Continuous-flow determination of reducing sugars in serum by reaction with periodate ions,with use of a flow-through periodate-sensitive electrode

A continuous-flow method for the determination of reducing sugars in serum is described. The sample reacts with an excess of periodate in a flow system and the decrease in periodate

activity is monitored with a periodate-sensitive flow-through electrode. The recorded potential peak heights are indirectly linearly related to the reducing sugar concentration expressed as glucose, in the range 50–290 mg/100 ml. The analysis is completely automated and requires no sample pretreatment, and samples can be analyzed at the rate of 30 per hour with average errors and relative standard deviation of about 1–2%. Comparison with an enzymatic method for serum gave satisfactory results.     

Kinetic potentiometric determination of creatinine in urine with a picrate-ion-selective electrode

A new kinetic method for the potentiometric determination of creatinine in urine based on the creatinine-picrate reaction in alkaline medium (Jaffé reaction) is described. The reaction is monitored with a picrate-selective electrode, and the increase in electrode potential within a fixed period of time (90 sec) is measured and related directly to the creatinine concentration. Analytical recovery of creatinine added to urine was 86–101% (average, 95.5%). Comparison with a spectrophotometric method gave a correlation coefficient of 0.992 over a concentration range of 0.6–2.6 g/liter.     

Determination of thiamine using continuous flow molecular emission cavity analysis

A continuous flow method for the determination of thiamine hydrochloride (20.0-240.0 microgram ml(-1), 5.9 x 10(-5)-7.1 x 10(-4)m) is described. The sample was mixed with an excess of sodium hydroxide and remained in the delay coil for 20 min at 90 degrees C. The solution was then mixed with an excess of orthophosphoric acid and the hydrogen sulphide evolved was transferred continuously into the cavity to generate a molecular++ emission of S2. The analysis is completely automated, requires no sample pre-treatment and samples can be analysed at a rate of 30 samples h(-1) with a relative error of 1-2%. The method was evaluated by carrying out an interference study with common excipients and other water-soluble vitamins, a recovery study and by the analysis of commercial formulations. Results compared well with those obtained using the official method. The method was also applied to content uniformity tests.     

Flow-injection stopped-flow kinetic spectrophotometric determination of drugs, based on micellar-catalysed reaction with 1-fluoro-2,4-dinitrobenzene

A flow-injection stopped-flow kinetic spectrophotometric method for the determination of hydrazines, hydrazides, amines and amino-acids, based on the cetyltrimethylammonium bromide catalysed reaction with 1-fluoro-2,4-dinitrobenzene is described. With the proposed method dihydralazine, isoniazid, levodopa and aspartame can be determined at concentrations of 0.1-6 x 10(-4)M. The calibration ranges can be varied by adjusting the pH and surfactant concentration. The determination of amphetamine, cysteine, s-carboxymethylcysteine, cephalexin, tobramycin and gentamicin is also feasible. The method has been applied to the determination of levodopa, isoniazid and aspartame in commercial pharmaceutical formulations. The determination of isoniazid in formulations containing the highly coloured antibiotic rifamycin, and of aspartame in coloured beverages was also accomplished. The results were in good agreement with those obtained by reference methods and the throughput was 40 measurements per hour with 0.4-3.9% RSD.     

Indirect potentiometric determination of hydrazine, isoniazid, sulphide and thiosulphate with a chloramine-T ion-selective electrode

Indirect potentiometric procedures with chloramine-T (CAT) as the oxidant and a chloramine-T ion-selective electrode are described for the determination of hydrazine and isonicotinic acid hydrazide (isoniazid) in the 1-100 mumole range and of sulphide and thiosulphate in the 0.5-50 mumole range. The reductants react stoichiometrically with a known and excessive volume of added CAT and the unconsumed excess of CAT is measured with the CAT-selective electrode. Aqueous solutions of the reductants were analysed with an error and precision of about 1-2%. Analytical recovery of isoniazid added to tablet diluents was 97-101% (average 98.9%). Results were comparable with those obtained with a titrimetric method for the determination of isoniazid in injection solutions and tablets.     

Construction of a guanine enzyme electrode and determination of guanase in human blood serum with an ammonia gas sensor

The guanine electrode is based on guanase used with an ammonia gas-sensing membrane electrode; immobilization of the enzyme is optimized. Guanine in the range 10^-4–10^-2 M gives a linear potential vs. log(concentration) plot with a response time of 4–1.5 min over the range specified. Guanase (0.12–12 I.U. I^-1) is determined in serum by adding guanine to the sample, and measuring the ammonia evolved with the gas-sensing electrode. Results compare favourably with the xanthine oxidase method.     

Kinetic study of the iron(ii)-induced perbromate—tartaric acid reaction with a perbromate-selective electrode : Determination of Tartaric Acid

A kinetic study of the iron(II)-induced perbromate-tartaric acid reaction was carried out with a perbromate-selective electrode to monitor the course of the reaction. Reaction rate and equilibrium constants are reported. A potentiometric method is described for the determination of 80–420 μg of tartaric acid with relative errors and standard deviations of 1–2%.     

Use of chloramine-T selective electrode in the kinetic microdetermination of iodide by means of its catalytic effect on the chloramine-T—hydrogen peroxide reaction

Summary A kinetic potentiometric method for the microdetermination of iodide, based on its catalytic effect on the chloramine-T-hydrogen peroxide reaction is described. The reaction is monitored with a chloramine-T selective electrode. The time required for the potential to change by a preselected amount (12.5 mV) is measured automatically and related directly to the iodide concentration. Microamounts of iodide in the range 1.5–9.0g were determined with a mean relative error and coefficient of variation of about 2%.

---

Zusammenfassung Ein kinetisch-potentiometrisches Verfahren zur Mikrobestimmung von Jodid auf der Grundlage seiner katalytischen Beeinflussung der ChloraminT-Wasserstoffperoxid-Reaktion wurde beschrieben. Die Reaktion wird mit einer für Chloramin-T selektiven Elektrode verfolgt. Die für die Potentialänderung über ein vorgegebenes Spannungsintervall (12,5 mV) erforderliche Zeit wird automatisch gemessen und daraus die Jodidkonzentration ermittelt. Jodidmengen von 1,5 bis 9,0g lassen sich mit einem relativen Fehler von etwa 2% bestimmen.