycyclic aromatic sulfur heterocycles in Egyptian petroleum condensate and volatile oils by gas chromatography with atomic emission detection

Eight Egyptian petroleum condensates and two volatile oils were analyzed by gas chromatography. The condensate oils range in color from colorless to yellow and brown. The samples are composed mainly of saturates hydrocarbons (C₃ to C₃₅). The polycyclic aromatic sulfur heterocycles (PASH) were isolated through use of a silica bonded palladium(II)-complex and their distribution investigated by gas chromatography (GC) with atomic emission detection (AED) in the sulfur-selective mode. The condensate oils show distinctly different distributions of the PASHs, some containing mainly benzothiophenes, and others both benzo- and dibenzothiophenes and a third group in which the dibenzothiophenes strongly dominate. The alkyl substituted sulfur compounds are quantified. The distribution patterns of the PASHs are correlated to the type of reservoir source rocks.     

Hydrocarbons detected in irradiated shell eggs during storage

Hydrocarbons produced by γ-radiation of shell eggs were analyzed to determine how irradiation affects their production. Shell eggs were nonirradiated or irradiated at 0.5, 1, and 3 kGy and the stored at 5°C for 8 wk or at 30°C for 10 d. Hydrocarbons were determined by a sequential procedure of lipid extraction by hexane, Florisil column chromatography, and gas chromatography. Hydrocarbons C_15:0, C_14:1, C_17:0, C_16:1, C_17:1, C_16:2, C_17:2, and C_16:3 were detected in shell eggs irradiated at 0.5 kGy or higher, but not in nonirradiated ones except C_15:0 and C_17:0. Storage of nonirradiated or irradiated eggs had little effect on detection levels of hydrocarbons. The detection levels in all the samples irradiated at 1 and 3 kGy were in the order of C_16:2+C_17:1, C_15:0+C_14:1, C_17:2+C_16:3, and C_17:0+C_16:1 from the highest to the lowest.     

COMPARISON OF TWO ANALYTICAL METHODS FOR THE DETERMINATION OF AZAARENES IN ATMOSPHERIC PARTICULATE MATTER

In this paper, the development of an analytical method for the separation and quantification of 20 azaarenes is described. Two methods are compared: high performance liquid chromatography with fluorescence detection (HPLC-fluorescence) and gas chromatography with mass spectrometry detection (GC-MS).

Although HPLC-fluorescence was proven to be the most sensitive method, GC-MS was selected in particular for the efficiency of the separation of the 20 azaarenes. The detection limits of the HPLC-fluorescence and GC-MS methods varied between 0.04 μ g.L^?1 (dibenz[a,c]acridine) and 1.30 μ g.L ^?1 (acridine) and between 1.50 μ g.L ^?1 (benz[c]acridine) and 2.56 μ g.L ^?1 (dibenz[a,c]acridine) respectively.

The GC-MS method was applied to particulate matter (PM ₁₀ ) samples collected over 48–72 h periods between April 2006 and February 2007 in Strasbourg (East of France). Before analysis aerosol samples were Soxhlet extracted and concentrated to a final volume of about 1 mL of hexane.

The seasonally mean concentrations of all azaarenes for this urban site have shown a seasonal variation in which the maximum concentration occurred in the winter (6.0 ng.m ³ ) and the minimum in the summer (0.90 ng.m³). For all the seasons the 2 rings species were the predominant azaarenes while the > 4 rings species were the less abundant.     

Quantitation of vitamin K in human milk

A quantitative method was developed for the assay of vitamin K in human colostrum and milk. The procedure combines preparative and analytical chromatography on silica gel in a nitrogen atmosphere followed by reversed phase high performance liquid chromatography (HPLC). Two HPLC steps were used: gradient separation with ultraviolet (UV) detection followed by isocratic separation detected electrochemically. Due to co-migrating impurities, UV detection alone is insufficient for identification of vitamin K. Exogenous vitamin K was shown to equilibrate with endogenous vitamin K in the samples. A statistical method was incorporated to control for experimental variability. Vitamin K₁ was analyzed in 16 pooled milk samples from 7 donors and in individual samples from 15 donors at 1 month post-partrum. Vitamin K₁ was present at 2.94±1.94 and 3.15±2.87 ng/mL in pools and in individuals, respectively. Menaquinones, the bacterial form of the vitamin, were not detected. The significance of experimental variation to studies of vitamin K in individuals is discussed.     

