Effective lecture slides and overhead transparencies

Almost every speaker at RACI conferences uses slides or overhead transparencies to illustrate topics and to emphasize important points. All too often however, these visual aids fail to achieve their desired purpose because they are illegible or too complex for easy assimilation by the audience. Such visual 'aids' annoy the viewers, devalue the information presented, and are therefore a waste of production effort

Analysis of wine: an undergraduate project

Experiments which use common, familiar substances as their basis generally prove popular in junior undergraduate courses since students can readily perceive their 'relevance'. The experiment described here involves analysis of wine for its major components and is based largely on standard enological analytical techniques used in industry

Effects of stationary phase cross-linking and ion-exchange capacity on the retention of carboxylic acids in ion-exclusion chromatography using sulfonated resins

Ion-exclusion chromatography (IEC) has been widely used in the separation of carboxylic acids, finding applications in the analysis of food and beverages, pharmaceuticals, biological samples, and acid rain samples.' The retention mechanism of carboxylic acids in ion-exclusion chromatography has also been investigated in many studies, and the factors which affect retention can be divided into three categories: analyte effects, mobile phase effects, and stationary phase effects. In IEC, the chromatographic system can be considered to consist of three phases: the mobile phase which comprises the eluent passing through the interstitial volume of the column, the stationary phase which comprises the occluded liquid trapped within the pores of the resin and the resin phase which is the solid resin network and functionalized groups.' In this mode of chromatography, the analytes being separated have the same charge as the functional group on the resin; that is, anions are separated on cation-exchange columns and cations are separated on anion-exchangec columns

Direct determination of bromide, nitrate, and iodide in saline matrixes using electrostatic ion chromatography with an electrolyte as eluent

A new ion chromatographic method that is applicable to the direct determination of UV-absorbing inorganic anions in saline matrixes is described. An octadecylsilica column modified with a zwitterionic surfactant (3-(N,N-dimethylmyristylammonio)propanesulfonate) is used as the stationary phase, and an electrolytic solution is used as the eluent. Under these conditions, the matrix species (such as chloride and sulfate) are only retained weakly and show little or no interference. It is proposed that a binary electrical double layer (EDL) is established by retention of the eluent cations on the negatively charged (sulfonate) functional groups of the zwitterionic surfactant (forming a cation-EDL) and by retention of eluent anions on the positively charged (quaternary ammonium) functional groups of the zwitterionic surfactant (forming an anion-EDL). Sample anions are able to distribute into the cation-EDL and to form ion pairs with the EDL cations, while at the same time experiencing repulsion from the anion-EDL. Anions are therefore eluted in order of increased propensity to form ion pairs. The method has been applied to the determination of bromide, nitrate, and iodide in artificial seawater, giving detection limits of 0.75 ppb for bromide, 0.52 ppb for nitrate, and 0.8 ppb for iodide using UV absorbance detection at 210 nm and relative standard deviations of <1.2%. Real seawater samples have also been analyzed successfully

Rapid ion chromatography of L -ascorbic acid, nitrite, sulfite, oxalate, iodide and thiosulfate by isocratic elution utilizing a postcolumn reaction with cerium(IV) and fluorescence detection

Rapid separation and determination of mixtures of Image -ascorbic acid, nitrite, sulfite, oxalate, iodide and thiosulfate by conventional ion chromatography is often difficult due to incomplete separation of Image -ascorbic acid and nitrite from the water peak when using eluents giving short elution times for iodide and thiosulfate. Separation of the six species within about 15 min has been achieved by isocratic elution using a resin-based ion-exchange column with a carbonate eluent containing a trace amount of 1,3,5-benzenetricarboxylic acid (BTA) and fluorescence measurement of cerium(III) formed via postcolumn reactions of the separated sample species with cerium(IV). Calibration plots of peak height versus concentration were linear up to 10.0 μM (1.76 ppm) for Image -ascorbic acid, 8.0 μM (0.37 ppm) for nitrite, 8.0 μM (0.70 ppm) for oxalate, 80.0 μM (10.2 ppm) for iodide and 25.0 μM (2.80 ppm) for thiosulfate, whilst the sulfite calibration was linear up to 25.0 μM (2.00 ppm) when peak area was plotted against concentration. Detection limits (defined as S/N=3) were 18 ppb for Image -ascorbic acid, 4 ppb for nitrite, 16 ppb for sulfite, 7 ppb for oxalate, 72 ppb for iodide and 37 ppb for thiosulfate. The proposed method was applied successfully to the determination of Image -ascorbic acid, nitrite, sulfite, oxalate, iodide or thiosulfate in water samples

