Spectrophotometric evaluation of interferences in three iron reactions for the determination of serum total cholesterol

A spectrophotometric and chemical evaluation of reported interferences for three iron reactions for the determinations of serum cholesterol has been presented. It has been shown that all three reactions are affected by various interfering substances, such as 2-thiouracil, nitrate, azide, bromide, diethylstilbesterol, and steroids. Spectral differences between the reactions are probably due to solvent and anion effects.The incorporation of uranyl acetate as a precipitating agent into the ferric acetate-uranyl acetate procedure did not make the results obtained comparable with the Abell-type extract of a very icteric serum. Incorporation of ferrous sulfate does not noticeably affect the intensity or stability of color development with standards.As proposed, the ferric acetate-uranyl acetate procedure for the determination of cholesterol represents a modified iron reagent, but the reaction mechanism and the procedure described for it is neither new nor direct. The use of the ferric acetate reagent for serum cholesterol as opposed to ferric chloride, ferric ammonium chloride, or ferric perchlorate appears to have no real advantages as a color reaction. In fact the reaction is less sensitive while reagent preparation is more tedious, time consuming, and expensive than the ferric chloride procedure. Although no quantitative studies were performed, the only effects that chloride had on the reactions were in the region of 400 nm, a wavelength sufficiently far enough away from the 560-nm peak that it did not affect determinations. The concept that the ferric acetate-uranyl acetate reagent contains only acetate and sulfate anions is nullified as soon as one adds serum to the reagents.     

Fluoride anion sensing using colorimetric reagents containing binaphthyl moiety and urea binding site

Four 1,1′-binaphthalene based bis-urea derivatives bearing aryl groups at end-on nitrogen atoms IIIa–d were synthesized as potential sensor molecules. These receptors show characteristic UV-VIS spectral changes on complexation with anions and they exhibit selective recognition of F⁻ over other halide anions. Interaction of a fluoride anion with urea NH groups was confirmed by ¹H NMR data. The presence of an electron-withdrawing nitro group in N′-aryls (receptors IIIa and IIIb) appeared to be necessary for naked-eye colorimetric detection. These receptors show dramatic color change from light-yellow to orange (IIIa) or to orange-red (IIIb) in the presence of guest fluoride anions already at concentrations of 10⁻⁵ mol dm⁻³ of the receptor and host.     

Correction for relative interferences in a cholesterol determination

The detrimental influences of thiouracil, propylthiouracil, and bromide on the ferric perchlorate reaction for cholesterol have been previously reported (2, 3). On the basis of recovery studies it can be shown that their role in the reaction results in a relative rather than an absolute error of cholesterol measurement. Because a relative error causes a linear fanning effect on increasing concentrations of analyte which depends for its slope on both the concentration of the interference as well as on the concentration of constituent being measured, the method of standard additions can be used to correct a matrix effect on the reaction. A system in which the standard is used internally can eliminate the need to pretreat the sample in order to separate the interfering compound from the analyte. Therefore, both the interference and its obviation by this method of internal standardization are discussed here in a procedure which results in a means for simpler rescue of a contaminated sample than is afforded by the more laborious and time consuming pretreatment of previous workers.     

Investigation of arsine-generating reactions using deuterium-labeled reagents and mass spectrometry

Mass spectrometry was used to detect transfer of deuterium from labeled reagents to arsines following hydride-generation reactions. The arsine gases liberated from the reactions of arsenite, arsenate, methylarsonic acid, and dimethylarsinic acid with HCl and NaBD(4) in H(2)O, or with DCl and NaBH(4) in D(2)O, were examined. Differences in the mode of deuterium incorporation for the various arsines were detected. These results may help explain some of the observed variations in arsine-generation efficiency for various arsenic compounds present in environmental and biological samples.     

Interesting interferences in a direct serum creatinine reaction

A spectrophotometric study on a direct picric acid reaction for creatinine in severely jaundiced serums is described. A problem appears to be caused by the oxidation of bilirubin which minimizes rising absorbance when using continuous measurement. Simple examples of interferences with the kinetic mode are shown along with the hitherto unreported interference of the drug, Cephalothin, which also undergoes a picric acid reaction. A procedure in which a delta absorbance is obtained after decolorization of the Jaffé complex by acidification is shown as one available means for obviating the bilirubin effect. However, the theory that Jaffé-reactive interferences do not decolorize with the same acid treatment is not totally applicable when the drug, Cephalothin, is present.     

Simple and rapid colorimetric enzyme sensing assays using non-crosslinking gold nanoparticle aggregation

Non-crosslinking gold nanoparticle (AuNP) aggregation induced by the loss (or screen) of surface charges is applied for enzymatic activity sensing and potentially inhibitor screening.     

One-pot sequences of reactions with sol-gel entrapped opposing reagents: an enzyme and metal-complex catalysts

We extend our sol-gel methodology of one-pot sequences of reactions with opposing reagents to an enzyme/metal-complex pair. Sol-gel entrapped lipase and sol-gel entrapped RhCl[P(C(6)H(5))(3)](3) or Rh(2)Co(2)(CO)(12) were used for one-pot esterification and C-C double bond hydrogenation reactions, leading to saturated esters in good yields. When only the enzyme is entrapped, the homogeneous catalysts quench its activity and poison it. Thus, when 10-undecenoic acid and 1-pentanol were subjected in one pot to the entrapped lipase and to homogeneously dissolved RhCl[P(C(6)H(5))(3)](3) under hydrogen pressure, only 7% of the saturated 1-pentyl undecanoate was obtained. The yield jumped 6.5-fold when both the enzyme and the catalyst were immobilized separately in silica sol-gel matrixes. Similar one-pot esterifications and hydrogenations by sol-gel entrapped lipase and heterogenized rhodium complexes were carried out successfully with the saturated nonoic, undecanoic, and lauric acids together with several saturated and unsaturated alcohols. The use of (S)-(-)-2-methylbutanol afforded an optically pure ester. The heterogenized lipase is capable of inducing asymmetry during esterification with a prochiral alcohol. Both the entrapped lipase and the immobilized rhodium catalysts can be recovered simply by filtration and recycled in further runs without loss of catalytic activity.     