Alkylphenol ethoxylates in the environment

A comprehensive monitoring study, sponsored by the Chemical Manufacturers Association and designed in cooperation with the Environmental Protection Agency (EPA), measured the levels of nonylphenol (NP) and its ethoxylates (NPE) in 30 rivers. The sites, all receiving municipal or industrial wastewater, were selected at random from EPA’s United States river reach database by a statistical procedure. Water column and bottom sediment samples were collected along a perpendicular transect at each site. All samples were assayed for NP and NPE₁, and the higher ethoxylates (NPE₂ to NPE₁₇) were determined in the water samples. Analysis was by high-performance liquid chromatography (HPLC) with fluorescence detection of microgram quantities of NPE obtained by extractive steam distillation (NP and NPE₁) or a dualcolumn extraction procedure (NPE₂ to NPE₁₇). Sample collection and analytical procedures were validated according to rigorous EPA guidelines, and quality assurance standards were met throughout the study. NP and NPE concentrations in river water were mostly (60 to 75% of the samples) below their detection limits (about 0.1 ppb for NP, NPE₁, and NPE₂; 1.6 ppb for NPE_3–17). The highest levels found were about 1 ppb for NP, NPE₁, and NPE₂, 15 ppb for NPE_3–17. A majority of sediment samples contained detectable amounts of NP and NPE₁, ranging up to 3000 ppb for NP and 170 ppb for NPE₁. Sediment interstitial water concentrations of NP were estimated to be similar to concentrations in the water column. A portion of this paper was presented at the 1991 Annual AOCS Meeting in Chicago     

Nitro-fatty Acids Occur in Human Plasma in the Picomolar Range: a Targeted Nitro-lipidomics GC–MS/MS Study

First studies on the occurrence of nitrated fatty acids in plasma of healthy subjects revealed basal concentrations of 600 nM for free/nonesterified nitro-oleic acid (NO₂-OA) as measured by liquid chromatography tandem mass spectrometry (LC–MS/MS). We recently showed by a gas chromatography tandem mass spectrometry (GC–MS/MS) method the physiological occurrence of two isomers, i.e., 9-NO₂-OA and 10-NO₂-OA, at mean basal plasma concentrations of 880 and 940 pM, respectively. In consideration of this large discrepancy we modified our originally reported method by replacing solid-phase extraction (SPE) by solvent extraction with ethyl acetate and by omitting the high-performance liquid chromatography (HPLC) step for a more direct detection and with the potential for lipidomics studies. Intra-assay imprecision and accuracy of the modified method in human plasma were 1–34% and 91–221%, respectively, for added NO₂-OA concentrations in the range 0–3,000 pM. This method provided basal plasma concentrations of 306 ± 44 pM for 9-NO₂-OA and 316 ± 33 pM for 10-NO₂-OA in 15 healthy subjects. Nitro-arachidonic acid and nitro-linolenic acid were not detectable in the plasma samples. In summary, our studies show 9-NO₂-OA and 10-NO₂-OA as endogenous nitrated fatty acids in human plasma in the pM range; HPLC is recommendable as a sample clean-up step for reliable quantification of nitro-oleic acids by GC–MS/MS.     

Preparation of heat‐resistant branched poly(styrene‐alt‐NPMI) by ATRP with divinylbenzene as the branching agent

Heat‐resistant branched poly(styrene‐alt‐NPMI) has been prepared via atom transfer radical polymerization (ATRP) of styrene (St) and N‐phenyl maleimide (NPMI) with divinylbenzene (DVB) as the branching agent in anisole at 80°C. Gas chromatography (GC) was used to determine the conversion of the reactants. Triple detection gel permeation chromatography (TD‐GPC) was used to analyze the copolymers. The results show that the polymerization yields primary chains predominately in the early stages and the formation of branched molecules occurs mainly when conversion is higher than 50%. As expected, higher dosage of DVB in our investigation range favors the formation of polymers with higher degree of branching. All the resulting branched poly(styrene‐alt‐NPMI)s have glass transition temperature (T_g) above 175°C, extrapolated initial weight loss temperature (T_i) above 410°C and statistic heat‐resistant index above 200°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Highly accurate photopyroelectric measurement of thermal diffusivity of vegetable oils

High‐accuracy photopyroelectric measurements, in the thermal‐wave‐resonator‐cavity configuration, were performed in order to measure the thermal diffusivity of some vegetable oils. The high resolution (relative error ±0.5%) of the above method allows for the detection of small changes in the values of this dynamic thermal parameter. The accuracy of the results is mainly due to the possibility to precisely control the variation (30‐nm step) of sample thickness, a proper selection of the range of the thickness scan (2 µ_m < L_m < 4 µ_m ? 5 µ_m), and an iterative procedure of data analysis. A correlation between thermal diffusivity and the fatty acid composition (obtained via gas chromatography) is suggested for some fresh (sunflower, hemp, flax, and soybean) oils and for hemp oil exposed to a microwave field: Thermal diffusivity appears to be determined by the overall content of polyunsaturated fatty acids.     

