Direct determination of copper in urine by atomic absorption spectrophotometry

Clinical, biochemical and molecular characterization of Wilson's disease in Moroccan patients

Background

Wilson Disease (WD) is an autosomal recessive inherited metabolic disease caused by mutations in the ATP7B gene. WD is characterized by heterogeneous clinical presentations expressed by hepatic and neuropsychiatric phenotypes. The disease is difficult to diagnose, and misdiagnosed cases are commonly seen.

Methods

In this study, the presented symptoms of WD, the biochemical parameters as well as its natural history are described based on cases collected in Mohammed VI Hospital University of Marrakech (Morocco). We screened and sequenced 21 exons of ATP7B gene from 12 WD patients that confirmed through biochemical diagnosis.

Results

Mutational assessment of the ATP7B gene showed six homozygous mutations in 12 individuals however, 2 patients had no evidence of any mutation in promoter and exonic regions. All mutations are pathogenic and most were missense mutations. c.2507G > A (p.G836E), c.3694A > C (p.T1232P) and c.3310 T > C (p.C1104R) that were identified in 4 patients. The other mutations were a non-sense mutation (c.865C > T (p.C1104R)) detected in 2 patients, a splice mutation (c.51 + 4A > T) detected in 2 patients and a frameshift mutation (c.1746 dup (p.E583Rfs*25) detected in 2 patients.

Conclusion

Our study is the first molecular analysis in Moroccan patients with Wilson's disease, the ATP7B mutational spectrum in the Moroccan population is diverse and still unexplored.

Urinary copper excretion before and after oral intake of d-penicillamine in parents of patients with Wilson's disease

BACKGROUND

Urinary copper excretion higher than 100 μg/24 h is useful for diagnosing Wilson's disease. d-Penicillamine challenge test may produce higher levels than 1400 μg/24 h, allowing for better diagnostic accuracy. This study investigated whether heterozygotes reach this value and compared copper serum levels, ceruloplasmin, and urinary copper excretion before and after administering d-penicillamine to the parents of Wilson's disease patients.

METHODS

Fifty parents of adult patients were enrolled to obtain copper serum levels and ceruloplasmin along with 24-h urinary copper excretion before and after administering 1g d-penicillamine.

RESULTS

Serum ceruloplasmin and copper levels were significantly lower in fathers than in mothers (mean 21.8×27.8 mg%; 71.4×88.0 μg%; p ≤ 0.001). The mean of basal 24-h urinary copper excretion was higher in fathers (26.2×18.7 μg/24 h, p=0.01), but did not differ between the genders after d-penicillamine (521.7×525.3, range 31.6-1085.1 μg/24h, p=0.8).

CONCLUSIONS

The mean values of serum copper, ceruloplasmin, and basal urinary copper excretion were different between males and females. The current diagnostic threshold of 24-h urinary copper excretion after d-penicillamine was not reached by heterozygotes. The increased urinary copper excretion after d-penicillamine challenge was much higher than fivefold the upper limit of normal urinary copper excretion in the majority of heterozygotes and should not be taken into account when diagnosing Wilson's disease.

Direct determination of copper in urine using a sol–gel optical sensor coupled to a multicommutated flow system

In this work, a multicommutated flow system incorporating a sol-gel optical sensor is proposed for direct spectrophotometric determination of Cu(II) in urine. The optical sensor was developed by physical entrapment of 4-(2-pyridylazo)resorcinol (PAR) in sol-gel thin films by means of a base-catalysed process. The immobilised PAR formed a red 2:1 complex with Cu(II) with maximum absorbance at 500 nm. Optical transduction was based on a dual-colour light-emitting diode (LED) (green/red) light source and a photodiode detector. The sensor had optimum response and good selectivity towards Cu(II) at pH 7.0 and its regeneration was accomplished with picolinic acid. Linear response was obtained for Cu(II) concentrations between 5.0 and 80.0 microg L(-1), with a detection limit of 3.0 microg L(-1) and sampling frequency of 14 samples h(-1). Interference from foreign ions was studied at a 10:1 ( w/ w) ion:Cu(II) ratio. Results obtained from analysis of urine samples were in very good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP-MS); there was no significant differences at a confidence level of 95%.

