David E. Nixon

Routine clinical determination of lead, arsenic, cadmium, and thallium in urine and whole blood by inductively coupled plasma mass spectrometry

Abstract For the measurement of As, Cd, Pb, and Tl in urine or whole blood, judicious choices of internal standard elements for matrix correction and the development of a refined isobaric arsenic correction are necessary to produce accurate ICP-MS results. Ga and Rh are chosen as internal standards for As and Cd respectively. Bi is better for the correction of Pb and Tl than Re. An empirically derived equation relating the measurement of 16 O 35 Cl to the 40 Ar 35 Cl contribution to the arsenic signal at mass 75 is refined by measuring the responses at mass 51 and 75 for urines with added hydrochloric acid. Overall, ICP-MS results for blood and urine are within 6% of Zeeman GFAAS results for patient samples. For surveys, the overall average of ICP-MS results is within 3% of target.

The determination of mercury in whole blood and urine by inductively coupled plasma mass spectrometry

Abstract An inductively coupled mass spectrometric (ICP-MS) method for the determination of mercury in whole blood and urine was developed. Gold and dichromate in hydrochloric acid were evaluated as agents to reduce mercury spray chamber memory. Dichromate with hydrochloric acid was found to be superior to gold. We evaluated the rapid introduction of sample to promote equilibrium and the rapid introduction of wash solutions after the sample analyses to minimize mercury memory. This ‘fast pump’ mode (2.5 ml/min) was used for 20 s at the beginning and end of each sample-wash cycle. The mercury detection limit is 0.15 μg/l in the original sample before dilution. Regressions and correlation coefficients for ICP-MS vs. target concentrations for interlaboratory comparison samples from the Centre de Toxicologie du Quebec were: whole blood: y=1.0x−0.6; r=0.9801; n=27 and urine: y=0.84x+8; r=0.9915; n=42. Patient samples were analyzed by ICP-MS and cold vapor atomic absorption spectrometry (CVAAS). Regressions and correlations for patient samples were: urines: y=0.93x+1; r=0.8763; n=456 and whole blood: y=1.1x+0.2; r=0.9357; n=251. ICP-MS correlation with CVAAS for 29 urine samples containing 15–150 μg Hg/specimen was: y=0.94x+4; r=0.9864.

Silicon analysis of breast and capsular tissue from patients with saline or silicone gel breast implants : II. Correlation with connective-tissue disease

&NA; The silicone breast implant controversy rages on. Recent work has demonstrated that normal or baseline breast tissue silicon levels in women who had had no prior exposure to any type of breast implant may be as high as 446 &mgr;g/gm of tissue. These data ranged from 4 to 446 &mgr;g/gm of tissue, with a median of 27.0 &mgr;g/gm of tissue. In addition, numerous other epidemiologic and rheumatologic studies have demonstrated no association between silicone breast implants and any connective‐tissue diseases. Despite these reports, the use of silicone implants remains restricted. The present study measured breast and capsular tissue silicon levels from 23 breasts in 14 patients with saline implants, and from 42 breasts in 29 patients with silicone implants. No patient in the saline implant group presented with signs or symptoms of connective‐tissue disease. Patients with silicone implants, however, were divided into three groups based on the presence or absence of signs or symptoms of connective‐tissue disease: group I, no symptoms or signs; group II, + symptoms, no signs; and group III, + symptoms, + signs. Six patients in group III were diagnosed with a specific connective‐tissue disease, including systemic lupus erythematosus, rheumatoid arthritis, or scleroderma. The most common indications for implant removal or exchange were capsular contracture and implant rupture, although 41 percent of patients with silicone implants expressed media‐related concern over the implant issue. The most common symptoms described by patients in groups II and III were joint pain and stiffness, arm pain and numbness, and fatigue. In all groups, capsular tissue silicon levels were significantly greater than breast tissue levels. This finding may indicate that the capsule serves as a barrier to the distribution of silicone from the implant into adjacent breast tissue. Although breast tissue silicon levels in patients with silicone implants were not significantly greater than those in patients with saline implants (p = 0.48), capsular tissue levels in patients with silicone implants were, indeed, significantly greater than those in patients with saline implants (p < 0.001). However, no statistically significant differences in tissue silicon levels were observed with relation to the presence or absence of connective‐tissue disease signs or symptoms in patients with silicone implants (groups I to III). Therefore, these data strengthen the conclusion that there is no association between tissue silicon levels and connective‐tissue disease. (Plast. Reconstr. Surg. 101: 1836, 1998.)

