Simultaneous Analysis of Iodine and Bromine Species in Infant Formula using HPLC-ICP-MS.

Background: A fast and sensitive method for the simultaneous analysis of iodine and bromine species in infant formula was developed using HPLC-inductively coupled plasma-MS (HPLC-ICP-MS). Method: To determine the four halogen species [iodide (I-), iodate (IO3-), bromide (Br-), and bromate (BrO3-)] in a milk-based Standard Reference Material and four commercially available infant formula products. Results: The four halogen species were baseline separated in less than 6.5 min using an anion exchange resin column and 5.0 mM NaH2PO4 / 15.0 mM Na2SO4 / 5.0 mM EDTA (pH 7.0) mobile phase. Following separation, the halogen species were detected by measuring m/z 79 for Br and m/z 127 for I using a triple quadrupole-ICP-MS. The instrument was operated in single quadrupole mode with helium cell gas. Excellent linearity (R = 0.9999 or better) was obtained for all four species with calibration standards ranging from 0 to 100 ppb. The LOD for I-, IO3-, Br-, and BrO3- were all less than 0.67 µg/kg. To test the suitability of the method for the accurate determination of low concentrations of the four species in infant formula samples, a spike recovery test was carried out at 20 and 40 µg/kg into the diluted infant formula samples. Conclusions: Total elemental determinations of iodine and bromine were also performed using the triple quadrupole-ICP-MS without HPLC.

Minerals and Trace Elements in Milk, Milk Products, Infant Formula, and Adult/Pediatric Nutritional Formula, ICP-MS Method: Collaborative Study, AOAC Final Action 2015.06, ISO/DIS 21424, IDF 243.

AOAC Final Action Official MethodSM 2015.06 "Minerals and Trace Elements in Milk, Milk Products, Infant Formula and Adult/Pediatric Nutritional Formula, ICP-MS Method" was collaboratively studied. Note that "milk, milk products" has now been added to the title of the Final Action method because whole milk and several dairy ingredients were successfully incorporated into the collaborative study for the purpose of developing an International Organization for Standardization/International Dairy Federation standard (ISO/DIS 21424; in progress). The method determines sodium, magnesium, phosphorus, potassium, calcium, iron, manganese, zinc, copper, chromium, molybdenum, and selenium by inductively coupled plasma (ICP)-MS after microwave digestion. Ten laboratories participated in the study, and data from five different model ICP-MS units were represented. Thirteen products, five placebo products, and six dairy samples were tested as blind duplicates in this study, along with a standard reference material, for a total 50 samples. The overall repeatability and reproducibility for all samples met Standard Method Performance Requirements put forth by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals, with a few exceptions. Comparisons are made to ICP-atomic emission data from a collaborative study of AOAC Official Method 2011.14 carried out concurrently on these same samples.

Characterization of Final Action Official MethodSM 2011.19 and First Action Official Method 2015.06 Performance at Analyte Levels Corresponding to CODEX STAN 72 (1981) Minimum Levels.

A limited single-laboratory validation (SLV) was conducted in the authors' laboratory to investigate the performance of AOAC Official MethodsSM 2011.19 Determination of Chromium (Cr), Selenium (Se), and Molybdenum (Mo) in Infant Formula and Adult Nutritional Products by Inductively Coupled Plasma/Mass Spectrometry and 2015.06 Determination of Minerals and Trace Elements in Infant Formula and Adult/Pediatric Nutritional Formula by Inductively Coupled Plasma/Mass Spectrometry at analyte levels below the practical LOQs (PLOQs) already published for these Final Action Official Methods. This work was needed to verify that the actual LOQs were below the minimum requirements for minerals in infant formula as given in CODEX STAN 72 (1981). Linearity studies at low levels were conducted as well as the analysis of blanks over multiple days to establish the LOQs (as opposed to PLOQs) for these nutrients. Several placebo matrixes from the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) program were tested over multiple days at two different sample sizes to quantitate the effect of doubling the sample size given in the original publications. The SLV results indicate that both methods can meet the Codex minimum requirements as-is, without modification of the methods, albeit with a relaxation of the stringent precision criteria originally established for these methods by SPIFAN. Precision can be improved by doubling the sample size, but this step is not necessary to use the method for its intended purpose. A concurrent collaborative study of Method 2015.06 showed that the RSDR obtained across eight laboratories for several infant formula placebos containing mineral concentrations between the PLOQ and LOQ were indeed worse than SPIFAN expectations, but reasonable Horwitz ratios (HorRat) were nonetheless obtained for these analytes.

Determination of Chromium, Selenium, and Molybdenum in Infant Formula and Adult Nutritional Products by Inductively Coupled Plasma/Mass Spectrometry: Collaborative Study, Final Action 2011.19.

AOAC First Action Method 2011.19: Chromium, Selenium, and Molybdenum in Infant Formula and Adult Nutritional Products, was collaboratively studied. This method uses microwave digestion of samples with nitric acid, hydrogen peroxide, and internal standard followed by simultaneous detection of the elements by an inductively coupled plasma (ICP)/MS instrument equipped with a collision/reaction cell. During this collaborative study, nine laboratories from four different countries, using seven different models of ICP/MS instruments, analyzed blind duplicates of seven infant, pediatric, and adult nutritional formulas. One laboratory's set of data was rejected in its entirety. The method demonstrated acceptable repeatability and reproducibility and met the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) Standard Method Performance Requirements (SMPRs®) for almost all of the matrixes analyzed. The Cr, Mo, and Se SPIFAN requirement for repeatability was ≤5% RSD. The SMPR called for a reproducibility of ≤15% RSD for products with ultratrace element concentrations above the targeted LOQ of 20 µg/kg Cr/Mo and 10 µg/kg Se (as ready-to-feed). During this collaborative study, RSDr ranged from 1.0 to 7.0% and RSDR ranged from 2.5 to 13.4% across all three ultratrace elements.