Liquid chromatography-mass spectrometry of nonionic surfactants using electrospray ionization

The analysis of nonionic surfactants was investigated by reversed-phase liquid chromatography with mass spectrometry detection. On a C₁₈ column, separation was achieved on the basis of chain lengths of both alkyl and ethoxy groups in a CH₃CN/CH₃OH/H₂O/HAc solvent system. Peaks were identified by electrospray mass spectrometry.     

Compositional and thermal characterization of genuine and randomized lard: A comparative study

Composition and thermal characterization of genuine and randomized lard were investigated comparatively in an attempt to find common merits that assess lard detection. The investigation included compositional and positional distribution of fatty acids, triacylglycerol profiling by gas chromatography (GC) and reversed-phase high-performance liquid chromatography (RP-HPLC), as well as thermal behavior by differential scanning calorimetry (DSC) of both samples. Individual and total saturated and unsaturated fatty acid composition in total fats of both genuine and randomized lard were identical. On the other hand, the results of pancreatic lipolysis/GC analysis showed that the average percent palmitic acid [PAEF(%)] and myristic acid [MAEF(%)] enrichment factors of genuine (280 and 270) and randomized lard (110 and 98) were quite different. Thus, application of PAEF to detect randomized lard is of no value. However, normalization of fatty acid distribution by randomization in 2-monoacylglycerols made the individual and total saturated and unsaturated fatty acids almost identical to that of total fat and neutral triacylglycerols (TG) of lard. TG compositional analysis by GC revealed that both genuine and randomized lard had six dominant TG (C_46′C_48′C_50′C_52′C_54′ and C₅₆) with quite different concentrations. TG with C₅₂ represent the major constituent of genuine and randomized lard. TG profiling of samples was also carried out by RP-HPLC with a refractive index detector. The same peaks were eluted in both samples, but the area % of major peaks changed due to randomization. 2-Palmitooleostearin (SPO) was found in high proportion in lard. However, the ratios of SPO to 2-palmitooleolinolein of both genuine and randomized lard are close (0.6±0.05) and significantly distinguishable from that of beef (4.24), mutton (6.17), chicken (0.21), and turkey (0.14) fats. The DSC thermogram and thermodynamics of phase transitions of both samples were quite different and do not reveal common characteristic(s) that could be used for immediate detection of lard substances in fat admixtures.     

The rhodium-catalyzed deuteration of unsaturated triglycerides

Tripalmitolein, triolein, trilinolein and trilinolenin were deuterated with deuterium gas and Wilkinson’s catalyst [(Ph₃P)₃RhCl(I)]. Recrystallization of the products from acetone yielded highly pure deuterium-labelled triglycerides (TG). The deuterated TG were converted to methyl esters and analyzed by gas chromatography/mass spectroscopy to determine the deuterium distribution. Methyl palmitate-9,10-d₂ (from tripalmitolein) and methyl stearate-9,10-d₂ (from triolein) yielded isotopic distributions of 93–97% d₂, methyl stearate-9,10,12,13-d₄ (from trilinolein) of 74% d₄ and methyl stearate-9,10,12,13,15,16-d₆ (from trilinolenin) of only 58% d₆. Because the deuterium-labelled TG were to be used in human metabolism studies, atomic absorption spectroscopy was used to determine if any residual rhodium was present. No rhodium was detected at 70 ppb (the minimum detection limit).     

Molecular weight characterization of polybutadiene rubber with high molecular weight and broad molecular weight distribution

Following the molecular weight characterization of two polybutadiene samples, it was found that M _w from gel permeation chromatography with universal calibration and light scattering were in agreement, but M _n by gel permeation chromatography was less than M _n from membrane osmometry. A more detailed analysis revealed that the high molecular weight and broad molecular weight distribution of the two samples forced two corrections to the membrane osmometry results for (a) diffusional layer effects caused by high solution viscosities, and (b) solute permeability of the membrane. In the latter effect, the high viscosities of the solutions prevented actual diffusion through the membrane, but “reflection” of these species as defined by the Staverman coefficient prevented an accurate M _n determination. After making these corrections, it was found that M _n from membrane osmometry using a very tight membrane was in very good agreement with M _n from gel permeation chromatography. A method is demonstrated for obtaining M _n from a combination of membrane osmometry and gel permeation chromatography, where membrane osmometry data from membranes of different porosities (after corrections for diffusional layers and membrane reflection) are used to verify the accuracy of the gel permeation chromatography data as representing the true molecular weight distribution, allowing the gel permeation chromatography data to be used to calculate M _n.     

