The importance of chain length for the polyphosphate enhancement of acidic potassium permanganate chemiluminescence

Sodium polyphosphate is commonly used to enhance chemiluminescence reactions with acidic potassium permanganate through a dual enhancement mechanism, but commercially available polyphosphates vary greatly in composition. We have examined the influence of polyphosphate composition and concentration on both the dual enhancement mechanism of chemiluminescence intensity and the stability of the reagent under analytically useful conditions. The average chain length (n) provides a convenient characterisation, but materials with similar values can exhibit markedly different distributions of phosphate oligomers. There is a minimum polyphosphate chain length (∼6) required for a large enhancement of the emission intensity, but no further advantage was obtained using polyphosphate materials with much longer average chain lengths. Providing there is a sufficient average chain length, the optimum concentration of polyphosphate is dependent on the analyte and in some cases, may be lower than the quantities previously used in routine detection. However, the concentration of polyphosphate should not be lowered in permanganate reagents that have been partially reduced to form high concentrations of the key manganese(III) co-reactant, as this intermediate needs to be stabilised to prevent formation of insoluble manganese(IV).     

Is proton cationization promoted by polyatomic primary ion bombardment during time-of-flight secondary ion mass spectrometry analysis of frozen aqueous solutions?

Ion bombardment of pure water ice by Au+ monoatomic and Au3 + and C60 + polyatomic projectiles results in the emission of two series of water cluster ions-(H2O)n + and (H2O)nH+-with n ranging from 1 to >40. The cluster ion yields are very significantly higher under polyatomic ion bombardment than when using an Au+ primary ion. The yield of the protonated water species (H2O)nH+ is found to be enhanced by increasing ion fluence. C60 + bombardment results in a very dramatic increase in the (H2O)nH+ yield and decrease in the yield of (H2O)n +. Au3 + also significantly increased the yield of protonated species relative to the non-protonated but to a lesser extent than C60 +. Bombardment by Au+ also increased the yield of protonated species but to a very much smaller extent. The hypothesis that the protonated species may enhance the yield of [M+H]+ from solute molecules in solution has been investigated using two amino acids, alanine and arginine, and a nucleic base, adenine. The data suggest that the protons produced by the sputtering of water ice are depleted in the presence of these solutes and concurrently the yields of solute-related [M+H]+ and immonium secondary ions are greatly enhanced. These yield enhancements are analysed in the light of other possible contributors such as increased rates of sputtering under polyatomic beams and increased secondary ion yields as a consequence of solute dispersion. It is concluded that enhanced proton attachment is occurring in polyatomic sputtered frozen aqueous solutions.     

Molecular depth profiling of organic and biological materials

Atomic depth profiling using secondary ion mass spectrometry, SIMS, is common in the field micro-electronics; however, the generation of molecular information as a function of sample depth is difficult due to the accumulation of damage both on and beneath the sample surface. The introduction of polyatomic ion beams such as SF₅ and C₆₀ have raised the possibility of overcoming this problem as they deposit the majority of their energy in the upper surface of the sample resulting in increased sputter yields but with a complimentary reduction in sub-surface damage accumulation. In this paper we report the depth profile analysis of the bio-polymer polycaprolactone, PCL, using the polyatomic ions and and the monoatomic Au⁺. Results are compared to recent analysis of a similar sample using . depth profiling of cellulose is also demonstrated, an experiment that has been reported as unsuccessful when attempted with implications for biological analysis are discussed.     

Patterning of antibodies using flexographic printing

Antibodies were patterned onto flexible plastic films using the flexographic printing process. An ink formulation was developed using high molecular weight polyvinyl alcohol in carbonate-bicarbonate buffer. In order to aid both antibody adhesion and the quality of definition in the printed features, a nitrocellulose coating was developed that was capable of being discretely patterned, thus increasing the signal-to-noise ratio of an antibody array. Printing antibody features such as dots, squares, text, and fine lines were reproduced effectively. Furthermore, this process could be easily adapted for printing of other biological materials, including, but not limited to, enzymes, DNA, proteins, aptamers, and cells.     

The determination and characterisation of 2-naphthyloxycarbonyl chloride derivatised biogenic amines in pet foods

The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices.     

Partial least squares and principal components analysis of wine vintage by high performance liquid chromatography with chemiluminescence detection

HPLC with acidic potassium permanganate chemiluminescence detection was employed to analyse 17 Cabernet Sauvignon wines across a range of vintages (1971-2003). Partial least squares regression analysis and principal components analysis was used in order to investigate the relationship between wine composition and vintage. Tartaric acid, vanillic acid, catechin, sinapic acid, ethyl gallate, myricetin, procyanadin B and resveratrol were found to be important components in terms of differences between the vintages.     

High-performance liquid chromatography with post-column 2,2′-diphenyl-1-picrylhydrazyl radical scavenging assay: Methodological considerations and application to complex samples

An improved post-column 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay for the screening of antioxidants in complex matrices was developed. Experimental parameters believed to be influential to DPPH response were studied in a univariate approach. Optimum conditions were found to be: 5 × 10⁻⁵ M DPPH reagent prepared in a 75% methanol: 25% 40 mM citric acid-sodium citrate buffer (pH 6) solution, degassed with nitrogen; reaction coil of 2 m × 0.25 mm i.d. PEEK tubing; detection at 521 nm; analysis at room temperature. The analytical utility of this protocol was evaluated by screening for antioxidants in thyme and green tea, in comparison with two commonly employed methodologies.