Evaluation of serum electrolytes measurement through the 6-year trueness verification program in China.

Objectives: The National Center for Clinical Laboratories (NCCL) in China initiated a serum electrolyte trueness verification (ETV) program in 2014 for measurement standardization. Methods: Every year, two levels of fresh frozen commutable serum samples determined by inductively coupled plasma mass spectrometry (ICP-MS) reference methods were transported to participating clinical laboratories for the measurement of sodium, potassium, calcium and magnesium. Both samples were measured 15 times in 3 days, and the mean values and coefficient variations (CVs) were calculated from the results. The tolerance limits of trueness (bias), precision (CV) and accuracy (TE) based on the biological variation database were used as the evaluation criteria. The overall trend of the ETV program over 6 years was surveyed by calculating the pass rates of the participating laboratories. The mean bias, inter-laboratory CV, and TE of all laboratory results were analysed. Furthermore, homogeneous and heterogeneous systems were compared, and the bias and CV results of mainstream analysis systems were analysed. Results: Pass rates of the three quality specifications increased, and the overall mean bias and inter-laboratory CVs decreased. The homogeneous system was superior to the heterogeneous system for calcium and magnesium measurements. For sodium, potassium, calcium and magnesium, the minimum bias corresponded to Hitachi, Siemens, Beckman AU and Roche, respectively. For inter-laboratory robust CVs, no obvious differences were observed between each peer group. Conclusions: The commutable ETV materials assigned via reference methods can evaluate the accuracy and reproducibility of an individual laboratory and the calibration traceability and uniformity between laboratories for measurements.

Physicochemical quality evaluation of groundwater and development of drinking water quality index for Araniar River Basin, Tamil Nadu, India.

Groundwater is the most important natural resource which cannot be optimally used and sustained unless its quality is properly assessed. In the present study, the spatial and temporal variations in physicochemical quality parameters of groundwater of Araniar River Basin, India were analyzed to determine its suitability for drinking purpose through development of drinking water quality index (DWQI) maps of the post- and pre-monsoon periods. The suitability for drinking purpose was evaluated by comparing the physicochemical parameters of groundwater in the study area with drinking water standards prescribed by the World Health Organization (WHO) and Bureau of Indian Standards (BIS). Interpretation of physicochemical data revealed that groundwater in the basin was slightly alkaline. The cations such as sodium (Na(+)) and potassium (K(+)) and anions such as bicarbonate (HCO3 (-)) and chloride (Cl(-)) exceeded the permissible limits of drinking water standards (WHO and BIS) in certain pockets in the northeastern part of the basin during the pre-monsoon period. The higher total dissolved solids (TDS) concentration was observed in the northeastern part of the basin, and the parameters such as calcium (Ca(2+)), magnesium (Mg(2+)), sulfate (SO4 (2-)), nitrate (NO3 (-)), and fluoride (F(-)) were within the limits in both the seasons. The hydrogeochemical evaluation of groundwater of the basin demonstrated with the Piper trilinear diagram indicated that the groundwater samples of the area were of Ca(2+)-Mg(2+)-Cl(-)-SO4 (2-), Ca(2+)-Mg(2+)-HCO3 (-) and Na(+)-K(+)-Cl(-)-SO4 (2-) types during the post-monsoon period and Ca(2+)-Mg(2+)-Cl(-)-SO4 (2-), Na(+)-K(+)-Cl(-)-SO4 (2-) and Ca(2+)-Mg(2+)-HCO3 (-) types during the pre-monsoon period. The DWQI maps for the basin revealed that 90.24 and 73.46% of the basin area possess good quality drinking water during the post- and pre-monsoon seasons, respectively.

Candidate reference measurement procedures for chloride, potassium, sodium, calcium, magnesium, and lithium by inductively coupled plasma (isotope dilution) sector field mass spectrometry (ICP-(ID) SFMS) in serum.

BACKGROUND: Standardization of the measurement of electrolyte concentrations in serum is of considerable interest for quality assurance in patient care. To promote the ongoing process of standardization we developed candidate reference measurement procedures of highest metrological order for Cl, K, Na, Ca, Mg, and Li using ICP-(ID) SFMS. METHODS: Serum samples were diluted with 4 mmol/L nitric acid and were spiked with the internal standard for quantification, separately for each analyte. The samples were introduced in the ICP-SFMS device by continuous infusion using a peristaltic pump. The measurement results were compared with reference measurement procedure values obtained by atom absorption spectroscopy, flame emission spectroscopy, and coulometry. The measurement accuracy and precision was calculated by analyzing certified reference materials and EQAS samples. RESULTS: The mean coefficient of variation (CV) of the ICP-MS procedures for the serum samples was 0.65% for Cl, 0.46% for K, 0.51% for Na, 0.77% for Ca, 0.78% for Mg, and 0.58% for Li. The mean bias from target values of NIST certified reference materials was +0.85% for Cl, -0.46% for K, +0.68% for Na, -0.21% for Ca, +0.27% for Mg, and -0.39% for Li. CONCLUSIONS: Candidate reference measurement procedures for 6 electrolytes were developed by high performance magnetic sector field ICP-MS fulfilling the requirements of ISO 15193:2009 for reference measurement procedures with traceability to SI according to ISO 17511:2003 and can be used for setting target values in EQAS and for certification of reference materials.

