Urine Standard Reference Material Research Articles

VALIDATED MEASUREMENT OF URANIUM IN A HUMAN URINE STANDARD REFERENCE MATERIAL BY ICP-MS WITH THE STANDARD ADDITION METHOD.

The Urine Analysis Laboratory of the Korea Atomic Energy Research Institute has developed an in vitro method for measuring uranium in spot urine samples using inductively coupled plasma-mass spectrometry (ICP-MS) with microwave-assisted digestion and standard addition. To validate this procedure, the frozen human urine standard reference material (SRM 2668), such as uranium and creatinine, were analyzed. To overcome the matrix effect and thereby obtain precise measurement data, the standard addition method with extrapolation of four additional points was applied. The measured values for uranium in the SRM were within the acceptable margin of error. The results were compared and evaluated with respect to the American National Standards Institute and Heath Physics Society (ANSI/HPS) N13.30 and International Organization for Standardization 28218 standards. The relative precision (SBr), relative bias (Br), and root-mean-square error values were within the acceptable ranges for the SRM.

Metabolomics Test Materials for Quality Control: A Study of a Urine Materials Suite.

There is a lack of experimental reference materials and standards for metabolomics measurements, such as urine, plasma, and other human fluid samples. Reasons include difficulties with supply, distribution, and dissemination of information about the materials. Additionally, there is a long lead time because reference materials need their compositions to be fully characterized with uncertainty, a labor-intensive process for material containing thousands of relevant compounds. Furthermore, data analysis can be hampered by different methods using different software by different vendors. In this work, we propose an alternative implementation of reference materials. Instead of characterizing biological materials based on their composition, we propose using untargeted metabolomic data such as nuclear magnetic resonance (NMR) or gas and liquid chromatography-mass spectrometry (GC-MS and LC-MS) profiles. The profiles are then distributed with the material accompanying the certificate, so that researchers can compare their own metabolomic measurements with the reference profiles. To demonstrate this approach, we conducted an interlaboratory study (ILS) in which seven National Institute of Standards and Technology (NIST) urine Standard Reference Material®s (SRM®s) were distributed to participants, who then returned the metabolomic data to us. We then implemented chemometric methods to analyze the data together to estimate the uncertainties in the current measurement techniques. The participants identified similar patterns in the profiles that distinguished the seven samples. Even when the number of spectral features is substantially different between platforms, a collective analysis still shows significant overlap that allows reliable comparison between participants. Our results show that a urine suite such as that used in this ILS could be employed for testing and harmonization among different platforms. A limited quantity of test materials will be made available for researchers who are willing to repeat the protocols presented here and contribute their data.

Towards establishing indicative values for metabolites of organophosphate ester contaminants in human urine

In 2015, nine laboratories from Belgium, USA, Canada, China, and Australia participated in an interlaboratory exercise to quantify metabolites of organophosphate ester (OPE) contaminants in pooled human urine. Pooled human urine available as SRM 3673 (Organic contaminants in non-smokers’ urine) was obtained from the U.S. National Institute of Standards and Technology and was analyzed for its content of OPE metabolites. Each participating laboratory received 10 mL sample and used its own validated method and standards to report the concentrations of the OPE metabolites of its choice. Four OPE metabolites were consistently measured by most laboratories and they were the following diesters: bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), and bis(1-chloro-2-propyl) phosphate (BCIPP). Concentrations of other OPE metabolites in SRM 3673 were also reported but are only considered as informative values since they were measured by three laboratories at most. All laboratories used liquid chromatography with tandem mass spectrometry (LC-MS/MS) with or without solid-phase extraction (SPE). This is the first study to report indicative values for OPE metabolites in a human urine Standard Reference Material. It is expected that these indicative values obtained for these four metabolites will be used as quality control to ensure compatibility of results in biomonitoring studies and by other researchers who validate their own methods for the quantification of OPE metabolites in human urine.

