Multivariate standard addition method solved by net analyte signal calculation and rank annihilation factor analysis.

This article describes the use of the net analyte signal (NAS) concept and rank annihilation factor analysis (RAFA) for building two different multivariate standard addition models called "SANAS" and "SARAF." In the former, by the definition of a new subspace, the NAS vector of the analyte of interest in an unknown sample as well as the NAS vectors of samples spiked with various amounts of the standard solutions are calculated and then their Euclidean norms are plotted against the concentration of added standard. In this way, a simple linear standard addition graph similar to that in univariate calibration is obtained, from which the concentration of the analyte in the unknown sample and the analytical figures of merit are readily calculated. In the SARAF method, the concentration of the analyte in the unknown sample is varied iteratively until the contribution of the analyte in the response data matrix is completely annihilated. The proposed methods were evaluated by analyzing simulated absorbance data as well as by the analysis of two indicators in synthetic matrices as experimental data. The resultant predicted concentrations of unknown samples showed that the SANAS and SARAF methods both produced accurate results with relative errors of prediction lower than 5% in most cases.

Effectiveness of a non-surgical alternative to the Mules operation in sheep.

OBJECTIVE: To measure changes to the perineal bare area, local tissue reaction and healing responses of young sheep, following intradermal administration of cetrimide and polyvinylpyrrolidone (PVP), with and without ethanol, to the breech and tail. METHOD: A needle-less injector was used to deposit formulations containing 40 g/L cetrimide and 30 g/L PVP (group 2) or 20 g/L cetrimide, 30 g/L PVP and 15 g/L ethanol (group 3), within the dermis of the tail and the region surrounding the perineal bare breech area of groups (N = 8) of Merino weaner sheep. The dimensions of the perineal bare area (length, width and diagonal distances left and right) and tail width were recorded before and at intervals after treatment for 60 days. Observations of swelling and bruising and scab formation at the treatment sites were recorded for up to 35 days after treatment. Rectal temperatures were monitored for up to 35 days after treatment and bodyweight for up to 60 days after treatment. An untreated control group (group 1) was included. RESULTS: Comparison of day -3 and day 35 measurement data showed that both treated groups had significantly (P < 0.05) wider breech bare areas compared to the untreated controls and that group 2 sheep had significantly (P < 0.05) longer breech bare areas compared to group 3 sheep or to the untreated controls, which were not significantly different. At this time scabs were still firmly in place on many treated sheep. At day 35 there was no increase in tail bare area caused by either treatment. By day 60 there was no significant difference between the treated and control groups in either the breech or tail regions indicating that the changes present at day 35, were not permanent. Mean weight gain in the groups throughout the 60-day interval was unaffected by treatment. Intradermal treatment was associated with a significant elevation in body temperature. This effect lasted for 3 days and was associated with signs of discomfort and depressed appearance in at least some of the treated sheep. Bruising was mild to severe in all treated sheep within two days of treatment but was not evident in any sheep by day 21. Mild to moderate swelling was also associated with treatment but was not uniform across sheep in the groups. The tail of one sheep was severely swollen for several days. Swelling remained obvious in most treated sheep until day 14 but was not present at day 21. CONCLUSION: Under the conditions of this study intradermal injection of cetrimide had no permanent effect on bare area measurements on the breech or the amount of wool-bearing skin on the tail. It also caused signs of discomfort and pain that raise welfare concerns.

Contamination levels of in-use disinfectants in a teaching hospital in Lagos, Nigeria.

In-use testing of the disinfectants; Hibitane (5% w/v Chlorhexidinegluconate), Hibiscrub (4% w/v Chlorhexidinegluconate), Savlon (3% w/v Chlorhexidine/Cetrimide), hydrogen peroxide (6% w/v hydrogen peroxide with stabilizer) and a common household bleach Jik (3.5% w/v sodium hypochlorite), was carried out over a two-month period at a university teaching hospital in Nigeria. Contamination levels were high with 82 (63.1%) of the 130 in-use disinfectants contaminated. However, a few of the stock solutions remained sterile. One hundred and thirty-four isolates were obtained of which 120 (91%) were gram-negative with Pseudomonas species being the commonest, constituting 67.2% of all the isolates. Gram-positive organisms made up the remaining 12 (9.0%) isolates. All the Pseudomonas spp. were resistant to gentamicin, ceftazidime, nalidixic acid and perfloxacin. Contributory factors for the high contamination levels were dilution of disinfectants with tap water, inadequate care of stock solution bottles and long storage of the diluted disinfectants in the wards.

Contamination of mercurochrome and chlorhexidine-cetrimide in a teaching hospital.

A study on the contamination of antiseptics was done in a teaching hospital, during March and April 1989. Ninety-five samples of 9 antiseptics from 23 wards were cultured. Results showed that 2 of 12 and 3 of 5 samples of mercurochrome and chlorhexidine-cetrimide compound were contaminated. This led to a wider scale study on the two products. It was found that over one-half of the samples of mercurochrome and 6 of 54 samples of chlorhexidine-etrimide compound were contaminated. Mercurochrome was contaminated by gram-positive and chlorhexidine-cetrimide compound by gram-negative bacteria. Contamination of mercurochrome was found in samples taken from the pharmacy and wards, and of chlorhexidine-cetrimide compound from wards only. Mercurochrome was removed from the hospital formulary and the use of chlorhexidine-cetrimide compound was more restricted.