Determination of nickel, calcium and magnesium in xylem sap by flame atomic absorption spectrometry using a microsampling technique.

INTRODUCTION: Knowledge of xylem sap chemical composition is important to the understanding of translocation, detoxification and tolerance mechanisms. However, the small amount of sample available often hampers its characterisation. Hence, low volume consumption techniques are needed for xylem sap analysis. OBJECTIVE: To develop a microsampling technique for the determination of elements in xylem sap from different plants by flame atomic absorption spectrometry (FAAS). METHODOLOGY: The microsampling device was optimised in terms of sample volume and integration time. The analytical characteristics of the microsampling technique (micro-FAAS) were established and compared with those of FAAS with traditional continuous nebulisation. The method was validated by means of an independent technique. RESULTS: Ca, Mg and Ni were determined in a 50 microL aliquot of xylem sap solution/element that was introduced directly into the flame via the microsampling accessory. Good precision was obtained with relative standard deviations of 1.1, 0.6 and 2.3% for Ca, Mg and Ni, respectively. Matrix effects resulting from the physical characteristics of the samples and possible chemical interferences caused by phosphate and/or sulphate were ruled out. CONCLUSION: A simple, rapid and reproducible microsampling technique coupled to FAAS was developed and successfully applied in the determination of Ca, Mg and Ni in xylem sap.

Comparison of Amberlite IR 120 and dolomite's performances for removal of heavy metals.

The presence of heavy metals in the environment is major concern due to their toxicity. Contamination of heavy metals in water supplies has steadily increased over the last years as a result of over population and expansion of industrial activities. A strong cation-exchange resin, Amberlite IR 120 and a natural zeolite, dolomite were used for the removal of lead(II) and cadmium(II). The optimum conditions were determined in a batch system as concentration range was between 5 and 100 mg/L, pH range between 1 and 8, contact time between 5 and 90 min, and the amount of adsorbent was from 0.1 to 1g. A constant stirring speed, 2000 rpm, was chosen during all of the experiments. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5, contact time of 60 min and 0.5 g of adsorbent. Also, for investigation of exchange equilibria different amounts of ion exchange resin and dolomite were contacted with a fixed volume and concentration of a heavy metal bearing solutions. Sorption data have been interpreted in terms of Langmuir and Freundlich equations. The effect of adsorption temperature on the heavy metals adsorption onto dolomite was investigated at three different temperatures (20, 40 and 60 degrees C). Thermodynamic parameters were calculated. The results obtained show that the Amberlite IR 120 strong cation-exchange resin and dolomite performed well for the removal of these heavy metals. As a low cost adsorbent, dolomite can preferable for removal of heavy metals from wastewaters.

A method for measuring intracellular free magnesium concentration in platelets using flow cytometry.

Magnesium is the fourth most abundant cation in the body and is involved in over 302 enzymatic reactions. Basic science research has implicated magnesium deficiency as a cause of insulin resistance which is related to hypertension, diabetes, hyperlipidemia and increased cardiovascular risk. Research in magnesium deficiency states has been hindered because magnesium is an intracellular ion and difficult to measure. Our goal was to develop a reproducible assay to measure intracellular magnesium in platelets. Healthy volunteers agreed to have blood drawn for magnesium measurement. Platelet rich plasma was harvested from a venipuncture specimen and run through the flow cytometer. A standard titer curve using known increasing concentrations of magnesium chloride was created for each specimen, and then with the other half the specimen was run to measure the true intracellular free magnesium concentration. 15 adults agreed to volunteer for this experiment. All standard titer curves for all specimens had a correlation of > 0.99. The mean concentration of intracellular free magnesium was 450.05 microM with a range of 203.68 microM to 673.50 microM. Intracellular free magnesium can reliably and reproducibly be measured in platelets using Mag Green fluorescent dye and flow cytometry. This should advance our ability to study magnesium deficient states.

Effects of dietary magnesium excess in White Leghorn hens.