A disposable chronocoulometric sensor for heavy metal ions using a diaminoterthiophene-modified electrode doped with graphene oxide

The rapid simultaneous determination of cadmium, lead, copper, and mercury ions is performed by employing a disposable sensor modified with graphene oxide (GO) doped diaminoterthiophene (GO/DTT) for chronocoulometry (CC). The performances of CC with and without pre-deposition in two opposite potential step directions were compared with square wave anodic stripping voltammetry (SWASV) under various conditions. The surface of the GO/DTT modified screen print carbon electrode (SPCE) was characterized by SEM, EDXS, and electrochemical impedance spectroscopy (EIS). Experimental variables that affect the response signal such as the pH, deposition time, type of supporting electrolyte, concentration of DTT, content ratio of GO to DTT, and Nafion content were optimized. Interference effects due to other heavy metal ions were also investigated. The dynamic ranges of SWASV and CC were between 1 ng mL−1 and 2.5 μg mL−1 and between 1 ng mL−1 and 10 μg mL−1, respectively. The detection limits for Cd2+, Pb2+, Cu2+, Hg2+ ions were 1.9 ± 0.4 ng mL−1, 2.8 ± 0.6 ng mL−1, 0.8 ± 0.2 ng mL−1, and 2.6 ± 0.9 ng mL−1 for the CC stripping method; 2.6 ± 0.2 ng mL−1, 0.5 ± 0.1 ng mL−1, 1.8 ± 0.3 ng mL−1, and 3.2 ± 0.3 ng mL−1 for the CC deposition method; and 7.1 ± 0.9, 1.9 ± 0.3, 0.4 ± 0.1, and 0.7 ± 0.1 ng mL−1 for SWASV. The reliability of the method for point-of-analysis was evaluated by analyzing a urine standard reference material and some water samples.

Development of urine standard reference materials for metabolites of organic chemicals including polycyclic aromatic hydrocarbons, phthalates, phenols, parabens, and volatile organic compounds.

Two new Standard Reference Materials (SRMs), SRM 3672 Organic Contaminants in Smokers' Urine (Frozen) and SRM 3673 Organic Contaminants in Non-Smokers' Urine (Frozen), have been developed in support of studies for assessment of human exposure to select organic environmental contaminants. Collaborations among three organizations resulted in certified values for 11 hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and reference values for 11 phthalate metabolites, 8 environmental phenols and parabens, and 24 volatile organic compound (VOC) metabolites. Reference values are also available for creatinine and the free forms of caffeine, theobromine, ibuprofen, nicotine, cotinine, and 3-hydroxycotinine. These are the first urine Certified Reference Materials characterized for metabolites of organic environmental contaminants. Noteworthy, the mass fractions of the environmental organic contaminants in the two SRMs are within the ranges reported in population survey studies such as the National Health and Nutrition Examination Survey (NHANES) and the Canadian Health Measures Survey (CHMS). These SRMs will be useful as quality control samples for ensuring compatibility of results among population survey studies and will fill a void to assess the accuracy of analytical methods used in studies monitoring human exposure to these organic environmental contaminants.

Analysis of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in urine samples by hollow fiber-liquid phase microextraction and gas chromatography–mass spectrometry in consideration of measurement uncertainty

Marijuana abuse can be detected by means of toxicological analysis of the most important metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in urine samples. The aim of this study is the establishment of the detailed procedure for analysis of THC-COOH in urine by combination of hollow fiber-liquid phase microextraction (HF-LPME) and gas chromatography–mass spectrometry (GC–MS). The conditions of hydrolysis and extraction were optimized. The method was shown to be very simple and rapid, and a low amount of organic solvent was necessary for extraction. The limit of detection was 1.5 ng/ml. The calibration curves were linear over the specified range (2.0–170 ng/ml; r 2 > 0.99). The main sources of uncertainty were found to be analyte concentration, accuracy, method precision and sample volume. The effect of the analyte concentration on the overall combined uncertainty was most significant. The developed method was successfully applied to a human urine standard reference material at two levels of concentration. The obtained relative combined uncertainty was 8 %, which can be considered acceptable according to international guidelines. The present method seems very useful in clinical and forensic toxicology, because of its simplicity, rapidness and inexpensiveness.

Certification of Total Arsenic in Blood and Urine Standard Reference Materials by Radiochemical Neutron Activation Analysis and Inductively Coupled Plasma - Mass Spectrometry.