Determination of zinc and copper in urine using Zeeman effect flame atomic absorption spectroscopy

Zinc and copper were determined in urine using polarized Zeeman effect flame atomic absorption spectrophotometry. For the zinc assay, urine was diluted 1/10 with deionized water. Concentrations could be determined by comparison to standards in a salt matrix or in a commercial urine control. The linearity of the assay was 350 micrograms/l, the detection limit was 1.2 micrograms/l and the within-run relative standard deviation (RSD) was 2.08%, 3.06%, 0.71% and 1.29% for specimens with zinc concentrations of 202 micrograms/l, 206 micrograms/l, 1 003 micrograms/l and 1 032 micrograms/l, respectively. The between-run RSD was 2.34% for a mean zinc concentration of 461 micrograms/l. For the copper assay, urine was aspirated directly and concentrations were determined by standard additions. The linearity of the assay was 5 000 micrograms/l, the detection limit was 4.6 micrograms/l and the within-run RSD was 24.49%, 16.10%, 4.00% and 3.19% for specimens with copper concentrations of 9.8 micrograms/l, 11.8 micrograms/l, 50.0 micrograms/l and 50.2 micrograms/l, respectively. The between-run RSD was 8.78% and 4.72% for specimens with copper concentrations of 21.1 micrograms/l and 40.3 micrograms/l, respectively.

Trace elements in human body fluids and tissues

Published figures for trace element concentrations in body fluids and tissues of apparently healthy subjects are widely divergent. For a considerable time, the apparent disparities were readily ascribed to biological sources of variation such as age, sex, dietary habits, physiological conditions, environmental exposure, geographical circumstances, or similar influences. Growing evidence, however, suggests that this interpretation may be seriously questioned in numerous instances. First, values obtained in reference materials leave no doubt that some previous studies must have been subject to gross analytical inaccuracies. Second, it has now been thoroughly documented that inadequate sample collection and manipulation may drastically distort the intrinsic trace element content of biological matrices. This review scrutinizes data reported by a number of investigators. In an effort to settle the currently flourishing confusion, critically selected reference values are set forth for trace element levels in human blood plasma or serum, packed blood cells, urine, lung, liver, kidney, and skeletal muscle tissue.

Determination of copper in urine by graphite furnace atomic absorption spectrometry

Two methods are described for the determination of copper in urine by graphite furnace atomic absorption spectrometry. The first, suitable for spectrometers capable of making good background correction at 325 nm, involves a direct determination against simple aqueous standards after 2 X dilution of the sample. The second requires no background correction and can be used when background correction is not available or is inadequate. The copper is extracted from the urine with ammonium tetramethylenedithiocarbamate into methylisobutylketone and the extract is analysed for copper. No significant matrix effect was observed for either method. Analysis of random urine samples from 16 normal subjects gave a mean concentration of 0.42 mumol/l with a range of 0.06--1.04 mumol/l.

Zinc and copper urinary excretions in children with burns and scalds

The daily urinary losses of zinc and copper have been measured over periods of up to 12 days following thermal injury in 18 children. Comparison with measurements of zinc and copper excretions in 35 control children showed that after injury by burning or scalding, the urinary excretions of both metals were increased in many of the patients. After severe injury, high urinary outputs of zinc and copper persisted for up to two months following injury.

Recent developments in the analysis of toxic elements

One may conclude that it is impractical to confine oneself to any one analytical method since ever more sensitive instrumentation continues to be produced. However, in certain methods such as anodic stripping voltammetry and flameless atomic absorption it may be background contamination from reagent impurities and surroundings rather than instrument sensitivity which controls the limits of element detection. The problem of contamination from dust or glassware is greatly magnified when the sample size becomes ever smaller. Air entering laboratories near highways may contain trace quantities of lead, cadmium, barium, antimony, and other elements from engine exhaust. Even plastic materials contacting the sample may be suspect as a source of contamination since specific metals may be used as catalysts in the synthesis of the plastic and traces may be retained in it. Certain elements may even be deliberately added to plastics during manufacture for identification purposes. Nondestructive methods such as neutron activation and x-ray techniques thus offer great advantages not only in time but in the elimination of impurities introduced during sample ashing. Future improvements in attainable limits of detection may arise largely from progress in the ultrapurification of reagents and "clean-room" techniques. Finally, the competence of the analyst is also vitally important in the skillful operation of modern complex analytical instrumentation and in the experienced evaluation of data.