The effects of excess dietary magnesium on White Leghorn laying hens were investigated in two experiments and a third experiment looked at the effect of dietary phosphorus on excess magnesium in the diet. In Experiment 1, magnesium levels of 0.15, 0.8, and 1.2% were fed in a diet containing 2.5% calcium to hens 30 wk of age for 5 wk. A control diet with 3.5% calcium and 0.15% magnesium was also fed. In Experiment 2, hens 65 wk of age fed 3.5% calcium were fed dietary magnesium levels of 0.15, 0.36, 0.53, 0.76, and 0.91% for 4 wk. In these two experiments, excess magnesium reduced egg production, decreased feed consumption, decreased body weight, decreased percentage eggshell, reduced plasma calcium, and increased plasma magnesium and tibia magnesium but changes seen in tibia weight, percentage ash, and tibia calcium and phosphorus were variable. More changes from feeding excess magnesium were seen in the young, high producing hens in Experiment 1. In Experiment 3, hens 50 wk of age were fed a marginal calcium level (2.5%) with an excess of magnesium (0.8%) and a control level of available phosphorus (0.45%) and this was compared to a low (0.25%) and a high level (0.9%) of available phosphorus for a 4-wk experimental period. At the end of the experimental period, hens fed low phosphorus had lower egg production and lower feed consumption than the hens fed higher levels of phosphorus. Body weight was lower in the hens fed the two lower levels of phosphorus. Percentage eggshell was lower than the controls when fed low phosphorus and higher when fed high phosphorus. These results suggest that high phosphorus diets are better than low phosphorus diets when excess magnesium is fed to laying hens. Further study is needed to investigate the role of phosphorus when excess magnesium is fed.

Parenteral magnesium loading test in the assessment of magnesium status in healthy adult French subjects.

Parenteral magnesium loading test has been proposed as an adequate mean to evaluate magnesium status. However, applied tests vary among different laboratories and standardized procedure is not available. In the present study, we assessed magnesium status in 32 healthy adult French subjects by magnesium loading test using MgCl2 and determination of magnesium concentrations in plasma and erythrocytes. We observed a positive correlation between plasma and erythrocyte magnesium concentrations, but there was no correlation between magnesium retention and basal urinary excretion of magnesium, and plasma or erythrocyte magnesium concentrations.

[Nutritive value of daily food rations prepared in different regions of the country. III. The levels of calcium, phosphorus, magnesium, iron and potassium]. / Wartosc odzywcza calodziennych racji pokarmowych odtwarzanych w kilku regionach kraju. Cz. III. Zawartosc wapnia, fosforu, magnezu, zelaza i potasu.

Studies on the content of macrominerals in daily diets reconstructed in 1988 on the basis of the analysis of family budgets in 1986 carried out by the Central Statistical Bureau were carried on. Two social groups i.e. manual and mental workers with medium income were considered. The diets were prepared for 5 regions (Warszawa, Lublin, Olsztyn, Poznan, Wroclaw). According to the studies the requirements for calcium and magnesium were met in about 70% and those for iron in about 84%. The content of potassium in the diets was in the range of recommended allowances while the phosphorus exceeded the allowances by about 20-30%. The comparison of the presently studied diets with the ones from 1973, 1980, 1981 showed a lower degree of realization of the recommended intake of calcium and magnesium in 1986. The content of studied minerals in the diets was usually similar in all five regions.

Magnesium-based implants: a mini-review.

The goal of this review is to bring to the attention of the readership of Magnesium Research another facet of the importance of magnesium, i.e. magnesium-based biomaterials. A concise history of biomaterials and magnesium are thus presented. In addition, historical and current, clinical magnesium-based applications are presented.

Analysis of physical and chemical parameters of bottled drinking water.

Seventeen different brands of bottled drinking water, collected from different retail shops in Amritsar, were analyzed for different physical and chemical parameters to ascertain their compliability with the prescribed/recommended limits of the World Heath Organization (WHO) and the United States Environmental Protection Agency (USEPA). It was found that the majority of the brands tested were over-treated. Lower values of hardness, total dissolved solids (TDS) and conductance than the prescribed limits of WHO showed that water was deficient in essential minerals. Minerals like magnesium, potassium, calcium and fluoride were present in some cases in such a low concentration that water seemed to be as good as distilled water. Samples showing fluoride lesser than 0.5 mg/l warranted additional sources of fluoride for the people consuming only bottled water for drinking purposes. Zero values for chlorine demand as shown by all the bottled water samples showed that water samples were safe from micro-organisms. In case of heavy metals, only lead had been found to be greater than the limit of 0.015 mg/l as prescribed by WHO and USEPA, in seven out of 17 samples. Lead even at such a low concentration can pose a great health hazard.

Risk assessment of physico-chemical contaminants in groundwater of Pettavaithalai area, Tiruchirappalli, Tamilnadu - India.