A newly developed procedure for determination of arsenic by radiochemical neutron activation analysis (RNAA) was used to measure arsenic at four levels in SRM 955c Toxic Elements in Caprine Blood and at two levels in SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing mass concentration values for certification. Samples were freeze-dried prior to analysis followed by neutron irradiation for 3 h at a fluence rate of 1×1014cm-2s-1. After sample dissolution in perchloric and nitric acids, arsenic was separated from the matrix by extraction into zinc diethyldithiocarbamate in chloroform, and 76As quantified by gamma-ray spectroscopy. Differences in chemical yield and counting geometry between samples and standards were monitored by measuring the count rate of a 77As tracer added before sample dissolution. RNAA results were combined with inductively coupled plasma - mass spectrometry (ICP-MS) values from NIST and collaborating laboratories to provide certified values of (10.81 ± 0.54) μg/kg and (213.1 ± 0.73) μg/kg for SRM 2668 Levels I and II, and certified values of (21.66 ± 0.73) μg/kg, (52.7 ± 1.1) μg/kg, and (78.8 ± 4.9) μg/kg for SRM 955c Levels 2, 3, and 4 respectively. Because of discrepancies between values obtained by different methods for SRM 955c Level 1, an information value of < 5 μg/kg was assigned for this material.

Characterization of perchlorate in a new frozen human urine standard reference material

Perchlorate, an inorganic anion, has recently been recognized as an environmental contaminant by the US Environmental Protection Agency. Urine is the preferred matrix for assessment of human exposure to perchlorate. Although the measurement technique for perchlorate in urine was developed in 2005, the calibration and quality assurance aspects of the metrology infrastructure for perchlorate are still lacking in that there is no certified reference material (CRM) traceable to the International System of Units. To meet the quality assurance needs in biomonitoring measurements of perchlorate and the related anions that affect thyroid health, the National Institute of Standards and Technology (NIST), in collaboration with the Centers for Disease Control and Prevention (CDC), developed Standard Reference Material (SRM) 3668 Mercury, Perchlorate, and Iodide in Frozen Human Urine. SRM 3668 consists of perchlorate, nitrate, thiocyanate, iodine, and mercury in urine at two levels that represent the 50th and 95th percentiles, respectively, of the concentrations (with some adjustments) in the US population. It is the first CRM being certified for perchlorate. Measurements leading to the certification of perchlorate were made collaboratively at NIST and CDC using three methods based on liquid or ion chromatography tandem mass spectrometry. Potential sources of bias were analyzed, and results were compared for the three methods. Perchlorate in SRM 3668 Level I urine was certified to be 2.70 ± 0.21 μg L(-1), and for SRM 3668 Level II urine, the certified value is 13.47 ± 0.96 μg L(-1).

A human urine standard reference material for accurate assessment of arsenic exposure

Arsenic is a toxic element, and the toxicity of the element is dependent on its molecular form. Accurate assessments of arsenic exposure require the measurement of a complete panel of inorganic, organic, and metabolite arsenic species in urine, including arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), arsenobetaine (AB), and arsenocholine (AC). A certified reference material (CRM) containing the panel of arsenic species in urine is needed for method validation and quality assurance of assessment measurements. Until now, such a CRM was unavailable, due in part to the difficulty in stabilizing arsenic species, especially As(III). For the first time, O2 in the ambient atmosphere was determined to be the primary cause for the instability of As(III) in an aqueous matrix, and a procedure was developed to stabilize the panel of arsenic species in a dark, low temperature (<−70 °C), and oxygen-free environment. Standard Reference Material® (SRM) 2669 arsenic species in frozen human urine has been developed to meet the needs in arsenic exposure measurements in general and to support National Health and Nutrition Examination Survey (NHANES), in particular. SRM 2669 is certified for each arsenic species mentioned above at two concentration levels intended to proximate the 50th percentile and 95th percentile distribution in the US population (concentrations of As(III), As(V), AC, and TMAO in the SRM are adjusted upward of the target percentiles to be above the method detection limits). The SRM was jointly produced by the National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC). Measurements leading to the certification were made collaboratively at NIST, CDC, and Rutgers, the State University of New Jersey.

