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Elemental analysis in infant formula and raw ingredients by ICP-MS

By John Lee
Agilent Food Market Manager

AOAC International test methods for infant formula and adult nutritionals are gaining momentum in the industry, and many are now being put through multilab validation and attaining Final Action Official Method status.

Financial support of this effort is made available through the Infant Nutrition Council of America (INCA), formerly the International Formula Council (IFC), on behalf of Abbott Nutrition, Fonterra, Mead Johnson, Nestle, and Perrigo.

This funding enables the organization of expert review panels (ERPs) that are part of a process to develop standard method performance requirements (SMPRs) for analytical methods. These well-documented SMPRs then act as a guideline and approval framework against which the industry can submit proposed methods and the requested performance data.

Sensitive, accurate testing methods are critical in food analysis

In the last couple of years, it has been exciting to see many methods proposed by industry and accepted by these panels as First Action Status (i.e. provisional) methods. These are all published by AOAC. Multi-laboratory testing (MLT) is performed for the most popular tests among the relevant AOAC expert panel; the results from some MLT are already in.

Industry experts are in demand, both to submit worthy proposals and to sit on ERPs to review them. One of these experts is Dr. Lawrence Pacquette, Senior Research Scientist for Global Research Services, Analytical Research & Food Safety at Abbott Nutrition.

A method developed by Dr. Pacquette’s laboratory has already been through multilab validation. The good results mean that it has become one of the first to be approved as an AOAC Final Action Official Method.

This method has also been recommended by the relevant AOAC ERP as a candidate dispute resolution method.

The method in question (AOAC Final Action Status 2011.19) relates to measurement of chromium, selenium, and molybdenum in infant formula and adult/pediatric nutritional formula by ICP-MS. Because of the narrow range between optimum and toxic levels, fortification of nutritional products with these ultra trace nutrients requires analytical methods that are sensitive, accurate, and precise.

Results of the MLT studies will be published shortly. In the meantime, Table 1 shows Abbott’s own data, demonstrating close agreement between Dr. Pacquette’s laboratory and one of Abbott’s other international labs using this new reference method (2011.19).

NIST SRM 1849 control sample, infant nutritional powder ref values (mg/kg) Cr 1.09 ± 0.21, Se 0.889 ± 0.057, Mo 1.6 ± 0.15

Table 1. Evaluation of accuracy, precision, and transfer between instruments in different locations for the analysis of three metals in a nutritional supplement.

More information is available in Agilent publication 5991-5865EN and from a webinar recently delivered by Dr. Pacquette.

ICP-MS is an excellent technique for this work because it can be applied to the many analyses in a QC laboratory that assesses supplement manufacture. In Dr. Pacquette’s webinar, he outlines other methods using the same ICP-MS, including total iodine supplementation in finished product and looking at As, Cd, Hg, and Pb in raw materials. In the latter, sensitivity is even more critical to detect these highly toxic metals at ultratrace levels (Table 2).

^aCalculated from blank SD values over 10 days
^bEquivalent to the lower linear limit of the calibration curve
^cPLoQ by dilution factor of 25
^dPLoQ by dilution factor of 125

Table 2. Heavy metals in raw materials.

Dr. Pacquette’s lab has developed a further multielement method, including chromium, selenium, and molybdenum, but this time in conjunction with nine other higher-level elements (Table 3). Clearly, pioneering scientists are still uncovering new potential in the latest ICP-MS systems, to increase efficiencies in the QC lab.

^aInfant/adult nutritional powder (also used as lab control) – superseded by 1849a
^bInfant/adult nutritional powder (lab control)

Table 3. Internal evaluation of accuracy and precision.

Agilent offers a broad spectrum of solutions for advanced metals analysis

Abbot laboratories use a wide range of Agilent ICP-MS instruments, including the 7700 and 7900 ICP-MS platforms. In all cases, it is the performance and flexibility of the Agilent octopole reaction system (ORS) collision cell that ensures the selective and reliable results shown here. The extremely linear response of these systems over a wide dynamic range provides the power to combine many elements into fewer assays.

Agilent has an extensive range of technologies and methods for metals analysis, including Microwave Plasma-Atomic Emission Spectrometer System (4200 MP-AES), 5100 ICP-OES, 7800 ICP-MS, 7900 ICP-MS, and 8800 Triple Quadrupole ICP-MS, all supported by leading sample preparation products and software. Measurement of total metals is sometimes not sufficient, and it may be necessary to differentiate between organic and inorganic species. In this case, Agilent also offers hyphenated systems including LC-ICP-MS and GC-ICP-MS solutions. Take a moment to explore Agilent’s metals testing solutions today.

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