MS/MS Screening Standards and Mixes

❛❛In clinical chemistry-based applications of mass spectrometry, the first lesson the laboratory learns is the requisite nature of stable isotope-enriched standards for quantification of metabolites in biological fluids. In newborn screening of amino acids and acylcarnitines, Cambridge Isotope Laboratories, Inc., set the standard for quantification of these metabolites in dried blood spots. As research and development of the newborn screening analysis by mass spectrometry progressed, it was clear that a half dozen isotope-labeled internal standards would not be adequate for the analysis of an amino acid and acylcarnitine profile, together comprising a range of 500 separate mass units and more than 30 important metabolites, most of which require accurate quantification. When screening began to expand beyond research, it was clear that weighing out small quantities of individual standards would reduce accuracy and introduce unnecessary error. Therefore, together, we set out to develop sets of standards for amino acids and acylcarnitine analysis that would enable quantification. We started this development more than 20 years ago adding, changing, and improving these standards. CIL, together with the early developers of tandem mass spectrometry-based newborn screening, set the standard by which all other laboratories follow. CIL’s commitment to supporting the metabolic and newborn screening community is exceptional. It is our good fortune in the clinical chemistry and mass spectrometry community to have CIL as part of our laboratory solutions.❜❜

– Donald H. Chace, PhD MSFS FACB | Medolac Laboratories

MS/MS Screening Standards and Mixes

To support MS/MS screening exercises and enhance method adoption, CIL is pleased to offer a breadth of high-quality mixtures in their stable isotope-labeled (and unlabeled) form. These mixes contain a collection of stable isotope-labeled standards (e.g., 12 amino acids in NSK-A) and are class-specific (e.g., amino acids, carnitine/acylcarnitines, steroids). These are available in 10-vial sets or single vials and are suitable for metabolite quantification in isotope dilution MS (IDMS) experiments. 

Amino Acid Standards and Mixes

CIL offers a variety of amino acid standards for MS/MS screening. These are available as individual standards (e.g., argininosuccinic acid, ASA; creatinine, Crn; guanidinoacetic acid, GUAC, homocystine, Hcy), with select compounds formulated into mixtures (e.g., labeled, NSK-A; unlabeled, NSK-A-US). The labeling is variable (in terms of position and isotope), with mixtures available in 1 vial and 10-vial sets.

Carnitine/Acylcarnitine Standards and Mixes

CIL offers a number of carnitine/acylcarnitine standards for MS/MS screening. These dried-down compounds are available as individual standards (e.g., L-carnitine, C0; O-glutaryl-L-carnitine, C5-DC; O-hexacosanoyl-L-carnitine, C26), in their unlabeled and/or deuterium-labeled form. Select carnitine/acylcarnitine standards have been formulated into mixtures (labeled, NSK-B and NSK-B-G1; unlabeled, NSK-B-US and NSK-B-G1-US) and are supplied in 1 vial or 10-vial sets.

Organic Acid Standards and Mixes

CIL offers a multitude of organic acid (OA) standards as individuals and multicomponent mixtures. These products are dried down in their stable isotope-labeled and/or unlabeled form for use in basic and/or translational MS-based applications.

Substrate and Internal Standard Sets

CIL is pleased to offer six dried-down standards sets of substrate (S) and internal standard (IS) combinations for use in basic and/or translational MS/MS screening research.

Other Standards and Mixes

CIL offers a number of other standards and mixes for basic and translational MS-based research applications (e.g., LysoPC mixes, steroid mixes, adenosine, L-argininosuccinic acid, D-galactose-1-phosphate). These products are dried down in their stable isotope-labeled and/or unlabeled form.

Frequently Asked Questions

What is the recommended procedure for solubilizing NSK-A and -B? The lyophilized amino acid mix in NSK-A (and NSK-A1) should be dissolved in 1 mL of 1:1 purified water:methanol and the carnitine/acylcarnitines in NSK-B (and NSK-B-G1) in 1 mL of purified methanol. Following the solvent addition, each vial should be vortexed manually for 1 min then auto-vortexed for 30 min (or longer until fully solubilized).

Are the component chemical purities considered in the NSK product formulations? Yes, the chemical purity of each component is determined at time of formulation (e.g., by quantitative NMR) and the gravimetry is adjusted as necessary to compensate for its given chemical purity.

What concentration should I use on the CoA to represent the standard in use – gravimetric target concentration, concentration by gravimetry, or analyzed concentration? The concentrations presented in the “Concentration by Gravimetry” column of the CoA should be used to represent the actual concentration of each component after reconstitution.

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