Lipidomic mass spectrometry and its application in neuroscience

Table 1 Comparison of leading mass spectrometers for lipidomics

	Resolution	Mass range(m/z)	Mass accuracy(ppm)
ToF			2-5 typical
Waters LCT premier	10000	18000	NA
Agilent LC/ToF	> 22000	50-20000	< 1
Bruker microToF	10000	3000	NA
QToF			Same as ToF
Agilent 6540	> 40000	50-10000	< 1
Waters QToF ultima	17500	32000	1
Waters QToF micro	5000	20000	1
Bruker max is 4G	> 60000	10000	< 1
LTQ velos	3000	4000	0.1 Da
LTQ-orbitrap velos	> 100000	4000	< 2
TSQ quantum access max	0.4 (FWHM)	3000	0.1 Da
TSQ quantiva	0.2 (FWHM)	1850	0.1 Da
Q-exactive	140000	6000	< 1
Orbitrap fusion tribrid	450000	4000	< 1
Synapt G2-HDMS	40000	32000 (1000001)	< 1
Synapt G2S-HDMS	20000	32000 (1000001)	Approx- imately 2

¹When fitted with a quadrupole. m/z: Mass to charge ratio, ppm: Parts per million; LCT: Liquid chromatograph; LTQ: Linear trap quadropole; TSQ: Triple stage quadrupole; HDMS: High definition mass spectrometry; FWHM: Full width at half maximum; ToF: Time of flight; NA: Not available.

Table 2 Select performance parameters of some commercially available mass spectrometers

Parameter	TSQ quantum access max	TSQquantiva	LTQ-orbitrap velos	Qq-ToF	Synapt G2-S HDMS	Q-exactive	Agilent 6540	Orbitrap fusion tribrid
Acquisition rate	5000 amu/s	15000 amu/s	1/s@60000 RP	3/s@30000 RP	30/s MS or MSe mode	13/s@17500	20 MS/s	15/sec@15000
			3/s@15000 RP		2000/s IMS mode	1.5/s@140000	10 MS2/s
Linear dynamic range	5 orders	6 orders	5-6 orders	2-3 orders	> 5 orders In-spectrum1	> 5 orders	5 orders	> 5 orders
Mass accuracy	0.1 Da	0.1 Da	< 3 ppm MS	< 5 ppm Full scan w/Lock Mass	< 1 ppm MS MSe or MS/MS	< 1 ppm	< 1 ppm MS	< 1 ppm
			< 3 ppm MSn	> 100 ppm MS/MS			< 2 ppm MS2	< 1 ppm MSn
			(no lock mass)
Resolution	0.4 Da FWHM	0.2 Da FWHM	> 100000 RP	Up to 30000 RP	Up to 40000RP	140000	> 15000 RP@ 1522	450000
Sensitivity	Sub-femto-mol	Atto-mol	Sub atto-mol	Sub femto-mol	Approximately 10 charges at the detector	Atto-mol	Femto-mol	Sub atto-mol

¹At full resolution and maximum acquisition rate. ToF: Time of flight; LTQ: Linear trap quadropole; TSQ: Triple stage quadrupole; HDMS: High definition mass spectrometry; MS: Mass spectrometry; IMS: Ion mobility spectometry.

Table 3 Class specific scanning parameters of different lipid classes using spatial resolution triple quadrupole mass spectrometer¹

Lipid class	Class-specific pre screen				Second-step quantification
	Ion mode	Daughter ion mass (m/z)	Collision energy (V)	Scan type	Daughter ion mass (m/z)	Collision energy (V)	Scan type
PC	+	184	35	PIS	189, 183.1, 59	35, 35, 24	NLS
lysoPC	+	59	22	NLS	205, 59	34, 22	NLS
PE, lysoPE	-	196	50	PIS	222.2	30	NLS
PI, LysoPI	-	241.1	45	PIS	241.1	45	PIS
PS, lysoPS	-	87.1	24	NLS	87.1	24	NLS
PG, lysoPG	-	153.1	35	PIS	153.1	35	PIS
PA, lysoPA	-	153.1	35	PIS	153.1	35	PIS
CL, monolysoCL	-	Full MS at high resolution
Triglycerides	+
Spingomyelin	+	213.2	50	NLS	213.2	50	NLS
Ceramide	-	256.2	32	NLS			NLS
Sphingoid base	+	48	18	NLS	48	18	NLS
Psychosine	+	180	24	NLS	180	24	NLS
Acyl -carnitine	+	85.1	30	PIS	85.1	30	PIS
Acyl-CoA	-	134	30	PIS	134	30	PIS

¹The parameters have been adopted from a review of vast literature, which has been reviewed in Yang et al[24]. Some lipid extraction for analyses in positive ion mode performed in presence of Sodium or Lithium ion will change the mass to charge ratio (m/z) of ions. Similarly, extraction performed for analyses in negative ion mode in presence of ammonium acetate may change the m/z of ions. MS: Mass spectrometry; PIS: Precursor ion scan; NLS: Neutral loss scan; PC: Phosphocholine; lysoPC: Lysophosphocholine; PE: Phosphoethanolamine; PI: Phosphoinositol; PS: Phosphoserine; PG: Glycerophosphoglycerols; PA: Phosphatidic acid; CL: Cardiolipin.