Methods for the separation and quantification of arsenic species in SRM 2669: arsenic species in frozen human urine

Two independent liquid chromatography inductively coupled plasma-mass spectrometry (LC/ICP-MS) methods for the separation of arsenic species in urine have been developed with quantification by standard additions. Seven arsenic species have been quantified in a new NIST frozen human urine Standard Reference Material (SRM) 2669 Arsenic Species in Frozen Human Urine, Levels 1 and 2. The species measured were: arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), dimethylarsinate (DMA), arsenobetaine (AB), arsenocholine (AC), and trimethylarsine oxide (TMAO). The purity of each arsenic standard used for quantification was measured as well as the arsenic species impurities determined in each standard. Analytical method limits of detection (L(D)) for the various species in both methods ranged from 0.2 to 0.8 microg L(-1) as arsenic. The results demonstrate that LC/ICP-MS is a sensitive, reproducible, and accurate technique for the determination of low-level arsenic species in urine. Measurements of the arsenic species 3 years after initial production of the SRM demonstrate the stability of the arsenic species in the urine reference material.

Determination of Trace Metals in Urine by Direct Dilution Inductively Coupled Plasma Optical Emission Spectrometry

ISEE-913 Objective: To evaluate a direct dilution method for multielement analyses in urine using Ultrasonic Nebulization Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Material and Methods: Ultrasonic nebulizer when combined with an ICP-OES provides a low detection limit capability. It can handle samples with significant amounts of dissolved solids, such as urine. In this work, urine samples were prepared by a simple direct dilution preparation method, and the concentration urinary of Ba, Cd, Co, Cr, Ni, Sr, V, Zn, Cu, Fe, Mn, and Mo were measured using an ultrasonic nebulizer CETAC U-5000T connected to an ICP-OES Perkin-Elmer 4200, DV-simultaneous. Results: Urine samples were diluted (1 + 9) with 2% v/v nitric acid. In addition, acid-decomposed samples were similarly investigated. On comparison of the measured values of samples prepared by direct dilution and acid-decomposition samples, the values were slightly lower in the samples prepared by direct dilution for many elements. The human urine standard reference material used was NIST SRM 2670a. For Ba-Cd-Co-Cr-Ni-Sr-V-Zn-Cu-Fe-Mn and Mo, the analytical results of the human urine standard reference material were well consistent with the certified values (90%–110% recovery). The system was operated for 12 hours with no evidence of deterioration (5% RSD). Conclusions: This method represents a useful tool for monitoring a variety of metals in urine at the levels of interest in a programme of biological monitoring of human exposure.

Direct determination of cadmium in urine by tungsten-coil inductively coupled plasma atomic emission spectrometry using palladium as a permanent modifier

Cadmium is determined in urine samples collected from patients with age-related diseases. The urine is simply diluted 1:1 with water and placed on a tungsten coil electrothermal vaporizer treated with 200 μg of a permanent Pd modifier. A straightforward vaporization program is used to deliver the Cd vapor to an inductively coupled plasma atomic emission spectrometer. A high resolution spectrometer and a charge coupled device detector provide spectra across a 4.8 nm window encompassing two separate Cd emission lines: 226.5 and 228.8 nm. The limit of detection is 0.2 μg/L at each wavelength, and the linear dynamic range spans three orders of magnitude. The accuracy as measured with a urine standard reference material is 94%. The Pd modifier continues to be effective even after 150 vaporization cycles. Direct analysis of urine with the Pd modifier using simple aqueous calibration solutions provides results that are comparable to those observed after a much more complex method: chelation, extraction, and internal standardization without the modifier. The mean concentrations found by the two techniques differ by only 9%. The permanent Pd modifier allows direct analysis of limited sample volumes with decreased risks of contamination.

Chelation of urinary cadmium with ammonium pyrrolidine dithio-carbamate prior to determination by tungsten-coil inductively coupled plasma atomic emission spectrometry

Cadmium in the urine samples of patients with age-related disease forms a complex with a chelating agent, ammonium pyrrolidine dithio-carbamate, and the complex is extracted with methyl isobutyl ketone. One milliliter of urine provides three separate 200-μl aliquots of extract, so a preconcentration factor of 5/3 is observed. In this manner, the Cd is effectively separated from the complex urine matrix. An internal standard, Bi, is added to improve both precision and accuracy. The extracts are analyzed by inductively coupled plasma atomic emission spectrometry using a tungsten-coil as an electrothermal vaporizer. A 20-μl aliquot of the extract is injected directly onto the coil. Two Cd atomic emission lines are observed simultaneously: 228.8 nm and 226.5 nm. The limits of detection at these wavelengths are 0.04 and 0.2 μg/l, respectively. Without the extraction technique, the detection limit is 0.4 μg/l at the 228.8-nm line. With the internal standard technique, the accuracy as measured with a urine standard reference material is 98%. Six urine samples collected from patients with age-related diseases are found to contain Cd levels in the range 0.9 to 4.1 μg/l. The precision associated with the measurement of these real samples is 6.2% relative standard deviation. The technique provides off-wavelength background correction and simultaneous determination at two different wavelengths, so samples that are limited in volume can still be analyzed with a high degree of confidence.