Advances in ion chromatography for monitoring the gold cyanidation process

During the gold cyanidation process, cyanide can be lost from the leachate by various chemical routes. Since cyanide is generally the most expensive reagent in this process, it is becoming increasingly important to monitor these cyanide losses. The products of these cyanide losses include base metal cyanide complexes, thiocyanate and cyanate. The two most significant cyanicides in order of importance are sulfides and copper bearing minerals. The problems caused by cyanide soluble copper minerals are well known to the gold processing industry and have been reviewed by several authors (e.g. 1, 2). One particular facet of this problem concerns the effect of the CN:Cu mole ratio, R, on the gold leaching kinetics. In order to efficiently leach cupriferous ores, it is important that R is maintained at a level that allows sufficiently rapid leaching without excessive use of cyanide. An additional consideration when leaching cupriferous ores is the oxidation of cyanide by Cu(11) minerals, resulting in the formation of cyanate. Ion chromatography (IC) has been successfully used for the determination of cyanide, metal cyanide complexes, thiocyanate and cyanate in leachates. Most of the important metal-cyanide complexes and thiocyanate can be determined by reverse phase ion interaction chromatography (e.g. 3, 4, 5, 6). Cyanide and cyanate are both unretained in the separation of the metal cyanide complexes and are not detectable as their respective anions. However, it has been possible to determine cyanide in this separation by either precolumn derivatisation with Ag to form [Ag(CN)J (4) or post-column derivatisation with a selective colourimetric reaction to produce a visible dye (5) .There are no reactions suitable for the analogous pre or post column derivatisation of cyanate in the above separation of metal cyanide complexes. Cyanate has been determined separately on an anion exchange column (e.g. 7, 8, 9). This paper presents two new IC techniques that enable the rapid determination of cyanate concentration and R in samples containing large concentrations of Cu(I)-cyanide complexes. Other metal cyanide complexes, in addition to Cu(I), can also be determined in conjunction with R, while other anions such as chloride and sulfate can be determined in conjunction with cyanate. The main aim of this work has been t

The use of HPLC for the analysis of ascorbic acid and dehydroascorbic acid in orange juice and powdered orange drink

Ascorbic acid and dehydroascorbic acid may be separated by High Performance Liquid Chromatography (HPLC) after pre-column reaction of dehydroascorbic acid with 1,2-phenylenediamine. Two methods are described, viz. reversed-phase ion-pairing HPLC, and the use of a CN column for the separation. When both methods were applied to the analysis of orange juice and powdered orande drink, the reversed-phase ion-pairing method was found to be subject to interference problems and variability in retention times. The Cn column method was more successful, particularly for powdered orange drink. Recovery and precision data are presented

Pitch fixative selection by capillary electrophoresis

Wood pitch deposition has antagonised the papermaker for over two hundred years. Fixatives, chemistries which are used to attach wood resin to wood fibre, have been used to alleviate wood pitch deposition to varying degrees of success. This paper aims to present a new method by which fixatives can be evaluated at a molecular level in a short period of time. Capillary Electrophoresis (CE) is used in many industries, including pulp and paper, as an analytical technique for the separation of analytes under the application of an electric field whereby the differences in the electrophoretic mobilities of the analytes lead to their separation. This paper makes use of CE, not for its separation of analytes but for quantification of interactions between analytes and selectivity modifiers. Electrokinetic chromatography (EKC) is a variation of CE where a selectivity modifier is included in the electrolyte. In using wood resin fixatives as selectivity modifiers and wood resin components as analytes, we were able to determine their interactions at a variety of pHs and temperatures. The result of this development is the ability to recommend a given fixative chemistry for the unique pH, temperature and extractive composition of a given pulp and/or paper mill. Details of the methods, results and data interpretation are included in this paper

The application of non-suppressed ion chromatography to clinical and pharmaceutical analysis

Ion chromatography is a relatively new technique for rapid, sensitive, multianion analysis which has many advantages over alternative techniques such as wet chemical methods, spectrophotometry or the use of ion-selective electrodes. Since it was first described by Small et all in 1975, ion chromatography has deservedly received a great deal of attention and is now routinely used in the analysis of environmental, water, food and industrial samples. However, applications on biological samples have been relatively few

Some modern approaches to the chromatographic determination of inorganic anions.

The determination of inorganic anions has traditionally been performed using classical titrimetric, volumetric or spectrophotometric techniques, or with the use of ion selective electrodes. In many cases, these techniques lack selectivity, sensitivity and speed, and are applicable to the determination of only a single species at one time. Conventional ion exchange, with diverse monitoring methods such as conductivity, polarography, spectrophotometry, etc. is also inadequate in terms of resolution and sensitivity. These drawbacks have provided impetus for the development of rapid and sensitive methods of analysis using liquid chromatography, and considerable advances have been made in this area in recent years. This development has been chiefly directed towards inorganic anion analysis; however, the experience gained can often be applied to cation analysis with equal success. The current availablity of satisfactory alternative methods for cation analysis (such as atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and polarography) means that cation analysis by liquid chromatography does not have the same priority as anion analysis