Conversion of allylic hydroxy oleate to conjugated linoleic acid and methoxy oleate by acid-catalyzed methylation procedures

Conjugated linoleic acid (CLA), a term describing a group of conjugated octadecadienoic acids that are both naturally occurring and formed during food processing, is the subject of considerable current research because of the recently reported antioxidant and anticarcinogenic properties of these compounds. Allylic hydroxy oleates (AHOs), secondary products of lipid autoxidation, have also been found in foods. By means of high-performance liquid chromatography with ultraviolet detection, gas chromatography/mass spectrometry and gas chromatography/matrix isolation/Fourier transform infrared spectroscopy, we determined that currently used acid-catalyzed methylation procedures convert AHOs to CLA and other products that potentially yield high values in determination of CLA in foods. A mixture of AHOs, containing mainly (8- and 11-)hydroxy-9-octadecadecenoates, was synthesized and tested by methylation procedures with the following catalysts: BF₃, HCl, NaOMe and tetramethylguanidine. Both the BF₃ and the HCl procedures converted AHOs to CLA. The base-catalyzed procedures did not convert AHOs to CLA.     

A New Method for the Analysis of Soluble and Insoluble Oxalate in Pulp and Paper Matrices

A novel method has been developed for determining soluble and insoluble forms of oxalate in pulp and paper samples by ion chromatography. Methanesulphonic acid is used to dissolve insoluble oxalate, and total oxalate is then determined by ion chromatography with suppressed conductivity detection. Soluble oxalate is determined directly by ion chromatography, without prior chemical treatment. Insoluble oxalate is obtained by difference. The method was applied to samples of pulp, process liquors, filtrates, and scale deposits from kraft mills. In kraft mills, considerably higher levels of oxalate were found in the Eop samples compared to those in the brownstock and D₀ samples. In both brownstock and Eop samples, oxalate was mainly present in soluble form, whereas the D₀-stage contained relatively higher levels of insoluble oxalate.     

Agonist-induced lipoxin A4 generation: Detection by a novel lipoxin A4-ELISA

Lipoxin A₄ (LXA₄) possesses potent bioactions. To facilitate its detection, an enzyme-linked immunosorbent assay (ELISA) was developed that proved sensitive and selective. Quantitation by ELISA of LXA₄ generated from cellular sources strongly correlated (r=0.99) with values obtained by high-pressure liquid chromatography (HPLC). We used this LXA₄-ELISA to examine parameters influencing LXA₄ generation from endogenous substrates during human platelet-neutrophil (PLT-PMN) interactionsin vitro. Agonist-induced LXA₄ production was clearly evident at a PLT-PMN ratio of 10∶1, and recombinant human granulocyte/monocyte colony stimulating factor-priming of PMN augmented LXA₄ generation 5–6 fold. The chemotactic peptide formylmethionyl-leucyl-phenylalanine, platelet-derived growth factor and arachidonic acid (20∶4n−6) each stimulated formation of immunoreactive LXA₄ (iLXA₄) in these co-incubations. The presence of iLXA₄ was also evaluatedin vivo in aspirin-sensitive asthmatic patients who, in a randomized, double-blind crossover design, underwent nasal lavage after they each ingested a predetermined threshold dose of aspirin or placebo. Aspirin challenge provoked statistically significant increases in iLXA₄ in each patient (P<0.005). These results validate the use of a solid-phase ELISA for detection of LXA₄. Furthermore, the use of this ELISA has allowed the first documentation of iLXA₄ formation in human subjects with aspirin-sensitive asthma following specific antigenic challenge.     

Rapid method for the quantitative determination of individual tocopherols in oils and fats

Oils and fats are frozen two times from acetone solution at -80 C under protection by ascorbyl palmitate. Tocopherols (T) and tocotrienols (T₃) present in the filtered extract are separated into their homologues by one-dimensional thin layer chromatography on precoated silica gel plates in the n-hexane/ethyl acetate system 92.5:7.5. Complete separation of the positional isomers β-T and γ-T is accomplished as well, whereas β-T₃ and γ-T are assumed to form identical bands. Suitable spray- and detection systems including new found coloring ones are described for the qualitative estimation of the chromatograms. The content of individual tocopherols (T and T₃) of 24 commercial vegetable oils is quantitatively determined using the Emmerie-Engel procedure.