Determination of Minerals and Trace Elements in Infant Formula and Adult/Pediatric Nutritional Formula by Inductively Coupled Plasma/Mass Spectrometry A Performance Evaluation: Single-Laboratory Validation, First Action 2015.06.

A method for determination of 12 minerals and trace elements (Na, Mg, P, K, Ca, Cr, Mn, Fe, Cu, Zn, Se, and Mo) in infant formula and adult/ pediatric nutritional formula was developed and evaluated in a single-laboratory validation. Some additional reproducibility data were obtained from a small interlaboratory study. The method involves microwave digestion of the sample followed by inductively coupled plasma/MS and uses Ge and Te as internal standards. The method is an extension of Official Method(SM) 2011.19 and was compared to AOAC Standard Method Performance Requirements (SMPRs®) 2011.009 and 2014.004 developed by the AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN). Repeatability precision for the 12 elements in 11 SPIFAN matrixes and National Institute of Standards and Technology Standard Reference Material (SRM) 1849a was <5%, meeting the SMPR criterion for repeatability. Intermediate reproducibility (8 days, two analysts, two instruments) in the 11 SPIFAN matrixes was <5% for nine (Na, Mg, P, K, Mn, Fe, Cu, Zn, Se) of the 12 elements in all 11 matrixes. The mean reproducibility across 6-7 laboratories and seven SPIFAN matrixes ranged from 2.5% for Cu to 7.1% for P. Recovery from spiked matrixes varied from 90.1 to 109%, and accuracy of determination using SRM 1849a ranged from 96.2 to 107.7%, meeting the requirement of 90-110% recovery/accuracy.

Total iodine in infant formula and nutritional products by inductively coupled plasma/mass spectrometry: First Action 2012.14.

After an assessment of data generated from a single-laboratory validation study published in the Journal of AOAC INTERNATIONAL 95, 169-176 (2012), a method for determining the total level of iodine in infant formula and nutritional products was presented for consideration for adoption by AOAC during the AOAC Annual Meeting held September 30-October 3, 2012 in Las Vegas, NV. An Expert Review Panel on Infant Formula and Adult Nutritionals concluded that the method met the established standard method performance requirements, and approved the method as AOAC Official First Action. The method involves digestion of the sample with nitric acid in a closed vessel microwave oven, followed by determination by inductively coupled plasma/MS using tellurium as the internal standard. The method LOQ for total iodine was 1.5 microg/100 g, but a practical LOQ was used at 5 microg/100 g total iodine. The analytical range of the method was 5-100 microg/100 g total iodine. The recoveries from 15 spiked nutritional products ranged from 90 to 105%.

Application of inductively coupled plasma/mass spectrometry for the measurement of chromium, selenium, and molybdenum in infant formula and adult nutritional products: First Action 2011.19.

An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formula and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specification limits; within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was < or = 2% RSD over 10 independent days. Cr, Se, and Mo results were within the certified limits in three National Institute of Standards and Technology standard reference materials. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix-matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in infant formula, adult nutritionals, and other nutritional

Determination of total iodine in infant formula and nutritional products by inductively coupled plasma/mass spectrometry: single-laboratory validation.

A single-laboratory validation by inductively coupled plasma-mass spectrometry was developed for the determination total iodine (m/z 127) in infant formula and adult nutritional products. All samples were digested in nitric acid using a closed vessel microwave oven system; Te (m/z 130) was used as an internal standard. To prevent loss of iodine, ammonium hydroxide solution was added to the samples immediately after digestion. The method quantitation limit for total iodine was 0.3 ng/mL, but a practical LOQ was used at 1.0 ng/mL, a concentration at which there was a negligible bias due to nonlinearity. The total iodine concentrations (112-1900 ng/g) in 14 out of 15 nutritional products were within specification limits. Within-day and day-to-day (6 independent days) precision values were < 10% RSD. The observed precision for the overall mean (18 independent days) of a control sample was approximately 4% RSD. In two National Institute of Standards and Technology standard reference materials, total iodine results were within certified limits. Sample spike recoveries for all 15 nutritional products were 92-105%. The data show that a conventional microwave oven digestion procedure can be used to prepare samples for iodine determination. Therefore, this technique is very compatible with other methods being proposed as modern official methods for the analysis of minerals in nutritional products.

Simultaneous determination of chromium, selenium, and molybdenum in nutritional products by inductively coupled plasma/mass spectrometry: single-laboratory validation.

An inductively coupled plasma/MS method was developed for the simultaneous determination of Cr, Se, and Mo in infant formulas and other nutritional products. All samples were digested using a closed vessel microwave oven system, together with Ni and Te internal standards. The practical quantitation limits for Cr, Se, and Mo were 0.4, 0.2, and 0.4 ng/mL, respectively; dilution factors were 250 for powders and 50 for liquids. The Cr, Se, and Mo concentrations in 10 nutritional products were within specification limits, and within-day and day-to-day (6 independent days) precision values were <5% RSD. For two control samples, the observed precision was < or = 2% RSD over 10 independent days. In three National Institute of Standards and Technology standard reference materials, Cr, Se, and Mo results were within the certified limits. The average sample spike recoveries for 10 nutritional products ranged from 93 to 107%. Robustness studies showed a minimal effect from concomitant easily ionized element concentrations. However, the choice of internal standard and matrix matching carbon content were critical to obtaining accurate Se results. All indications are that this method would be a suitable candidate as a global reference method for the determination of these trace elements in nutritional products.