ICP-MSMS | Determination of Nine Trace Elements in Blood

1. Introduction

Trace elements, though present in extremely small quantities in the human body, exert profound biological effects. They participate in the metabolic processes of enzymes, hormones, vitamins, and nucleic acids. Their physiological functions include assisting in the transport of macronutrients, serving as essential components or activators of enzymes, playing unique roles in hormones and vitamins, and influencing nucleic acid metabolism. In clinical medicine, analyzing the concentrations of trace elements in blood can help evaluate an individual’s health status, diagnose acute or chronic intoxication caused by certain elements, and support the formulation of subsequent treatment strategies.

Inductively coupled plasma mass spectrometry (ICP-MS) offers high sensitivity, low detection limits, a wide dynamic linear range, high analytical efficiency, multi-element simultaneous quantification, simple spectral characteristics, and minimal interference. These advantages are particularly prominent in clinical inorganic elemental analysis. Several national standards already exist for the ICP-MS determination of individual elements in blood, such as Determination of Lead in Blood — Part 2: ICP-MS (GBZ/T 316.2-2018) and Determination of Cadmium in Blood — Part 2: ICP-MS (GBZ/T 317.2-2018). However, standards for the simultaneous determination of multiple elements in blood by ICP-MS remain limited. For instance, Determination of Chromium, Cadmium, Arsenic, Thallium and Lead in Blood — ICP-MS (SF/Z JD0107012-2011) requires sample digestion prior to analysis, making it less suitable for rapid analysis of clinical blood samples.

Given the increasing need in clinical laboratories for rapid, multi-element determination, this study presents a method based on triple quadrupole ICP-MS (ICP-MS/MS) for the simultaneous measurement of nine elements—Ca, Mg, As, Cu, Fe, Mn, Pb, Se, and Zn—in blood. The method requires no digestion; diluted blood samples can be directly introduced for analysis, enabling fast and convenient detection. Experimental results show that all elements exhibit excellent linearity with correlation coefficients (r) greater than 0.999. Method detection limits range from 0.00008 to 0.01624 mg/kg, precision is better than 2.51%, and spiked recoveries fall within 88.41%–112.90%. This method is stable and reliable, providing robust technical support for the determination of trace elements in blood.

Keywords: ICP-MS/MS; blood; oxygen reaction mode; collision mode; trace element concentrations

2. Experimental Section

2.1 Instruments

Figure 1 Inductively Coupled Plasma Mass Spectrometer (ICP-MS/MS)

Model：EXPEC 7350 ICP-MS/MS

Configuration: Standard quartz sample introduction system.

Table 1 Operating parameters of the ICP-MS/MS system

Instrument Parameter	Setting	Instrument Parameter	Setting
Plasma power	1550 W	Collision gas (He)	1.57 mL/min
Cooling gas	14.0 L/min	Peristaltic pump speed	25 r/min
Auxiliary gas	1.0 L/min	Dwell time	20 ms
Nebulizer gas	0.895 L/min	Sampling depth	2.78 mm
Makeup gas	0.20 L/min	Cell bias voltage	-23 V
Reaction gas-O₂	0.210 mL/min	Extraction lens voltage	-188 V

2.2 Reagents and Standards

Reagents: Triton X-100, ultrapure nitric acid, ultrapure isopropanol, and ultrapure water (resistivity ≥18.2 MΩ·cm at 25 °C).

Standard solutions: Multi-element mixed standard solution (1000 μg/mL, National Research Center for Nonferrous Metals, China) and multi-element internal standard solution.

3. Sample Preparation and Calibration Curve Construction

3.1 Sample Preparation

(1) Preparation of blood sample diluent: A diluent consisting of 0.5% nitric acid, 0.01% Triton X-100, and 2% isopropanol was prepared as follows: 5 mL nitric acid, 0.1 mL Triton X-100, and 20 mL isopropanol were added to a volumetric flask and diluted to 1000 mL with ultrapure water, followed by thorough mixing.

(2) Pretreatment of blood samples: A 0.5 mL aliquot of whole blood was diluted to 10 mL using the prepared diluent. The mixture was shaken gently, vortexed for 10 minutes, and centrifuged at 5000 r/min for 10 minutes. The supernatant was then collected for ICP-MS/MS analysis.
Note: The blood sample must be thoroughly mixed before pipetting.

3.2 Calibration Curve

Mixed standard solutions were prepared by accurately pipetting single-element standard stock solutions of Ca, Mg, Fe, As, Cu, Mn, Pb, Se, and Zn, followed by dilution to obtain the working standards. The concentration gradients for the calibration curves are shown in the table below：

Table 2 Concentration gradients for calibration standards

Element	Concentration range for calibration standards：μg/L
Ca、Mg、Fe	0.0/5.0/10.0/50.0/100.0/500.0/1000.0/5000.0
As、Cu、Mn、Pb、Se、Zn	0.0/0.50/1.0/5.0/10.0/50.0/100.0/500.0

4. Results and Discussion

4.1 Calibration Curves and Limits of Detection

Within the concentration ranges listed in Table 2, all analytes showed excellentlinearity, with correlation coefficients (r) greater than 0.999. To determine the limits of detection (LODs), the full-procedure blank was analyzed 11 consecutive times, and the LOD for each element was calculated as three times the standard deviation multiplied by the dilution factor. The results are summarized in Table 3. Table 3 also lists the monitored mass-to-charge ratios for each element, the analytical mode (collision or reaction), and the linearity (expressed as the correlation coefficient r). Representative calibration curves are provided in the Appendix.

