Spectrophotometric procedures

Mizutani and colleagues reported the development of a new method for the analysis of 1-malate. As part of their study they analyzed a series of beverages using both their method and a standard spectrophotometric procedure based on a clinical kit purchased from Boerhinger Scientific. A summary follows of their results (in parts per million). 

Saito described a quantitative spectrophotometric procedure for iron based on a solid-phase extraction using bathophenanthroline in a poly(vinyl chloride) membrane. ... 

Different extraction-spectrophotometric procedures were proposed for the P(V) and As(V) determination as ionic associates (lA) of polyoxometalates with basic dyes. Main disadvantage is difficulty in separation of reagent excess. Flotation, centrifugation or extraction does not allow to create sufficiently sensitive procedures due to worsening of reproducibility. 

Test method using lA with MG and spectrophotometric procedure were developed for the phosphate determination. Test method allows determination of P(V) in the 10-100 p.g/1 concentration range. Spectrophotometric procedure able to determining lower than 3 p.g/1 P(V) was used for determination it in waters. 

A simple spectrophotometric procedure for the determination of hydroxyurea (HU) has been developed. This procedure is based on the complex formation between HU and FeCl. The violet colored complex between HU and FeCl 560 nm) was not sufficiently stable to allow... 

Dagnall and West8 have described the formation and extraction of a blue ternary complex, Ag(I)-l,10-phenanthroline-bromopyrogallol red (BPR), as the basis of a highly sensitive spectrophotometric procedure for the determination of traces of silver (Section 6.16). The reaction mechanism for the formation of the blue complex in aqueous solution was investigated by photometric and potentiometric methods and these studies led to the conclusion that the complex is an ion association system, (Ag(phen)2)2BPR2, i.e. involving a cationic chelate complex of a metal ion (Ag + ) associated with an anionic counter ion derived from the dyestuff (BPR). Ternary complexes have been reviewed by Babko.9... 

The three flame spectrophotometric procedures require the following essential apparatus. 

The most effective spectrophotometric procedures for pfQ determination are based on the processing of whole absorption curves over a broad range of wavelengths. 

LDPE or HDPE extracts has been determined colorimet-rically at 430 nm by oxidation with H202 in the presence of H2S04 [66]. p-Phenylenediamine derivatives such as Flexzone 3C, used as antiozonants in rubber products, have been determined colorimetrically after oxidation to the corresponding Wurster salts [67]. A wide range of amine AOs in polyolefins has been determined by the p-nitroaniline spectrophotometric procedure [68]. Monoethanolamine (MEA) in a slip agent in PE film has been determined as a salicylaldehyde derivative by spectrophotometric quantification at 385 nm [69]. Table 5.6 contains additional examples of the use of 1JV/VIS spectrophotometry for the determination of additives in polymers. 

The most effective spectrophotometric procedures for pKa determination are based on the processing of whole absorption curves over a broad range of wavelengths, with data collected over a suitable range of pH. Most of the approaches are based on mass balance equations incorporating absorbance data (of solutions adjusted to various pH values) as dependent variables and equilibrium constants as parameters, refined by nonlinear least-squares refinement, using Gauss-Newton, Marquardt, or Simplex procedures [120-126,226],... 

Spectrophotometric procedures based on the lanthanum alizarin complex have also been described [52]. 

Matthews and Riley [99] preconcentrated iodide by co-precipitation with chloride ions. This is achieved by adding 0.23 g silver nitrate per 500 ml of seawater sample. Treatment of the precipitate with aqueous bromine and ultrasonic agitation promote recovery of iodide as iodate which is caused to react with excess iodide under acid conditions, yielding I3. This is determined either spectrophotometrically or by photometric titration with sodium thiosulfate. Photometric titration gave a recovery of 99.0 0.4% and a coefficient of variation of 0.4% compared with 98.5 0.6% and 0.8%, respectively, for the spectrophotometric procedure. 

The accuracy of the inductively-coupled plasma procedure was assessed by analysing waters of known sulfate composition, and by comparing measured sulfate values for a wide range of samples with those obtained for the same waters by an automated spectrophotometric procedure. Good agreement is obtained between the derived sulfate measurements and the normal values for International Standard Sea Water and an EPA Quality Control Standard. 

In another spectrophotometric procedure Motomizu [224] adds to the sample (2 litres) 40% (w/v) sodium citrate dihydrate solution (10 ml) and a 0.2% solution of 2-ethylamino-5-nitrosophenol in 0.01 M hydrochloric acid (20 ml). After 30 min, add 10% aqueous EDTA (10 ml) and 1,2-dichloroethane (20 ml), mechanically shake the mixture for 10 minutes, separate the organic phase and wash it successively with hydrochloric acid (1 2) (3 x 5 ml), potassium hydroxide (5 ml), and hydrochloric acid (1 2) (5 ml). Filter, and measure the extinction at 462 nm in a 50 mm cell. Determine the reagent blank by adding EDTA solution before the citrate solution. The sample is either set aside for about 1 day before analysis (the organic extract should then be centrifuged), or preferably it is passed through a 0.45 xm membrane-filter. The optimum pH range for samples is 5.5 - 7.5. From 0.07 to 0.12 p,g/l of cobalt was determined there is no interference from species commonly present in seawater. 

