A multicommuted flow system for the determination of copper, chromium, iron and lead in lubricating oils with detection by flame AAS.

In this work, a flow analysis procedure for the determination of copper, chromium, iron and lead in lubricating oils using flame AAS as detection technique is described. The flow manifold was designed to implement the multicommutation approach and it comprised three 3-way solenoid valves controlled by a personal computer. The flow system presented allowed to process the oil samples to determine wear metals without any prior preparation. Aiming to assess accuracy the results were compared with those obtained by manual procedure using flame AAS. Applying the joint-confidence ellipse test, no significant difference at the 95% confidence level was observed. Other profitable features such as a sample throughput of 50 determinations per hour; relative standard deviations (n = 5) below 2% for Cu, and below 8% for Cr, Fe and Pb; and linear responses in the range 0-40ppm (w/w) (Cu, Fe) and 0-15ppm (w/w) (Cr, Pb) were also achieved.

Determination of insolubles in diesel lubricating oil by FIA-visible spectrometry.

Insolubles determination is one of the parameters usually recommended to evaluate the residual life of oil because their presence at elevated levels in diesel lubricating oil changes the viscosity, prematurely clogs filters and is one of the major factors in causing abrasive engine wear. The proposed method employs visible spectrophotometric detection in association with flow injection analysis. The results obtained by this method were compared with the ones obtained by Fourier transform infrared spectrometry (FT-IR) since this is the most employed method for insolubles determination. The proposed method presented a linear response from 0 to 3% (w/w) of insolubles in pentane (ASTM D-893). The sampling frequency was about 30 samplesh(-1), with a relative standard deviation (n=5) of 2.4% or better. Accuracy was evaluated analysing 98 real samples and the results obtained with the FIA-spectrophotometric method were plotted against those obtained by the FT-IR method by means of linear regression. Slope and intercept of the straight line obtained were compared with the theoretical values of 1 and 0 by means of the joint-confidence ellipse F-test. At the confidence level of 95% no evidence of a difference was found between both methods.

Determination of lithium at ultratrace levels in biological fluids by flame atomic emission spectrometry. Use of first-derivative spectrometry.

The use of zero-order and first-derivative flame emission spectrometry has been investigated for the determination of basal concentrations of lithium in serum and urine at the microgram dm-3 level. No significant matrix effect was observed; however, it was necessary to make use of background correction techniques. Two or three wavelength measurements and first-derivative spectrometry were used for this purpose; both methods gave similar results. Detection limits for serum of approximately 0.09 micrograms dm-3 were found by both zero-order and first-derivative emission measurements, while normal lithium levels were found to be 29.3 and 1.17 micrograms dm-3 for urine and serum, respectively.

Simultaneous determination of tranylcypromine sulfate and trifluoperazine dihydrochloride in tablets by first- and fourth- derivative ultraviolet spectrophotometry.

A rapid and simple method for the simultaneous determination of trifluoperazine dihydrochloride and tranylcypromine sulphate by first- and fourth-derivative UV spectrophotometry is presented. The procedure consists of extraction in 0.2 m hydrochloric acid, filtration and measurement of the amplitudes of the first- and fourth-derivative spectra at 260 and 274 nm, respectively. A zero-crossing technique is used for the determination of trifluoperazine. Good linearity, accuracy, precision and selectivity were found, and the method is proposed for routine quality control purposes, even for the uniformity of contents test.