Table 3 Monitored masses, correlation coefficients, and limits of detection for the target elements

Element	Mass-to-charge ratio	Mode	Correlation coefficient	Instrument LOD (μg/L)	Method LOD (mg/kg)
Mg	24	Q2-He	0.9997	0.059	0.00118
Ca	44	Q2-He	0.9999	0.812	0.01624
Mn	55→55	QQ-He	0.9999	0.020	0.0004
Fe	57	Q2-He	1.0000	0.350	0.007
Cu	65	Q2-He	0.9999	0.025	0.0005
Zn	66	Q2-He	1.0000	0.094	0.00188
As	75→91	QQ-O₂ mass-shift	1.0000	0.040	0.0008
Se	78	Q2-He	1.0000	0.224	0.00448
Pb	207	Q2-He	1.0000	0.004	0.00008

4.2 Method Precision

To evaluate the stability and repeatability of the analytical method, seven prepared blood samples were analyzed under the same conditions. The precision results for each element are summarized in Table 4. The relative standard deviations (RSDs) for all measured elements were better than 2.51%, demonstrating that the method exhibits excellent precision.

Table 4 Method precision（μg/L）

Sample Name	Mg [Q2-He]	Ca [Q2-He]	Mn [QQ-He]	Fe [Q2-He]	Cu [Q2-He]	Zn [Q2-He]	As [QQ-O₂ mass-shift]	Se [Q2-He]	Pb [Q2-He]
Blood-1	41864	61388	25.61	303740	828	4920	1.21	96.02	27.44
Blood-1	41968	60570	23.87	316980	879	5144	1.28	94.58	27.13
Blood-1	41916	60979	24.74	310360	853	5032	1.24	95.3	27.28
Blood-1	41901	61318	24.61	303740	828	4920	1.22	96.12	27.64
Blood-1	41892	61570	24.87	316980	879	5144	1.25	95.58	27.33
Blood-1	41892	61279	24.74	310360	853	5032	1.26	95.34	27.38
Blood-1	41954	61198	25.012	309921	865	5012	1.19	95.67	27.12
Average	41912	61186	24.78	310297	855	5029	1.24	95.52	27.33
RSD(%)	0.09	0.53	2.09	1.74	2.49	1.82	2.51	0.54	0.66

4.3 Analysis of Real Samples

The concentrations of the target elements in the blood samples are summarized in Table 5.

Table 5 Measured concentrations of elements in blood samples (μg/L)

Sample	Mg [Q2-He]	Ca [Q2-He]	Mn [QQ-He]	Fe [Q2-He]	Cu [Q2-He]	Zn [Q2-He]	As [QQ- O₂ mass-shift]	Se [Q2-He]	Pb [Q2-He]
Blood -1	41916	60979	24.74	310360	853	5032	1.24	95.30	27.28
Spiked recovery (%)	103.37	111.07	108.72	108.50	107.59	101.01	99.16	101.70	91.44

Blood-2	38872	60989	24.21	284400	1072	5073	1.23	77.00	39.47
Spiked recovery (%)	110.01	112.01	112.13	89.49	100.20	102.03	91.71	96.83	99.30

Blood -3	45149	67564	28.66	336440	1018	4027	2.73	109.90	24.47
Spiked recovery (%)	110.35	111.42	110.46	109.30	104.11	100.55	100.75	106.64	92.53

Blood -4	45809	70545	22.16	281910	1082	6089	1.95	104.31	22.07
Spiked recovery (%)	109.40	106.60	103.02	105.00	103.49	102.90	103.70	104.27	105.95

Blood -5	42879	73048	28.72	283080	864	5893	1.57	114.94	22.37
Spiked recovery (%)	111.34	107.53	112.90	94.81	99.13	93.52	93.45	100.22	91.84

Blood -6	45147	76166	27.18	266550	924	4649	1.44	70.94	36.97
Spiked recovery (%)	108.83	104.30	112.88	91.11	98.51	94.02	102.92	110.54	93.35

Blood-7	42997	70926	23.70	293020	1170	4169	1.81	120.92	26.62
Spiked recovery (%)	109.27	111.19	110.04	89.60	105.73	95.40	102.18	112.60	93.34

Blood -8	46058	71089	28.90	281140	1041	5415	2.02	115.12	24.44
Spiked recovery (%)	108.09	103.15	110.78	88.67	96.16	91.07	100.22	110.05	95.41

Blood -9	35271	76420	22.44	287140	980	5454	1.50	101.95	24.55
Spiked recovery (%)	110.67	111.90	112.60	91.33	95.24	91.29	101.66	110.04	88.41

Blood -10	43717	75327	19.89	377370	850	5042	2.03	101.90	32.59
Spiked recovery (%)	107.75	105.19	112.04	108.69	96.12	94.25	100.76	104.55	88.96

5. Conclusion

In this study, nine elements in blood samples were analyzed using a triple quadrupole inductively coupled plasma mass spectrometer (ICP-MS/MS). The results demonstrated that all calibration curves exhibited excellent linearity, with correlation coefficients exceeding 0.999, and the parallel measurements showed good consistency. Appropriate spike levels were selected for each element, and the corresponding spike recovery rates ranged from 88.41% to 112.90%.

These findings indicate that, for biological samples such as blood with highly complex matrices, operating the instrument in collision mode effectively reduces matrix-induced interferences while maintaining high sensitivity, stability, accuracy, and precision. Overall, the ICP-MS/MS method described herein enables rapid and reliable simultaneous determination of multiple trace elements in blood.

6. Appendix

6.1 Calibration Curves

Mn[QQ-He]