Eberhardt and Sieburth [133] also devised a spectrophotometric procedure for the determination of aldehydes in seawater. The method is based on the reaction of aldehydes with 3-methyl-2-benzothiazolinone, hydrazone hydrochloride, and ferric chloride to produce a coloured compound. A detection limit of0.072 jlM formaldehyde per litre was obtained using a 5 cm path-length. 

Florence and Farmer [295] determined parts per million of aliphatic amines in sea water using spectrophotometric procedures. 

Luskima and Syavtsillo [120] have described a spectrophotometric procedure utilising phenylfluorone for the determination of organotin compounds in water. 

Polyatomic Organic Molecules. Metal Complexes. Qualitative Analysis - The Identification of Structural Features. Quantitative Analysis - Absorptiometry. Choice of Colorimetric and Spectrophotometric Procedures. Fluorimetry. Applications of UV/Visible Spectrometry and Fluorimetry. 

Vigorous hydrolysis of neomycin results in the formation of furfural which may be quantitated in a number of different ways- 5 156. Dutcher et all57 use(j a UV spectrophotometric procedure, measuring the absorbance of the solution at 280nm. A similar procedure combined with measurement of the optical rotation has been used by Brooks et all58 to determine the neomycin B and C content... 

Numerous methods based on different analytical principles have been offered for the measurement of dehydrogenase reactions. Most reliable and simple are spectrophotometric procedures ( optical test ) founded on the assay of one of the participating coenzymes (or substrates). 

The automated spectrophotometric procedure [47] for the determination of total nitrogen in soils discussed in section 12.5.1.2 has also been applied to the determination of 0-0.75% phosphorus in soils. The method is based on the formation of the yellow molybdate-vanadate complex which has an absorption maximum at 420nm. 

Spectro grade or spectranalyzed Solvents of suitable purity for use in spectrophotometric procedures. A certificate of analysis is on the label. 

An extractive spectrophotometric procedure based on the complexation of reduced Iron(II) with 5-Chloro-7-iodo-8-hydroxyquinoline (CIHQ) for the estimation of micro amounts of vitamin C. The resulting brown colored complex was extracted into chloroform to give a reddish brown extract which shows an absorption band at 485 nm. This chelate was formed immediately and the apparent molar absorptivity and Sandell s sensitivity for vitamin C was found to be 8.5 x 105 dm3 mol"1 cm 1 and 2.072xl0 4g cm 2. Linear relationship between absorbance and concentration of ascorbic acid is observed up to 0.8 pg ml"1. Interference studies of different substances including sugars, vitamins and amino acids, metal ions and organic acids were carried out. The utility of the method was tested by analysing some of the marketed products of vitamin C... 

The British P 1993 [15] describes a procedure to determine benzoic acid in benzoic acid ointment that also contains salicylic acid. In this method, 2 g of the ointment is added to 150 mL water, and warmed until melted. The solution is titrated with 0.1 M NaOH, using phenolphthalein solution as the indicator. Salicylic acid is assayed by a spectrophotometric procedure, and its content subtracted from the total acid value to obtain the benzoic acid content. 

Measurement of Reaction Rates by Titrimetry. The rates of cerium(IV) consumption by each of Cr(C204)3 3, m-Cr(OH2)2(C204)2 and Cr(0H2)4C204+ were also measured by a direct titrimetric method. Solutions were prepared and mixed as for the spectrophotometric procedure. At appropriate times aliquots of the reactant solutions were quenched with known volumes of standard ferrous sulfate, and the excess ferrous ion was titrated potentiometrically with standard potassium dichromate,... 

Trimethylsilyl derivatives of sugars can be made and separated by GLC (60). For musts, where 90% or more of the soluble solids are glucose and fructose, proximate procedures are usually sufficient—hydrometry or refractometry. Since only the sugar content up to 1% is often needed, sugar test pills are useful (5, 6, 61, 62, 63). Rapid spectrophotometric procedures are sometimes convenient, especially if they do not require prior filtration or decoloration (62). 

V vs. Ag/AgCl in acid has been described [132]. The assay requires the extraction of the compound from a tablet into the 0.5 M sulfuric acid, dilution, and direct polarographic assay of an aliquot of this solution. The assay is accurate, sensitive, and, since it does not require the removal of insoluble matter, more rapid than the spectrophotometric procedures. 

Three spectrophotometric procedures are given in the AOAC compendium of methods (960.22, 962.13 and 967.11) for the analysis of caffeine, all of which have an extraction stage followed by a quantification procedure. There is also an HPLC method, discussed earlier, which was designed to measure saccharin, benzoic acid and caffeine at the same time (AOAC, 978.08). Again, the HPLC method, EN 12856 1999 (Anon, 1999a), can be used for the analysis of caffeine, but this analyte was not included in the collaborative study. 

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