Evaluation of a tunable bandpass reaction cell for an inductively coupled plasma mass spectrometer for the determination of chromium and vanadium in serum and urine

Abstract A Dynamic Reaction Cell™ inductively coupled argon plasma mass spectrometer (DRC-ICP-MS) was evaluated for the determination of chromium and vanadium in serum and urine. Reaction cell conditions were evaluated for the elimination of ArC + and ClOH + interferences on chromium at mass 52 and OCl + on vanadium at mass 51. A diluent containing only 1% nitric acid and internal standards (Y and Ga) was used to prepare serum and urine for analysis. Instrument response calibration was achieved by using aqueous acidic standards spiked into pooled sera or urine matrices. The slopes of the calibration curves prepared in urine and serum matrices were nearly identical. On average, chromium detection limits are 2.5 times lower using the DRC than Zeeman graphite furnace atomic absorption spectrometry (ZGFAAS). Vanadium detection limits are approximately 50 times lower. Average detection limits achieved with DRC-ICP-MS are 0.075 μg Cr/l and 0.028 μg V/l. Average results for the analysis of National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1598 Bovine Serum (attained over 22 days) are: 0.14 μg Cr/l and 0.068 μg V/l. The reference concentrations for vanadium and chromium in NIST SRM 1598 are (0.06) μg V/l and 0.14±0.08 μg Cr/l, respectively. Results for chromium and vanadium determinations on ICP-MS survey samples from the Toxocologie du Quebec are equivalent to those reported by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) for the same survey samples.

Silicon analysis of breast and periprosthetic capsular tissue from patients with saline or silicone gel breast implants.

&NA; The ubiquitousness of silicon is well known. Recent work has demonstrated measurable baseline levels of silicon in nonaugmented cadavers, subsequent to numerous reports of significant elevations of such levels within patients with silicone breast implants and even more reports alleging a causal relation between silicone gel prostheses and connective‐tissue diseases. Despite the lack of scientifically substantiated data that such a relation exists, the calamitous silicone breast implant controversy has ensued. Saline‐filled breast implants are constructed with a silicone elastomer envelope that remains in direct contact with periprosthetic capsular tissue following implantation. Although there is no evidence to link saline implants with any disorders, it is important to know if saline breast implants contribute any silicon to human body baseline silicon levels. The present study measured tissue silicon levels in 28 breasts of 16 patients with saline‐filled implants to determine if the silicone envelope of these prostheses can contribute to the elevation of such levels. These data were compared with data from 116 breasts of 65 patients with silicone gel‐filled prostheses as well as breast tissue from 17 patients (controls) who had never been exposed to either type of implant. Samples of breast tissue and periprosthetic capsular tissue were obtained from patients with both intact and ruptured implants. Silicon levels of breast tissue specimens from patients with saline‐filled implants were within the range of the controls if the implants were intact. Silicon levels in periprosthetic capsular tissue from patients with intact saline‐filled implants were significantly higher than controls (p < 0.02); however, they were still 100‐fold less than capsular tissue levels from patients with intact gel‐filled implants. Silicon levels measured in both types of tissue were significantly elevated in patients with silicone gelfilled implants compared with controls (p < 0.01). In the case of ruptured gel implants, breast tissue demonstrated higher silicon levels than did similar specimens from patients with intact implants (p < 0.054); periprosthetic capsular tissue levels also were elevated, although the differences were not statistically significant (p = 0.54). These findings are independent of the implant brand or length of exposure to the particular prosthesis. The finding of elevated levels of silicon in both breast and periprosthetic capsular tissue in patients with silicone gel‐filled implants in no way implies or substantiates any claim of a causal relationship between silicone and any reported illnesses. (Plast. Reconstr. Surg. 98: 798, 1996.)

Determination of serum nickel by graphite furnace atomic absorption spectrometry with Zeeman-effect background correction: values in a normal population and a population undergoing dialysis

An atomic absorption spectrometric method with Zeeman-effect background correction for the determination of nickel, which requires only serum dilution with an aqueous surfactant, is described. The average nickel concentration in sera collected from 38 healthy adult volunteers was 0.14 +/- 0.09 micrograms l-1 of Ni, which is approximately four times lower than normals reported previously (0.65 +/- 0.35 or 0.46 +/- 0.26 microgram l-1 of Ni). The procedure yielded accurate results for the analysis of three different reference serum pools. A comparison of the average nickel concentrations from a patient population undergoing regular haemodialysis with our normal population showed that the average concentration of serum nickel in the dialysis patient group (n = 27 patients) was 46 times higher than normal (6.38 +/- 3.36 micrograms l-1 of Ni; n = 40 specimens).