Dinickel catalyzed carbonylation reactions using metal carbonyl reagents as CO sources

Dinickel complexes promote stoichiometric Pauson–Khand reactions of enynes and CO (g). However, catalytic turnover is precluded by the strong binding of CO to the Ni₂ active site. This article describes the use of M(CO)_x reagents as stoichiometric CO precursors in Ni₂-catalyzed carbonylation reactions. As part of these studies, well-defined heterotrinuclear Ni₂Fe, Ni₂Co, and Ni₂Mn carbonyl clusters are synthesized using the [NDI]Ni₂ platform as a template (NDI = naphthyridine–diimine).     

Elimination of some spectral interferences and matrix effects in inductively coupled plasma-mass spectrometry using direct sample insertion techniques

Two key problem areas in inductively coupled plasma-mass spectrometry (ICP-MS) are spectral interferences from analyte and matrix based molecular ions, particularly oxide species; and non-spectroscopic matrix effects where an excess of an element, particularly heavier elements, suppresses the signal of lighter elements. It is shown that direct sample insertion (DSI) techniques can be used to eliminate some of these problems. With the absence of water in a DSI system, oxide species are reduced to a very low level ( .1%). Examples are shown for BaO⁺, CeO⁺ and ClO⁺. In addition, by relying on differential thermal volatilization, the suppressive matrix effect of U on Zn can be eliminated. Chemical modification with NaF is a key operational factor in achieving these benefits.     

Use of non-selective reagents in direct thermometry

A method has been developed for the simultaneous determination of sulphide and thiosulphate with non-selective reagents on the basis of the difference in their heats of reaction. Iodine solution was used as one reagent and bromine water as the other. An error diagram has been calculated and the theoretical errors compared with those obtained in practice.     

β-Aziridinylacroleins in reactions with nucleophilic reagents

The reactivities of -aziridinylcinnamaldehyde and -(2-methylaziridinyl)acrylaldehyde with respect to amines, hydrazines, and semicarbazide were studied, -Aminoacroleins were obtained by reaction of secondary amines with aziridinylacroleins. The reaction of aziridinylcinnamaldehyde with primary amines gives the corresponding imines. It was established that in its reaction with hydrazines and semicarbazide aziridinylacrolein is more inclined to undergo heterocyclization reactions (the formation of pyrazoles and pyrazolines) than aziridinylcinnamaldehyde.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–488, April, 1978.     

Synthesis and reactions of substituted nitro-allylating reagents

Nitro-cyclohexenylation and α-phenyl-nitro-allylation of nucleophilic centres are achieved (see $\text{11}$-$\text{16}$) with the nitroallyl pivalates $\text{2}$ and $\text{5}$, and with the chloride $\text{3}$, which are in turn prepared from the diols $\text{9}$ and $\text{10}$, respectively.     

Alternative reagents for chemical noise reduction in liquid chromatography-mass spectrometry using selective ion-molecule reactions

Reduction of ionic chemical background noise based on selective gas-phase reactions with chosen neutral reagents has been proven to be a very promising approach in liquid chromatography—mass spectrometry (LC-MS). In this study further investigations on alternative reagents including the disulfides (dimethyl disulfide, diethyl disulfide, methyl propyl disulfide), dimethyl trisulfide, ethylene oxide, and butadiene monoxide, for example, have been carried out. Tandem mass spectrometric studies of ion/molecule reactions indicate that—besides dimethyl disulfide—ethylene oxide and butadiene monoxide also exhibit very efficient reactions with background ions. Furthermore, it is confirmed that the reactions are very selective according to the test with some analyte ions. In contrast to its rapid reactions with background ions, ethylene oxide does not react, or reacts much less, with these analytes. Therefore, it can be used as an alternative reagent for noise reduction. Although reactions of the other tested neutral reagents with background ions are evaluated, they are generally not suitable as reagents for this purpose because of lack of reactivity or dramatic ion losses during reactions.     

Use of polymer-supported Pd reagents for rapid and efficient Suzuki reactions using microwave heating

A rapid and efficient Suzuki coupling protocol has been developed utilizing polymer-supported palladium catalysts and microwave irradiation. It is also shown that solid-phase extraction of excess boronic acids can be rapidly and conveniently accomplished by utilization of a silica-supported carbonate base. [reaction: see text]     

Derivatives of anthrarufin,chrysazin and quinizarin as colorimetric reagents for boron

The spectrophotometric characteristics of the color reactions of six new reagents for boron are presented. These are derivatives of the dihydroxyanthraquinones, anthrarufin, chrysazin, and quinizarin, with amino, nitro, cyano, or halogen substituents. The spectral absorption characteristics of these reagents and their borate complexes are much more favorable for the colorimetric determination of boron than is the case with quinalizarin, which is commonly used for this purpose. With the exception of one of the six, all are more sensitive than quinalizarin. Two of them, tribromoanthrarufin and dicyanoquinizarin, are especially sensitive (spectrophotometric sensitivity: 0.0010 μg/cm²).