Fast and accurate determination of K, Ca, and Mg in human serum by sector field ICP-MS

Abstract

Electrolytes in serum are important biomarkers for skeletal and cellular health. The levels of electrolytes are monitored by measuring the Ca, Mg, K, and Na in blood serum. Many reference methods have been developed for the determination of Ca, Mg, and K in clinical measurements; however, isotope dilution thermal ionization mass spectrometry (ID-TIMS) has traditionally been the primary reference method serving as an anchor for traceability and accuracy to these secondary reference methods. The sample matrix must be separated before ID-TIMS measurements, which is a slow and tedious process that hindered the adoption of the technique in routine clinical measurements. We have developed a fast and accurate method for the determination of Ca, Mg, and K in serum by taking advantage of the higher mass resolution capability of the modern sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Each serum sample was spiked with a mixture containing enriched (44)Ca, (26)Mg, and (41)K, and the (42)Ca(+):(44)Ca(+), (24)Mg(+):(26)Mg(+), and (39)K(+):(41)K(+) ratios were measured. The Ca and Mg ratios were measured in medium resolution mode (m/Δm ≈ 4 500), and the K ratio in high resolution mode (m/Δm ≈ 10 000). Residual (40)Ar(1)H(+) interference was still observed but the deleterious effects of the interference were minimized by measuring the sample at K > 100 ng g(-1). The interferences of Sr(++) at the two Ca isotopes were less than 0.25 % of the analyte signal, and they were corrected with the (88)Sr(+) intensity by using the Sr(++):Sr(+) ratio. The sample preparation involved only simple dilutions, and the measurement using this sample preparation approach is known as dilution-and-shoot (DNS). The DNS approach was validated with samples prepared via the traditional acid digestion approach followed by ID-SF-ICP-MS measurement. DNS and digested samples of SRM 956c were measured with ID-SF-ICP-MS for quality assurance, and the results (mean ± expanded uncertainty in mg dL(-1) unit) for Ca (DNS = 10.14 ± 0.13, digested = 10.11 ± 0.10), Mg (DNS = 2.093 ± 0.008, digested = 2.098 ± 0.007), and K (DNS = 15.48 ± 0.11, digested = 15.50 ± 0.28) were in good agreement with the certified values (Ca = 10.17 ± 0.06, Mg = 2.084 ± 0.023, K = 15.55 ± 0.13). Major sources of uncertainty are sample measurement, spike calibration, and instrument factor including mass discrimination of the spectrometer and the detector deadtime.

Characterization of plasma metal profiles in Alzheimer’s disease using multivariate statistical analysis

“…In addition, Inductively coupled plasma mass spectrometry (ICP-MS) was utilized for metal quantification and validated in human plasma by means of a single preparation procedure for each sample. ICP-MS is an excellent tool for the direct or after-digestion determination of a wide range of trace elements in body fluids because of its greater sensitivity and fewer polyatomic interferences compared with other traditional techniques[12]. ELISA kit was highly specific, sensitive, and suitable for large sample analysis[13], it was used to determine levels of metalloproteinases.…”

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…Yu et al 20 at NIST described a faster method, as compared to the tedious preparation required by TIMS, for the determination of Ca, K and Mg aer a simple dilution of serum samples. Two groups of researchers reported improvements of reference methods in this area.…”

Développement d’une méthode primaire pour la détermination du fer total dans du sérum

“…Cette caractéristique est d'une grande importance pour la détermination de nombreux éléments dans des échantillons biologiques, où des effets de matrice importants sont couramment observés [22,28]. La DI-ICP-MS est ainsi utilisée pour analyser un grand nombre d'éléments comme le calcium (Ca), le cuivre (Cu), le potassium (K) dans le sérum humain [22,29,30]. D'autres matrices comme le sang, l'urine, le foie, le rein peuvent aussi être analysées [28].…”