Determination of Trace Levels of Elements in Urine by Inductively Coupled Plasma Mass Spectrometry

A biological specimen, urine, was prepared by the most simple sample preparation method, direct dilution, and determination of seven elements in the urine samples, Fe, Cu, Zn, Se, As, Cd, and Pb, was investigated by inductively coupled plasma mass spectrometry (ICP-MS). In addition, acid-decomposed samples were similarly investigated. Regarding the matrix effect of concomitant components, as the sodium hydrochloride concentration increased, the observed ion intensity of the measured element linearly decreased. Matrix interference by sodium hydrochloride could be fairly corrected by addition of internal standard elements excluding determination of Fe and Zn. On comparison of the measured values of samples prepared by direct dilution and acid-decomposition samples, the values were slightly lower in the samples prepared by direct dilution for many elements. For Zn and As, the analytical results of the human urine standard reference material were well consistent with the certified values.

Sequential hydride generation/pneumatic nebulisation inductively coupled plasma mass spectrometry for the fractionation of arsenic and selenium species

The toxicity of certain elements is known to be related to their organic substituents and/or oxidation states. As such, total elemental determinations do not always yield sufficient information for accurate risk assessments and therefore speciation or fractionation data are required. In order to obtain fractionation data for trace levels of arsenic and selenium, a novel sequential pneumatic nebulisation (PN)/hydride generation (HG) inductively coupled plasma mass spectrometry (ICP-MS) method was developed. The method offers the advantage of sample introduction via either PN or HG by simply rotating a 4-way switching valve while the system is in operation. In PN mode, the liquid sample is aspirated into ICP, allowing for the determination of the total amount of each element, whilst in HG mode only the arsenic and selenium species that form volatile hydrides are determined. Conveniently, in the case of arsenic, this allows for differentiation between the four most toxic arsenic species (arsenate, arsenite, monomethylarsonic acid and dimethylarsinic acid), which form volatile hydrides, and the virtually non-toxic forms (arsenobetaine, arsenosugars, etc.), which do not. This allows for the rapid estimation of the amounts of toxic and non-toxic arsenic species present in a sample. For arsenic, the technique gave detection limits of 36 ng l −1 in PN mode and 1 ng l −1 in HG mode. For selenium, detection limits of 150 ng l −1 were achieved in PN mode and 220 ng l −1 in HG mode. The technique also gave good long- and short-term stabilities of under 6% RSD for both elements. A variety of samples, including water and urine standard reference materials, were analysed in both modes, and the precision and accuracy of the results for total arsenic and selenium levels were assessed. Using the technique in both modes also allowed for the fractionation of As and Se species into their volatile hydride-forming and non-hydride-forming species. This was particularly informative, with respect to As species present, in the case of a kelp powder extract. Digested tobacco samples were only analysed for their total As levels, in which case results obtained via both sample introduction modes showed good agreement.

Elimination of Chemical and Spectral Interferences in Measurement of Trace Elements in Urine and Blood by Combined Electrodeposition-Electrothermal Atomic Absorption Spectrometry

A combined electrodeposition-ETAAS technique has been applied to the analysis of Pb, Cd, Co, Ni, Cr and Mn in biological samples in order to overcome interferences and to mini- mize sample pretreatment. It requires minimal sample preparation with the electrolysis process aid- ing partial decomposition of the organic matrix, adequate for the release and deposition of trace elements. In an initial electrode position step, the graphite furnace is coated by Pd. Analytes are then electrode posited in situ from the sample at optimized applied voltage and time onto the Pd- coated furnace, followed by removal of spent electrolyte and atomization. The high background sig- nals due to matrix components of urine and blood were eliminated by the technique and the sensi- tivity of determination was improved up to jive-fold with respect to conventional ETAAS technique. A good precision of 1-3 %RSD (depending on the element and sample matrix) has been obtained. The recovery of added analytes is close to 100%, based on comparison with conventional ETAAS of aqueous samples. The accuracy of the technique was established by analyzing the urine standard reference material, SRM2670. The results of determinations of the elements tested are within the range of certified values given by the NIST with an acceptable %RSD.