A study was carried out in Pettavaithalai area to evaluate the current status of physico-chemical contaminants and their sources in groundwater. Groundwater samples collected from pettavaithalai area in 15 different stations were analyzed every alternative months over a period of two years from August 2000 to June 2002. A sugar mill is situated at the heart of the study area. Three profiles (profile A, B and C) were selected based on the direction in which the sugar mill effluent flows. In each profile five samples were collected from five different station at a regular distance of about 1 Km. The physico-chemical parameters such as pH, EC TDS, TH, NO3, SO4, PO4, Na, K, Ca, Mg, DO, BOD and COD have been analyzed. The results showed that among the three profiles, many of the estimated physico-chemical parameters of profile C were very high when compared to profile B and A which indicates the poor quality of the groundwater around this area.

Fluorometric determination of magnesium in serum with 2-hydroxy-1-naphthaldehyde salicyloylhydrazone.

This simple, rapid, sensitive fluorometric method for determining magnesium is based on formation of a fluorescent complex of magnesium with 2-hydroxy-1-naphthaldehyde salicyloyl-hydrazone in alkaline ethanolic medium (lambda ex = 420 nm, lambda em = 460 nm). The detection limit of the method is 0.05 microgram/L (2 nmol/L) and the relative standard deviations (CVs) are 0.8%, 1.1%, and 2.5% at magnesium concentrations of 50, 5.0, and 0.50 microgram/L, respectively. The standard curve is linear from 0 to 250 micrograms/L (0-10 mumol/L). We investigated the chemistry of the reaction, and have applied the method to determine magnesium in 100-fold-diluted, otherwise untreated serum samples. Within-run CVs for the method were 1.7%, 1.1%, and 1.3% at mean magnesium concentrations of 15.7, 26.4, and 36.2 mg/L, respectively. Day-to-day CVs were 2.7%, and 3.6% at mean magnesium concentrations of 10.1 and 25.5 mg/L, respectively. Samples from 96 hospitalized patients in intensive-care units were analyzed by the proposed method (y) and by an automated colorimetric method involving Magon sulfonate reagent (x). Linear regression analysis of the results yielded: y = 1.01x - 0.04 (r = 0.982, Sxy = 0.90).

Determination of reference intervals for serum magnesium.

Using a discrete analyzer and a dye-binding method, we measured magnesium in 800 patients' samples received for routine analysis. By excluding data from samples for which the calcium and (or) alkaline phosphatase values were outside defined reference limits, we established a reference interval for magnesium. Because the data showed a gaussian distribution, we could use parametric analysis to establish age-related intervals for both males and females.

Micronutrients (magnesium, zinc, and copper): are mineral supplements needed for athletes?

Mineral elements, including magnesium, zinc, and copper, are required by the body in modest amounts for the maintenance of health and for the development of optimal physiological function. For athletes, adequate amounts of these minerals are required for physical training and performance. Studies of athletes during training, as compared to nontraining control subjects, indicate the potential for increased losses of minerals in sweat and urine. Some studies report suboptimal intakes of minerals, particularly among athletes who are actively attempting to lose weight to meet standards for competition. However, most athletes consume diets that provide adequate amounts of minerals to meet population standards. Athletes should be counseled to consume foods with high nutrient density rather than to rely on mineral supplements. General use of mineral supplements can alter physiological function and impair health.

Calcium, phosphorus, and magnesium: how much is too much for infant formulas?

Despite the use of metabolic balance studies and measurements of bone mineral content, it is difficult to assess the requirements of Ca and P in growing infants. From observations made forty years ago with cow's milk formulas it is obvious what is too much calcium and phosphorus in infant formulas. These observations were utilized in the development of "humanized cow's milk formulas" in the 1950s. Though the total concentrations of Ca and P have been greatly reduced in these formulas, the Ca/P ratio imbalance, compared to human milk, persists. Infants fed these formulas still receive a relative phosphorus load, and cases of neonatal tetany are still occasionally reported. Thus, formula-fed infants have higher serum P and lower serum Ca concentrations than do human milk-fed infants. Unlike Ca and P, the magnesium concentration of infant formulas is similar to that of human milk, and Mg toxicity from formulas has not been reported. Like Ca and P, however, it is difficult to determine the growing infant's requirement for magnesium. The available information does not favor either increasing or decreasing the present concentrations of Ca, P or Mg in infant formulas. The upper limit for these minerals should remain at the present concentrations: 45-50 mg/dl (65-75 mg/100 kcal) for Ca, 30-40 mg/dl (48-58 mg/100 kcal) for P and 12 mg/dl (18 mg/100 kcal) for Mg.