Methods, reagents, indicators

Reagents, Indicators, and Solutions. This section includes the specifications and testing methods for reagents to be used in the tests specified in the USP-NF, and directions for making the various indicator, buffer, colorimetric, test, and volumetric solutions used in the testing. Reagents for which ACS specifications exist are referenced to the ACS book (7). 

Methods of indicator immobilization in sol-gels include physical and chemical (covalent binding) doping by incorporation of an indicator or reagent during formation of the sol-gel glass. 

The extent of sulfonation of 8% crosslinked styrene divinylbenzene co-polymer beads (Biorad Bio Bead SX 8) was investigated by comparing the surface composition after sulfonation of the beads using chlorosulfonic acid, sulfuric acid and fuming sulfuric (54). Each reagent was refluxed in methylene chloride for a similar period of time. A wide-scan spectrum indicates the presence of sulfur 2p and 2s electrons, indicative of sulfonation. The surface sulfur content was fairly similar in the surface region analyzed by XPS. The composition determined from beads sulfonated by the three methods is indicated in Table VI. 

Method. Add the sample to 0.5 ml of the reagent. Indications. A red or pink colour is given only by nitrates and nitrites, e.g. glyceryl trinitrate. 

The accuracy of the method was indicated by the value of (F )g, which was 1.05 ppm, and which would correspond to a value of 1.3 ppm for the sample of salinity, S = 35%o. For comparison, the calculated value for salinity of 35%o would be 1.28, based upon the reported value for standard seawater (13). The precision was estimated for samples 6S and 6B for which the mean and standard deviations were 34.2 0.8 and 35.0 0.3, respectively the corresponding relative deviations were 2.3 and 0.9%. There was no significant variation in fluoride values during the 24 hr after being stored in a plastic container and refrigerated at < 4°C. In addition, fluoride was also determined for one unique sample colorimetrically, using an lanthanum-alizarin complexone reagent (14). Data are compared in Table I. 

Application. The application of the method should indicate the analyte and reagent s purity, its state (oxidation, ligand, etc.) where appropriate, concentration range, effects, if any, with sample matrix, description of sample(s) and equipment, and procedures including permissible variation in specifications of samples under tests, etc. 

In the second method, the (l-selanylcyclopropyl)lithium reagent 2 is used to alkylate another a-selanyl aldehyde. Elimination, as above, of the resulting hydroxy diselenide 3 gives the alkenyl(selanyl)cyclopropane 4 with high selectivity for the E -isomer. The yields and isomer distributions of selenides 4 prepared by the two methods are indicated. These products can be converted to allylidene cyclopropanes by two cycles of alkylation and treatment with base (Section 5.2.2.4.). 

The use of the combined standards mixtures (as indicated in the method, reagents part) can lead to a not-so-accurate quantification owing to the fact that current certified standards of a given PSP toxin have impurities of others. Chromatograms of the standards mix-... 

A meaningful definition should reflect the differences between the radio-reagent method and indicator... 

The Tollens reagent indicates the presence of an aldose or ketose when the surface of the reaction flask is coated with metaUic silver (looking like a mirror), while the other two tests indicate the presence of an aldose or ketose with the formation of a reddish precipitate (CU2O). These three reactions are used only as tests to obtain structural information about unknown carbohydrates but are not efficient as preparative methods when sufficient quantities of the aldonic acid are desired. A carbohydrate that tests positively for any of these three tests is said to be a reducing sugar because the carbohydrate can reduce the oxidizing agent. 

The other method is less accurate but more rapid and involves direct Nessleri2ation of the sample for colorimetric deterrnination. Other colorimetric indicators with more sensitivity, such as indophenol, have been used in place of Nessler s reagent. Ion-selective electrodes have also found use in analysis for trace ammonia (93). 

In presence of polyamines the maximum of light absorption of indicated triphenylmethane dyes displaces on 10-30 nm, for azo dyes the shift of the band reaches 50-80 nm. The greatest difference of light absorption of associates and reagents is watched for BKM at pH 5,05, for BPR at pH 4,20, for CPR in an interval pH 5,05-5,45. At these pH dyes are anions, it promotes interaction with a cationic surface-active substance. The ratios between polymer and BKM, BPR, CPR are established by spectroscopy method, its equal 1 20, 1 20 and 1 30 accordingly. 

The main idea of research is application of accessible, simple and express methods that don t need expensive reagent techniques for analysis of phanuaceutical products based on bischofite. The determination of metal ions such as Mg, Zn, Cu, Fe by complex-formation titrations using a widely applicable chelating agent, EDTA, have been studied as a function of pH, complexing agents and indicators. The analysis consists of four parts ... 

---