Trace level determination of perchlorate in water matrices and human urine using ESI-FAIMS-MS.

High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates perchlorate from interfering isobaric ions of bisulfate and dihydrogenphosphate in the gas-phase. The use of a new FAIMS prototype and waveform generator, along with the use of a mixed carrier gas, in this electrospray ionisation (ESI)-FAIMS-mass spectrometry (MS) study gave a detection limit for perchlorate in a relatively "clean" matrix of tap water of 0.050 ppb. Flow injection analysis (FIA) of dilutions of fortified waste water, a fortified river water certified reference material (CRM; SLRS-4, National Research Council of Canada), and a fortified human urine Standard Reference Material (SRM; 2381, National Institute of Standards and Technology) gave detection limits of 0.37 ppb, 0.50 ppb, and 4.8 ppb, respectively, in the undiluted matrices.

Comparison of cryogenic and membrane desolvation for attenuation of oxide, hydride and hydroxide ions and ions containing chlorine in inductively coupled plasma mass spectrometry

Conventional, cryogenic and membrane desolvation methods were compared with respect to sensitivity, MO+/M+ signal ratios and the aerosol gas flow rate required to maximize M+ and MO+ signals. Thorium was used to represent the actinides, which form relatively strong hydrides and hydroxides. The LaO+/La+ ratio is reduced from 0.24% with conventional desolvation to 0.08% with membrane desolvation and 0.01% with cryogenic desolvation. Membrane desolvation reduces ThH+ and ThOH+ 2-fold compared with conventional desolvation. Cryogenic desolvation attenuates ThH+ 7-fold and ThOH+ 20-fold compared with conventional desolvation. The three desolvation methods were also evaluated for the removal of ClO+ and ArCl+ for the determination of vanadium and arsenic at trace levels in the presence of chloride. The density of oxygen atoms is reduced as water vapor is removed, and chloride is also removed, presumably as hydrogen chloride. The concentration of vanadium in a urine standard reference material was determined by standard additions to be 7 ppb with cryogenic desolvation and 5 ppb with membrane desolvation. Analysis of several nasal wash samples using cryogenic and membrane desolvation yielded results that agreed within 5% for the two methods in all cases except for the sample with the highest V+ concentration.

Certification of morphine-3-β-D-glucuronide in a human urine standard reference material

The U.S. National Institute of Standards and Technology (NIST) has developed and certified a standard reference material, SRM 2382, for use in testing for bias in the determination of morphine present as a glucuronide in human urine. This SRM consists of three levels of morphine-3-β-D-glucuronide (M-3-G) in lyophilized urine. Two independent hydrolysis procedures, enzymatic and acidic, for quantitative release of morphine were investigated. The results of hydrolysis efficiency from these two procedures agreed well. These two hydrolysis procedures along with two analytical methods developed previously for measurement of free morphine [1] were used to certify M-3-G in SRM 2382. Enzymatic hydrolysis was used with the GC/MS method and acidic hydrolysis was used with LC/MS. The results from these two pairs of methods were in good agreement, and were statistically combined to yield certified values of 209 ± 20, 437 ± 21, and 853 ± 39 ng/mL for morphine, as the free base. Round-robin studies on this material among ten military laboratories demonstrated the suitability of the SRM for its intended purpose.

Determination of Copper, Cadmium and Lead in Biological Samples by Electrothermal Vaporization Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of Cu, Cd and Pb in several biological samples. The isotope ratios for each element in each analytical run were calculated from the peak areas of each isotope. Various chemical modifiers were tested to obtain the optimum signal of cadmium and palladium was selected. The pyrolytic graphite platforms of the graphite tubes were then pretreated with palladium by three different methods, thermal pretreatment, electroplating and sputtering, and after careful evaluation of the analytical performance of these methods, thermal pretreatment of the platform with Pd before each analysis was selected. The ETV-ID-ICP-MS method was applied to the determination of Cu, Cd and Pb in dogfish liver reference material DOLT-1, dogfish muscle reference material DORM-1 and freeze-dried urine standard reference material NIST SRM 2670. The results agreed satisfactorily with the certified values.