Evaluation of a tunable bandpass reaction cell inductively coupled plasma mass spectrometer for the determination of selenium in serum and urine

Abstract A Dynamic Reaction Cell™ inductively coupled plasma mass spectrometer (DRC-ICP-MS) was evaluated for the determination of selenium in serum and urine. Reaction cell conditions were evaluated for the suppression of Ar2+ dimer at m/z 78 and 80 using methane as the reaction gas. A diluent containing 10% ethanol, 1% nitric acid, 0.5% Triton X-100 with gallium and yttrium internal standards was used to dilute urine and serum samples. Instrument response calibration was achieved by using aqueous acidic standards spiked into a urine matrix. Slopes for aqueous inorganic selenium, seleno- dl -cystine, seleno- dl -methionine and trimethylselenonium iodide spiked into urine and serum matrices were nearly identical. In general, reagent blank readings and detection limits were significantly lower in the DRC mode (reaction cell pressurized) than the standard mode (cell vented). Average results for the analysis of National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1598 bovine serum (attained over 13 days) are: 43.8±3.6 μg Se/l. Reference concentration is 43.6±3.6 μg Se/l. For NIST SRM 2670 Normal Urine the DRC-ICP-MS results are 30.7±4.6 μg Se/l with a certified concentration of 30±8 μg Se/l. For NIST SRM 2670 Elevated Urine the DRC-ICP-MS results are 463±35 μg Se/l with a certified concentration of 460±30 μg Se/l. The DRC-ICP-MS results for selenium determinations in urine and serum survey samples from the Institut National de Sante Publique du Quebec were compared with the reference concentrations and results produced by conventional ICP-MS. While conventional ICP-MS gave acceptable results for survey samples, DRC-ICP-MS gave excellent results for both urine and sera. Closer correlation was observed for DRC-ICP-MS results with target concentrations than with conventional ICP-MS.

The determination of selenium in serum and urine by inductively Coupled Plasma Mass Spectrometry: Comparison with Zeeman Graphite Furnace Atomic Absorption Spectrometry

Abstract An inductively Coupled Plasma Mass Spectrometric (ICPMS) method for the determination of selenium in both serum and urine is described. 78Se is used analytically in spite of 38Ar40Ar isobaric interference at mass 78. Initially 82Se was monitored but, limited isotope abundance and therefore limited detection capability for urine selenium precluded continued use. An ethanol–Triton X-100-nitric acid diluent was used to dilute serum and urine and enhance selenium ionization so that both serum and urine can be analyzed with the same calibration curve. Results derived by the ICPMS method were compared with Zeeman Graphite Furnace Atomic Absorption Spectrometry (ZGFAAS) using nickel as the matrix modifier. Detection limits for ZGFAAS and ICPMS using mass 78 are 2.9 and 0.25 μg/l, respectively. ICPMS and ZGFAAS instrument responses were recorded for additions of inorganic selenium, trimethylselenonium iodide, seleno- dl -methionine, and seleno- dl -cystine to urine and serum. ICPMS slopes for all compounds added to urine and serum were found to be nearly identical. ZGFAAS response for each compound was more variable than ICPMS. ZGFAAS response for trimethylselenonium iodide was approximately 3-fold lower than for the other compounds. ZGFAAS regression slopes and correlation coefficients were 0.72 and 0.8139 for reference urine samples. ICPMS regression slope and correlation coefficient vs. the reference target values were 0.95 and 0.9700 for the same urines. Regressions slopes and correlation coefficients for reference sera were 1.01 and 0.9912 for ICPMS and 1.12 and 0.9648 for ZGFAAS. We conclude that ICPMS produced more accurate results than ZGFAAS for selenium in serum and urine.

Comparison of two Meinhard nebulizers operating at the same argon flow but different pressures

Two Meinhard nebulizers were designed to operate at 0.8 lmin, one with a pressure of 31 psig and the other 46 psig. Both nebulizers had identical liquid uptake rates of 2 mlmin, uptake tube cross-sectional areas (A1), and uptake tube wall thicknesses. Values for Wtot and Stot were virtually identical for each nebulizer. The 31 psig nebulizer produced a larger volume of particles in the 1.1–2.5 μm range than the 46 psig model even though the mean tertiary D3,2 were 2.46 and 2.14 μm respectively. The 46 psig nebulizer produced a larger volume of particles < 1.1 μm. Inductively coupled plasma emission intensities for high excitation potential lines were enhanced at all observation heights and liquid flow rates with the 46 psig nebulizer. The effects of changing gas orifice area and other physical parameters of concentric nebulizers are discussed.